Implement Guard Patterns

[max-niederman]

Work-in-progress implementation of RFC 3637; not ready for review.
See the tracking issue for more info.

[rustbot]

r? @nnethercote

rustbot has assigned @nnethercote.
They will have a look at your PR within the next two weeks and either review your PR or reassign to another reviewer.

Use r? to explicitly pick a reviewer

[max-niederman]

@rustbot label +S-waiting-on-author -S-waiting-on-review

[bors]

☔ The latest upstream changes (presumably #123877) made this pull request unmergeable. Please resolve the merge conflicts.

[bors]

☔ The latest upstream changes (presumably #130724) made this pull request unmergeable. Please resolve the merge conflicts.

[rust-log-analyzer]

The job mingw-check failed! Check out the build log: (web) (plain)

Click to see the possible cause of the failure (guessed by this bot)

#16 2.922 Building wheels for collected packages: reuse
#16 2.923   Building wheel for reuse (pyproject.toml): started
#16 3.171   Building wheel for reuse (pyproject.toml): finished with status 'done'
#16 3.172   Created wheel for reuse: filename=reuse-4.0.3-cp310-cp310-manylinux_2_35_x86_64.whl size=132715 sha256=dfa09868353292d98f811d3efdb0d54d07389e808efc71d68e3b93c514bf8bec
#16 3.172   Stored in directory: /tmp/pip-ephem-wheel-cache-3p7zhjm0/wheels/3d/8d/0a/e0fc6aba4494b28a967ab5eaf951c121d9c677958714e34532
#16 3.175 Installing collected packages: boolean-py, binaryornot, tomlkit, reuse, python-debian, markupsafe, license-expression, jinja2, chardet, attrs
#16 3.565 Successfully installed attrs-23.2.0 binaryornot-0.4.4 boolean-py-4.0 chardet-5.2.0 jinja2-3.1.4 license-expression-30.3.0 markupsafe-2.1.5 python-debian-0.1.49 reuse-4.0.3 tomlkit-0.13.0
#16 3.565 WARNING: Running pip as the 'root' user can result in broken permissions and conflicting behaviour with the system package manager. It is recommended to use a virtual environment instead: https://pip.pypa.io/warnings/venv
#16 DONE 3.7s
---
    Checking rustc_codegen_llvm v0.0.0 (/checkout/compiler/rustc_codegen_llvm)
    Checking rustc_borrowck v0.0.0 (/checkout/compiler/rustc_borrowck)
    Checking rustc_passes v0.0.0 (/checkout/compiler/rustc_passes)
    Checking rustc_hir_typeck v0.0.0 (/checkout/compiler/rustc_hir_typeck)
error[E0004]: non-exhaustive patterns: `rustc_hir::PatKind::Guard(_, _)` not covered
     |
409  |         match pat.kind {
409  |         match pat.kind {
     |               ^^^^^^^^ pattern `rustc_hir::PatKind::Guard(_, _)` not covered
note: `rustc_hir::PatKind<'_>` defined here
    --> /checkout/compiler/rustc_hir/src/hir.rs:1280:1
     |
     |
1280 | pub enum PatKind<'hir> {
...
...
1327 |     Guard(&'hir Pat<'hir>, &'hir Expr<'hir>),
     = note: the matched value is of type `rustc_hir::PatKind<'_>`
help: ensure that all possible cases are being handled by adding a match arm with a wildcard pattern or an explicit pattern as shown
     |
441  ~             | hir::PatKind::Err(_) => true,
441  ~             | hir::PatKind::Err(_) => true,
442  ~             rustc_hir::PatKind::Guard(_, _) => todo!(),

For more information about this error, try `rustc --explain E0004`.
error: could not compile `rustc_hir_typeck` (lib) due to 1 previous error
warning: build failed, waiting for other jobs to finish...