Auto merge of #122119 - estebank:issue-117846, r=Nadrieril

Silence unecessary !Sized binding error

When gathering locals, we introduce a `Sized` obligation for each
binding in the pattern. *After* doing so, we typecheck the init
expression. If this has a type failure, we store `{type error}`, for
both the expression and the pattern. But later we store an inference
variable for the pattern.

We now avoid any override of an existing type on a hir node when they've
already been marked as `{type error}`, and on E0277, when it comes from
`VariableType` we silence the error in support of the type error.

Fix https://github.com/rust-lang/rust/issues/117846

1 files changed, 10 insertions, 0 deletions

diff --git a/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs b/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs
index ee390d9c9f0..c472f876e66 100644
--- a/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs
+++ b/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs
@@ -2953,6 +2953,16 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                 }
             }
             ObligationCauseCode::VariableType(hir_id) => {
+                if let Some(typeck_results) = &self.typeck_results
+                    && let Some(ty) = typeck_results.node_type_opt(hir_id)
+                    && let ty::Error(_) = ty.kind()
+                {
+                    err.note(format!(
+                        "`{predicate}` isn't satisfied, but the type of this pattern is \
+                         `{{type error}}`",
+                    ));
+                    err.downgrade_to_delayed_bug();
+                }
                 match tcx.parent_hir_node(hir_id) {
                     Node::Local(hir::Local { ty: Some(ty), .. }) => {
                         err.span_suggestion_verbose(