Restrict recursive opaque type check

compiler/rustc_hir_typeck/src/writeback.rs

@@ -3,21 +3,19 @@
 // substitutions.
 
 use crate::FnCtxt;
-use hir::def_id::LocalDefId;
 use rustc_data_structures::unord::ExtendUnord;
 use rustc_errors::{ErrorGuaranteed, StashKey};
 use rustc_hir as hir;
 use rustc_hir::intravisit::{self, Visitor};
 use rustc_infer::infer::error_reporting::TypeAnnotationNeeded::E0282;
 use rustc_middle::ty::adjustment::{Adjust, Adjustment, PointerCoercion};
 use rustc_middle::ty::fold::{TypeFoldable, TypeFolder, TypeSuperFoldable};
-use rustc_middle::ty::visit::{TypeSuperVisitable, TypeVisitable, TypeVisitableExt};
+use rustc_middle::ty::visit::TypeVisitableExt;
 use rustc_middle::ty::{self, Ty, TyCtxt};
 use rustc_span::symbol::sym;
 use rustc_span::Span;
 
 use std::mem;
-use std::ops::ControlFlow;
 
 ///////////////////////////////////////////////////////////////////////////
 // Entry point
@@ -565,23 +563,9 @@ impl<'cx, 'tcx> WritebackCx<'cx, 'tcx> {
             let hidden_type = self.resolve(decl.hidden_type, &decl.hidden_type.span);
             let opaque_type_key = self.resolve(opaque_type_key, &decl.hidden_type.span);
 
-            struct RecursionChecker {
-                def_id: LocalDefId,
-            }
-            impl<'tcx> ty::TypeVisitor<TyCtxt<'tcx>> for RecursionChecker {
-                type BreakTy = ();
-                fn visit_ty(&mut self, t: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
-                    if let ty::Alias(ty::Opaque, ty::AliasTy { def_id, .. }) = *t.kind() {
-                        if def_id == self.def_id.to_def_id() {
-                            return ControlFlow::Break(());
-                        }
-                    }
-                    t.super_visit_with(self)
-                }
-            }
-            if hidden_type
-                .visit_with(&mut RecursionChecker { def_id: opaque_type_key.def_id })
-                .is_break()
+            if let ty::Alias(ty::Opaque, alias_ty) = hidden_type.ty.kind()
+                && alias_ty.def_id == opaque_type_key.def_id.to_def_id()
+                && alias_ty.args == opaque_type_key.args
             {
                 continue;
             }

tests/ui/type-alias-impl-trait/recursive-tait-conflicting-defn-2.rs

@@ -0,0 +1,21 @@
+// issue: 113314
+
+#![feature(type_alias_impl_trait)]
+
+type Op = impl std::fmt::Display;
+fn foo() -> Op { &"hello world" }
+
+fn transform<S>() -> impl std::fmt::Display {
+    &0usize
+}
+fn bad() -> Op {
+    transform::<Op>()
+    //~^ ERROR concrete type differs from previous defining opaque type use
+}
+
+fn main() {
+    let mut x = foo();
+    println!("{x}");
+    x = bad();
+    println!("{x}");
+}

tests/ui/type-alias-impl-trait/recursive-tait-conflicting-defn-2.stderr

@@ -0,0 +1,14 @@
+error: concrete type differs from previous defining opaque type use
+  --> $DIR/recursive-tait-conflicting-defn-2.rs:12:5
+   |
+LL |     transform::<Op>()
+   |     ^^^^^^^^^^^^^^^^^ expected `&'static &'static str`, got `impl std::fmt::Display`
+   |
+note: previous use here
+  --> $DIR/recursive-tait-conflicting-defn-2.rs:6:18
+   |
+LL | fn foo() -> Op { &"hello world" }
+   |                  ^^^^^^^^^^^^^^
+
+error: aborting due to previous error
+

tests/ui/type-alias-impl-trait/recursive-tait-conflicting-defn.rs

@@ -0,0 +1,34 @@
+// issue: 113596
+
+#![feature(type_alias_impl_trait)]
+
+trait Test {}
+
+struct A;
+
+impl Test for A {}
+
+struct B<T> {
+  inner: T,
+}
+
+impl<T: Test> Test for B<T> {}
+
+type TestImpl = impl Test;
+
+fn test() -> TestImpl {
+  A
+}
+
+fn make_option() -> Option<TestImpl> {
+  Some(test())
+}
+
+fn make_option2() -> Option<TestImpl> {
+  let inner = make_option().unwrap();
+
+  Some(B { inner })
+  //~^ ERROR concrete type differs from previous defining opaque type use
+}
+
+fn main() {}

tests/ui/type-alias-impl-trait/recursive-tait-conflicting-defn.stderr

@@ -0,0 +1,14 @@
+error: concrete type differs from previous defining opaque type use
+  --> $DIR/recursive-tait-conflicting-defn.rs:30:3
+   |
+LL |   Some(B { inner })
+   |   ^^^^^^^^^^^^^^^^^ expected `A`, got `B<TestImpl>`
+   |
+note: previous use here
+  --> $DIR/recursive-tait-conflicting-defn.rs:20:3
+   |
+LL |   A
+   |   ^
+
+error: aborting due to previous error
+