(DO NOT MERGE) Don't build user-type projections unnecessarily

Author: Zalathar

compiler/rustc_mir_build/src/builder/block.rs

@@ -199,10 +199,9 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                             None,
                             Some((Some(&destination), initializer_span)),
                         );
-                        this.visit_primary_bindings(
+                        this.visit_primary_bindings_only(
                             pattern,
-                            UserTypeProjections::none(),
-                            &mut |this, _, _, node, span, _, _| {
+                            |this, node, span| {
                                 this.storage_live_binding(
                                     block,
                                     node,
@@ -295,10 +294,9 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                         });
 
                         debug!("ast_block_stmts: pattern={:?}", pattern);
-                        this.visit_primary_bindings(
+                        this.visit_primary_bindings_only(
                             pattern,
-                            UserTypeProjections::none(),
-                            &mut |this, _, _, node, span, _, _| {
+                            |this, node, span| {
                                 this.storage_live_binding(
                                     block,
                                     node,

compiler/rustc_mir_build/src/builder/matches/mod.rs

@@ -849,10 +849,22 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         }
     }
 
+    pub(crate) fn visit_primary_bindings_only(
+        &mut self,
+        pattern: &Pat<'tcx>,
+        mut f: impl FnMut(&mut Self, LocalVarId, Span),
+    ) {
+        pattern.walk_always(|pat| {
+            if let PatKind::Binding { var, is_primary: true, .. } = pat.kind {
+                f(self, var, pat.span);
+            }
+        });
+    }
+
     /// Visit all of the primary bindings in a patterns, that is, visit the
     /// leftmost occurrence of each variable bound in a pattern. A variable
     /// will occur more than once in an or-pattern.
-    pub(super) fn visit_primary_bindings(
+    fn visit_primary_bindings(
         &mut self,
         pattern: &Pat<'tcx>,
         pattern_user_ty: UserTypeProjections,