Integrate and update 'veera-sivarajan:add-letElse'

- Merge in changes from `main`, including moving the chapter.
- Merge in newly-written introduction of `let-else` in the same section
  as the `if let` discussion.
- Rewrap lines.

.git-blame-ignore-revs

@@ -0,0 +1,2 @@
+# Ran dprint fmt on the repo
+3a30e4c1fbe641afc066b3af9eb01dcdf5ed8b24

.github/workflows/main.yml

@@ -12,20 +12,50 @@ jobs:
     - name: Install Rust
       run: |
         rustup set profile minimal
-        rustup toolchain install 1.67 -c rust-docs
-        rustup default 1.67
+        rustup toolchain install 1.82 -c rust-docs
+        rustup default 1.82
     - name: Install mdbook
       run: |
         mkdir bin
         curl -sSL https://github.com/rust-lang/mdBook/releases/download/v0.4.21/mdbook-v0.4.21-x86_64-unknown-linux-gnu.tar.gz | tar -xz --directory=bin
-        echo "$(pwd)/bin" >> ${GITHUB_PATH}
+        echo "$(pwd)/bin" >> "${GITHUB_PATH}"
     - name: Report versions
       run: |
         rustup --version
         rustc -Vv
         mdbook --version
+
+    # mdBook does not currently have particularly good support for “external”
+    # crates. To make the test suite work correctly with `trpl`, we must first
+    # build `trpl` itself (`mdbook` will not do it), and then explicitly pass
+    # its `deps` path as a library search path for `mdbook test`. That will make
+    # sure all the crates can be resolved when running the tests.
+    - name: Build `trpl` crate
+      run: |
+        cd packages/trpl
+        cargo build
     - name: Run tests
-      run: mdbook test
+      run:
+        mdbook test --library-path packages/trpl/target/debug/deps
+  package_tests:
+    name: Run package tests
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@master
+    - name: Update rustup
+      run: rustup self update
+    - name: Install Rust
+      run: |
+        rustup set profile minimal
+        rustup toolchain install 1.82 -c rust-docs
+        rustup default 1.82
+    - name: Run `tools` package tests
+      run: |
+        cargo test
+    - name: Run `mdbook-trpl` package tests
+      working-directory: packages/mdbook-trpl
+      run: |
+        cargo test
   lint:
     name: Run lints
     runs-on: ubuntu-latest
@@ -42,7 +72,9 @@ jobs:
       run: |
         mkdir bin
         curl -sSL https://github.com/rust-lang/mdBook/releases/download/v0.4.21/mdbook-v0.4.21-x86_64-unknown-linux-gnu.tar.gz | tar -xz --directory=bin
-        echo "$(pwd)/bin" >> ${GITHUB_PATH}
+        echo "$(pwd)/bin" >> "${GITHUB_PATH}"
+    - name: Install mdbook-trpl binaries
+      run: cargo install --path packages/mdbook-trpl
     - name: Install aspell
       run: sudo apt-get install aspell
     - name: Install shellcheck
@@ -55,7 +87,7 @@ jobs:
         aspell --version
         shellcheck --version
     - name: Shellcheck
-      run: find . -name '*.sh' | xargs shellcheck
+      run: find . -name '*.sh' -print0 | xargs -0 shellcheck
     - name: Spellcheck
       run: bash ci/spellcheck.sh list
     - name: Lint for local file paths

.gitignore

@@ -5,3 +5,6 @@ book/
 target
 tmp
 
+.nova
+.vscode
+.zed

2018-edition/src/ch17-00-oop.md

@@ -3,8 +3,8 @@
 The 2018 edition of the book is no longer distributed with Rust's documentation.
 
 If you came here via a link or web search, you may want to check out [the current
-version of the book](../ch17-00-oop.html) instead.
+version of the book](../ch18-00-oop.html) instead.
 
 If you have an internet connection, you can [find a copy distributed with
 Rust
-1.30](https://doc.rust-lang.org/1.30.0/book/2018-edition/ch17-00-oop.html).
+1.30](https://doc.rust-lang.org/1.30.0/book/2018-edition/ch17-00-oop.html).

2018-edition/src/ch17-01-what-is-oo.md

@@ -3,8 +3,8 @@
 The 2018 edition of the book is no longer distributed with Rust's documentation.
 
 If you came here via a link or web search, you may want to check out [the current
-version of the book](../ch17-01-what-is-oo.html) instead.
+version of the book](../ch18-01-what-is-oo.html) instead.
 
 If you have an internet connection, you can [find a copy distributed with
 Rust
-1.30](https://doc.rust-lang.org/1.30.0/book/2018-edition/ch17-01-what-is-oo.html).
+1.30](https://doc.rust-lang.org/1.30.0/book/2018-edition/ch17-01-what-is-oo.html).

2018-edition/src/ch17-02-trait-objects.md

@@ -3,8 +3,8 @@
 The 2018 edition of the book is no longer distributed with Rust's documentation.
 
 If you came here via a link or web search, you may want to check out [the current
-version of the book](../ch17-02-trait-objects.html) instead.
+version of the book](../ch18-02-trait-objects.html) instead.
 
 If you have an internet connection, you can [find a copy distributed with
 Rust
-1.30](https://doc.rust-lang.org/1.30.0/book/2018-edition/ch17-02-trait-objects.html).
+1.30](https://doc.rust-lang.org/1.30.0/book/2018-edition/ch17-02-trait-objects.html).

2018-edition/src/ch17-03-oo-design-patterns.md

@@ -3,8 +3,8 @@
 The 2018 edition of the book is no longer distributed with Rust's documentation.
 
 If you came here via a link or web search, you may want to check out [the current
-version of the book](../ch17-03-oo-design-patterns.html) instead.
+version of the book](../ch18-03-oo-design-patterns.html) instead.
 
 If you have an internet connection, you can [find a copy distributed with
 Rust
-1.30](https://doc.rust-lang.org/1.30.0/book/2018-edition/ch17-03-oo-design-patterns.html).
+1.30](https://doc.rust-lang.org/1.30.0/book/2018-edition/ch17-03-oo-design-patterns.html).

2018-edition/src/ch18-00-patterns.md

@@ -3,8 +3,8 @@
 The 2018 edition of the book is no longer distributed with Rust's documentation.
 
 If you came here via a link or web search, you may want to check out [the current
-version of the book](../ch18-00-patterns.html) instead.
+version of the book](../ch19-00-patterns.html) instead.
 
 If you have an internet connection, you can [find a copy distributed with
 Rust
-1.30](https://doc.rust-lang.org/1.30.0/book/2018-edition/ch18-00-patterns.html).
+1.30](https://doc.rust-lang.org/1.30.0/book/2018-edition/ch18-00-patterns.html).

2018-edition/src/ch18-01-all-the-places-for-patterns.md

@@ -3,8 +3,8 @@
 The 2018 edition of the book is no longer distributed with Rust's documentation.
 
 If you came here via a link or web search, you may want to check out [the current
-version of the book](../ch18-01-all-the-places-for-patterns.html) instead.
+version of the book](../ch19-01-all-the-places-for-patterns.html) instead.
 
 If you have an internet connection, you can [find a copy distributed with
 Rust
-1.30](https://doc.rust-lang.org/1.30.0/book/2018-edition/ch18-01-all-the-places-for-patterns.html).
+1.30](https://doc.rust-lang.org/1.30.0/book/2018-edition/ch18-01-all-the-places-for-patterns.html).

2018-edition/src/ch18-02-refutability.md

@@ -3,8 +3,8 @@
 The 2018 edition of the book is no longer distributed with Rust's documentation.
 
 If you came here via a link or web search, you may want to check out [the current
-version of the book](../ch18-02-refutability.html) instead.
+version of the book](../ch19-02-refutability.html) instead.
 
 If you have an internet connection, you can [find a copy distributed with
 Rust
-1.30](https://doc.rust-lang.org/1.30.0/book/2018-edition/ch18-02-refutability.html).
+1.30](https://doc.rust-lang.org/1.30.0/book/2018-edition/ch18-02-refutability.html).

2018-edition/src/ch18-03-pattern-syntax.md

@@ -3,8 +3,8 @@
 The 2018 edition of the book is no longer distributed with Rust's documentation.
 
 If you came here via a link or web search, you may want to check out [the current
-version of the book](../ch18-03-pattern-syntax.html) instead.
+version of the book](../ch19-03-pattern-syntax.html) instead.
 
 If you have an internet connection, you can [find a copy distributed with
 Rust
-1.30](https://doc.rust-lang.org/1.30.0/book/2018-edition/ch18-03-pattern-syntax.html).
+1.30](https://doc.rust-lang.org/1.30.0/book/2018-edition/ch18-03-pattern-syntax.html).

2018-edition/src/ch19-00-advanced-features.md

@@ -3,8 +3,8 @@
 The 2018 edition of the book is no longer distributed with Rust's documentation.
 
 If you came here via a link or web search, you may want to check out [the current
-version of the book](../ch19-00-advanced-features.html) instead.
+version of the book](../ch20-00-advanced-features.html) instead.
 
 If you have an internet connection, you can [find a copy distributed with
 Rust
-1.30](https://doc.rust-lang.org/1.30.0/book/2018-edition/ch19-00-advanced-features.html).
+1.30](https://doc.rust-lang.org/1.30.0/book/2018-edition/ch19-00-advanced-features.html).

2018-edition/src/ch19-01-unsafe-rust.md

@@ -3,8 +3,8 @@
 The 2018 edition of the book is no longer distributed with Rust's documentation.
 
 If you came here via a link or web search, you may want to check out [the current
-version of the book](../ch19-01-unsafe-rust.html) instead.
+version of the book](../ch20-01-unsafe-rust.html) instead.
 
 If you have an internet connection, you can [find a copy distributed with
 Rust
-1.30](https://doc.rust-lang.org/1.30.0/book/2018-edition/ch19-01-unsafe-rust.html).
+1.30](https://doc.rust-lang.org/1.30.0/book/2018-edition/ch19-01-unsafe-rust.html).

2018-edition/src/ch19-03-advanced-traits.md

@@ -3,8 +3,8 @@
 The 2018 edition of the book is no longer distributed with Rust's documentation.
 
 If you came here via a link or web search, you may want to check out [the current
-version of the book](../ch19-03-advanced-traits.html) instead.
+version of the book](../ch20-03-advanced-traits.html) instead.
 
 If you have an internet connection, you can [find a copy distributed with
 Rust
-1.30](https://doc.rust-lang.org/1.30.0/book/2018-edition/ch19-03-advanced-traits.html).
+1.30](https://doc.rust-lang.org/1.30.0/book/2018-edition/ch19-03-advanced-traits.html).

2018-edition/src/ch19-04-advanced-types.md

@@ -3,8 +3,8 @@
 The 2018 edition of the book is no longer distributed with Rust's documentation.
 
 If you came here via a link or web search, you may want to check out [the current
-version of the book](../ch19-04-advanced-types.html) instead.
+version of the book](../ch20-04-advanced-types.html) instead.
 
 If you have an internet connection, you can [find a copy distributed with
 Rust
-1.30](https://doc.rust-lang.org/1.30.0/book/2018-edition/ch19-04-advanced-types.html).
+1.30](https://doc.rust-lang.org/1.30.0/book/2018-edition/ch19-04-advanced-types.html).

2018-edition/src/ch19-05-advanced-functions-and-closures.md

@@ -3,8 +3,8 @@
 The 2018 edition of the book is no longer distributed with Rust's documentation.
 
 If you came here via a link or web search, you may want to check out [the current
-version of the book](../ch19-05-advanced-functions-and-closures.html) instead.
+version of the book](../ch20-05-advanced-functions-and-closures.html) instead.
 
 If you have an internet connection, you can [find a copy distributed with
 Rust
-1.30](https://doc.rust-lang.org/1.30.0/book/2018-edition/ch19-05-advanced-functions-and-closures.html).
+1.30](https://doc.rust-lang.org/1.30.0/book/2018-edition/ch19-05-advanced-functions-and-closures.html).

2018-edition/src/ch19-06-macros.md

@@ -3,8 +3,8 @@
 The 2018 edition of the book is no longer distributed with Rust's documentation.
 
 If you came here via a link or web search, you may want to check out [the current
-version of the book](../ch19-06-macros.html) instead.
+version of the book](../ch20-06-macros.html) instead.
 
 If you have an internet connection, you can [find a copy distributed with
 Rust
-1.30](https://doc.rust-lang.org/1.30.0/book/2018-edition/ch19-06-macros.html).
+1.30](https://doc.rust-lang.org/1.30.0/book/2018-edition/ch19-06-macros.html).

2018-edition/src/ch20-00-final-project-a-web-server.md

@@ -3,8 +3,8 @@
 The 2018 edition of the book is no longer distributed with Rust's documentation.
 
 If you came here via a link or web search, you may want to check out [the current
-version of the book](../ch20-00-final-project-a-web-server.html) instead.
+version of the book](../ch21-00-final-project-a-web-server.html) instead.
 
 If you have an internet connection, you can [find a copy distributed with
 Rust
-1.30](https://doc.rust-lang.org/1.30.0/book/2018-edition/ch20-00-final-project-a-web-server.html).
+1.30](https://doc.rust-lang.org/1.30.0/book/2018-edition/ch20-00-final-project-a-web-server.html).

2018-edition/src/ch20-01-single-threaded.md

@@ -3,8 +3,8 @@
 The 2018 edition of the book is no longer distributed with Rust's documentation.
 
 If you came here via a link or web search, you may want to check out [the current
-version of the book](../ch20-01-single-threaded.html) instead.
+version of the book](../ch21-01-single-threaded.html) instead.
 
 If you have an internet connection, you can [find a copy distributed with
 Rust
-1.30](https://doc.rust-lang.org/1.30.0/book/2018-edition/ch20-01-single-threaded.html).
+1.30](https://doc.rust-lang.org/1.30.0/book/2018-edition/ch20-01-single-threaded.html).

2018-edition/src/ch20-02-multithreaded.md

@@ -3,8 +3,8 @@
 The 2018 edition of the book is no longer distributed with Rust's documentation.
 
 If you came here via a link or web search, you may want to check out [the current
-version of the book](../ch20-02-multithreaded.html) instead.
+version of the book](../ch21-02-multithreaded.html) instead.
 
 If you have an internet connection, you can [find a copy distributed with
 Rust
-1.30](https://doc.rust-lang.org/1.30.0/book/2018-edition/ch20-02-multithreaded.html).
+1.30](https://doc.rust-lang.org/1.30.0/book/2018-edition/ch20-02-multithreaded.html).

2018-edition/src/ch20-03-graceful-shutdown-and-cleanup.md

@@ -3,8 +3,8 @@
 The 2018 edition of the book is no longer distributed with Rust's documentation.
 
 If you came here via a link or web search, you may want to check out [the current
-version of the book](../ch20-03-graceful-shutdown-and-cleanup.html) instead.
+version of the book](../ch21-03-graceful-shutdown-and-cleanup.html) instead.
 
 If you have an internet connection, you can [find a copy distributed with
 Rust
-1.30](https://doc.rust-lang.org/1.30.0/book/2018-edition/ch20-03-graceful-shutdown-and-cleanup.html).
+1.30](https://doc.rust-lang.org/1.30.0/book/2018-edition/ch20-03-graceful-shutdown-and-cleanup.html).