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Merged
merged 2 commits into from
Oct 27, 2023
Merged

Invalid ? suggestion on mismatched Ok(T) #116968

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6c97f13
Invalid `?` suggestion on mismatched `Ok(T)`
eopb Oct 20, 2023
24cdb27
let_chainify `suggest_coercing_result_via_try_operator`
eopb Oct 22, 2023
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53 changes: 22 additions & 31 deletions compiler/rustc_hir_typeck/src/demand.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -961,38 +961,29 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
expected: Ty<'tcx>,
found: Ty<'tcx>,
) -> bool {
let ty::Adt(e, args_e) = expected.kind() else {
return false;
};
let ty::Adt(f, args_f) = found.kind() else {
return false;
};
if e.did() != f.did() {
return false;
}
if Some(e.did()) != self.tcx.get_diagnostic_item(sym::Result) {
return false;
}
let map = self.tcx.hir();
if let Some(hir::Node::Expr(expr)) = map.find_parent(expr.hir_id)
&& let hir::ExprKind::Ret(_) = expr.kind
{
// `return foo;`
} else if map.get_return_block(expr.hir_id).is_some() {
// Function's tail expression.
} else {
return false;
}
let e = args_e.type_at(1);
let f = args_f.type_at(1);
if self
.infcx
.type_implements_trait(
self.tcx.get_diagnostic_item(sym::Into).unwrap(),
[f, e],
self.param_env,
)
.must_apply_modulo_regions()
let returned = matches!(
map.find_parent(expr.hir_id),
Some(hir::Node::Expr(hir::Expr { kind: hir::ExprKind::Ret(_), .. }))
) || map.get_return_block(expr.hir_id).is_some();
if returned
&& let ty::Adt(e, args_e) = expected.kind()
&& let ty::Adt(f, args_f) = found.kind()
&& e.did() == f.did()
&& Some(e.did()) == self.tcx.get_diagnostic_item(sym::Result)
&& let e_ok = args_e.type_at(0)
&& let f_ok = args_f.type_at(0)
&& self.infcx.can_eq(self.param_env, f_ok, e_ok)
&& let e_err = args_e.type_at(1)
&& let f_err = args_f.type_at(1)
&& self
.infcx
.type_implements_trait(
self.tcx.get_diagnostic_item(sym::Into).unwrap(),
[f_err, e_err],
self.param_env,
)
.must_apply_modulo_regions()
{
err.multipart_suggestion(
"use `?` to coerce and return an appropriate `Err`, and wrap the resulting value \
Expand Down
6 changes: 6 additions & 0 deletions tests/ui/type/type-check/issue-116967-cannot-coerce-returned-result.rs
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Original file line number Diff line number Diff line change
@@ -0,0 +1,6 @@
fn foo() -> Result<String, ()> {
let out: Result<(), ()> = Ok(());
out //~ ERROR mismatched types
}

fn main() {}
15 changes: 15 additions & 0 deletions tests/ui/type/type-check/issue-116967-cannot-coerce-returned-result.stderr
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Original file line number Diff line number Diff line change
@@ -0,0 +1,15 @@
error[E0308]: mismatched types
--> $DIR/issue-116967-cannot-coerce-returned-result.rs:3:5
|
LL | fn foo() -> Result<String, ()> {
| ------------------ expected `Result<String, ()>` because of return type
LL | let out: Result<(), ()> = Ok(());
LL | out
| ^^^ expected `Result<String, ()>`, found `Result<(), ()>`
|
= note: expected enum `Result<String, _>`
found enum `Result<(), _>`

error: aborting due to previous error

For more information about this error, try `rustc --explain E0308`.