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Suppress suggest try wrap when found is unresolved infer #145707

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Suppress suggest try wrap when found is unresolved infer #145707

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df5a341
Add test type-mismatch-suggest-wrap-issue-145634
xizheyin Aug 21, 2025
906b6e8
Suppress suggest try wrap when found is unresolved var
xizheyin Aug 21, 2025
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9 changes: 8 additions & 1 deletion compiler/rustc_trait_selection/src/error_reporting/infer/suggest.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -11,7 +11,9 @@ use rustc_hir::{MatchSource, Node};
use rustc_middle::traits::{MatchExpressionArmCause, ObligationCause, ObligationCauseCode};
use rustc_middle::ty::error::TypeError;
use rustc_middle::ty::print::with_no_trimmed_paths;
use rustc_middle::ty::{self as ty, GenericArgKind, IsSuggestable, Ty, TypeVisitableExt};
use rustc_middle::ty::{
self as ty, GenericArgKind, IsSuggestable, Ty, TypeFlags, TypeVisitableExt,
};
use rustc_span::{Span, sym};
use tracing::debug;

Expand Down Expand Up @@ -89,6 +91,11 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
exp_found: &ty::error::ExpectedFound<Ty<'tcx>>,
diag: &mut Diag<'_>,
) {
// when found is unresolved var, we can't suggest anything
if exp_found.found.has_type_flags(TypeFlags::HAS_INFER_TY_VAR) {
Comment on lines +94 to +95
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@dianne dianne Aug 22, 2025 •
edited
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If you're checking for inference variables on the error path, would it make sense to do so in a way that doesn't require tracking them for all types on the happy path too?

I think the "found" type may also be very likely to have inference variables when it doesn't match the expected type, on account of how pattern type-checking works. The type of the constructor pattern is checked against the type of the scrutinee, without knowledge of what the constructor's type's generic arguments are; I think those are all left for type inference to handle. As such, I think something more targeted may be needed if the suggestion is to support types with generic arguments.

return;
}

// Heavily inspired by `FnCtxt::suggest_compatible_variants`, with
// some modifications due to that being in typeck and this being in infer.
if let ObligationCauseCode::Pattern { .. } = cause.code()
Expand Down
10 changes: 7 additions & 3 deletions compiler/rustc_type_ir/src/flags.rs
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Expand Up @@ -133,6 +133,9 @@ bitflags::bitflags! {

/// Does this type have any coroutines in it?
const HAS_TY_CORO = 1 << 24;

/// Does this type have any Infer(TyVar(_)) in it?
const HAS_INFER_TY_VAR = 1 << 25;
}
}

Expand Down Expand Up @@ -267,9 +270,10 @@ impl<I: Interner> FlagComputation<I> {
ty::FreshTy(_) | ty::FreshIntTy(_) | ty::FreshFloatTy(_) => {
self.add_flags(TypeFlags::HAS_TY_FRESH)
}

ty::TyVar(_) | ty::IntVar(_) | ty::FloatVar(_) => {
self.add_flags(TypeFlags::HAS_TY_INFER)
ty::IntVar(_) | ty::FloatVar(_) => self.add_flags(TypeFlags::HAS_TY_INFER),
ty::TyVar(_) => {
self.add_flags(TypeFlags::HAS_INFER_TY_VAR);
self.add_flags(TypeFlags::HAS_TY_INFER);
}
},

Expand Down
4 changes: 0 additions & 4 deletions tests/ui/issues/issue-3680.stderr
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Expand Up @@ -8,10 +8,6 @@ LL | Err(_) => ()
|
= note: expected enum `Option<_>`
found enum `Result<_, _>`
help: try wrapping the pattern in `Some`
|
LL | Some(Err(_)) => ()
| +++++ +

error: aborting due to 1 previous error

Expand Down
4 changes: 0 additions & 4 deletions tests/ui/issues/issue-5358-1.stderr
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Expand Up @@ -8,10 +8,6 @@ LL | Either::Right(_) => {}
|
= note: expected struct `S`
found enum `Either<_, _>`
help: try wrapping the pattern in `S`
|
LL | S(Either::Right(_)) => {}
| ++ +
help: you might have meant to use field `0` whose type is `Either<usize, usize>`
|
LL | match S(Either::Left(5)).0 {
Expand Down
8 changes: 0 additions & 8 deletions tests/ui/match/issue-12552.stderr
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Expand Up @@ -8,10 +8,6 @@ LL | Some(k) => match k {
|
= note: expected enum `Result<_, {integer}>`
found enum `Option<_>`
help: try wrapping the pattern in `Ok`
|
LL | Ok(Some(k)) => match k {
| +++ +

error[E0308]: mismatched types
--> $DIR/issue-12552.rs:9:5
Expand All @@ -24,10 +20,6 @@ LL | None => ()
|
= note: expected enum `Result<_, {integer}>`
found enum `Option<_>`
help: try wrapping the pattern in `Ok`
|
LL | Ok(None) => ()
| +++ +

error: aborting due to 2 previous errors

Expand Down
9 changes: 9 additions & 0 deletions tests/ui/type/type-mismatch-suggest-wrap-issue-145634.rs
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@@ -0,0 +1,9 @@
// We should not suggest wrapping rhs with `Some`
// when the found type is an unresolved type variable
//
// See https://github.com/rust-lang/rust/issues/145634

fn main() {
let foo = Some(&(1, 2));
assert!(matches!(foo, &Some((1, 2)))); //~ ERROR mismatched types [E0308]
}
14 changes: 14 additions & 0 deletions tests/ui/type/type-mismatch-suggest-wrap-issue-145634.stderr
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@@ -0,0 +1,14 @@
error[E0308]: mismatched types
--> $DIR/type-mismatch-suggest-wrap-issue-145634.rs:8:27
|
LL | assert!(matches!(foo, &Some((1, 2))));
| --- ^^^^^^^^^^^^^ expected `Option<&({integer}, {integer})>`, found `&_`
| |
| this expression has type `Option<&({integer}, {integer})>`
|
= note: expected enum `Option<&({integer}, {integer})>`
found reference `&_`

error: aborting due to 1 previous error

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