Merge pull request #1683 from rust-lang/all-contributors/add-OfirLauber

docs: add OfirLauber as a contributor for content
docs: update .all-contributorsrc [skip ci]
2023-09-21 12:12:36 +02:00 · 2023-09-21 10:01:31 +00:00 · 2023-09-21 10:01:30 +00:00 · 2023-09-21 12:01:16 +02:00 · 2023-09-21 01:54:11 +03:00 · 2023-09-18 10:16:05 +02:00
128 changed files with 2354 additions and 852 deletions
--- a/.all-contributorsrc
+++ b/.all-contributorsrc
@ -1947,6 +1947,492 @@
      "contributions": [
        "content"
      ]
+    },
+    {
+      "login": "VegardMatthey",
+      "name": "Vegard",
+      "avatar_url": "https://avatars.githubusercontent.com/u/59250656?v=4",
+      "profile": "https://github.com/VegardMatthey",
+      "contributions": [
+        "content"
+      ]
+    },
+    {
+      "login": "ryanwhitehouse",
+      "name": "Ryan Whitehouse",
+      "avatar_url": "https://avatars.githubusercontent.com/u/13400784?v=4",
+      "profile": "https://github.com/ryanwhitehouse",
+      "contributions": [
+        "content"
+      ]
+    },
+    {
+      "login": "guoard",
+      "name": "Ali Afsharzadeh",
+      "avatar_url": "https://avatars.githubusercontent.com/u/65511355?v=4",
+      "profile": "https://github.com/guoard",
+      "contributions": [
+        "content"
+      ]
+    },
+    {
+      "login": "keogami",
+      "name": "Keogami",
+      "avatar_url": "https://avatars.githubusercontent.com/u/41939011?v=4",
+      "profile": "http://keogami.ml",
+      "contributions": [
+        "doc"
+      ]
+    },
+    {
+      "login": "ahresse",
+      "name": "Alexandre Esse",
+      "avatar_url": "https://avatars.githubusercontent.com/u/28402488?v=4",
+      "profile": "https://github.com/ahresse",
+      "contributions": [
+        "content"
+      ]
+    },
+    {
+      "login": "sagarvora",
+      "name": "Sagar Vora",
+      "avatar_url": "https://avatars.githubusercontent.com/u/16315650?v=4",
+      "profile": "https://resilient.tech",
+      "contributions": [
+        "content"
+      ]
+    },
+    {
+      "login": "poneciak57",
+      "name": "Kacper Poneta",
+      "avatar_url": "https://avatars.githubusercontent.com/u/94321164?v=4",
+      "profile": "https://github.com/poneciak57",
+      "contributions": [
+        "content"
+      ]
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+      "name": "Aaron Suggs",
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+      "profile": "https://ktheory.com/",
+      "contributions": [
+        "content"
+      ]
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+      "profile": "https://github.com/alexwh",
+      "contributions": [
+        "content"
+      ]
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+      "login": "stornquist",
+      "name": "Sebastian Törnquist",
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+      "profile": "https://github.com/stornquist",
+      "contributions": [
+        "content"
+      ]
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+      "name": "Sebastian LaVine",
+      "avatar_url": "https://avatars.githubusercontent.com/u/33563640?v=4",
+      "profile": "http://smlavine.com",
+      "contributions": [
+        "code"
+      ]
+    },
+    {
+      "login": "akgerber",
+      "name": "Alan Gerber",
+      "avatar_url": "https://avatars.githubusercontent.com/u/201313?v=4",
+      "profile": "http://www.alangerber.us",
+      "contributions": [
+        "content"
+      ]
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+      "name": "Eric",
+      "avatar_url": "https://avatars.githubusercontent.com/u/104941850?v=4",
+      "profile": "http://esotuvaka.github.io",
+      "contributions": [
+        "content"
+      ]
+    },
+    {
+      "login": "az0977776",
+      "name": "Aaron Wang",
+      "avatar_url": "https://avatars.githubusercontent.com/u/9172038?v=4",
+      "profile": "https://github.com/az0977776",
+      "contributions": [
+        "content"
+      ]
+    },
+    {
+      "login": "nmay231",
+      "name": "Noah",
+      "avatar_url": "https://avatars.githubusercontent.com/u/35386821?v=4",
+      "profile": "https://github.com/nmay231",
+      "contributions": [
+        "content"
+      ]
+    },
+    {
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+      "name": "rb5014",
+      "avatar_url": "https://avatars.githubusercontent.com/u/105397317?v=4",
+      "profile": "https://github.com/rb5014",
+      "contributions": [
+        "content"
+      ]
+    },
+    {
+      "login": "deedy5",
+      "name": "deedy5",
+      "avatar_url": "https://avatars.githubusercontent.com/u/65482418?v=4",
+      "profile": "https://github.com/deedy5",
+      "contributions": [
+        "content"
+      ]
+    },
+    {
+      "login": "lionel-rowe",
+      "name": "lionel-rowe",
+      "avatar_url": "https://avatars.githubusercontent.com/u/26078826?v=4",
+      "profile": "https://github.com/lionel-rowe",
+      "contributions": [
+        "content"
+      ]
+    },
+    {
+      "login": "Ben2917",
+      "name": "Ben",
+      "avatar_url": "https://avatars.githubusercontent.com/u/10279994?v=4",
+      "profile": "https://github.com/Ben2917",
+      "contributions": [
+        "content"
+      ]
+    },
+    {
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+      "name": "b1ue64",
+      "avatar_url": "https://avatars.githubusercontent.com/u/77976308?v=4",
+      "profile": "https://github.com/b1ue64",
+      "contributions": [
+        "content"
+      ]
+    },
+    {
+      "login": "lazywalker",
+      "name": "lazywalker",
+      "avatar_url": "https://avatars.githubusercontent.com/u/53956?v=4",
+      "profile": "https://github.com/lazywalker",
+      "contributions": [
+        "content"
+      ]
+    },
+    {
+      "login": "proofconstruction",
+      "name": "proofconstruction",
+      "avatar_url": "https://avatars.githubusercontent.com/u/74747193?v=4",
+      "profile": "https://github.com/proofconstruction",
+      "contributions": [
+        "infra"
+      ]
+    },
+    {
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+      "name": "IVIURRAY",
+      "avatar_url": "https://avatars.githubusercontent.com/u/16007179?v=4",
+      "profile": "https://www.youtube.com/channel/UCQCjA6qUutAtWqkCA4Z36CQ",
+      "contributions": [
+        "content"
+      ]
+    },
+    {
+      "login": "b-apperlo",
+      "name": "Bert Apperlo",
+      "avatar_url": "https://avatars.githubusercontent.com/u/91734527?v=4",
+      "profile": "https://github.com/b-apperlo",
+      "contributions": [
+        "content"
+      ]
+    },
+    {
+      "login": "FWDekker",
+      "name": "Florine W. Dekker",
+      "avatar_url": "https://avatars.githubusercontent.com/u/13442533?v=4",
+      "profile": "https://fwdekker.com/",
+      "contributions": [
+        "content"
+      ]
+    },
+    {
+      "login": "luhem7",
+      "name": "Mehul Gangavelli",
+      "avatar_url": "https://avatars.githubusercontent.com/u/4008215?v=4",
+      "profile": "https://github.com/luhem7",
+      "contributions": [
+        "content"
+      ]
+    },
+    {
+      "login": "Frosthage",
+      "name": "Mikael Frosthage",
+      "avatar_url": "https://avatars.githubusercontent.com/u/14823314?v=4",
+      "profile": "https://github.com/Frosthage",
+      "contributions": [
+        "content"
+      ]
+    },
+    {
+      "login": "robertefry",
+      "name": "Robert Fry",
+      "avatar_url": "https://avatars.githubusercontent.com/u/43712054?v=4",
+      "profile": "https://robertfry.xyz",
+      "contributions": [
+        "content"
+      ]
+    },
+    {
+      "login": "tajo48",
+      "name": "tajo48",
+      "avatar_url": "https://avatars.githubusercontent.com/u/55502906?v=4",
+      "profile": "https://github.com/tajo48",
+      "contributions": [
+        "content"
+      ]
+    },
+    {
+      "login": "novanish",
+      "name": "Anish",
+      "avatar_url": "https://avatars.githubusercontent.com/u/98446102?v=4",
+      "profile": "https://anishchhetri.com.np",
+      "contributions": [
+        "content"
+      ]
+    },
+    {
+      "login": "vnprc",
+      "name": "vnprc",
+      "avatar_url": "https://avatars.githubusercontent.com/u/9425366?v=4",
+      "profile": "https://github.com/vnprc",
+      "contributions": [
+        "content"
+      ]
+    },
+    {
+      "login": "jrcarl624",
+      "name": "Joshua Carlson",
+      "avatar_url": "https://avatars.githubusercontent.com/u/61999256?v=4",
+      "profile": "http://androecia.net",
+      "contributions": [
+        "content"
+      ]
+    },
+    {
+      "login": "johnDeSilencio",
+      "name": "Nicholas R. Smith",
+      "avatar_url": "https://avatars.githubusercontent.com/u/20136554?v=4",
+      "profile": "https://johndesilencio.me",
+      "contributions": [
+        "code"
+      ]
+    },
+    {
+      "login": "alexfertel",
+      "name": "Alexander González",
+      "avatar_url": "https://avatars.githubusercontent.com/u/22298999?v=4",
+      "profile": "https://alexfertel.me",
+      "contributions": [
+        "content"
+      ]
+    },
+    {
+      "login": "softarn",
+      "name": "Marcus Höjvall",
+      "avatar_url": "https://avatars.githubusercontent.com/u/517619?v=4",
+      "profile": "https://github.com/softarn",
+      "contributions": [
+        "content"
+      ]
+    },
+    {
+      "login": "barlevalon",
+      "name": "Alon Hearter",
+      "avatar_url": "https://avatars.githubusercontent.com/u/3397911?v=4",
+      "profile": "https://github.com/barlevalon",
+      "contributions": [
+        "content"
+      ]
+    },
+    {
+      "login": "shirts",
+      "name": "shirts",
+      "avatar_url": "https://avatars.githubusercontent.com/u/4952151?v=4",
+      "profile": "https://github.com/shirts",
+      "contributions": [
+        "content"
+      ]
+    },
+    {
+      "login": "eLVas",
+      "name": "Ivan Vasiunyk",
+      "avatar_url": "https://avatars.githubusercontent.com/u/6797156?v=4",
+      "profile": "https://github.com/eLVas",
+      "contributions": [
+        "content"
+      ]
+    },
+    {
+      "login": "mo8it",
+      "name": "Mo",
+      "avatar_url": "https://avatars.githubusercontent.com/u/76752051?v=4",
+      "profile": "https://mo8it.com",
+      "contributions": [
+        "code"
+      ]
+    },
+    {
+      "login": "x10an14",
+      "name": "x10an14",
+      "avatar_url": "https://avatars.githubusercontent.com/u/710608?v=4",
+      "profile": "https://github.com/x10an14",
+      "contributions": [
+        "infra"
+      ]
+    },
+    {
+      "login": "gabay",
+      "name": "Roi Gabay",
+      "avatar_url": "https://avatars.githubusercontent.com/u/5773610?v=4",
+      "profile": "https://github.com/gabay",
+      "contributions": [
+        "content"
+      ]
+    },
+    {
+      "login": "mkovaxx",
+      "name": "Máté Kovács",
+      "avatar_url": "https://avatars.githubusercontent.com/u/481354?v=4",
+      "profile": "https://github.com/mkovaxx",
+      "contributions": [
+        "content"
+      ]
+    },
+    {
+      "login": "szabgab",
+      "name": "Gábor Szabó",
+      "avatar_url": "https://avatars.githubusercontent.com/u/48833?v=4",
+      "profile": "https://szabgab.com/",
+      "contributions": [
+        "content"
+      ]
+    },
+    {
+      "login": "yamila-moreno",
+      "name": "Yamila Moreno",
+      "avatar_url": "https://avatars.githubusercontent.com/u/3340793?v=4",
+      "profile": "https://moduslaborandi.net",
+      "contributions": [
+        "content"
+      ]
+    },
+    {
+      "login": "willhack",
+      "name": "Will Hack",
+      "avatar_url": "https://avatars.githubusercontent.com/u/18036720?v=4",
+      "profile": "https://github.com/willhack",
+      "contributions": [
+        "content"
+      ]
+    },
+    {
+      "login": "bean5",
+      "name": "Michael",
+      "avatar_url": "https://avatars.githubusercontent.com/u/2052646?v=4",
+      "profile": "http://cancompute.tech",
+      "contributions": [
+        "content"
+      ]
+    },
+    {
+      "login": "pksadiq",
+      "name": "Mohammed Sadiq",
+      "avatar_url": "https://avatars.githubusercontent.com/u/1289514?v=4",
+      "profile": "https://www.sadiqpk.org",
+      "contributions": [
+        "content"
+      ]
+    },
+    {
+      "login": "Jak-Ch-ll",
+      "name": "Jakob",
+      "avatar_url": "https://avatars.githubusercontent.com/u/56225668?v=4",
+      "profile": "https://github.com/Jak-Ch-ll",
+      "contributions": [
+        "content"
+      ]
+    },
+    {
+      "login": "ob",
+      "name": "Oscar Bonilla",
+      "avatar_url": "https://avatars.githubusercontent.com/u/4950?v=4",
+      "profile": "http://oscarbonilla.com",
+      "contributions": [
+        "content"
+      ]
+    },
+    {
+      "login": "husjon",
+      "name": "Jon Erling Hustadnes",
+      "avatar_url": "https://avatars.githubusercontent.com/u/554229?v=4",
+      "profile": "https://github.com/husjon",
+      "contributions": [
+        "content"
+      ]
+    },
+    {
+      "login": "CobaltCause",
+      "name": "Charles Hall",
+      "avatar_url": "https://avatars.githubusercontent.com/u/7003738?v=4",
+      "profile": "https://github.com/CobaltCause",
+      "contributions": [
+        "infra"
+      ]
+    },
+    {
+      "login": "krmpotic",
+      "name": "Luka Krmpotić",
+      "avatar_url": "https://avatars.githubusercontent.com/u/10350645?v=4",
+      "profile": "https://github.com/krmpotic",
+      "contributions": [
+        "content"
+      ]
+    },
+    {
+      "login": "jurglic",
+      "name": "Jurglic",
+      "avatar_url": "https://avatars.githubusercontent.com/u/112600?v=4",
+      "profile": "https://github.com/jurglic",
+      "contributions": [
+        "content"
+      ]
+    },
+    {
+      "login": "OfirLauber",
+      "name": "Ofir Lauber",
+      "avatar_url": "https://avatars.githubusercontent.com/u/5631030?v=4",
+      "profile": "https://github.com/OfirLauber",
+      "contributions": [
+        "content"
+      ]
    }
  ],
  "contributorsPerLine": 8,
@ -1955,5 +2441,6 @@
  "repoType": "github",
  "repoHost": "https://github.com",
  "skipCi": true,
-  "commitConvention": "angular"
+  "commitConvention": "angular",
+  "commitType": "docs"
 }
--- a/.envrc
+++ b/.envrc
@ -0,0 +1,4 @@
+#!/usr/bin/env bash
+
+# Automatically Load nix devShell w/dotenv
+use flake
--- a/.github/workflows/rust.yml
+++ b/.github/workflows/rust.yml
@ -10,11 +10,28 @@ env:
  CARGO_TERM_COLOR: always

 jobs:
-  build:
+  fmt:
    runs-on: ubuntu-latest
    steps:
-    - uses: actions/checkout@v3
-    - name: Build
-      run: cargo build --verbose
-    - name: Run tests
-      run: cargo test --verbose
+      - uses: actions/checkout@v3
+      - uses: dtolnay/rust-toolchain@stable
+        with:
+          components: rustfmt
+      - uses: DavidAnson/markdownlint-cli2-action@v9
+        with:
+          globs: "exercises/**/*.md"
+      - name: Run cargo fmt
+        run: |
+          cargo fmt --all -- --check
+  test:
+    runs-on: ${{ matrix.os }}
+    strategy:
+      matrix:
+        os: [ubuntu-latest, windows-latest, macOS-latest]
+    steps:
+      - uses: actions/checkout@v3
+      - uses: dtolnay/rust-toolchain@stable
+      - uses: swatinem/rust-cache@v2
+      - name: Run cargo test
+        run: |
+          cargo test
--- a/.github/workflows/web.yml
+++ b/.github/workflows/web.yml
@ -0,0 +1,88 @@
+# Workflow to build your docs with oranda (and mdbook)
+# and deploy them to Github Pages
+name: Web
+
+# We're going to push to the gh-pages branch, so we need that permission
+permissions:
+  contents: write
+
+# What situations do we want to build docs in?
+# All of these work independently and can be removed / commented out
+# if you don't want oranda/mdbook running in that situation
+on:
+  # Check that a PR didn't break docs!
+  #
+  # Note that the "Deploy to Github Pages" step won't run in this mode,
+  # so this won't have any side-effects. But it will tell you if a PR
+  # completely broke oranda/mdbook. Sadly we don't provide previews (yet)!
+  pull_request:
+
+  # Whenever something gets pushed to main, update the docs!
+  # This is great for getting docs changes live without cutting a full release.
+  #
+  # Note that if you're using cargo-dist, this will "race" the Release workflow
+  # that actually builds the Github Release that oranda tries to read (and
+  # this will almost certainly complete first). As a result you will publish
+  # docs for the latest commit but the oranda landing page won't know about
+  # the latest release. The workflow_run trigger below will properly wait for
+  # cargo-dist, and so this half-published state will only last for ~10 minutes.
+  #
+  # If you only want docs to update with releases, disable this, or change it to
+  # a "release" branch. You can, of course, also manually trigger a workflow run
+  # when you want the docs to update.
+  push:
+    branches:
+      - main
+
+  # Whenever a workflow called "Release" completes, update the docs!
+  #
+  # If you're using cargo-dist, this is recommended, as it will ensure that
+  # oranda always sees the latest release right when it's available. Note
+  # however that Github's UI is wonky when you use workflow_run, and won't
+  # show this workflow as part of any commit. You have to go to the "actions"
+  # tab for your repo to see this one running (the gh-pages deploy will also
+  # only show up there).
+  workflow_run:
+    workflows: [ "Release" ]
+    types:
+      - completed
+
+# Alright, let's do it!
+jobs:
+  web:
+    name: Build and deploy site and docs
+    runs-on: ubuntu-latest
+    steps:
+      # Setup
+      - uses: actions/checkout@v3
+        with:
+          fetch-depth: 0
+      - uses: dtolnay/rust-toolchain@stable
+      - uses: swatinem/rust-cache@v2
+
+      # If you use any mdbook plugins, here's the place to install them!
+
+      # Install and run oranda (and mdbook)
+      # This will write all output to ./public/ (including copying mdbook's output to there)
+      - name: Install and run oranda
+        run: |
+          curl --proto '=https' --tlsv1.2 -LsSf https://github.com/axodotdev/oranda/releases/download/v0.3.1/oranda-installer.sh | sh
+          oranda build
+
+      # Deploy to our gh-pages branch (creating it if it doesn't exist)
+      # the "public" dir that oranda made above will become the root dir
+      # of this branch.
+      #
+      # Note that once the gh-pages branch exists, you must
+      # go into repo's settings > pages and set "deploy from branch: gh-pages"
+      # the other defaults work fine.
+      - name: Deploy to Github Pages
+        uses: JamesIves/github-pages-deploy-action@v4.4.1
+        # ONLY if we're on main (so no PRs or feature branches allowed!)
+        if: ${{ github.ref == 'refs/heads/main' }}
+        with:
+          branch: gh-pages
+          # Gotta tell the action where to find oranda's output
+          folder: public
+          token: ${{ secrets.GITHUB_TOKEN }}
+          single-commit: true
--- a/.gitignore
+++ b/.gitignore
@ -11,3 +11,8 @@ rust-project.json
 !.vscode/extensions.json
 *.iml
 *.o
+public/
+.direnv/
+
+# Local Netlify folder
+.netlify
--- a/.markdownlint.yml
+++ b/.markdownlint.yml
@ -0,0 +1,2 @@
+# MD013/line-length Line length, Expected: 80
+MD013: false
--- a/AUTHORS.md
+++ b/AUTHORS.md
@ -276,6 +276,74 @@ authors.
      <td align="center" valign="top" width="12.5%"><a href="https://github.com/eugkhp"><img src="https://avatars.githubusercontent.com/u/25910599?v=4?s=100" width="100px;" alt="Eugene"/><br /><sub><b>Eugene</b></sub></a><br /><a href="#tool-eugkhp" title="Tools">🔧</a></td>
      <td align="center" valign="top" width="12.5%"><a href="https://social.linux.pizza/@navicore"><img src="https://avatars.githubusercontent.com/u/110999?v=4?s=100" width="100px;" alt="Ed Sweeney"/><br /><sub><b>Ed Sweeney</b></sub></a><br /><a href="#content-navicore" title="Content">🖋</a></td>
      <td align="center" valign="top" width="12.5%"><a href="https://github.com/javihernant"><img src="https://avatars.githubusercontent.com/u/73640929?v=4?s=100" width="100px;" alt="javihernant"/><br /><sub><b>javihernant</b></sub></a><br /><a href="#content-javihernant" title="Content">🖋</a></td>
+      <td align="center" valign="top" width="12.5%"><a href="https://github.com/VegardMatthey"><img src="https://avatars.githubusercontent.com/u/59250656?v=4?s=100" width="100px;" alt="Vegard"/><br /><sub><b>Vegard</b></sub></a><br /><a href="#content-VegardMatthey" title="Content">🖋</a></td>
+      <td align="center" valign="top" width="12.5%"><a href="https://github.com/ryanwhitehouse"><img src="https://avatars.githubusercontent.com/u/13400784?v=4?s=100" width="100px;" alt="Ryan Whitehouse"/><br /><sub><b>Ryan Whitehouse</b></sub></a><br /><a href="#content-ryanwhitehouse" title="Content">🖋</a></td>
+      <td align="center" valign="top" width="12.5%"><a href="https://github.com/guoard"><img src="https://avatars.githubusercontent.com/u/65511355?v=4?s=100" width="100px;" alt="Ali Afsharzadeh"/><br /><sub><b>Ali Afsharzadeh</b></sub></a><br /><a href="#content-guoard" title="Content">🖋</a></td>
+    </tr>
+    <tr>
+      <td align="center" valign="top" width="12.5%"><a href="http://keogami.ml"><img src="https://avatars.githubusercontent.com/u/41939011?v=4?s=100" width="100px;" alt="Keogami"/><br /><sub><b>Keogami</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=keogami" title="Documentation">📖</a></td>
+      <td align="center" valign="top" width="12.5%"><a href="https://github.com/ahresse"><img src="https://avatars.githubusercontent.com/u/28402488?v=4?s=100" width="100px;" alt="Alexandre Esse"/><br /><sub><b>Alexandre Esse</b></sub></a><br /><a href="#content-ahresse" title="Content">🖋</a></td>
+      <td align="center" valign="top" width="12.5%"><a href="https://resilient.tech"><img src="https://avatars.githubusercontent.com/u/16315650?v=4?s=100" width="100px;" alt="Sagar Vora"/><br /><sub><b>Sagar Vora</b></sub></a><br /><a href="#content-sagarvora" title="Content">🖋</a></td>
+      <td align="center" valign="top" width="12.5%"><a href="https://github.com/poneciak57"><img src="https://avatars.githubusercontent.com/u/94321164?v=4?s=100" width="100px;" alt="Kacper Poneta"/><br /><sub><b>Kacper Poneta</b></sub></a><br /><a href="#content-poneciak57" title="Content">🖋</a></td>
+      <td align="center" valign="top" width="12.5%"><a href="https://ktheory.com/"><img src="https://avatars.githubusercontent.com/u/975?v=4?s=100" width="100px;" alt="Aaron Suggs"/><br /><sub><b>Aaron Suggs</b></sub></a><br /><a href="#content-ktheory" title="Content">🖋</a></td>
+      <td align="center" valign="top" width="12.5%"><a href="https://github.com/alexwh"><img src="https://avatars.githubusercontent.com/u/1723612?v=4?s=100" width="100px;" alt="Alex"/><br /><sub><b>Alex</b></sub></a><br /><a href="#content-alexwh" title="Content">🖋</a></td>
+      <td align="center" valign="top" width="12.5%"><a href="https://github.com/stornquist"><img src="https://avatars.githubusercontent.com/u/42915664?v=4?s=100" width="100px;" alt="Sebastian Törnquist"/><br /><sub><b>Sebastian Törnquist</b></sub></a><br /><a href="#content-stornquist" title="Content">🖋</a></td>
+      <td align="center" valign="top" width="12.5%"><a href="http://smlavine.com"><img src="https://avatars.githubusercontent.com/u/33563640?v=4?s=100" width="100px;" alt="Sebastian LaVine"/><br /><sub><b>Sebastian LaVine</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=smlavine" title="Code">💻</a></td>
+    </tr>
+    <tr>
+      <td align="center" valign="top" width="12.5%"><a href="http://www.alangerber.us"><img src="https://avatars.githubusercontent.com/u/201313?v=4?s=100" width="100px;" alt="Alan Gerber"/><br /><sub><b>Alan Gerber</b></sub></a><br /><a href="#content-akgerber" title="Content">🖋</a></td>
+      <td align="center" valign="top" width="12.5%"><a href="http://esotuvaka.github.io"><img src="https://avatars.githubusercontent.com/u/104941850?v=4?s=100" width="100px;" alt="Eric"/><br /><sub><b>Eric</b></sub></a><br /><a href="#content-esotuvaka" title="Content">🖋</a></td>
+      <td align="center" valign="top" width="12.5%"><a href="https://github.com/az0977776"><img src="https://avatars.githubusercontent.com/u/9172038?v=4?s=100" width="100px;" alt="Aaron Wang"/><br /><sub><b>Aaron Wang</b></sub></a><br /><a href="#content-az0977776" title="Content">🖋</a></td>
+      <td align="center" valign="top" width="12.5%"><a href="https://github.com/nmay231"><img src="https://avatars.githubusercontent.com/u/35386821?v=4?s=100" width="100px;" alt="Noah"/><br /><sub><b>Noah</b></sub></a><br /><a href="#content-nmay231" title="Content">🖋</a></td>
+      <td align="center" valign="top" width="12.5%"><a href="https://github.com/rb5014"><img src="https://avatars.githubusercontent.com/u/105397317?v=4?s=100" width="100px;" alt="rb5014"/><br /><sub><b>rb5014</b></sub></a><br /><a href="#content-rb5014" title="Content">🖋</a></td>
+      <td align="center" valign="top" width="12.5%"><a href="https://github.com/deedy5"><img src="https://avatars.githubusercontent.com/u/65482418?v=4?s=100" width="100px;" alt="deedy5"/><br /><sub><b>deedy5</b></sub></a><br /><a href="#content-deedy5" title="Content">🖋</a></td>
+      <td align="center" valign="top" width="12.5%"><a href="https://github.com/lionel-rowe"><img src="https://avatars.githubusercontent.com/u/26078826?v=4?s=100" width="100px;" alt="lionel-rowe"/><br /><sub><b>lionel-rowe</b></sub></a><br /><a href="#content-lionel-rowe" title="Content">🖋</a></td>
+      <td align="center" valign="top" width="12.5%"><a href="https://github.com/Ben2917"><img src="https://avatars.githubusercontent.com/u/10279994?v=4?s=100" width="100px;" alt="Ben"/><br /><sub><b>Ben</b></sub></a><br /><a href="#content-Ben2917" title="Content">🖋</a></td>
+    </tr>
+    <tr>
+      <td align="center" valign="top" width="12.5%"><a href="https://github.com/b1ue64"><img src="https://avatars.githubusercontent.com/u/77976308?v=4?s=100" width="100px;" alt="b1ue64"/><br /><sub><b>b1ue64</b></sub></a><br /><a href="#content-b1ue64" title="Content">🖋</a></td>
+      <td align="center" valign="top" width="12.5%"><a href="https://github.com/lazywalker"><img src="https://avatars.githubusercontent.com/u/53956?v=4?s=100" width="100px;" alt="lazywalker"/><br /><sub><b>lazywalker</b></sub></a><br /><a href="#content-lazywalker" title="Content">🖋</a></td>
+      <td align="center" valign="top" width="12.5%"><a href="https://github.com/proofconstruction"><img src="https://avatars.githubusercontent.com/u/74747193?v=4?s=100" width="100px;" alt="proofconstruction"/><br /><sub><b>proofconstruction</b></sub></a><br /><a href="#infra-proofconstruction" title="Infrastructure (Hosting, Build-Tools, etc)">🚇</a></td>
+      <td align="center" valign="top" width="12.5%"><a href="https://www.youtube.com/channel/UCQCjA6qUutAtWqkCA4Z36CQ"><img src="https://avatars.githubusercontent.com/u/16007179?v=4?s=100" width="100px;" alt="IVIURRAY"/><br /><sub><b>IVIURRAY</b></sub></a><br /><a href="#content-IVIURRAY" title="Content">🖋</a></td>
+      <td align="center" valign="top" width="12.5%"><a href="https://github.com/b-apperlo"><img src="https://avatars.githubusercontent.com/u/91734527?v=4?s=100" width="100px;" alt="Bert Apperlo"/><br /><sub><b>Bert Apperlo</b></sub></a><br /><a href="#content-b-apperlo" title="Content">🖋</a></td>
+      <td align="center" valign="top" width="12.5%"><a href="https://fwdekker.com/"><img src="https://avatars.githubusercontent.com/u/13442533?v=4?s=100" width="100px;" alt="Florine W. Dekker"/><br /><sub><b>Florine W. Dekker</b></sub></a><br /><a href="#content-FWDekker" title="Content">🖋</a></td>
+      <td align="center" valign="top" width="12.5%"><a href="https://github.com/luhem7"><img src="https://avatars.githubusercontent.com/u/4008215?v=4?s=100" width="100px;" alt="Mehul Gangavelli"/><br /><sub><b>Mehul Gangavelli</b></sub></a><br /><a href="#content-luhem7" title="Content">🖋</a></td>
+      <td align="center" valign="top" width="12.5%"><a href="https://github.com/Frosthage"><img src="https://avatars.githubusercontent.com/u/14823314?v=4?s=100" width="100px;" alt="Mikael Frosthage"/><br /><sub><b>Mikael Frosthage</b></sub></a><br /><a href="#content-Frosthage" title="Content">🖋</a></td>
+    </tr>
+    <tr>
+      <td align="center" valign="top" width="12.5%"><a href="https://robertfry.xyz"><img src="https://avatars.githubusercontent.com/u/43712054?v=4?s=100" width="100px;" alt="Robert Fry"/><br /><sub><b>Robert Fry</b></sub></a><br /><a href="#content-robertefry" title="Content">🖋</a></td>
+      <td align="center" valign="top" width="12.5%"><a href="https://github.com/tajo48"><img src="https://avatars.githubusercontent.com/u/55502906?v=4?s=100" width="100px;" alt="tajo48"/><br /><sub><b>tajo48</b></sub></a><br /><a href="#content-tajo48" title="Content">🖋</a></td>
+      <td align="center" valign="top" width="12.5%"><a href="https://anishchhetri.com.np"><img src="https://avatars.githubusercontent.com/u/98446102?v=4?s=100" width="100px;" alt="Anish"/><br /><sub><b>Anish</b></sub></a><br /><a href="#content-novanish" title="Content">🖋</a></td>
+      <td align="center" valign="top" width="12.5%"><a href="https://github.com/vnprc"><img src="https://avatars.githubusercontent.com/u/9425366?v=4?s=100" width="100px;" alt="vnprc"/><br /><sub><b>vnprc</b></sub></a><br /><a href="#content-vnprc" title="Content">🖋</a></td>
+      <td align="center" valign="top" width="12.5%"><a href="http://androecia.net"><img src="https://avatars.githubusercontent.com/u/61999256?v=4?s=100" width="100px;" alt="Joshua Carlson"/><br /><sub><b>Joshua Carlson</b></sub></a><br /><a href="#content-jrcarl624" title="Content">🖋</a></td>
+      <td align="center" valign="top" width="12.5%"><a href="https://johndesilencio.me"><img src="https://avatars.githubusercontent.com/u/20136554?v=4?s=100" width="100px;" alt="Nicholas R. Smith"/><br /><sub><b>Nicholas R. Smith</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=johnDeSilencio" title="Code">💻</a></td>
+      <td align="center" valign="top" width="12.5%"><a href="https://alexfertel.me"><img src="https://avatars.githubusercontent.com/u/22298999?v=4?s=100" width="100px;" alt="Alexander González"/><br /><sub><b>Alexander González</b></sub></a><br /><a href="#content-alexfertel" title="Content">🖋</a></td>
+      <td align="center" valign="top" width="12.5%"><a href="https://github.com/softarn"><img src="https://avatars.githubusercontent.com/u/517619?v=4?s=100" width="100px;" alt="Marcus Höjvall"/><br /><sub><b>Marcus Höjvall</b></sub></a><br /><a href="#content-softarn" title="Content">🖋</a></td>
+    </tr>
+    <tr>
+      <td align="center" valign="top" width="12.5%"><a href="https://github.com/barlevalon"><img src="https://avatars.githubusercontent.com/u/3397911?v=4?s=100" width="100px;" alt="Alon Hearter"/><br /><sub><b>Alon Hearter</b></sub></a><br /><a href="#content-barlevalon" title="Content">🖋</a></td>
+      <td align="center" valign="top" width="12.5%"><a href="https://github.com/shirts"><img src="https://avatars.githubusercontent.com/u/4952151?v=4?s=100" width="100px;" alt="shirts"/><br /><sub><b>shirts</b></sub></a><br /><a href="#content-shirts" title="Content">🖋</a></td>
+      <td align="center" valign="top" width="12.5%"><a href="https://github.com/eLVas"><img src="https://avatars.githubusercontent.com/u/6797156?v=4?s=100" width="100px;" alt="Ivan Vasiunyk"/><br /><sub><b>Ivan Vasiunyk</b></sub></a><br /><a href="#content-eLVas" title="Content">🖋</a></td>
+      <td align="center" valign="top" width="12.5%"><a href="https://mo8it.com"><img src="https://avatars.githubusercontent.com/u/76752051?v=4?s=100" width="100px;" alt="Mo"/><br /><sub><b>Mo</b></sub></a><br /><a href="https://github.com/rust-lang/rustlings/commits?author=mo8it" title="Code">💻</a></td>
+      <td align="center" valign="top" width="12.5%"><a href="https://github.com/x10an14"><img src="https://avatars.githubusercontent.com/u/710608?v=4?s=100" width="100px;" alt="x10an14"/><br /><sub><b>x10an14</b></sub></a><br /><a href="#infra-x10an14" title="Infrastructure (Hosting, Build-Tools, etc)">🚇</a></td>
+      <td align="center" valign="top" width="12.5%"><a href="https://github.com/gabay"><img src="https://avatars.githubusercontent.com/u/5773610?v=4?s=100" width="100px;" alt="Roi Gabay"/><br /><sub><b>Roi Gabay</b></sub></a><br /><a href="#content-gabay" title="Content">🖋</a></td>
+      <td align="center" valign="top" width="12.5%"><a href="https://github.com/mkovaxx"><img src="https://avatars.githubusercontent.com/u/481354?v=4?s=100" width="100px;" alt="Máté Kovács"/><br /><sub><b>Máté Kovács</b></sub></a><br /><a href="#content-mkovaxx" title="Content">🖋</a></td>
+      <td align="center" valign="top" width="12.5%"><a href="https://szabgab.com/"><img src="https://avatars.githubusercontent.com/u/48833?v=4?s=100" width="100px;" alt="Gábor Szabó"/><br /><sub><b>Gábor Szabó</b></sub></a><br /><a href="#content-szabgab" title="Content">🖋</a></td>
+    </tr>
+    <tr>
+      <td align="center" valign="top" width="12.5%"><a href="https://moduslaborandi.net"><img src="https://avatars.githubusercontent.com/u/3340793?v=4?s=100" width="100px;" alt="Yamila Moreno"/><br /><sub><b>Yamila Moreno</b></sub></a><br /><a href="#content-yamila-moreno" title="Content">🖋</a></td>
+      <td align="center" valign="top" width="12.5%"><a href="https://github.com/willhack"><img src="https://avatars.githubusercontent.com/u/18036720?v=4?s=100" width="100px;" alt="Will Hack"/><br /><sub><b>Will Hack</b></sub></a><br /><a href="#content-willhack" title="Content">🖋</a></td>
+      <td align="center" valign="top" width="12.5%"><a href="http://cancompute.tech"><img src="https://avatars.githubusercontent.com/u/2052646?v=4?s=100" width="100px;" alt="Michael"/><br /><sub><b>Michael</b></sub></a><br /><a href="#content-bean5" title="Content">🖋</a></td>
+      <td align="center" valign="top" width="12.5%"><a href="https://www.sadiqpk.org"><img src="https://avatars.githubusercontent.com/u/1289514?v=4?s=100" width="100px;" alt="Mohammed Sadiq"/><br /><sub><b>Mohammed Sadiq</b></sub></a><br /><a href="#content-pksadiq" title="Content">🖋</a></td>
+      <td align="center" valign="top" width="12.5%"><a href="https://github.com/Jak-Ch-ll"><img src="https://avatars.githubusercontent.com/u/56225668?v=4?s=100" width="100px;" alt="Jakob"/><br /><sub><b>Jakob</b></sub></a><br /><a href="#content-Jak-Ch-ll" title="Content">🖋</a></td>
+      <td align="center" valign="top" width="12.5%"><a href="http://oscarbonilla.com"><img src="https://avatars.githubusercontent.com/u/4950?v=4?s=100" width="100px;" alt="Oscar Bonilla"/><br /><sub><b>Oscar Bonilla</b></sub></a><br /><a href="#content-ob" title="Content">🖋</a></td>
+      <td align="center" valign="top" width="12.5%"><a href="https://github.com/husjon"><img src="https://avatars.githubusercontent.com/u/554229?v=4?s=100" width="100px;" alt="Jon Erling Hustadnes"/><br /><sub><b>Jon Erling Hustadnes</b></sub></a><br /><a href="#content-husjon" title="Content">🖋</a></td>
+      <td align="center" valign="top" width="12.5%"><a href="https://github.com/CobaltCause"><img src="https://avatars.githubusercontent.com/u/7003738?v=4?s=100" width="100px;" alt="Charles Hall"/><br /><sub><b>Charles Hall</b></sub></a><br /><a href="#infra-CobaltCause" title="Infrastructure (Hosting, Build-Tools, etc)">🚇</a></td>
+    </tr>
+    <tr>
+      <td align="center" valign="top" width="12.5%"><a href="https://github.com/krmpotic"><img src="https://avatars.githubusercontent.com/u/10350645?v=4?s=100" width="100px;" alt="Luka Krmpotić"/><br /><sub><b>Luka Krmpotić</b></sub></a><br /><a href="#content-krmpotic" title="Content">🖋</a></td>
+      <td align="center" valign="top" width="12.5%"><a href="https://github.com/jurglic"><img src="https://avatars.githubusercontent.com/u/112600?v=4?s=100" width="100px;" alt="Jurglic"/><br /><sub><b>Jurglic</b></sub></a><br /><a href="#content-jurglic" title="Content">🖋</a></td>
+      <td align="center" valign="top" width="12.5%"><a href="https://github.com/OfirLauber"><img src="https://avatars.githubusercontent.com/u/5631030?v=4?s=100" width="100px;" alt="Ofir Lauber"/><br /><sub><b>Ofir Lauber</b></sub></a><br /><a href="#content-OfirLauber" title="Content">🖋</a></td>
    </tr>
  </tbody>
 </table>
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@ -1,3 +1,101 @@
+<a name="5.6.1"></a>
+## 5.6.1 (2023-09-18)
+
+#### Changed
+
+- Converted all exercises with assertions to test mode.
+
+#### Fixed
+
+- `cow1`: Reverted regression introduced by calling `to_mut` where it
+  shouldn't have been called, and clarified comment.
+- `primitive_types3`: Require at least an array of 100 elements.
+- Removed hint comments when no hint exists for the exercise.
+- `as_ref_mut`: Fixed a typo in a test function name.
+- `enums3`: Fixed formatting with `rustfmt`.
+
+<a name="5.6.0"></a>
+## 5.6.0 (2023-09-04)
+
+#### Added
+
+- New exercise: `if3`, teaching the user about `if let` statements.
+- `hashmaps2`: Added an extra test function to check if the amount of fruits is higher than zero.
+- `enums3`: Added a test for `Message`.
+- `if1`: Added a test case to check equal values.
+- `if3`: Added a note specifying that there are no test changes needed.
+
+#### Changed
+
+- Swapped the order of threads and smart pointer exercises.
+- Rewrote the CLI to use `clap` - it's matured much since we switched to `argh` :)
+- `structs3`: Switched from i32 to u32.
+- `move_semantics`: Switched 1-4 to tests, and rewrote them to be way simpler, while still teaching about the same 
+  concepts.
+
+#### Fixed
+
+- `iterators5`:
+  - Removed an outdated part of the hint.
+  - Renamed variables to use snake_case.
+- `vecs2`: Updated the hint to reference the renamed loop variable.
+- `enums3`: Changed message string in test so that it gets properly tested.
+- `strings2`: Corrected line number in hint, then removed it (this both happened as part of this release cycle).
+- `primitive_types4`: Updated hint to the correct ending index.
+- `quiz1`: Removed duplicated sentence from exercise comments.
+- `errors4`: Improved comment.
+- `from_into`: Fixed test values.
+- `cow1`: Added `.to_mut()` to distinguish from the previous test case.
+- `threads2`: Updated hint text to reference the correct book heading.
+
+#### Housekeeping
+
+- Cleaned up the explanation paragraphs at the start of each exercise.
+- Lots of Nix housekeeping that I don't feel qualified to write about!
+- Improved CI workflows, we're now testing on multiple platforms at once.
+
+<a name="5.5.1"></a>
+## 5.5.1 (2023-05-17)
+
+#### Fixed
+
+- Reverted `rust-project.json` path generation due to an upstream `rust-analyzer` fix.
+
+<a name="5.5.0"></a>
+## 5.5.0 (2023-05-17)
+
+#### Added
+
+- `strings2`: Added a reference to the book chapter for reference conversion
+- `lifetimes`: Added a link to the lifetimekata project
+- Added a new `tests4` exercises, which teaches about testing for panics
+- Added a `!` prefix command to watch mode that runs an external command
+- Added a `--success-hints` option to watch mode that shows hints on exercise success
+
+#### Changed
+
+- `vecs2`: Renamed iterator variable bindings for clarify
+- `lifetimes`: Changed order of book references
+- `hashmaps2`: Clarified instructions in the todo block
+- Moved lifetime exercises before test exercises (via the recommended book ordering)
+- `options2`: Improved tests for layering options
+- `modules2`: Added more information to the hint
+
+#### Fixed
+
+- `errors2`: Corrected a comment wording
+- `iterators2`: Fixed a spelling mistake in the hint text
+- `variables`: Wrapped the mut keyword with backticks for readability
+- `move_semantics2`: Removed references to line numbers
+- `cow1`: Clarified the `owned_no_mutation` comments
+- `options3`: Changed exercise to panic when no match is found
+- `rustlings lsp` now generates absolute paths, which should fix VSCode `rust-analyzer` usage on Windows
+
+#### Housekeeping
+
+- Added a markdown linter to run on GitHub actions
+- Split quick installation section into two code blocks
+
 <a name="5.4.1"></a>
 ## 5.4.1 (2023-03-10)

--- a/Cargo.lock
+++ b/Cargo.lock
@ -12,43 +12,66 @@ dependencies = [
 ]

 [[package]]
-name = "argh"
-version = "0.1.10"
+name = "anstream"
+version = "0.5.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
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+ "utf8parse",
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- "proc-macro2",
- "quote",
- "syn 1.0.109",
+ "utf8parse",
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+ "windows-sys 0.48.0",
+]

 [[package]]
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 dependencies = [
- "escargot",
+ "anstyle",
+ "bstr",
+ "doc-comment",
 "predicates",
 "predicates-core",
 "predicates-tree",
+ "wait-timeout",
 ]

 [[package]]
@ -63,6 +86,17 @@ version = "1.3.2"
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 checksum = "bef38d45163c2f1dde094a7dfd33ccf595c92905c8f8f4fdc18d06fb1037718a"

+[[package]]
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+dependencies = [
+ "memchr",
+ "regex-automata",
+ "serde",
+]
+
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@ -75,6 +109,52 @@ version = "1.0.0"
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 checksum = "baf1de4339761588bc0619e3cbc0120ee582ebb74b53b4efbf79117bd2da40fd"

+[[package]]
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+checksum = "84ed82781cea27b43c9b106a979fe450a13a31aab0500595fb3fc06616de08e6"
+dependencies = [
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+ "clap_derive",
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+dependencies = [
+ "anstream",
+ "anstyle",
+ "clap_lex",
+ "strsim",
+]
+
+[[package]]
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+dependencies = [
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+ "proc-macro2",
+ "quote",
+ "syn",
+]
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+
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+
 [[package]]
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@ -89,10 +169,22 @@ dependencies = [
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 [[package]]
-name = "difference"
-version = "2.0.0"
+name = "difflib"
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-checksum = "524cbf6897b527295dff137cec09ecf3a05f4fddffd7dfcd1585403449e74198"
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+
+[[package]]
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+
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 [[package]]
 name = "encode_unicode"
@ -101,16 +193,10 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
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 [[package]]
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-version = "0.4.0"
+name = "equivalent"
+version = "1.0.1"
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-dependencies = [
- "lazy_static",
- "log",
- "serde",
- "serde_json",
-]
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 [[package]]
 name = "filetime"
@ -126,9 +212,9 @@ dependencies = [

 [[package]]
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+checksum = "98de4bbd547a563b716d8dfa9aad1cb19bfab00f4fa09a6a4ed21dbcf44ce9c4"
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@ -174,6 +260,18 @@ version = "0.3.1"
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 checksum = "d2fabcfbdc87f4758337ca535fb41a6d701b65693ce38287d856d1674551ec9b"

+[[package]]
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+
 [[package]]
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 version = "0.5.4"
@ -184,15 +282,26 @@ dependencies = [
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 [[package]]
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-version = "0.16.2"
+name = "indexmap"
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-checksum = "2d207dc617c7a380ab07ff572a6e52fa202a2a8f355860ac9c38e23f8196be1b"
+checksum = "d5477fe2230a79769d8dc68e0eabf5437907c0457a5614a9e8dddb67f65eb65d"
+dependencies = [
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+ "hashbrown",
+]
+
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+source = "registry+https://github.com/rust-lang/crates.io-index"
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 dependencies = [
 "console",
- "lazy_static",
+ "instant",
 "number_prefix",
- "regex",
+ "portable-atomic",
+ "unicode-width",
 ]

 [[package]]
@ -215,6 +324,15 @@ dependencies = [
 "libc",
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+[[package]]
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+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7a5bbe824c507c5da5956355e86a746d82e0e1464f65d862cc5e71da70e94b2c"
+dependencies = [
+ "cfg-if 1.0.0",
+]
+
 [[package]]
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 version = "0.1.4"
@ -224,6 +342,15 @@ dependencies = [
 "libc",
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+[[package]]
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+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b0fd2260e829bddf4cb6ea802289de2f86d6a7a690192fbe91b3f46e0f2c8473"
+dependencies = [
+ "either",
+]
+
 [[package]]
 name = "itoa"
 version = "1.0.6"
@ -269,9 +396,9 @@ dependencies = [

 [[package]]
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-version = "2.5.0"
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 [[package]]
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@ -367,13 +494,21 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
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 [[package]]
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+checksum = "31114a898e107c51bb1609ffaf55a0e011cf6a4d7f1170d0015a165082c0338b"
+
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 dependencies = [
- "difference",
+ "anstyle",
+ "difflib",
 "float-cmp",
+ "itertools",
 "normalize-line-endings",
 "predicates-core",
 "regex",
@ -433,6 +568,12 @@ dependencies = [
 "regex-syntax",
 ]

+[[package]]
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+version = "0.3.8"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c2f401f4955220693b56f8ec66ee9c78abffd8d1c4f23dc41a23839eb88f0795"
+
 [[package]]
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@ -441,10 +582,10 @@ checksum = "f162c6dd7b008981e4d40210aca20b4bd0f9b60ca9271061b07f78537722f2e1"

 [[package]]
 name = "rustlings"
-version = "5.4.1"
+version = "5.6.1"
 dependencies = [
- "argh",
 "assert_cmd",
+ "clap",
 "console",
 "glob",
 "home",
@ -489,7 +630,7 @@ checksum = "e801c1712f48475582b7696ac71e0ca34ebb30e09338425384269d9717c62cad"
 dependencies = [
 "proc-macro2",
 "quote",
- "syn 2.0.8",
+ "syn",
 ]

 [[package]]
@ -503,6 +644,15 @@ dependencies = [
 "serde",
 ]

+[[package]]
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+version = "0.6.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
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+dependencies = [
+ "serde",
+]
+
 [[package]]
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@ -513,15 +663,10 @@ dependencies = [
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 [[package]]
-name = "syn"
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+name = "strsim"
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-dependencies = [
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+checksum = "73473c0e59e6d5812c5dfe2a064a6444949f089e20eec9a2e5506596494e4623"

 [[package]]
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@ -542,11 +687,36 @@ checksum = "3369f5ac52d5eb6ab48c6b4ffdc8efbcad6b89c765749064ba298f2c68a16a76"

 [[package]]
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+checksum = "dd79e69d3b627db300ff956027cc6c3798cef26d22526befdfcd12feeb6d2257"
 dependencies = [
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+ "toml_datetime",
+ "toml_edit",
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+dependencies = [
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+ "serde",
+ "serde_spanned",
+ "toml_datetime",
+ "winnow",
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 [[package]]
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+dependencies = [
+ "libc",
+]
+
 [[package]]
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@ -620,13 +805,13 @@ version = "0.42.0"
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- "windows_i686_msvc",
- "windows_x86_64_gnu",
- "windows_x86_64_gnullvm",
- "windows_x86_64_msvc",
+ "windows_aarch64_gnullvm 0.42.2",
+ "windows_aarch64_msvc 0.42.2",
+ "windows_i686_gnu 0.42.2",
+ "windows_i686_msvc 0.42.2",
+ "windows_x86_64_gnu 0.42.2",
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- "windows_i686_msvc",
- "windows_x86_64_gnu",
- "windows_x86_64_gnullvm",
- "windows_x86_64_msvc",
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+ "windows_aarch64_msvc 0.42.2",
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+ "windows_i686_msvc 0.42.2",
+ "windows_x86_64_gnu 0.42.2",
+ "windows_x86_64_gnullvm 0.42.2",
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 version = "0.42.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "8de912b8b8feb55c064867cf047dda097f92d51efad5b491dfb98f6bbb70cb36"

+[[package]]
+name = "windows_x86_64_gnu"
+version = "0.48.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "53d40abd2583d23e4718fddf1ebec84dbff8381c07cae67ff7768bbf19c6718e"
+
 [[package]]
 name = "windows_x86_64_gnullvm"
 version = "0.42.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "26d41b46a36d453748aedef1486d5c7a85db22e56aff34643984ea85514e94a3"

+[[package]]
+name = "windows_x86_64_gnullvm"
+version = "0.48.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0b7b52767868a23d5bab768e390dc5f5c55825b6d30b86c844ff2dc7414044cc"
+
 [[package]]
 name = "windows_x86_64_msvc"
 version = "0.42.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "9aec5da331524158c6d1a4ac0ab1541149c0b9505fde06423b02f5ef0106b9f0"

+[[package]]
+name = "windows_x86_64_msvc"
+version = "0.48.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ed94fce61571a4006852b7389a063ab983c02eb1bb37b47f8272ce92d06d9538"
+
+[[package]]
+name = "winnow"
+version = "0.5.15"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7c2e3184b9c4e92ad5167ca73039d0c42476302ab603e2fec4487511f38ccefc"
+dependencies = [
+ "memchr",
+]
+
 [[package]]
 name = "ws2_32-sys"
 version = "0.2.1"
--- a/Cargo.toml
+++ b/Cargo.toml
@ -1,6 +1,7 @@
 [package]
 name = "rustlings"
-version = "5.4.1"
+description = "Small exercises to get you used to reading and writing Rust code!"
+version = "5.6.1"
 authors = [
  "Liv <mokou@fastmail.com>",
  "Carol (Nichols || Goulding) <carol.nichols@gmail.com>",
@ -8,22 +9,22 @@ authors = [
 edition = "2021"

 [dependencies]
-argh = "0.1"
-indicatif = "0.16"
+indicatif = "0.17.6"
 console = "0.15"
 notify = "4.0"
-toml = "0.5"
+toml = "0.7.6"
 regex = "1.5"
 serde = { version = "1.0", features = ["derive"] }
 serde_json = "1.0.81"
 home = "0.5.3"
 glob = "0.3.0"
+clap = { version = "4.4.0", features = ["derive"] }

 [[bin]]
 name = "rustlings"
 path = "src/main.rs"

 [dev-dependencies]
-assert_cmd = "0.11.0"
-predicates = "1.0.1"
+assert_cmd = "2.0.12"
+predicates = "3.0.3"
 glob = "0.3.0"
--- a/README.md
+++ b/README.md
@ -1,5 +1,9 @@
+<div class="oranda-hide">
+
 # rustlings 🦀❤️

+</div>
+
 Greetings and welcome to `rustlings`. This project contains small exercises to get you used to reading and writing Rust code. This includes reading and responding to compiler messages!

 _...looking for the old, web-based version of Rustlings? Try [here](https://github.com/rust-lang/rustlings/tree/rustlings-1)_
@ -14,7 +18,7 @@ Alternatively, for a first-time Rust learner, there are several other resources:
 _Note: If you're on MacOS, make sure you've installed Xcode and its developer tools by typing `xcode-select --install`._
 _Note: If you're on Linux, make sure you've installed gcc. Deb: `sudo apt install gcc`. Yum: `sudo yum -y install gcc`._

-You will need to have Rust installed. You can get it by visiting https://rustup.rs. This'll also install Cargo, Rust's package/project manager.
+You will need to have Rust installed. You can get it by visiting <https://rustup.rs>. This'll also install Cargo, Rust's package/project manager.

 ## MacOS/Linux

@ -22,7 +26,11 @@ Just run:

 ```bash
 curl -L https://raw.githubusercontent.com/rust-lang/rustlings/main/install.sh | bash
-# Or if you want it to be installed to a different path:
+```
+
+Or if you want it to be installed to a different path:
+
+```bash
 curl -L https://raw.githubusercontent.com/rust-lang/rustlings/main/install.sh | bash -s mypath/
 ```

@ -33,8 +41,8 @@ This will install Rustlings and give you access to the `rustlings` command. Run
 Basically: Clone the repository at the latest tag, finally run `nix develop` or `nix-shell`.

 ```bash
-# find out the latest version at https://github.com/rust-lang/rustlings/releases/latest (on edit 5.4.1)
-git clone -b 5.4.1 --depth 1 https://github.com/rust-lang/rustlings
+# find out the latest version at https://github.com/rust-lang/rustlings/releases/latest (on edit 5.6.1)
+git clone -b 5.6.1 --depth 1 https://github.com/rust-lang/rustlings
 cd rustlings
 # if nix version > 2.3
 nix develop
@ -71,8 +79,8 @@ If you get a permission denied message, you might have to exclude the directory
 Basically: Clone the repository at the latest tag, run `cargo install --path .`.

 ```bash
-# find out the latest version at https://github.com/rust-lang/rustlings/releases/latest (on edit 5.4.1)
-git clone -b 5.4.1 --depth 1 https://github.com/rust-lang/rustlings
+# find out the latest version at https://github.com/rust-lang/rustlings/releases/latest (on edit 5.6.1)
+git clone -b 5.6.1 --depth 1 https://github.com/rust-lang/rustlings
 cd rustlings
 cargo install --force --path .
 ```
@ -165,12 +173,8 @@ Now you should be done!

 ## Contributing

-See [CONTRIBUTING.md](./CONTRIBUTING.md).
-
-Development-focused discussion about Rustlings happens in the [**rustlings** stream](https://rust-lang.zulipchat.com/#narrow/stream/334454-rustlings)
-on the [Rust Project Zulip](https://rust-lang.zulipchat.com). Feel free to start a new thread there
-if you have ideas or suggestions!
+See [CONTRIBUTING.md](https://github.com/rust-lang/rustlings/blob/main/CONTRIBUTING.md).

 ## Contributors ✨

-Thanks goes to the wonderful people listed in [AUTHORS.md](./AUTHORS.md) 🎉
+Thanks goes to the wonderful people listed in [AUTHORS.md](https://github.com/rust-lang/rustlings/blob/main/AUTHORS.md) 🎉
--- a/exercises/clippy/clippy1.rs
+++ b/exercises/clippy/clippy1.rs
@ -1,10 +1,13 @@
 // clippy1.rs
-// The Clippy tool is a collection of lints to analyze your code
-// so you can catch common mistakes and improve your Rust code.
 //
-// For these exercises the code will fail to compile when there are clippy warnings
-// check clippy's suggestions from the output to solve the exercise.
-// Execute `rustlings hint clippy1` or use the `hint` watch subcommand for a hint.
+// The Clippy tool is a collection of lints to analyze your code so you can
+// catch common mistakes and improve your Rust code.
+//
+// For these exercises the code will fail to compile when there are clippy
+// warnings check clippy's suggestions from the output to solve the exercise.
+//
+// Execute `rustlings hint clippy1` or use the `hint` watch subcommand for a
+// hint.

 // I AM NOT DONE

--- a/exercises/clippy/clippy2.rs
+++ b/exercises/clippy/clippy2.rs
@ -1,5 +1,7 @@
 // clippy2.rs
-// Execute `rustlings hint clippy2` or use the `hint` watch subcommand for a hint.
+// 
+// Execute `rustlings hint clippy2` or use the `hint` watch subcommand for a
+// hint.

 // I AM NOT DONE

--- a/exercises/clippy/clippy3.rs
+++ b/exercises/clippy/clippy3.rs
@ -1,5 +1,7 @@
 // clippy3.rs
+// 
 // Here's a couple more easy Clippy fixes, so you can see its utility.
+// No hints.

 // I AM NOT DONE

--- a/exercises/conversions/README.md
+++ b/exercises/conversions/README.md
@ -6,6 +6,7 @@ The simplest form of type conversion is a type cast expression. It is denoted wi

 Rust also offers traits that facilitate type conversions upon implementation. These traits can be found under the [`convert`](https://doc.rust-lang.org/std/convert/index.html) module.
 The traits are the following:
+
 - `From` and `Into` covered in [`from_into`](from_into.rs)
 - `TryFrom` and `TryInto` covered in [`try_from_into`](try_from_into.rs)
 - `AsRef` and `AsMut` covered in [`as_ref_mut`](as_ref_mut.rs)
@ -17,5 +18,6 @@ These should be the main ways ***within the standard library*** to convert data
 ## Further information

 These are not directly covered in the book, but the standard library has a great documentation for it.
+
 - [conversions](https://doc.rust-lang.org/std/convert/index.html)
- [`FromStr` trait](https://doc.rust-lang.org/std/str/trait.FromStr.html)
+- [`FromStr` trait](https://doc.rust-lang.org/std/str/trait.FromStr.html)
--- a/exercises/conversions/as_ref_mut.rs
+++ b/exercises/conversions/as_ref_mut.rs
@ -1,7 +1,11 @@
-// AsRef and AsMut allow for cheap reference-to-reference conversions.
-// Read more about them at https://doc.rust-lang.org/std/convert/trait.AsRef.html
-// and https://doc.rust-lang.org/std/convert/trait.AsMut.html, respectively.
-// Execute `rustlings hint as_ref_mut` or use the `hint` watch subcommand for a hint.
+// as_ref_mut.rs
+//
+// AsRef and AsMut allow for cheap reference-to-reference conversions. Read more
+// about them at https://doc.rust-lang.org/std/convert/trait.AsRef.html and
+// https://doc.rust-lang.org/std/convert/trait.AsMut.html, respectively.
+//
+// Execute `rustlings hint as_ref_mut` or use the `hint` watch subcommand for a
+// hint.

 // I AM NOT DONE

@ -53,7 +57,7 @@ mod tests {
    }

    #[test]
-    fn mult_box() {
+    fn mut_box() {
        let mut num: Box<u32> = Box::new(3);
        num_sq(&mut num);
        assert_eq!(*num, 9);
--- a/exercises/conversions/from_into.rs
+++ b/exercises/conversions/from_into.rs
@ -1,7 +1,11 @@
-// The From trait is used for value-to-value conversions.
-// If From is implemented correctly for a type, the Into trait should work conversely.
-// You can read more about it at https://doc.rust-lang.org/std/convert/trait.From.html
-// Execute `rustlings hint from_into` or use the `hint` watch subcommand for a hint.
+// from_into.rs
+//
+// The From trait is used for value-to-value conversions. If From is implemented
+// correctly for a type, the Into trait should work conversely. You can read
+// more about it at https://doc.rust-lang.org/std/convert/trait.From.html
+//
+// Execute `rustlings hint from_into` or use the `hint` watch subcommand for a
+// hint.

 #[derive(Debug)]
 struct Person {
@ -20,20 +24,21 @@ impl Default for Person {
    }
 }

-// Your task is to complete this implementation
-// in order for the line `let p = Person::from("Mark,20")` to compile
-// Please note that you'll need to parse the age component into a `usize`
-// with something like `"4".parse::<usize>()`. The outcome of this needs to
-// be handled appropriately.
+// Your task is to complete this implementation in order for the line `let p =
+// Person::from("Mark,20")` to compile Please note that you'll need to parse the
+// age component into a `usize` with something like `"4".parse::<usize>()`. The
+// outcome of this needs to be handled appropriately.
 //
 // Steps:
-// 1. If the length of the provided string is 0, then return the default of Person
-// 2. Split the given string on the commas present in it
-// 3. Extract the first element from the split operation and use it as the name
-// 4. If the name is empty, then return the default of Person
-// 5. Extract the other element from the split operation and parse it into a `usize` as the age
-// If while parsing the age, something goes wrong, then return the default of Person
-// Otherwise, then return an instantiated Person object with the results
+// 1. If the length of the provided string is 0, then return the default of
+//    Person.
+// 2. Split the given string on the commas present in it.
+// 3. Extract the first element from the split operation and use it as the name.
+// 4. If the name is empty, then return the default of Person.
+// 5. Extract the other element from the split operation and parse it into a
+//    `usize` as the age.
+// If while parsing the age, something goes wrong, then return the default of
+// Person Otherwise, then return an instantiated Person object with the results

 // I AM NOT DONE

@ -77,7 +82,8 @@ mod tests {
    }
    #[test]
    fn test_bad_age() {
-        // Test that "Mark,twenty" will return the default person due to an error in parsing age
+        // Test that "Mark,twenty" will return the default person due to an
+        // error in parsing age
        let p = Person::from("Mark,twenty");
        assert_eq!(p.name, "John");
        assert_eq!(p.age, 30);
@ -121,14 +127,14 @@ mod tests {
    #[test]
    fn test_trailing_comma() {
        let p: Person = Person::from("Mike,32,");
-        assert_eq!(p.name, "John");
-        assert_eq!(p.age, 30);
+        assert_eq!(p.name, "Mike");
+        assert_eq!(p.age, 32);
    }

    #[test]
    fn test_trailing_comma_and_some_string() {
        let p: Person = Person::from("Mike,32,man");
-        assert_eq!(p.name, "John");
-        assert_eq!(p.age, 30);
+        assert_eq!(p.name, "Mike");
+        assert_eq!(p.age, 32);
    }
 }
--- a/exercises/conversions/from_str.rs
+++ b/exercises/conversions/from_str.rs
@ -1,10 +1,13 @@
 // from_str.rs
-// This is similar to from_into.rs, but this time we'll implement `FromStr`
-// and return errors instead of falling back to a default value.
-// Additionally, upon implementing FromStr, you can use the `parse` method
-// on strings to generate an object of the implementor type.
-// You can read more about it at https://doc.rust-lang.org/std/str/trait.FromStr.html
-// Execute `rustlings hint from_str` or use the `hint` watch subcommand for a hint.
+//
+// This is similar to from_into.rs, but this time we'll implement `FromStr` and
+// return errors instead of falling back to a default value. Additionally, upon
+// implementing FromStr, you can use the `parse` method on strings to generate
+// an object of the implementor type. You can read more about it at
+// https://doc.rust-lang.org/std/str/trait.FromStr.html
+//
+// Execute `rustlings hint from_str` or use the `hint` watch subcommand for a
+// hint.

 use std::num::ParseIntError;
 use std::str::FromStr;
@ -33,15 +36,18 @@ enum ParsePersonError {
 // Steps:
 // 1. If the length of the provided string is 0, an error should be returned
 // 2. Split the given string on the commas present in it
-// 3. Only 2 elements should be returned from the split, otherwise return an error
+// 3. Only 2 elements should be returned from the split, otherwise return an
+//    error
 // 4. Extract the first element from the split operation and use it as the name
-// 5. Extract the other element from the split operation and parse it into a `usize` as the age
-//    with something like `"4".parse::<usize>()`
-// 6. If while extracting the name and the age something goes wrong, an error should be returned
+// 5. Extract the other element from the split operation and parse it into a
+//    `usize` as the age with something like `"4".parse::<usize>()`
+// 6. If while extracting the name and the age something goes wrong, an error
+//    should be returned
 // If everything goes well, then return a Result of a Person object
 //
-// As an aside: `Box<dyn Error>` implements `From<&'_ str>`. This means that if you want to return a
-// string error message, you can do so via just using return `Err("my error message".into())`.
+// As an aside: `Box<dyn Error>` implements `From<&'_ str>`. This means that if
+// you want to return a string error message, you can do so via just using
+// return `Err("my error message".into())`.

 impl FromStr for Person {
    type Err = ParsePersonError;
--- a/exercises/conversions/try_from_into.rs
+++ b/exercises/conversions/try_from_into.rs
@ -1,9 +1,13 @@
 // try_from_into.rs
-// TryFrom is a simple and safe type conversion that may fail in a controlled way under some circumstances.
-// Basically, this is the same as From. The main difference is that this should return a Result type
-// instead of the target type itself.
-// You can read more about it at https://doc.rust-lang.org/std/convert/trait.TryFrom.html
-// Execute `rustlings hint try_from_into` or use the `hint` watch subcommand for a hint.
+//
+// TryFrom is a simple and safe type conversion that may fail in a controlled
+// way under some circumstances. Basically, this is the same as From. The main
+// difference is that this should return a Result type instead of the target
+// type itself. You can read more about it at
+// https://doc.rust-lang.org/std/convert/trait.TryFrom.html
+//
+// Execute `rustlings hint try_from_into` or use the `hint` watch subcommand for
+// a hint.

 use std::convert::{TryFrom, TryInto};

@ -25,14 +29,13 @@ enum IntoColorError {

 // I AM NOT DONE

-// Your task is to complete this implementation
-// and return an Ok result of inner type Color.
-// You need to create an implementation for a tuple of three integers,
-// an array of three integers, and a slice of integers.
+// Your task is to complete this implementation and return an Ok result of inner
+// type Color. You need to create an implementation for a tuple of three
+// integers, an array of three integers, and a slice of integers.
 //
-// Note that the implementation for tuple and array will be checked at compile time,
-// but the slice implementation needs to check the slice length!
-// Also note that correct RGB color values must be integers in the 0..=255 range.
+// Note that the implementation for tuple and array will be checked at compile
+// time, but the slice implementation needs to check the slice length! Also note
+// that correct RGB color values must be integers in the 0..=255 range.

 // Tuple implementation
 impl TryFrom<(i16, i16, i16)> for Color {
--- a/exercises/conversions/using_as.rs
+++ b/exercises/conversions/using_as.rs
@ -1,10 +1,14 @@
-// Type casting in Rust is done via the usage of the `as` operator.
-// Please note that the `as` operator is not only used when type casting.
-// It also helps with renaming imports.
+// using_as.rs
 //
-// The goal is to make sure that the division does not fail to compile
-// and returns the proper type.
-// Execute `rustlings hint using_as` or use the `hint` watch subcommand for a hint.
+// Type casting in Rust is done via the usage of the `as` operator. Please note
+// that the `as` operator is not only used when type casting. It also helps with
+// renaming imports.
+//
+// The goal is to make sure that the division does not fail to compile and
+// returns the proper type.
+//
+// Execute `rustlings hint using_as` or use the `hint` watch subcommand for a
+// hint.

 // I AM NOT DONE

--- a/exercises/enums/enums1.rs
+++ b/exercises/enums/enums1.rs
@ -1,4 +1,5 @@
 // enums1.rs
+//
 // No hints this time! ;)

 // I AM NOT DONE
--- a/exercises/enums/enums2.rs
+++ b/exercises/enums/enums2.rs
@ -1,5 +1,7 @@
 // enums2.rs
-// Execute `rustlings hint enums2` or use the `hint` watch subcommand for a hint.
+//
+// Execute `rustlings hint enums2` or use the `hint` watch subcommand for a
+// hint.

 // I AM NOT DONE

--- a/exercises/enums/enums3.rs
+++ b/exercises/enums/enums3.rs
@ -1,6 +1,9 @@
 // enums3.rs
+//
 // Address all the TODOs to make the tests pass!
-// Execute `rustlings hint enums3` or use the `hint` watch subcommand for a hint.
+//
+// Execute `rustlings hint enums3` or use the `hint` watch subcommand for a
+// hint.

 // I AM NOT DONE

@ -17,6 +20,7 @@ struct State {
    color: (u8, u8, u8),
    position: Point,
    quit: bool,
+    message: String,
 }

 impl State {
@ -28,8 +32,8 @@ impl State {
        self.quit = true;
    }

-    fn echo(&self, s: String) {
-        println!("{}", s);
+    fn echo(&mut self, s: String) {
+        self.message = s
    }

    fn move_position(&mut self, p: Point) {
@ -38,7 +42,8 @@ impl State {

    fn process(&mut self, message: Message) {
        // TODO: create a match expression to process the different message variants
-        // Remember: When passing a tuple as a function argument, you'll need extra parentheses: fn function((t, u, p, l, e))
+        // Remember: When passing a tuple as a function argument, you'll need extra parentheses:
+        // fn function((t, u, p, l, e))
    }
 }

@ -52,9 +57,10 @@ mod tests {
            quit: false,
            position: Point { x: 0, y: 0 },
            color: (0, 0, 0),
+            message: "hello world".to_string(),
        };
        state.process(Message::ChangeColor(255, 0, 255));
-        state.process(Message::Echo(String::from("hello world")));
+        state.process(Message::Echo(String::from("Hello world!")));
        state.process(Message::Move(Point { x: 10, y: 15 }));
        state.process(Message::Quit);

@ -62,5 +68,6 @@ mod tests {
        assert_eq!(state.position.x, 10);
        assert_eq!(state.position.y, 15);
        assert_eq!(state.quit, true);
+        assert_eq!(state.message, "Hello world!");
    }
 }
--- a/exercises/error_handling/README.md
+++ b/exercises/error_handling/README.md
@ -1,5 +1,6 @@
 # Error handling
-Most errors aren’t serious enough to require the program to stop entirely. 
+
+Most errors aren’t serious enough to require the program to stop entirely.
 Sometimes, when a function fails, it’s for a reason that you can easily interpret and respond to.
 For example, if you try to open a file and that operation fails because the file doesn’t exist, you might want to create the file instead of terminating the process.

--- a/exercises/error_handling/errors1.rs
+++ b/exercises/error_handling/errors1.rs
@ -1,9 +1,13 @@
 // errors1.rs
-// This function refuses to generate text to be printed on a nametag if
-// you pass it an empty string. It'd be nicer if it explained what the problem
-// was, instead of just sometimes returning `None`. Thankfully, Rust has a similar
-// construct to `Option` that can be used to express error conditions. Let's use it!
-// Execute `rustlings hint errors1` or use the `hint` watch subcommand for a hint.
+//
+// This function refuses to generate text to be printed on a nametag if you pass
+// it an empty string. It'd be nicer if it explained what the problem was,
+// instead of just sometimes returning `None`. Thankfully, Rust has a similar
+// construct to `Option` that can be used to express error conditions. Let's use
+// it!
+//
+// Execute `rustlings hint errors1` or use the `hint` watch subcommand for a
+// hint.

 // I AM NOT DONE

--- a/exercises/error_handling/errors2.rs
+++ b/exercises/error_handling/errors2.rs
@ -1,21 +1,23 @@
 // errors2.rs
+//
 // Say we're writing a game where you can buy items with tokens. All items cost
 // 5 tokens, and whenever you purchase items there is a processing fee of 1
-// token. A player of the game will type in how many items they want to buy,
-// and the `total_cost` function will calculate the total cost of the tokens.
-// Since the player typed in the quantity, though, we get it as a string-- and
-// they might have typed anything, not just numbers!
-
+// token. A player of the game will type in how many items they want to buy, and
+// the `total_cost` function will calculate the total cost of the tokens. Since
+// the player typed in the quantity, though, we get it as a string-- and they
+// might have typed anything, not just numbers!
+//
 // Right now, this function isn't handling the error case at all (and isn't
-// handling the success case properly either). What we want to do is:
-// if we call the `parse` function on a string that is not a number, that
-// function will return a `ParseIntError`, and in that case, we want to
-// immediately return that error from our function and not try to multiply
-// and add.
-
-// There are at least two ways to implement this that are both correct-- but
-// one is a lot shorter!
-// Execute `rustlings hint errors2` or use the `hint` watch subcommand for a hint.
+// handling the success case properly either). What we want to do is: if we call
+// the `total_cost` function on a string that is not a number, that function
+// will return a `ParseIntError`, and in that case, we want to immediately
+// return that error from our function and not try to multiply and add.
+//
+// There are at least two ways to implement this that are both correct-- but one
+// is a lot shorter!
+//
+// Execute `rustlings hint errors2` or use the `hint` watch subcommand for a
+// hint.

 // I AM NOT DONE

--- a/exercises/error_handling/errors3.rs
+++ b/exercises/error_handling/errors3.rs
@ -1,8 +1,11 @@
 // errors3.rs
+//
 // This is a program that is trying to use a completed version of the
 // `total_cost` function from the previous exercise. It's not working though!
 // Why not? What should we do to fix it?
-// Execute `rustlings hint errors3` or use the `hint` watch subcommand for a hint.
+//
+// Execute `rustlings hint errors3` or use the `hint` watch subcommand for a
+// hint.

 // I AM NOT DONE

--- a/exercises/error_handling/errors4.rs
+++ b/exercises/error_handling/errors4.rs
@ -1,5 +1,7 @@
 // errors4.rs
-// Execute `rustlings hint errors4` or use the `hint` watch subcommand for a hint.
+//
+// Execute `rustlings hint errors4` or use the `hint` watch subcommand for a
+// hint.

 // I AM NOT DONE

@ -14,7 +16,7 @@ enum CreationError {

 impl PositiveNonzeroInteger {
    fn new(value: i64) -> Result<PositiveNonzeroInteger, CreationError> {
-        // Hmm...? Why is this only returning an Ok value?
+        // Hmm... Why is this always returning an Ok value?
        Ok(PositiveNonzeroInteger(value as u64))
    }
 }
--- a/exercises/error_handling/errors5.rs
+++ b/exercises/error_handling/errors5.rs
@ -1,20 +1,26 @@
 // errors5.rs
-
+//
 // This program uses an altered version of the code from errors4.
-
-// This exercise uses some concepts that we won't get to until later in the course, like `Box` and the
-// `From` trait. It's not important to understand them in detail right now, but you can read ahead if you like.
-// For now, think of the `Box<dyn ???>` type as an "I want anything that does ???" type, which, given
-// Rust's usual standards for runtime safety, should strike you as somewhat lenient!
-
-// In short, this particular use case for boxes is for when you want to own a value and you care only that it is a
-// type which implements a particular trait. To do so, The Box is declared as of type Box<dyn Trait> where Trait is the trait
-// the compiler looks for on any value used in that context. For this exercise, that context is the potential errors
-// which can be returned in a Result.
-
-// What can we use to describe both errors? In other words, is there a trait which both errors implement?
-
-// Execute `rustlings hint errors5` or use the `hint` watch subcommand for a hint.
+//
+// This exercise uses some concepts that we won't get to until later in the
+// course, like `Box` and the `From` trait. It's not important to understand
+// them in detail right now, but you can read ahead if you like. For now, think
+// of the `Box<dyn ???>` type as an "I want anything that does ???" type, which,
+// given Rust's usual standards for runtime safety, should strike you as
+// somewhat lenient!
+//
+// In short, this particular use case for boxes is for when you want to own a
+// value and you care only that it is a type which implements a particular
+// trait. To do so, The Box is declared as of type Box<dyn Trait> where Trait is
+// the trait the compiler looks for on any value used in that context. For this
+// exercise, that context is the potential errors which can be returned in a
+// Result.
+//
+// What can we use to describe both errors? In other words, is there a trait
+// which both errors implement?
+//
+// Execute `rustlings hint errors5` or use the `hint` watch subcommand for a
+// hint.

 // I AM NOT DONE

--- a/exercises/error_handling/errors6.rs
+++ b/exercises/error_handling/errors6.rs
@ -1,12 +1,13 @@
 // errors6.rs
-
+//
 // Using catch-all error types like `Box<dyn error::Error>` isn't recommended
 // for library code, where callers might want to make decisions based on the
-// error content, instead of printing it out or propagating it further. Here,
-// we define a custom error type to make it possible for callers to decide
-// what to do next when our function returns an error.
-
-// Execute `rustlings hint errors6` or use the `hint` watch subcommand for a hint.
+// error content, instead of printing it out or propagating it further. Here, we
+// define a custom error type to make it possible for callers to decide what to
+// do next when our function returns an error.
+//
+// Execute `rustlings hint errors6` or use the `hint` watch subcommand for a
+// hint.

 // I AM NOT DONE

--- a/exercises/functions/functions1.rs
+++ b/exercises/functions/functions1.rs
@ -1,5 +1,7 @@
 // functions1.rs
-// Execute `rustlings hint functions1` or use the `hint` watch subcommand for a hint.
+//
+// Execute `rustlings hint functions1` or use the `hint` watch subcommand for a
+// hint.

 // I AM NOT DONE

--- a/exercises/functions/functions2.rs
+++ b/exercises/functions/functions2.rs
@ -1,5 +1,7 @@
 // functions2.rs
-// Execute `rustlings hint functions2` or use the `hint` watch subcommand for a hint.
+//
+// Execute `rustlings hint functions2` or use the `hint` watch subcommand for a
+// hint.

 // I AM NOT DONE

--- a/exercises/functions/functions3.rs
+++ b/exercises/functions/functions3.rs
@ -1,5 +1,7 @@
 // functions3.rs
-// Execute `rustlings hint functions3` or use the `hint` watch subcommand for a hint.
+//
+// Execute `rustlings hint functions3` or use the `hint` watch subcommand for a
+// hint.

 // I AM NOT DONE

--- a/exercises/functions/functions4.rs
+++ b/exercises/functions/functions4.rs
@ -1,11 +1,12 @@
 // functions4.rs
-// Execute `rustlings hint functions4` or use the `hint` watch subcommand for a hint.
-
-// This store is having a sale where if the price is an even number, you get
-// 10 Rustbucks off, but if it's an odd number, it's 3 Rustbucks off.
-// (Don't worry about the function bodies themselves, we're only interested
-// in the signatures for now. If anything, this is a good way to peek ahead
-// to future exercises!)
+//
+// This store is having a sale where if the price is an even number, you get 10
+// Rustbucks off, but if it's an odd number, it's 3 Rustbucks off. (Don't worry
+// about the function bodies themselves, we're only interested in the signatures
+// for now. If anything, this is a good way to peek ahead to future exercises!)
+//
+// Execute `rustlings hint functions4` or use the `hint` watch subcommand for a
+// hint.

 // I AM NOT DONE

--- a/exercises/functions/functions5.rs
+++ b/exercises/functions/functions5.rs
@ -1,5 +1,7 @@
 // functions5.rs
-// Execute `rustlings hint functions5` or use the `hint` watch subcommand for a hint.
+//
+// Execute `rustlings hint functions5` or use the `hint` watch subcommand for a
+// hint.

 // I AM NOT DONE

--- a/exercises/generics/generics1.rs
+++ b/exercises/generics/generics1.rs
@ -1,7 +1,10 @@
-// This shopping list program isn't compiling!
-// Use your knowledge of generics to fix it.
-
-// Execute `rustlings hint generics1` or use the `hint` watch subcommand for a hint.
+// generics1.rs
+//
+// This shopping list program isn't compiling! Use your knowledge of generics to
+// fix it.
+//
+// Execute `rustlings hint generics1` or use the `hint` watch subcommand for a
+// hint.

 // I AM NOT DONE

--- a/exercises/generics/generics2.rs
+++ b/exercises/generics/generics2.rs
@ -1,7 +1,10 @@
+// generics2.rs
+//
 // This powerful wrapper provides the ability to store a positive integer value.
 // Rewrite it using generics so that it supports wrapping ANY type.
-
-// Execute `rustlings hint generics2` or use the `hint` watch subcommand for a hint.
+//
+// Execute `rustlings hint generics2` or use the `hint` watch subcommand for a
+// hint.

 // I AM NOT DONE

--- a/exercises/hashmaps/README.md
+++ b/exercises/hashmaps/README.md
@ -1,6 +1,7 @@
 # Hashmaps
+
 A *hash map* allows you to associate a value with a particular key.
-You may also know this by the names [*unordered map* in C++](https://en.cppreference.com/w/cpp/container/unordered_map), 
+You may also know this by the names [*unordered map* in C++](https://en.cppreference.com/w/cpp/container/unordered_map),
 [*dictionary* in Python](https://docs.python.org/3/tutorial/datastructures.html#dictionaries) or an *associative array* in other languages.

 This is the other data structure that we've been talking about before, when
--- a/exercises/hashmaps/hashmaps1.rs
+++ b/exercises/hashmaps/hashmaps1.rs
@ -1,14 +1,15 @@
 // hashmaps1.rs
-// A basket of fruits in the form of a hash map needs to be defined.
-// The key represents the name of the fruit and the value represents
-// how many of that particular fruit is in the basket. You have to put
-// at least three different types of fruits (e.g apple, banana, mango)
-// in the basket and the total count of all the fruits should be at
-// least five.
+//
+// A basket of fruits in the form of a hash map needs to be defined. The key
+// represents the name of the fruit and the value represents how many of that
+// particular fruit is in the basket. You have to put at least three different
+// types of fruits (e.g apple, banana, mango) in the basket and the total count
+// of all the fruits should be at least five.
 //
 // Make me compile and pass the tests!
 //
-// Execute `rustlings hint hashmaps1` or use the `hint` watch subcommand for a hint.
+// Execute `rustlings hint hashmaps1` or use the `hint` watch subcommand for a
+// hint.

 // I AM NOT DONE

--- a/exercises/hashmaps/hashmaps2.rs
+++ b/exercises/hashmaps/hashmaps2.rs
@ -1,15 +1,18 @@
 // hashmaps2.rs
-
-// A basket of fruits in the form of a hash map is given. The key
-// represents the name of the fruit and the value represents how many
-// of that particular fruit is in the basket. You have to put *MORE
-// THAN 11* fruits in the basket. Three types of fruits - Apple (4),
-// Mango (2) and Lychee (5) are already given in the basket. You are
-// not allowed to insert any more of these fruits!
+//
+// We're collecting different fruits to bake a delicious fruit cake. For this,
+// we have a basket, which we'll represent in the form of a hash map. The key
+// represents the name of each fruit we collect and the value represents how
+// many of that particular fruit we have collected. Three types of fruits -
+// Apple (4), Mango (2) and Lychee (5) are already in the basket hash map. You
+// must add fruit to the basket so that there is at least one of each kind and
+// more than 11 in total - we have a lot of mouths to feed. You are not allowed
+// to insert any more of these fruits!
 //
 // Make me pass the tests!
 //
-// Execute `rustlings hint hashmaps2` or use the `hint` watch subcommand for a hint.
+// Execute `rustlings hint hashmaps2` or use the `hint` watch subcommand for a
+// hint.

 // I AM NOT DONE

@ -34,9 +37,9 @@ fn fruit_basket(basket: &mut HashMap<Fruit, u32>) {
    ];

    for fruit in fruit_kinds {
-        // TODO: Put new fruits if not already present. Note that you
-        // are not allowed to put any type of fruit that's already
-        // present!
+        // TODO: Insert new fruits if they are not already present in the
+        // basket. Note that you are not allowed to put any type of fruit that's
+        // already present!
    }
 }

@ -44,6 +47,7 @@ fn fruit_basket(basket: &mut HashMap<Fruit, u32>) {
 mod tests {
    use super::*;

+    // Don't modify this function!
    fn get_fruit_basket() -> HashMap<Fruit, u32> {
        let mut basket = HashMap::<Fruit, u32>::new();
        basket.insert(Fruit::Apple, 4);
@ -77,4 +81,13 @@ mod tests {
        let count = basket.values().sum::<u32>();
        assert!(count > 11);
    }
+    
+    #[test]
+    fn all_fruit_types_in_basket() {
+        let mut basket = get_fruit_basket();
+        fruit_basket(&mut basket);
+        for amount in basket.values() {
+            assert_ne!(amount, &0);
+        }
+    }
 }
--- a/exercises/hashmaps/hashmaps3.rs
+++ b/exercises/hashmaps/hashmaps3.rs
@ -1,26 +1,25 @@
 // hashmaps3.rs
-
-// A list of scores (one per line) of a soccer match is given. Each line
-// is of the form :
-// <team_1_name>,<team_2_name>,<team_1_goals>,<team_2_goals>
+//
+// A list of scores (one per line) of a soccer match is given. Each line is of
+// the form : "<team_1_name>,<team_2_name>,<team_1_goals>,<team_2_goals>"
 // Example: England,France,4,2 (England scored 4 goals, France 2).
-
-// You have to build a scores table containing the name of the team, goals
-// the team scored, and goals the team conceded. One approach to build
-// the scores table is to use a Hashmap. The solution is partially
-// written to use a Hashmap, complete it to pass the test.
-
+//
+// You have to build a scores table containing the name of the team, goals the
+// team scored, and goals the team conceded. One approach to build the scores
+// table is to use a Hashmap. The solution is partially written to use a
+// Hashmap, complete it to pass the test.
+//
 // Make me pass the tests!
-
-// Execute `rustlings hint hashmaps3` or use the `hint` watch subcommand for a hint.
+//
+// Execute `rustlings hint hashmaps3` or use the `hint` watch subcommand for a
+// hint.

 // I AM NOT DONE

 use std::collections::HashMap;

-// A structure to store team name and its goal details.
+// A structure to store the goal details of a team.
 struct Team {
-    name: String,
    goals_scored: u8,
    goals_conceded: u8,
 }
--- a/exercises/if/if1.rs
+++ b/exercises/if/if1.rs
@ -1,4 +1,5 @@
 // if1.rs
+//
 // Execute `rustlings hint if1` or use the `hint` watch subcommand for a hint.

 // I AM NOT DONE
@ -24,4 +25,9 @@ mod tests {
    fn fortytwo_is_bigger_than_thirtytwo() {
        assert_eq!(42, bigger(32, 42));
    }
+
+    #[test]
+    fn equal_numbers() {
+        assert_eq!(42, bigger(42, 42));
+    }
 }
--- a/exercises/if/if2.rs
+++ b/exercises/if/if2.rs
@ -1,7 +1,8 @@
 // if2.rs
-
+//
 // Step 1: Make me compile!
 // Step 2: Get the bar_for_fuzz and default_to_baz tests passing!
+//
 // Execute `rustlings hint if2` or use the `hint` watch subcommand for a hint.

 // I AM NOT DONE
--- a/exercises/if/if3.rs
+++ b/exercises/if/if3.rs
@ -0,0 +1,56 @@
+// if3.rs
+//
+// Execute `rustlings hint if3` or use the `hint` watch subcommand for a hint.
+
+// I AM NOT DONE
+
+pub fn animal_habitat(animal: &str) -> &'static str {
+    let identifier = if animal == "crab" {
+        1
+    } else if animal == "gopher" {
+        2.0
+    } else if animal == "snake" {
+        3
+    } else {
+        "Unknown"
+    };
+
+    // DO NOT CHANGE THIS STATEMENT BELOW
+    let habitat = if identifier == 1 {
+        "Beach"
+    } else if identifier == 2 {
+        "Burrow"
+    } else if identifier == 3 {
+        "Desert"
+    } else {
+        "Unknown"
+    };
+
+    habitat
+}
+
+// No test changes needed.
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn gopher_lives_in_burrow() {
+        assert_eq!(animal_habitat("gopher"), "Burrow")
+    }
+
+    #[test]
+    fn snake_lives_in_desert() {
+        assert_eq!(animal_habitat("snake"), "Desert")
+    }
+
+    #[test]
+    fn crab_lives_on_beach() {
+        assert_eq!(animal_habitat("crab"), "Beach")
+    }
+
+    #[test]
+    fn unknown_animal() {
+        assert_eq!(animal_habitat("dinosaur"), "Unknown")
+    }
+}
--- a/exercises/intro/intro1.rs
+++ b/exercises/intro/intro1.rs
@ -1,13 +1,17 @@
 // intro1.rs
+//
 // About this `I AM NOT DONE` thing:
 // We sometimes encourage you to keep trying things on a given exercise, even
 // after you already figured it out. If you got everything working and feel
 // ready for the next exercise, remove the `I AM NOT DONE` comment below.
-// Execute `rustlings hint intro1` or use the `hint` watch subcommand for a hint.
 //
-// If you're running this using `rustlings watch`: The exercise file will be reloaded
-// when you change one of the lines below! Try adding a `println!` line, or try changing
-// what it outputs in your terminal. Try removing a semicolon and see what happens!
+// If you're running this using `rustlings watch`: The exercise file will be
+// reloaded when you change one of the lines below! Try adding a `println!`
+// line, or try changing what it outputs in your terminal. Try removing a
+// semicolon and see what happens!
+//
+// Execute `rustlings hint intro1` or use the `hint` watch subcommand for a
+// hint.

 // I AM NOT DONE

--- a/exercises/intro/intro2.rs
+++ b/exercises/intro/intro2.rs
@ -1,6 +1,9 @@
 // intro2.rs
+//
 // Make the code print a greeting to the world.
-// Execute `rustlings hint intro2` or use the `hint` watch subcommand for a hint.
+//
+// Execute `rustlings hint intro2` or use the `hint` watch subcommand for a
+// hint.

 // I AM NOT DONE

--- a/exercises/iterators/iterators1.rs
+++ b/exercises/iterators/iterators1.rs
@ -1,15 +1,17 @@
 // iterators1.rs
 //
-//  Make me compile by filling in the `???`s
+// When performing operations on elements within a collection, iterators are
+// essential. This module helps you get familiar with the structure of using an
+// iterator and how to go through elements within an iterable collection.
 //
-// When performing operations on elements within a collection, iterators are essential.
-// This module helps you get familiar with the structure of using an iterator and
-// how to go through elements within an iterable collection.
+// Make me compile by filling in the `???`s
 //
-// Execute `rustlings hint iterators1` or use the `hint` watch subcommand for a hint.
+// Execute `rustlings hint iterators1` or use the `hint` watch subcommand for a
+// hint.

 // I AM NOT DONE

+#[test]
 fn main() {
    let my_fav_fruits = vec!["banana", "custard apple", "avocado", "peach", "raspberry"];

--- a/exercises/iterators/iterators2.rs
+++ b/exercises/iterators/iterators2.rs
@ -1,7 +1,10 @@
 // iterators2.rs
+//
 // In this exercise, you'll learn some of the unique advantages that iterators
 // can offer. Follow the steps to complete the exercise.
-// Execute `rustlings hint iterators2` or use the `hint` watch subcommand for a hint.
+//
+// Execute `rustlings hint iterators2` or use the `hint` watch subcommand for a
+// hint.

 // I AM NOT DONE

--- a/exercises/iterators/iterators3.rs
+++ b/exercises/iterators/iterators3.rs
@ -1,10 +1,13 @@
 // iterators3.rs
-// This is a bigger exercise than most of the others! You can do it!
-// Here is your mission, should you choose to accept it:
+//
+// This is a bigger exercise than most of the others! You can do it! Here is
+// your mission, should you choose to accept it:
 // 1. Complete the divide function to get the first four tests to pass.
 // 2. Get the remaining tests to pass by completing the result_with_list and
 //    list_of_results functions.
-// Execute `rustlings hint iterators3` or use the `hint` watch subcommand for a hint.
+//
+// Execute `rustlings hint iterators3` or use the `hint` watch subcommand for a
+// hint.

 // I AM NOT DONE

@ -26,14 +29,16 @@ pub fn divide(a: i32, b: i32) -> Result<i32, DivisionError> {
    todo!();
 }

-// Complete the function and return a value of the correct type so the test passes.
+// Complete the function and return a value of the correct type so the test
+// passes.
 // Desired output: Ok([1, 11, 1426, 3])
 fn result_with_list() -> () {
    let numbers = vec![27, 297, 38502, 81];
    let division_results = numbers.into_iter().map(|n| divide(n, 27));
 }

-// Complete the function and return a value of the correct type so the test passes.
+// Complete the function and return a value of the correct type so the test
+// passes.
 // Desired output: [Ok(1), Ok(11), Ok(1426), Ok(3)]
 fn list_of_results() -> () {
    let numbers = vec![27, 297, 38502, 81];
--- a/exercises/iterators/iterators4.rs
+++ b/exercises/iterators/iterators4.rs
@ -1,5 +1,7 @@
 // iterators4.rs
-// Execute `rustlings hint iterators4` or use the `hint` watch subcommand for a hint.
+//
+// Execute `rustlings hint iterators4` or use the `hint` watch subcommand for a
+// hint.

 // I AM NOT DONE

--- a/exercises/iterators/iterators5.rs
+++ b/exercises/iterators/iterators5.rs
@ -1,14 +1,15 @@
 // iterators5.rs
+//
 // Let's define a simple model to track Rustlings exercise progress. Progress
 // will be modelled using a hash map. The name of the exercise is the key and
 // the progress is the value. Two counting functions were created to count the
-// number of exercises with a given progress. These counting functions use
-// imperative style for loops. Recreate this counting functionality using
-// iterators. Only the two iterator methods (count_iterator and
-// count_collection_iterator) need to be modified.
-// Execute `rustlings hint iterators5` or use the `hint` watch subcommand for a hint.
+// number of exercises with a given progress. Recreate this counting
+// functionality using iterators. Try not to use imperative loops (for, while).
+// Only the two iterator methods (count_iterator and count_collection_iterator)
+// need to be modified.
 //
-// Make the code compile and the tests pass.
+// Execute `rustlings hint iterators5` or use the `hint` watch subcommand for a
+// hint.

 // I AM NOT DONE

@ -67,12 +68,27 @@ mod tests {
    }

    #[test]
-    fn count_equals_for() {
+    fn count_some() {
        let map = get_map();
-        assert_eq!(
-            count_for(&map, Progress::Complete),
-            count_iterator(&map, Progress::Complete)
-        );
+        assert_eq!(1, count_iterator(&map, Progress::Some));
+    }
+
+    #[test]
+    fn count_none() {
+        let map = get_map();
+        assert_eq!(2, count_iterator(&map, Progress::None));
+    }
+
+    #[test]
+    fn count_complete_equals_for() {
+        let map = get_map();
+        let progress_states = vec![Progress::Complete, Progress::Some, Progress::None];
+        for progress_state in progress_states {
+            assert_eq!(
+                count_for(&map, progress_state),
+                count_iterator(&map, progress_state)
+            );
+        }
    }

    #[test]
@ -85,12 +101,28 @@ mod tests {
    }

    #[test]
-    fn count_collection_equals_for() {
+    fn count_collection_some() {
        let collection = get_vec_map();
-        assert_eq!(
-            count_collection_for(&collection, Progress::Complete),
-            count_collection_iterator(&collection, Progress::Complete)
-        );
+        assert_eq!(1, count_collection_iterator(&collection, Progress::Some));
+    }
+
+    #[test]
+    fn count_collection_none() {
+        let collection = get_vec_map();
+        assert_eq!(4, count_collection_iterator(&collection, Progress::None));
+    }
+
+    #[test]
+    fn count_collection_equals_for() {
+        let progress_states = vec![Progress::Complete, Progress::Some, Progress::None];
+        let collection = get_vec_map();
+
+        for progress_state in progress_states {
+            assert_eq!(
+                count_collection_for(&collection, progress_state),
+                count_collection_iterator(&collection, progress_state)
+            );
+        }
    }

    fn get_map() -> HashMap<String, Progress> {
--- a/exercises/lifetimes/README.md
+++ b/exercises/lifetimes/README.md
@ -3,17 +3,17 @@
 Lifetimes tell the compiler how to check whether references live long
 enough to be valid in any given situation. For example lifetimes say
 "make sure parameter 'a' lives as long as parameter 'b' so that the return
-value is valid". 
+value is valid".

-They are only necessary on borrows, i.e. references, 
+They are only necessary on borrows, i.e. references,
 since copied parameters or moves are owned in their scope and cannot
 be referenced outside. Lifetimes mean that calling code of e.g. functions
-can be checked to make sure their arguments are valid. Lifetimes are 
+can be checked to make sure their arguments are valid. Lifetimes are
 restrictive of their callers.

-If you'd like to learn more about lifetime annotations, the 
-[lifetimekata](https://tfpk.github.io/lifetimekata/) project 
-has a similar style of exercises to Rustlings, but is all about 
+If you'd like to learn more about lifetime annotations, the
+[lifetimekata](https://tfpk.github.io/lifetimekata/) project
+has a similar style of exercises to Rustlings, but is all about
 learning to write lifetime annotations.

 ## Further information
--- a/exercises/lifetimes/lifetimes1.rs
+++ b/exercises/lifetimes/lifetimes1.rs
@ -1,11 +1,12 @@
 // lifetimes1.rs
 //
 // The Rust compiler needs to know how to check whether supplied references are
-// valid, so that it can let the programmer know if a reference is at risk
-// of going out of scope before it is used. Remember, references are borrows
-// and do not own their own data. What if their owner goes out of scope?
+// valid, so that it can let the programmer know if a reference is at risk of
+// going out of scope before it is used. Remember, references are borrows and do
+// not own their own data. What if their owner goes out of scope?
 //
-// Execute `rustlings hint lifetimes1` or use the `hint` watch subcommand for a hint.
+// Execute `rustlings hint lifetimes1` or use the `hint` watch subcommand for a
+// hint.

 // I AM NOT DONE

--- a/exercises/lifetimes/lifetimes2.rs
+++ b/exercises/lifetimes/lifetimes2.rs
@ -1,10 +1,10 @@
 // lifetimes2.rs
 //
-// So if the compiler is just validating the references passed
-// to the annotated parameters and the return type, what do
-// we need to change?
+// So if the compiler is just validating the references passed to the annotated
+// parameters and the return type, what do we need to change?
 //
-// Execute `rustlings hint lifetimes2` or use the `hint` watch subcommand for a hint.
+// Execute `rustlings hint lifetimes2` or use the `hint` watch subcommand for a
+// hint.

 // I AM NOT DONE

--- a/exercises/lifetimes/lifetimes3.rs
+++ b/exercises/lifetimes/lifetimes3.rs
@ -2,7 +2,8 @@
 //
 // Lifetimes are also needed when structs hold references.
 //
-// Execute `rustlings hint lifetimes3` or use the `hint` watch subcommand for a hint.
+// Execute `rustlings hint lifetimes3` or use the `hint` watch subcommand for a
+// hint.

 // I AM NOT DONE

--- a/exercises/macros/README.md
+++ b/exercises/macros/README.md
@ -4,7 +4,7 @@ Rust's macro system is very powerful, but also kind of difficult to wrap your
 head around. We're not going to teach you how to write your own fully-featured
 macros. Instead, we'll show you how to use and create them.

-If you'd like to learn more about writing your own macros, the 
+If you'd like to learn more about writing your own macros, the
 [macrokata](https://github.com/tfpk/macrokata) project has a similar style
 of exercises to Rustlings, but is all about learning to write Macros.

--- a/exercises/macros/macros1.rs
+++ b/exercises/macros/macros1.rs
@ -1,5 +1,7 @@
 // macros1.rs
-// Execute `rustlings hint macros1` or use the `hint` watch subcommand for a hint.
+//
+// Execute `rustlings hint macros1` or use the `hint` watch subcommand for a
+// hint.

 // I AM NOT DONE

--- a/exercises/macros/macros2.rs
+++ b/exercises/macros/macros2.rs
@ -1,5 +1,7 @@
 // macros2.rs
-// Execute `rustlings hint macros2` or use the `hint` watch subcommand for a hint.
+//
+// Execute `rustlings hint macros2` or use the `hint` watch subcommand for a
+// hint.

 // I AM NOT DONE

--- a/exercises/macros/macros3.rs
+++ b/exercises/macros/macros3.rs
@ -1,6 +1,9 @@
 // macros3.rs
+//
 // Make me compile, without taking the macro out of the module!
-// Execute `rustlings hint macros3` or use the `hint` watch subcommand for a hint.
+//
+// Execute `rustlings hint macros3` or use the `hint` watch subcommand for a
+// hint.

 // I AM NOT DONE

--- a/exercises/macros/macros4.rs
+++ b/exercises/macros/macros4.rs
@ -1,5 +1,7 @@
 // macros4.rs
-// Execute `rustlings hint macros4` or use the `hint` watch subcommand for a hint.
+//
+// Execute `rustlings hint macros4` or use the `hint` watch subcommand for a
+// hint.

 // I AM NOT DONE

--- a/exercises/modules/modules1.rs
+++ b/exercises/modules/modules1.rs
@ -1,5 +1,7 @@
 // modules1.rs
-// Execute `rustlings hint modules1` or use the `hint` watch subcommand for a hint.
+//
+// Execute `rustlings hint modules1` or use the `hint` watch subcommand for a
+// hint.

 // I AM NOT DONE

--- a/exercises/modules/modules2.rs
+++ b/exercises/modules/modules2.rs
@ -1,7 +1,11 @@
 // modules2.rs
-// You can bring module paths into scopes and provide new names for them with the
-// 'use' and 'as' keywords. Fix these 'use' statements to make the code compile.
-// Execute `rustlings hint modules2` or use the `hint` watch subcommand for a hint.
+//
+// You can bring module paths into scopes and provide new names for them with
+// the 'use' and 'as' keywords. Fix these 'use' statements to make the code
+// compile.
+//
+// Execute `rustlings hint modules2` or use the `hint` watch subcommand for a
+// hint.

 // I AM NOT DONE

--- a/exercises/modules/modules3.rs
+++ b/exercises/modules/modules3.rs
@ -1,9 +1,12 @@
 // modules3.rs
-// You can use the 'use' keyword to bring module paths from modules from anywhere
-// and especially from the Rust standard library into your scope.
-// Bring SystemTime and UNIX_EPOCH
-// from the std::time module. Bonus style points if you can do it with one line!
-// Execute `rustlings hint modules3` or use the `hint` watch subcommand for a hint.
+//
+// You can use the 'use' keyword to bring module paths from modules from
+// anywhere and especially from the Rust standard library into your scope. Bring
+// SystemTime and UNIX_EPOCH from the std::time module. Bonus style points if
+// you can do it with one line!
+//
+// Execute `rustlings hint modules3` or use the `hint` watch subcommand for a
+// hint.

 // I AM NOT DONE

--- a/exercises/move_semantics/move_semantics1.rs
+++ b/exercises/move_semantics/move_semantics1.rs
@ -1,26 +1,23 @@
 // move_semantics1.rs
-// Execute `rustlings hint move_semantics1` or use the `hint` watch subcommand for a hint.
+//
+// Execute `rustlings hint move_semantics1` or use the `hint` watch subcommand
+// for a hint.

 // I AM NOT DONE

+#[test]
 fn main() {
-    let vec0 = Vec::new();
+    let vec0 = vec![22, 44, 66];

    let vec1 = fill_vec(vec0);

-    println!("{} has length {} content `{:?}`", "vec1", vec1.len(), vec1);
-
-    vec1.push(88);
-
-    println!("{} has length {} content `{:?}`", "vec1", vec1.len(), vec1);
+    assert_eq!(vec1, vec![22, 44, 66, 88]);
 }

 fn fill_vec(vec: Vec<i32>) -> Vec<i32> {
-    let mut vec = vec;
+    let vec = vec;

-    vec.push(22);
-    vec.push(44);
-    vec.push(66);
+    vec.push(88);

    vec
 }
--- a/exercises/move_semantics/move_semantics2.rs
+++ b/exercises/move_semantics/move_semantics2.rs
@ -1,28 +1,26 @@
 // move_semantics2.rs
-// Make me compile without changing line 13 or moving line 10!
-// Execute `rustlings hint move_semantics2` or use the `hint` watch subcommand for a hint.
+//
+// Make the test pass by finding a way to keep both Vecs separate!
+//
+// Execute `rustlings hint move_semantics2` or use the `hint` watch subcommand
+// for a hint.

 // I AM NOT DONE

+#[test]
 fn main() {
-    let vec0 = Vec::new();
+    let vec0 = vec![22, 44, 66];

    let mut vec1 = fill_vec(vec0);

-    // Do not change the following line!
-    println!("{} has length {} content `{:?}`", "vec0", vec0.len(), vec0);
-
-    vec1.push(88);
-
-    println!("{} has length {} content `{:?}`", "vec1", vec1.len(), vec1);
+    assert_eq!(vec0, vec![22, 44, 66]);
+    assert_eq!(vec1, vec![22, 44, 66, 88]);
 }

 fn fill_vec(vec: Vec<i32>) -> Vec<i32> {
    let mut vec = vec;

-    vec.push(22);
-    vec.push(44);
-    vec.push(66);
+    vec.push(88);

    vec
 }
--- a/exercises/move_semantics/move_semantics3.rs
+++ b/exercises/move_semantics/move_semantics3.rs
@ -1,26 +1,24 @@
 // move_semantics3.rs
-// Make me compile without adding new lines-- just changing existing lines!
-// (no lines with multiple semicolons necessary!)
-// Execute `rustlings hint move_semantics3` or use the `hint` watch subcommand for a hint.
+//
+// Make me compile without adding new lines -- just changing existing lines! (no
+// lines with multiple semicolons necessary!)
+//
+// Execute `rustlings hint move_semantics3` or use the `hint` watch subcommand
+// for a hint.

 // I AM NOT DONE

+#[test]
 fn main() {
-    let vec0 = Vec::new();
+    let vec0 = vec![22, 44, 66];

    let mut vec1 = fill_vec(vec0);

-    println!("{} has length {} content `{:?}`", "vec1", vec1.len(), vec1);
-
-    vec1.push(88);
-
-    println!("{} has length {} content `{:?}`", "vec1", vec1.len(), vec1);
+    assert_eq!(vec1, vec![22, 44, 66, 88]);
 }

 fn fill_vec(vec: Vec<i32>) -> Vec<i32> {
-    vec.push(22);
-    vec.push(44);
-    vec.push(66);
+    vec.push(88);

    vec
 }
--- a/exercises/move_semantics/move_semantics4.rs
+++ b/exercises/move_semantics/move_semantics4.rs
@ -1,30 +1,29 @@
 // move_semantics4.rs
-// Refactor this code so that instead of passing `vec0` into the `fill_vec` function,
-// the Vector gets created in the function itself and passed back to the main
-// function.
-// Execute `rustlings hint move_semantics4` or use the `hint` watch subcommand for a hint.
+//
+// Refactor this code so that instead of passing `vec0` into the `fill_vec`
+// function, the Vector gets created in the function itself and passed back to
+// the main function.
+//
+// Execute `rustlings hint move_semantics4` or use the `hint` watch subcommand
+// for a hint.

 // I AM NOT DONE

+#[test]
 fn main() {
-    let vec0 = Vec::new();
+    let vec0 = vec![22, 44, 66];

    let mut vec1 = fill_vec(vec0);

-    println!("{} has length {} content `{:?}`", "vec1", vec1.len(), vec1);
-
-    vec1.push(88);
-
-    println!("{} has length {} content `{:?}`", "vec1", vec1.len(), vec1);
+    assert_eq!(vec1, vec![22, 44, 66, 88]);
 }

-// `fill_vec()` no longer takes `vec: Vec<i32>` as argument
+// `fill_vec()` no longer takes `vec: Vec<i32>` as argument - don't change this!
 fn fill_vec() -> Vec<i32> {
+    // Instead, let's create and fill the Vec in here - how do you do that?
    let mut vec = vec;

-    vec.push(22);
-    vec.push(44);
-    vec.push(66);
+    vec.push(88);

    vec
 }
--- a/exercises/move_semantics/move_semantics5.rs
+++ b/exercises/move_semantics/move_semantics5.rs
@ -1,10 +1,14 @@
 // move_semantics5.rs
-// Make me compile only by reordering the lines in `main()`, but without
-// adding, changing or removing any of them.
-// Execute `rustlings hint move_semantics5` or use the `hint` watch subcommand for a hint.
+//
+// Make me compile only by reordering the lines in `main()`, but without adding,
+// changing or removing any of them.
+//
+// Execute `rustlings hint move_semantics5` or use the `hint` watch subcommand
+// for a hint.

 // I AM NOT DONE

+#[test]
 fn main() {
    let mut x = 100;
    let y = &mut x;
--- a/exercises/move_semantics/move_semantics6.rs
+++ b/exercises/move_semantics/move_semantics6.rs
@ -1,6 +1,9 @@
 // move_semantics6.rs
-// Execute `rustlings hint move_semantics6` or use the `hint` watch subcommand for a hint.
+//
 // You can't change anything except adding or removing references.
+//
+// Execute `rustlings hint move_semantics6` or use the `hint` watch subcommand
+// for a hint.

 // I AM NOT DONE

--- a/exercises/options/README.md
+++ b/exercises/options/README.md
@ -1,7 +1,8 @@
 # Options

-Type Option represents an optional value: every Option is either Some and contains a value, or None, and does not. 
+Type Option represents an optional value: every Option is either Some and contains a value, or None, and does not.
 Option types are very common in Rust code, as they have a number of uses:
+
 - Initial values
 - Return values for functions that are not defined over their entire input range (partial functions)
 - Return value for otherwise reporting simple errors, where None is returned on error
--- a/exercises/options/options1.rs
+++ b/exercises/options/options1.rs
@ -1,5 +1,7 @@
 // options1.rs
-// Execute `rustlings hint options1` or use the `hint` watch subcommand for a hint.
+//
+// Execute `rustlings hint options1` or use the `hint` watch subcommand for a
+// hint.

 // I AM NOT DONE

@ -7,8 +9,9 @@
 // If it's before 10PM, there's 5 pieces left. At 10PM, someone eats them
 // all, so there'll be no more left :(
 fn maybe_icecream(time_of_day: u16) -> Option<u16> {
-    // We use the 24-hour system here, so 10PM is a value of 22 and 12AM is a value of 0
-    // The Option output should gracefully handle cases where time_of_day > 23.
+    // We use the 24-hour system here, so 10PM is a value of 22 and 12AM is a
+    // value of 0 The Option output should gracefully handle cases where
+    // time_of_day > 23.
    // TODO: Complete the function body - remember to return an Option!
    ???
 }
@ -28,7 +31,8 @@ mod tests {

    #[test]
    fn raw_value() {
-        // TODO: Fix this test. How do you get at the value contained in the Option?
+        // TODO: Fix this test. How do you get at the value contained in the
+        // Option?
        let icecreams = maybe_icecream(12);
        assert_eq!(icecreams, 5);
    }
--- a/exercises/options/options2.rs
+++ b/exercises/options/options2.rs
@ -1,5 +1,7 @@
 // options2.rs
-// Execute `rustlings hint options2` or use the `hint` watch subcommand for a hint.
+//
+// Execute `rustlings hint options2` or use the `hint` watch subcommand for a
+// hint.

 // I AM NOT DONE

@ -18,17 +20,23 @@ mod tests {

    #[test]
    fn layered_option() {
-        let mut range = 10;
-        let mut optional_integers: Vec<Option<i8>> = Vec::new();
-        for i in 0..(range + 1) {
+        let range = 10;
+        let mut optional_integers: Vec<Option<i8>> = vec![None];
+
+        for i in 1..(range + 1) {
            optional_integers.push(Some(i));
        }

-        // TODO: make this a while let statement - remember that vector.pop also adds another layer of Option<T>
-        // You can stack `Option<T>`'s into while let and if let
+        let mut cursor = range;
+
+        // TODO: make this a while let statement - remember that vector.pop also
+        // adds another layer of Option<T>. You can stack `Option<T>`s into
+        // while let and if let.
        integer = optional_integers.pop() {
-            assert_eq!(integer, range);
-            range -= 1;
+            assert_eq!(integer, cursor);
+            cursor -= 1;
        }
+
+        assert_eq!(cursor, 0);
    }
 }
--- a/exercises/options/options3.rs
+++ b/exercises/options/options3.rs
@ -1,5 +1,7 @@
 // options3.rs
-// Execute `rustlings hint options3` or use the `hint` watch subcommand for a hint.
+//
+// Execute `rustlings hint options3` or use the `hint` watch subcommand for a
+// hint.

 // I AM NOT DONE

@ -13,7 +15,7 @@ fn main() {

    match y {
        Some(p) => println!("Co-ordinates are {},{} ", p.x, p.y),
-        _ => println!("no match"),
+        _ => panic!("no match!"),
    }
    y; // Fix without deleting this line.
 }
--- a/exercises/primitive_types/primitive_types1.rs
+++ b/exercises/primitive_types/primitive_types1.rs
@ -1,6 +1,7 @@
 // primitive_types1.rs
-// Fill in the rest of the line that has code missing!
-// No hints, there's no tricks, just get used to typing these :)
+//
+// Fill in the rest of the line that has code missing! No hints, there's no
+// tricks, just get used to typing these :)

 // I AM NOT DONE

--- a/exercises/primitive_types/primitive_types2.rs
+++ b/exercises/primitive_types/primitive_types2.rs
@ -1,6 +1,7 @@
 // primitive_types2.rs
-// Fill in the rest of the line that has code missing!
-// No hints, there's no tricks, just get used to typing these :)
+//
+// Fill in the rest of the line that has code missing! No hints, there's no
+// tricks, just get used to typing these :)

 // I AM NOT DONE

--- a/exercises/primitive_types/primitive_types3.rs
+++ b/exercises/primitive_types/primitive_types3.rs
@ -1,6 +1,9 @@
 // primitive_types3.rs
+//
 // Create an array with at least 100 elements in it where the ??? is.
-// Execute `rustlings hint primitive_types3` or use the `hint` watch subcommand for a hint.
+//
+// Execute `rustlings hint primitive_types3` or use the `hint` watch subcommand
+// for a hint.

 // I AM NOT DONE

@ -11,5 +14,6 @@ fn main() {
        println!("Wow, that's a big array!");
    } else {
        println!("Meh, I eat arrays like that for breakfast.");
+        panic!("Array not big enough, more elements needed")
    }
 }
--- a/exercises/primitive_types/primitive_types4.rs
+++ b/exercises/primitive_types/primitive_types4.rs
@ -1,6 +1,9 @@
 // primitive_types4.rs
+//
 // Get a slice out of Array a where the ??? is so that the test passes.
-// Execute `rustlings hint primitive_types4` or use the `hint` watch subcommand for a hint.
+//
+// Execute `rustlings hint primitive_types4` or use the `hint` watch subcommand
+// for a hint.

 // I AM NOT DONE

--- a/exercises/primitive_types/primitive_types5.rs
+++ b/exercises/primitive_types/primitive_types5.rs
@ -1,6 +1,9 @@
 // primitive_types5.rs
+//
 // Destructure the `cat` tuple so that the println will work.
-// Execute `rustlings hint primitive_types5` or use the `hint` watch subcommand for a hint.
+//
+// Execute `rustlings hint primitive_types5` or use the `hint` watch subcommand
+// for a hint.

 // I AM NOT DONE

--- a/exercises/primitive_types/primitive_types6.rs
+++ b/exercises/primitive_types/primitive_types6.rs
@ -1,7 +1,10 @@
 // primitive_types6.rs
-// Use a tuple index to access the second element of `numbers`.
-// You can put the expression for the second element where ??? is so that the test passes.
-// Execute `rustlings hint primitive_types6` or use the `hint` watch subcommand for a hint.
+//
+// Use a tuple index to access the second element of `numbers`. You can put the
+// expression for the second element where ??? is so that the test passes.
+//
+// Execute `rustlings hint primitive_types6` or use the `hint` watch subcommand
+// for a hint.

 // I AM NOT DONE

--- a/exercises/quiz1.rs
+++ b/exercises/quiz1.rs
@ -1,14 +1,17 @@
 // quiz1.rs
+//
 // This is a quiz for the following sections:
 // - Variables
 // - Functions
 // - If
-
+//
 // Mary is buying apples. The price of an apple is calculated as follows:
 // - An apple costs 2 rustbucks.
 // - If Mary buys more than 40 apples, each apple only costs 1 rustbuck!
-// Write a function that calculates the price of an order of apples given
-// the quantity bought. No hints this time!
+// Write a function that calculates the price of an order of apples given the
+// quantity bought.
+//
+// No hints this time ;)

 // I AM NOT DONE

--- a/exercises/quiz2.rs
+++ b/exercises/quiz2.rs
@ -1,14 +1,15 @@
 // quiz2.rs
+//
 // This is a quiz for the following sections:
 // - Strings
 // - Vecs
 // - Move semantics
 // - Modules
 // - Enums
-
-// Let's build a little machine in the form of a function.
-// As input, we're going to give a list of strings and commands. These commands
-// determine what action is going to be applied to the string. It can either be:
+//
+// Let's build a little machine in the form of a function. As input, we're going
+// to give a list of strings and commands. These commands determine what action
+// is going to be applied to the string. It can either be:
 // - Uppercase the string
 // - Trim the string
 // - Append "bar" to the string a specified amount of times
@ -16,6 +17,7 @@
 // - The input is going to be a Vector of a 2-length tuple,
 //   the first element is the string, the second one is the command.
 // - The output element is going to be a Vector of strings.
+//
 // No hints this time!

 // I AM NOT DONE
--- a/exercises/quiz3.rs
+++ b/exercises/quiz3.rs
@ -1,17 +1,19 @@
 // quiz3.rs
+//
 // This quiz tests:
 // - Generics
 // - Traits
-// An imaginary magical school has a new report card generation system written in Rust!
-// Currently the system only supports creating report cards where the student's grade
-// is represented numerically (e.g. 1.0 -> 5.5).
-// However, the school also issues alphabetical grades (A+ -> F-) and needs
-// to be able to print both types of report card!
-
+//
+// An imaginary magical school has a new report card generation system written
+// in Rust! Currently the system only supports creating report cards where the
+// student's grade is represented numerically (e.g. 1.0 -> 5.5). However, the
+// school also issues alphabetical grades (A+ -> F-) and needs to be able to
+// print both types of report card!
+//
 // Make the necessary code changes in the struct ReportCard and the impl block
-// to support alphabetical report cards. Change the Grade in the second test to "A+"
-// to show that your changes allow alphabetical grades.
-
+// to support alphabetical report cards. Change the Grade in the second test to
+// "A+" to show that your changes allow alphabetical grades.
+//
 // Execute `rustlings hint quiz3` or use the `hint` watch subcommand for a hint.

 // I AM NOT DONE
--- a/exercises/smart_pointers/README.md
+++ b/exercises/smart_pointers/README.md
@ -1,4 +1,5 @@
 # Smart Pointers
+
 In Rust, smart pointers are variables that contain an address in memory and reference some other data, but they also have additional metadata and capabilities.
 Smart pointers in Rust often own the data they point to, while references only borrow data.

--- a/exercises/smart_pointers/arc1.rs
+++ b/exercises/smart_pointers/arc1.rs
@ -1,21 +1,24 @@
 // arc1.rs
-// In this exercise, we are given a Vec of u32 called "numbers" with values ranging
-// from 0 to 99 -- [ 0, 1, 2, ..., 98, 99 ]
-// We would like to use this set of numbers within 8 different threads simultaneously.
-// Each thread is going to get the sum of every eighth value, with an offset.
+//
+// In this exercise, we are given a Vec of u32 called "numbers" with values
+// ranging from 0 to 99 -- [ 0, 1, 2, ..., 98, 99 ] We would like to use this
+// set of numbers within 8 different threads simultaneously. Each thread is
+// going to get the sum of every eighth value, with an offset.
+//
 // The first thread (offset 0), will sum 0, 8, 16, ...
 // The second thread (offset 1), will sum 1, 9, 17, ...
 // The third thread (offset 2), will sum 2, 10, 18, ...
 // ...
 // The eighth thread (offset 7), will sum 7, 15, 23, ...
-
+//
 // Because we are using threads, our values need to be thread-safe.  Therefore,
 // we are using Arc.  We need to make a change in each of the two TODOs.
-
-
+//
 // Make this code compile by filling in a value for `shared_numbers` where the
 // first TODO comment is, and create an initial binding for `child_numbers`
-// where the second TODO comment is. Try not to create any copies of the `numbers` Vec!
+// where the second TODO comment is. Try not to create any copies of the
+// `numbers` Vec!
+//
 // Execute `rustlings hint arc1` or use the `hint` watch subcommand for a hint.

 // I AM NOT DONE
--- a/exercises/smart_pointers/box1.rs
+++ b/exercises/smart_pointers/box1.rs
@ -1,13 +1,15 @@
 // box1.rs
 //
-// At compile time, Rust needs to know how much space a type takes up. This becomes problematic
-// for recursive types, where a value can have as part of itself another value of the same type.
-// To get around the issue, we can use a `Box` - a smart pointer used to store data on the heap,
-// which also allows us to wrap a recursive type.
+// At compile time, Rust needs to know how much space a type takes up. This
+// becomes problematic for recursive types, where a value can have as part of
+// itself another value of the same type. To get around the issue, we can use a
+// `Box` - a smart pointer used to store data on the heap, which also allows us
+// to wrap a recursive type.
 //
-// The recursive type we're implementing in this exercise is the `cons list` - a data structure
-// frequently found in functional programming languages. Each item in a cons list contains two
-// elements: the value of the current item and the next item. The last item is a value called `Nil`.
+// The recursive type we're implementing in this exercise is the `cons list` - a
+// data structure frequently found in functional programming languages. Each
+// item in a cons list contains two elements: the value of the current item and
+// the next item. The last item is a value called `Nil`.
 //
 // Step 1: use a `Box` in the enum definition to make the code compile
 // Step 2: create both empty and non-empty cons lists by replacing `todo!()`
--- a/exercises/smart_pointers/cow1.rs
+++ b/exercises/smart_pointers/cow1.rs
@ -1,12 +1,16 @@
 // cow1.rs
-
-// This exercise explores the Cow, or Clone-On-Write type.
-// Cow is a clone-on-write smart pointer.
-// It can enclose and provide immutable access to borrowed data, and clone the data lazily when mutation or ownership is required.
-// The type is designed to work with general borrowed data via the Borrow trait.
+//
+// This exercise explores the Cow, or Clone-On-Write type. Cow is a
+// clone-on-write smart pointer. It can enclose and provide immutable access to
+// borrowed data, and clone the data lazily when mutation or ownership is
+// required. The type is designed to work with general borrowed data via the
+// Borrow trait.
 //
 // This exercise is meant to show you what to expect when passing data to Cow.
-// Fix the unit tests by checking for Cow::Owned(_) and Cow::Borrowed(_) at the TODO markers.
+// Fix the unit tests by checking for Cow::Owned(_) and Cow::Borrowed(_) at the
+// TODO markers.
+//
+// Execute `rustlings hint cow1` or use the `hint` watch subcommand for a hint.

 // I AM NOT DONE

@ -50,9 +54,9 @@ mod tests {

    #[test]
    fn owned_no_mutation() -> Result<(), &'static str> {
-        // We can also pass `slice` without `&` so Cow owns it directly.
-        // In this case no mutation occurs and thus also no clone,
-        // but the result is still owned because it always was.
+        // We can also pass `slice` without `&` so Cow owns it directly. In this
+        // case no mutation occurs and thus also no clone, but the result is
+        // still owned because it was never borrowed or mutated.
        let slice = vec![0, 1, 2];
        let mut input = Cow::from(slice);
        match abs_all(&mut input) {
@ -62,9 +66,9 @@ mod tests {

    #[test]
    fn owned_mutation() -> Result<(), &'static str> {
-        // Of course this is also the case if a mutation does occur.
-        // In this case the call to `to_mut()` returns a reference to
-        // the same data as before.
+        // Of course this is also the case if a mutation does occur. In this
+        // case the call to `to_mut()` in the abs_all() function returns a
+        // reference to the same data as before.
        let slice = vec![-1, 0, 1];
        let mut input = Cow::from(slice);
        match abs_all(&mut input) {
--- a/exercises/smart_pointers/rc1.rs
+++ b/exercises/smart_pointers/rc1.rs
@ -1,9 +1,14 @@
 // rc1.rs
-// In this exercise, we want to express the concept of multiple owners via the Rc<T> type.
-// This is a model of our solar system - there is a Sun type and multiple Planets.
-// The Planets take ownership of the sun, indicating that they revolve around the sun.
-
-// Make this code compile by using the proper Rc primitives to express that the sun has multiple owners.
+//
+// In this exercise, we want to express the concept of multiple owners via the
+// Rc<T> type. This is a model of our solar system - there is a Sun type and
+// multiple Planets. The Planets take ownership of the sun, indicating that they
+// revolve around the sun.
+//
+// Make this code compile by using the proper Rc primitives to express that the
+// sun has multiple owners.
+//
+// Execute `rustlings hint rc1` or use the `hint` watch subcommand for a hint.

 // I AM NOT DONE

@ -30,6 +35,7 @@ impl Planet {
    }
 }

+#[test]
 fn main() {
    let sun = Rc::new(Sun {});
    println!("reference count = {}", Rc::strong_count(&sun)); // 1 reference
--- a/exercises/strings/strings1.rs
+++ b/exercises/strings/strings1.rs
@ -1,6 +1,9 @@
 // strings1.rs
+//
 // Make me compile without changing the function signature!
-// Execute `rustlings hint strings1` or use the `hint` watch subcommand for a hint.
+//
+// Execute `rustlings hint strings1` or use the `hint` watch subcommand for a
+// hint.

 // I AM NOT DONE

--- a/exercises/strings/strings2.rs
+++ b/exercises/strings/strings2.rs
@ -1,6 +1,9 @@
 // strings2.rs
+//
 // Make me compile without changing the function signature!
-// Execute `rustlings hint strings2` or use the `hint` watch subcommand for a hint.
+//
+// Execute `rustlings hint strings2` or use the `hint` watch subcommand for a
+// hint.

 // I AM NOT DONE

--- a/exercises/strings/strings3.rs
+++ b/exercises/strings/strings3.rs
@ -1,5 +1,7 @@
 // strings3.rs
-// Execute `rustlings hint strings3` or use the `hint` watch subcommand for a hint.
+//
+// Execute `rustlings hint strings3` or use the `hint` watch subcommand for a
+// hint.

 // I AM NOT DONE

--- a/exercises/strings/strings4.rs
+++ b/exercises/strings/strings4.rs
@ -1,9 +1,10 @@
 // strings4.rs
-
+//
 // Ok, here are a bunch of values-- some are `String`s, some are `&str`s. Your
 // task is to call one of these two functions on each value depending on what
 // you think each value is. That is, add either `string_slice` or `string`
 // before the parentheses on each line. If you're right, it will compile!
+//
 // No hints this time!

 // I AM NOT DONE
--- a/exercises/structs/structs1.rs
+++ b/exercises/structs/structs1.rs
@ -1,6 +1,9 @@
 // structs1.rs
+//
 // Address all the TODOs to make the tests pass!
-// Execute `rustlings hint structs1` or use the `hint` watch subcommand for a hint.
+//
+// Execute `rustlings hint structs1` or use the `hint` watch subcommand for a
+// hint.

 // I AM NOT DONE

--- a/exercises/structs/structs2.rs
+++ b/exercises/structs/structs2.rs
@ -1,6 +1,9 @@
 // structs2.rs
+//
 // Address all the TODOs to make the tests pass!
-// Execute `rustlings hint structs2` or use the `hint` watch subcommand for a hint.
+//
+// Execute `rustlings hint structs2` or use the `hint` watch subcommand for a
+// hint.

 // I AM NOT DONE

--- a/exercises/structs/structs3.rs
+++ b/exercises/structs/structs3.rs
@ -1,8 +1,11 @@
 // structs3.rs
+//
 // Structs contain data, but can also have logic. In this exercise we have
 // defined the Package struct and we want to test some logic attached to it.
 // Make the code compile and the tests pass!
-// Execute `rustlings hint structs3` or use the `hint` watch subcommand for a hint.
+//
+// Execute `rustlings hint structs3` or use the `hint` watch subcommand for a
+// hint.

 // I AM NOT DONE

@ -10,13 +13,15 @@
 struct Package {
    sender_country: String,
    recipient_country: String,
-    weight_in_grams: i32,
+    weight_in_grams: u32,
 }

 impl Package {
-    fn new(sender_country: String, recipient_country: String, weight_in_grams: i32) -> Package {
-        if weight_in_grams <= 0 {
-            panic!("Can not ship a weightless package.")
+    fn new(sender_country: String, recipient_country: String, weight_in_grams: u32) -> Package {
+        if weight_in_grams < 10 {
+            // This is not how you should handle errors in Rust,
+            // but we will learn about error handling later.
+            panic!("Can not ship a package with weight below 10 grams.")
        } else {
            Package {
                sender_country,
@ -30,7 +35,7 @@ impl Package {
        // Something goes here...
    }

-    fn get_fees(&self, cents_per_gram: i32) -> ??? {
+    fn get_fees(&self, cents_per_gram: u32) -> ??? {
        // Something goes here...
    }
 }
@ -45,7 +50,7 @@ mod tests {
        let sender_country = String::from("Spain");
        let recipient_country = String::from("Austria");

-        Package::new(sender_country, recipient_country, -2210);
+        Package::new(sender_country, recipient_country, 5);
    }

    #[test]
--- a/exercises/tests/tests1.rs
+++ b/exercises/tests/tests1.rs
@ -1,11 +1,14 @@
 // tests1.rs
-// Tests are important to ensure that your code does what you think it should do.
-// Tests can be run on this file with the following command:
-// rustlings run tests1
-
-// This test has a problem with it -- make the test compile! Make the test
-// pass! Make the test fail!
-// Execute `rustlings hint tests1` or use the `hint` watch subcommand for a hint.
+//
+// Tests are important to ensure that your code does what you think it should
+// do. Tests can be run on this file with the following command: rustlings run
+// tests1
+//
+// This test has a problem with it -- make the test compile! Make the test pass!
+// Make the test fail!
+//
+// Execute `rustlings hint tests1` or use the `hint` watch subcommand for a
+// hint.

 // I AM NOT DONE

--- a/exercises/tests/tests2.rs
+++ b/exercises/tests/tests2.rs
@ -1,7 +1,10 @@
 // tests2.rs
-// This test has a problem with it -- make the test compile! Make the test
-// pass! Make the test fail!
-// Execute `rustlings hint tests2` or use the `hint` watch subcommand for a hint.
+//
+// This test has a problem with it -- make the test compile! Make the test pass!
+// Make the test fail!
+//
+// Execute `rustlings hint tests2` or use the `hint` watch subcommand for a
+// hint.

 // I AM NOT DONE

--- a/exercises/tests/tests3.rs
+++ b/exercises/tests/tests3.rs
@ -1,8 +1,11 @@
 // tests3.rs
+//
 // This test isn't testing our function -- make it do that in such a way that
-// the test passes. Then write a second test that tests whether we get the result
-// we expect to get when we call `is_even(5)`.
-// Execute `rustlings hint tests3` or use the `hint` watch subcommand for a hint.
+// the test passes. Then write a second test that tests whether we get the
+// result we expect to get when we call `is_even(5)`.
+//
+// Execute `rustlings hint tests3` or use the `hint` watch subcommand for a
+// hint.

 // I AM NOT DONE

--- a/exercises/tests/tests4.rs
+++ b/exercises/tests/tests4.rs
@ -0,0 +1,48 @@
+// tests4.rs
+//
+// Make sure that we're testing for the correct conditions!
+//
+// Execute `rustlings hint tests4` or use the `hint` watch subcommand for a
+// hint.
+
+// I AM NOT DONE
+
+struct Rectangle {
+    width: i32,
+    height: i32
+}
+
+impl Rectangle {
+    // Only change the test functions themselves
+    pub fn new(width: i32, height: i32) -> Self {
+        if width <= 0 || height <= 0 {
+            panic!("Rectangle width and height cannot be negative!")
+        }
+        Rectangle {width, height}
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn correct_width_and_height() {
+        // This test should check if the rectangle is the size that we pass into its constructor
+        let rect = Rectangle::new(10, 20);
+        assert_eq!(???, 10); // check width
+        assert_eq!(???, 20); // check height
+    }
+
+    #[test]
+    fn negative_width() {
+        // This test should check if program panics when we try to create rectangle with negative width
+        let _rect = Rectangle::new(-10, 10);
+    }
+
+    #[test]
+    fn negative_height() {
+        // This test should check if program panics when we try to create rectangle with negative height
+        let _rect = Rectangle::new(10, -10);
+    }
+}
--- a/exercises/threads/README.md
+++ b/exercises/threads/README.md
@ -1,6 +1,6 @@
 # Threads

-In most current operating systems, an executed program’s code is run in a process, and the operating system manages multiple processes at once.
+In most current operating systems, an executed program's code is run in a process, and the operating system manages multiple processes at once.
 Within your program, you can also have independent parts that run simultaneously. The features that run these independent parts are called threads.

 ## Further information
--- a/exercises/threads/threads1.rs
+++ b/exercises/threads/threads1.rs
@ -1,10 +1,12 @@
 // threads1.rs
-// Execute `rustlings hint threads1` or use the `hint` watch subcommand for a hint.
-
-// This program spawns multiple threads that each run for at least 250ms,
-// and each thread returns how much time they took to complete.
-// The program should wait until all the spawned threads have finished and
-// should collect their return values into a vector.
+//
+// This program spawns multiple threads that each run for at least 250ms, and
+// each thread returns how much time they took to complete. The program should
+// wait until all the spawned threads have finished and should collect their
+// return values into a vector.
+//
+// Execute `rustlings hint threads1` or use the `hint` watch subcommand for a
+// hint.

 // I AM NOT DONE

@ -30,7 +32,7 @@ fn main() {
    if results.len() != 10 {
        panic!("Oh no! All the spawned threads did not finish!");
    }
-    
+
    println!();
    for (i, result) in results.into_iter().enumerate() {
        println!("thread {} took {}ms", i, result);
--- a/Show More
+++ b/Show More