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compiler/rustc_typeck/src/expr_use_visitor.rs

@@ -29,6 +29,10 @@ pub trait Delegate<'tcx> {
     // The value found at `place` is moved, depending
     // on `mode`. Where `diag_expr_id` is the id used for diagnostics for `place`.
     //
+    // Use of a `Copy` type in a ByValue context is considered a use
+    // by `ImmBorrow` and `borrow` is called instead.
+    //
+    //
     // The parameter `diag_expr_id` indicates the HIR id that ought to be used for
     // diagnostics. Around pattern matching such as `let pat = expr`, the diagnostic
     // id will be the id of the expression `expr` but the place itself will have
@@ -134,16 +138,7 @@ impl<'a, 'tcx> ExprUseVisitor<'a, 'tcx> {
     }
 
     fn delegate_consume(&mut self, place_with_id: &PlaceWithHirId<'tcx>, diag_expr_id: hir::HirId) {
-        debug!("delegate_consume(place_with_id={:?})", place_with_id);
-
-        let mode = copy_or_move(&self.mc, place_with_id);
-
-        match mode {
-            ConsumeMode::Move => self.delegate.consume(place_with_id, diag_expr_id),
-            ConsumeMode::Copy => {
-                self.delegate.borrow(place_with_id, diag_expr_id, ty::BorrowKind::ImmBorrow)
-            }
-        }
+        delegate_consume(&self.mc, self.delegate, place_with_id, diag_expr_id)
     }
 
     fn consume_exprs(&mut self, exprs: &[hir::Expr<'_>]) {
@@ -653,15 +648,7 @@ impl<'a, 'tcx> ExprUseVisitor<'a, 'tcx> {
                         }
                         ty::BindByValue(..) => {
                             debug!("walk_pat binding consuming pat");
-                            let mode = copy_or_move(mc, &place);
-                            match mode {
-                                ConsumeMode::Move => delegate.consume(place, discr_place.hir_id),
-                                ConsumeMode::Copy => delegate.borrow(
-                                    place,
-                                    discr_place.hir_id,
-                                    ty::BorrowKind::ImmBorrow,
-                                ),
-                            }
+                            delegate_consume(mc, *delegate, place, discr_place.hir_id);
                         }
                     }
                 }
@@ -808,3 +795,23 @@ fn copy_or_move<'a, 'tcx>(
         ConsumeMode::Copy
     }
 }
+
+// - If a place is used in a `ByValue` context then move it if it's not a `Copy` type.
+// - If the place that is a `Copy` type consider it a `ImmBorrow`.
+fn delegate_consume<'a, 'tcx>(
+    mc: &mc::MemCategorizationContext<'a, 'tcx>,
+    delegate: &mut (dyn Delegate<'tcx> + 'a),
+    place_with_id: &PlaceWithHirId<'tcx>,
+    diag_expr_id: hir::HirId,
+) {
+    debug!("delegate_consume(place_with_id={:?})", place_with_id);
+
+    let mode = copy_or_move(&mc, place_with_id);
+
+    match mode {
+        ConsumeMode::Move => delegate.consume(place_with_id, diag_expr_id),
+        ConsumeMode::Copy => {
+            delegate.borrow(place_with_id, diag_expr_id, ty::BorrowKind::ImmBorrow)
+        }
+    }
+}