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Point at previous breaks that have the expected type

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This commit is contained in:
Esteban Küber 2023-09-22 22:17:12 +00:00
parent af68593179
commit f6d4950fee
2 changed files with 53 additions and 3 deletions
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45
compiler/rustc_hir_typeck/src/demand.rs
View File

@ -530,7 +530,7 @@ fn visit_expr(&mut self, ex: &'tcx hir::Expr<'tcx>) {
// When encountering a type error on the value of a `break`, try to point at the reason for the
// expected type.
fn annotate_loop_expected_due_to_inference(
pub fn annotate_loop_expected_due_to_inference(
&self,
err: &mut Diagnostic,
expr: &hir::Expr<'_>,
@ -540,11 +540,13 @@ fn annotate_loop_expected_due_to_inference(
return;
};
let mut parent_id = self.tcx.hir().parent_id(expr.hir_id);
let mut parent;
loop {
// Climb the HIR tree to see if the current `Expr` is part of a `break;` statement.
let Some(hir::Node::Expr(parent)) = self.tcx.hir().find(parent_id) else {
let Some(hir::Node::Expr(p)) = self.tcx.hir().find(parent_id) else {
break;
};
parent = p;
parent_id = self.tcx.hir().parent_id(parent.hir_id);
let hir::ExprKind::Break(destination, _) = parent.kind else {
continue;
@ -582,6 +584,45 @@ fn annotate_loop_expected_due_to_inference(
span,
format!("this loop is expected to be of type `{expected}`"),
);
} else {
// Locate all other `break` statements within the same `loop` that might
// have affected inference.
struct FindBreaks<'tcx> {
destination: hir::Destination,
uses: Vec<&'tcx hir::Expr<'tcx>>,
}
impl<'tcx> Visitor<'tcx> for FindBreaks<'tcx> {
fn visit_expr(&mut self, ex: &'tcx hir::Expr<'tcx>) {
if let hir::ExprKind::Break(destination, _) = ex.kind
&& self.destination.label == destination.label
{
self.uses.push(ex);
}
hir::intravisit::walk_expr(self, ex);
}
}
let mut expr_finder = FindBreaks { destination, uses: vec![] };
expr_finder.visit_expr(parent);
for ex in expr_finder.uses {
let hir::ExprKind::Break(_, val) = ex.kind else {
continue;
};
let ty = match val {
Some(val) => {
match self.typeck_results.borrow().expr_ty_adjusted_opt(val) {
None => continue,
Some(ty) => ty,
}
}
None => self.tcx.types.unit,
};
if self.can_eq(self.param_env, ty, expected) {
err.span_label(
ex.span,
format!("expected because of this `break`"),
);
}
}
}
break;
}

11
tests/ui/loops/loop-break-value.stderr
View File

@ -142,6 +142,9 @@ LL | let val: ! = loop { break break; };
error[E0308]: mismatched types
--> $DIR/loop-break-value.rs:11:19
|
LL | break "asdf";
| ------------ expected because of this `break`
LL | } else {
LL | break 123;
| ^^^ expected `&str`, found integer
@ -176,7 +179,11 @@ error[E0308]: mismatched types
--> $DIR/loop-break-value.rs:80:15
|
LL | break (break, break);
| ^^^^^^^^^^^^^^ expected `()`, found `(!, !)`
| ^-----^^-----^
| || |
| || expected because of this `break`
| |expected because of this `break`
| expected `()`, found `(!, !)`
|
= note: expected unit type `()`
found tuple `(!, !)`
@ -184,6 +191,8 @@ LL | break (break, break);
error[E0308]: mismatched types
--> $DIR/loop-break-value.rs:85:15
|
LL | break;
| ----- expected because of this `break`
LL | break 2;
| ^ expected `()`, found integer