bjoernager/rust
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Rollup merge of #100338 - lyming2007:issue-100285-fix, r=petrochenkov

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when there are 3 or more return statements in the loop

emit the first 3 errors and duplicated diagnostic information
	modified:   compiler/rustc_typeck/src/check/coercion.rs
	new file:   src/test/ui/typeck/issue-100285.rs
	new file:   src/test/ui/typeck/issue-100285.stderr
This commit is contained in:
Matthias Krüger 2022-08-16 06:05:55 +02:00 • committed by GitHub
commit 836f706d9a
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3 changed files with 65 additions and 1 deletions
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10
compiler/rustc_typeck/src/check/coercion.rs
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@ -1594,7 +1594,9 @@ impl<'tcx, 'exprs, E: AsCoercionSite> CoerceMany<'tcx, 'exprs, E> {
let hir::ExprKind::Loop(_, _, _, loop_span) = expr.kind else { return;};
let mut span: MultiSpan = vec![loop_span].into();
span.push_span_label(loop_span, "this might have zero elements to iterate on");
for ret_expr in ret_exprs {
const MAXITER: usize = 3;
let iter = ret_exprs.iter().take(MAXITER);
for ret_expr in iter {
span.push_span_label(
ret_expr.span,
"if the loop doesn't execute, this value would never get returned",
@ -1604,6 +1606,12 @@ impl<'tcx, 'exprs, E: AsCoercionSite> CoerceMany<'tcx, 'exprs, E> {
span,
"the function expects a value to always be returned, but loops might run zero times",
);
if MAXITER < ret_exprs.len() {
err.note(&format!(
"if the loop doesn't execute, {} other values would never get returned",
ret_exprs.len() - MAXITER
));
}
err.help(
"return a value for the case when the loop has zero elements to iterate on, or \
consider changing the return type to account for that possibility",