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Rollup merge of #90925 - krasimirgg:rustc_mir_build_fix, r=petrochenkov

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rustc_mir_build: reorder bindings

No functional changes intended.

I'm playing around with building compiler components using nightly rust
(2021-11-02) in a non-standard way. I encountered the following error while
trying to build rustc_mir_build:

```
error[E0597]: `wildcard` does not live long enough
    --> rust/src/nightly/compiler/rustc_mir_build/src/build/matches/mod.rs:1767:82
     |
1767 |         let mut otherwise_candidate = Candidate::new(expr_place_builder.clone(), &wildcard, false);
     |                                                                                  ^^^^^^^^^ borrowed value does not live long enough
...
1799 |     }
     |     -
     |     |
     |     `wildcard` dropped here while still borrowed
     |     borrow might be used here, when `guard_candidate` is dropped and runs the destructor for type `Candidate<'_, '_>`
     |
     = note: values in a scope are dropped in the opposite order they are defined
```

I believe this flags an issue that may become an error in the future.
Swapping the order of `wildcard` and `guard_candidate` resolves it.
This commit is contained in:
Yuki Okushi 2021-11-16 15:59:42 +09:00 committed by GitHub
commit cdc12ba5a3
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1 changed files with 1 additions and 1 deletions
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2
compiler/rustc_mir_build/src/build/matches/mod.rs
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@ -1762,8 +1762,8 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
) -> BlockAnd<()> {
let expr_span = expr.span;
let expr_place_builder = unpack!(block = self.lower_scrutinee(block, expr, expr_span));
let mut guard_candidate = Candidate::new(expr_place_builder.clone(), &pat, false);
let wildcard = Pat::wildcard_from_ty(pat.ty);
let mut guard_candidate = Candidate::new(expr_place_builder.clone(), &pat, false);
let mut otherwise_candidate = Candidate::new(expr_place_builder.clone(), &wildcard, false);
let fake_borrow_temps = self.lower_match_tree(
block,