Auto merge of #118114 - compiler-errors:closure-kind-fnonce, r=<try>

Always make progress on `FnOnce` `ClosureKind` goals in the old solver All closures always implement `FnOnce`. IDK if this is worthwhile, but it does mean goals get flushed sooner.
rust-lang · Nov 21, 2023 · cfc4c29 · cfc4c29
2 parents 3a85a5c + 0e9241c
commit cfc4c29
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diff --git a/compiler/rustc_trait_selection/src/traits/fulfill.rs b/compiler/rustc_trait_selection/src/traits/fulfill.rs
@@ -420,7 +420,13 @@ impl<'a, 'tcx> ObligationProcessor for FulfillProcessor<'a, 'tcx> {
                                 ProcessResult::Error(CodeSelectionError(Unimplemented))
                             }
                         }
-                        None => ProcessResult::Unchanged,
+                        None => {
+                            if kind == ty::ClosureKind::FnOnce {
+                                ProcessResult::Changed(vec![])
+                            } else {
+                                ProcessResult::Unchanged
+                            }
+                        }
                     }
                 }
 

diff --git a/compiler/rustc_trait_selection/src/traits/select/mod.rs b/compiler/rustc_trait_selection/src/traits/select/mod.rs
@@ -894,7 +894,13 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                                 Ok(EvaluatedToErr)
                             }
                         }
-                        None => Ok(EvaluatedToAmbig),
+                        None => {
+                            if kind == ty::ClosureKind::FnOnce {
+                                Ok(EvaluatedToOk)
+                            } else {
+                                Ok(EvaluatedToAmbig)
+                            }
+                        }
                     }
                 }