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Rollup merge of #71494 - flip1995:while_let_span, r=petrochenkov

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Fix span of while (let) expressions after lowering

Credit goes to @alex-700 who found this while trying to fix a suggestion in Clippy.

While `if`, `try`, `for` and `await` expressions get the span of the original expression when desugared, `while` loops got the span of the scrutinee, which lead to weird code, when building the suggestion, that randomly worked: https://github.com/rust-lang/rust-clippy/pull/5511/files#diff-df4e9d2bf840a5f2e3b580bef73da3bcR106-R108

I'm wondering, if `DesugaringKind` should get a variant `WhileLoop` and instead of using the span of the `ast::ExprKind::While` expr directly, a new span with `self.mark_span_with_reason` should be used, like it is done with `for` loops.

There was some fallout, but I think that is acceptable. If not, I need some help to find out where this can be fixed.
This commit is contained in:
Dylan DPC 2020-04-25 11:25:50 +02:00 committed by GitHub
commit 6ded356d9c
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3 changed files with 12 additions and 10 deletions
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8
src/librustc_ast_lowering/expr.rs
View File

@ -397,12 +397,8 @@ impl<'hir> LoweringContext<'_, 'hir> {
let then_arm = self.arm(then_pat, self.arena.alloc(then_expr));
// `match <scrutinee> { ... }`
let match_expr = self.expr_match(
scrutinee.span,
scrutinee,
arena_vec![self; then_arm, else_arm],
desugar,
);
let match_expr =
self.expr_match(span, scrutinee, arena_vec![self; then_arm, else_arm], desugar);
// `[opt_ident]: loop { ... }`
hir::ExprKind::Loop(self.block_expr(self.arena.alloc(match_expr)), opt_label, source)

4
src/test/mir-opt/while-storage/rustc.while_loop.PreCodegen.after.mir
View File

@ -57,7 +57,7 @@ fn while_loop(_1: bool) -> () {
bb5: {
StorageDead(_4); // bb5[0]: scope 0 at $DIR/while-storage.rs:14:5: 14:6
StorageDead(_2); // bb5[1]: scope 0 at $DIR/while-storage.rs:10:21: 10:22
StorageDead(_2); // bb5[1]: scope 0 at $DIR/while-storage.rs:14:5: 14:6
goto -> bb0; // bb5[2]: scope 0 at $DIR/while-storage.rs:10:5: 14:6
}
@ -74,7 +74,7 @@ fn while_loop(_1: bool) -> () {
}
bb7: {
StorageDead(_2); // bb7[0]: scope 0 at $DIR/while-storage.rs:10:21: 10:22
StorageDead(_2); // bb7[0]: scope 0 at $DIR/while-storage.rs:14:5: 14:6
return; // bb7[1]: scope 0 at $DIR/while-storage.rs:15:2: 15:2
}
}

10
src/test/ui/block-result/block-must-not-have-result-while.stderr
View File

@ -9,8 +9,14 @@ LL | while true {
error[E0308]: mismatched types
--> $DIR/block-must-not-have-result-while.rs:3:9
|
LL | true
| ^^^^ expected `()`, found `bool`
LL | / while true {
LL | | true
| | ^^^^ expected `()`, found `bool`
LL | |
LL | | }
| | -- help: consider using a semicolon here
| |_____|
| expected this to be `()`
error: aborting due to previous error; 1 warning emitted