Auto merge of #89576 - tom7980:issue-89275-fix, r=estebank

Prevent error reporting from outputting a recursion error if it finds an ambiguous trait impl during suggestions

Closes #89275

This fixes the compiler reporting a recursion error during another already in progress error by trying to make a conversion method suggestion and encounters ambiguous trait implementations that can convert a the original type into a type that can then be recursively converted into itself via another method in the trait.

Updated OverflowError struct to be an enum so I could differentiate between passes - it's no longer a ZST but I don't think that should be a problem as they only generate when there's an error in compiling code anyway

2 files changed, 11 insertions, 4 deletions

diff --git a/compiler/rustc_middle/src/traits/mod.rs b/compiler/rustc_middle/src/traits/mod.rs
index 88a7722c9cc..b089ae22d6d 100644
--- a/compiler/rustc_middle/src/traits/mod.rs
+++ b/compiler/rustc_middle/src/traits/mod.rs
@@ -449,6 +449,7 @@ pub enum SelectionError<'tcx> {
     TraitNotObjectSafe(DefId),
     NotConstEvaluatable(NotConstEvaluatable),
     Overflow,
+    ErrorReporting,
 }
 
 /// When performing resolution, it is typically the case that there
diff --git a/compiler/rustc_middle/src/traits/select.rs b/compiler/rustc_middle/src/traits/select.rs
index e236c4712c8..87495a2d5b3 100644
--- a/compiler/rustc_middle/src/traits/select.rs
+++ b/compiler/rustc_middle/src/traits/select.rs
@@ -261,12 +261,18 @@ impl EvaluationResult {
     }
 }
 
-/// Indicates that trait evaluation caused overflow.
+/// Indicates that trait evaluation caused overflow and in which pass.
 #[derive(Copy, Clone, Debug, PartialEq, Eq, HashStable)]
-pub struct OverflowError;
+pub enum OverflowError {
+    Cannonical,
+    ErrorReporting,
+}
 
 impl<'tcx> From<OverflowError> for SelectionError<'tcx> {
-    fn from(OverflowError: OverflowError) -> SelectionError<'tcx> {
-        SelectionError::Overflow
+    fn from(overflow_error: OverflowError) -> SelectionError<'tcx> {
+        match overflow_error {
+            OverflowError::Cannonical => SelectionError::Overflow,
+            OverflowError::ErrorReporting => SelectionError::ErrorReporting,
+        }
     }
 }