Restore cyclic closure message

compiler/rustc_hir_typeck/src/closure.rs

@@ -227,7 +227,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 );
                 // Make sure that we didn't infer a signature that mentions itself.
                 // This can happen when we elaborate certain supertrait bounds that
-                // mention projections containing the `Self` type. See 
+                // mention projections containing the `Self` type. See #105401.
                 struct MentionsTy<'tcx> {
                     expected_ty: Ty<'tcx>,
                 }

compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs

@@ -33,7 +33,7 @@ use rustc_infer::infer::error_reporting::TypeErrCtxt;
 use rustc_infer::infer::{InferOk, TypeTrace};
 use rustc_middle::traits::select::OverflowError;
 use rustc_middle::ty::abstract_const::NotConstEvaluatable;
-use rustc_middle::ty::error::ExpectedFound;
+use rustc_middle::ty::error::{ExpectedFound, TypeError};
 use rustc_middle::ty::fold::{TypeFolder, TypeSuperFoldable};
 use rustc_middle::ty::print::{with_forced_trimmed_paths, FmtPrinter, Print};
 use rustc_middle::ty::{
@@ -1215,6 +1215,25 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
                 }
             }
 
+            OutputTypeParameterMismatch(
+                found_trait_ref,
+                expected_trait_ref,
+                terr @ TypeError::CyclicTy(_),
+            ) => {
+                let self_ty = found_trait_ref.self_ty().skip_binder();
+                let (cause, terr) = if let ty::Closure(def_id, _) = self_ty.kind() {
+                    (
+                        ObligationCause::dummy_with_span(tcx.def_span(def_id)),
+                        TypeError::CyclicTy(self_ty),
+                    )
+                } else {
+                    (obligation.cause.clone(), terr)
+                };
+                self.report_and_explain_type_error(
+                    TypeTrace::poly_trait_refs(&cause, true, expected_trait_ref, found_trait_ref),
+                    terr,
+                )
+            }
             OutputTypeParameterMismatch(found_trait_ref, expected_trait_ref, _) => {
                 let found_trait_ref = self.resolve_vars_if_possible(found_trait_ref);
                 let expected_trait_ref = self.resolve_vars_if_possible(expected_trait_ref);

src/test/ui/issues/issue-25439.stderr

@@ -1,13 +1,13 @@
-error[E0631]: type mismatch in closure arguments
+error[E0644]: closure/generator type that references itself
-  --> $DIR/issue-25439.rs:8:5
+  --> $DIR/issue-25439.rs:8:9
    |
 LL |     fix(|_, x| x);
-   |     ^^^ ------ found signature defined here
+   |         ^^^^^^ cyclic type of infinite size
-   |     |
-   |     expected due to this
    |
-   = note: expected closure signature `for<'a> fn(Helper<'a, [closure@$DIR/issue-25439.rs:8:9: 8:15]>, i32) -> _`
+   = note: closures cannot capture themselves or take themselves as argument;
-              found closure signature `fn(_, _) -> _`
+           this error may be the result of a recent compiler bug-fix,
+           see issue #46062 <https://github.com/rust-lang/rust/issues/46062>
+           for more information
 note: required by a bound in `fix`
   --> $DIR/issue-25439.rs:3:33
    |
@@ -16,4 +16,4 @@ LL | fn fix<F>(f: F) -> i32 where F: Fn(Helper<F>, i32) -> i32 {
 
 error: aborting due to previous error
 
-For more information about this error, try `rustc --explain E0631`.
+For more information about this error, try `rustc --explain E0644`.

src/test/ui/unboxed-closures/unboxed-closure-no-cyclic-sig.stderr

@@ -1,13 +1,13 @@
-error[E0631]: type mismatch in closure arguments
+error[E0644]: closure/generator type that references itself
-  --> $DIR/unboxed-closure-no-cyclic-sig.rs:8:5
+  --> $DIR/unboxed-closure-no-cyclic-sig.rs:8:7
    |
 LL |     g(|_| {  });
-   |     ^ --- found signature defined here
+   |       ^^^ cyclic type of infinite size
-   |     |
-   |     expected due to this
    |
-   = note: expected closure signature `fn(Option<[closure@$DIR/unboxed-closure-no-cyclic-sig.rs:8:7: 8:10]>) -> _`
+   = note: closures cannot capture themselves or take themselves as argument;
-              found closure signature `fn(_) -> _`
+           this error may be the result of a recent compiler bug-fix,
+           see issue #46062 <https://github.com/rust-lang/rust/issues/46062>
+           for more information
 note: required by a bound in `g`
   --> $DIR/unboxed-closure-no-cyclic-sig.rs:5:24
    |
@@ -16,4 +16,4 @@ LL | fn g<F>(_: F) where F: FnOnce(Option<F>) {}
 
 error: aborting due to previous error
 
-For more information about this error, try `rustc --explain E0631`.
+For more information about this error, try `rustc --explain E0644`.