From ac5aa8c1a4370b34674d18ef20b642645d2172e0 Mon Sep 17 00:00:00 2001
From: Michael Goulet <michael@errs.io>
Date: Mon, 25 Sep 2023 18:57:12 +0000
Subject: [PATCH] Don't suggest nonsense suggestions for unconstrained type
vars in note_source_of_type_mismatch_constraint
---
compiler/rustc_hir_typeck/src/demand.rs | 10 ++++++++--
.../point-at-inference-issue-116155.rs | 17 +++++++++++++++++
.../point-at-inference-issue-116155.stderr | 18 ++++++++++++++++++
3 files changed, 43 insertions(+), 2 deletions(-)
create mode 100644 tests/ui/type/type-check/point-at-inference-issue-116155.rs
create mode 100644 tests/ui/type/type-check/point-at-inference-issue-116155.stderr
diff --git a/compiler/rustc_hir_typeck/src/demand.rs b/compiler/rustc_hir_typeck/src/demand.rs
index d97691369c958..5c3f2b85966a8 100644
--- a/compiler/rustc_hir_typeck/src/demand.rs
+++ b/compiler/rustc_hir_typeck/src/demand.rs
@@ -14,7 +14,7 @@ use rustc_middle::ty::adjustment::AllowTwoPhase;
use rustc_middle::ty::error::{ExpectedFound, TypeError};
use rustc_middle::ty::fold::BottomUpFolder;
use rustc_middle::ty::print::with_no_trimmed_paths;
-use rustc_middle::ty::{self, Article, AssocItem, Ty, TypeAndMut, TypeFoldable};
+use rustc_middle::ty::{self, Article, AssocItem, Ty, TypeAndMut, TypeFoldable, TypeVisitableExt};
use rustc_span::symbol::sym;
use rustc_span::{BytePos, Span, DUMMY_SP};
use rustc_trait_selection::infer::InferCtxtExt as _;
@@ -504,12 +504,18 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
// incompatible fix at the original mismatch site.
if matches!(source, TypeMismatchSource::Ty(_))
&& let Some(ideal_method) = ideal_method
+ && let ideal_arg_ty = self.resolve_vars_if_possible(ideal_method.sig.inputs()[idx + 1])
+ // HACK(compiler-errors): We don't actually consider the implications
+ // of our inference guesses in `emit_type_mismatch_suggestions`, so
+ // only suggest things when we know our type error is precisely due to
+ // a type mismatch, and not via some projection or something. See #116155.
+ && !ideal_arg_ty.has_non_region_infer()
{
self.emit_type_mismatch_suggestions(
err,
arg_expr,
arg_ty,
- self.resolve_vars_if_possible(ideal_method.sig.inputs()[idx + 1]),
+ ideal_arg_ty,
None,
None,
);
diff --git a/tests/ui/type/type-check/point-at-inference-issue-116155.rs b/tests/ui/type/type-check/point-at-inference-issue-116155.rs
new file mode 100644
index 0000000000000..1e9942d42e867
--- /dev/null
+++ b/tests/ui/type/type-check/point-at-inference-issue-116155.rs
@@ -0,0 +1,17 @@
+struct S<T>(T);
+
+impl<T> S<T> {
+ fn new() -> Self {
+ loop {}
+ }
+
+ fn constrain<F: Fn() -> T>(&self, _f: F) {}
+}
+
+fn main() {
+ let s = S::new();
+ let c = || true;
+ s.constrain(c);
+ let _: S<usize> = s;
+ //~^ ERROR mismatched types
+}
diff --git a/tests/ui/type/type-check/point-at-inference-issue-116155.stderr b/tests/ui/type/type-check/point-at-inference-issue-116155.stderr
new file mode 100644
index 0000000000000..c8c01603cb848
--- /dev/null
+++ b/tests/ui/type/type-check/point-at-inference-issue-116155.stderr
@@ -0,0 +1,18 @@
+error[E0308]: mismatched types
+ --> $DIR/point-at-inference-issue-116155.rs:15:23
+ |
+LL | s.constrain(c);
+ | - - this argument has type `{closure@$DIR/point-at-inference-issue-116155.rs:13:13: 13:15}`...
+ | |
+ | ... which causes `s` to have type `S<bool>`
+LL | let _: S<usize> = s;
+ | -------- ^ expected `S<usize>`, found `S<bool>`
+ | |
+ | expected due to this
+ |
+ = note: expected struct `S<usize>`
+ found struct `S<bool>`
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0308`.