Run AST validation on match guards correctly

Author: matthewjasper

compiler/rustc_ast_passes/src/ast_validation.rs

@@ -736,11 +736,10 @@ impl<'a> Visitor<'a> for AstValidator<'a> {
                         this.visit_expr(&arm.body);
                         this.visit_pat(&arm.pat);
                         walk_list!(this, visit_attribute, &arm.attrs);
-                        if let Some(guard) = &arm.guard && let ExprKind::Let(_, guard_expr, _) = &guard.kind {
+                        if let Some(guard) = &arm.guard {
                             this.with_let_management(None, |this, _| {
-                                this.visit_expr(guard_expr)
+                                this.visit_expr(guard)
                             });
-                            return;
                         }
                     }
                 }

compiler/rustc_mir_build/src/build/expr/as_operand.rs

@@ -118,15 +118,19 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         let category = Category::of(&expr.kind).unwrap();
         debug!(?category, ?expr.kind);
         match category {
-            Category::Constant if let NeedsTemporary::No = needs_temporary || !expr.ty.needs_drop(this.tcx, this.param_env) => {
+            Category::Constant
+                if matches!(needs_temporary, NeedsTemporary::No)
+                    || !expr.ty.needs_drop(this.tcx, this.param_env) =>
+            {
                 let constant = this.as_constant(expr);
                 block.and(Operand::Constant(Box::new(constant)))
             }
             Category::Constant | Category::Place | Category::Rvalue(..) => {
                 let operand = unpack!(block = this.as_temp(block, scope, expr, Mutability::Mut));
                 // Overwrite temp local info if we have something more interesting to record.
                 if !matches!(local_info, LocalInfo::Boring) {
-                    let decl_info = this.local_decls[operand].local_info.as_mut().assert_crate_local();
+                    let decl_info =
+                        this.local_decls[operand].local_info.as_mut().assert_crate_local();
                     if let LocalInfo::Boring | LocalInfo::BlockTailTemp(_) = **decl_info {
                         **decl_info = local_info;
                     }

tests/ui/rfc-2294-if-let-guard/feature-gate.rs

@@ -10,10 +10,12 @@ fn _if_let_guard() {
         () if (let 0 = 1) => {}
         //~^ ERROR `let` expressions in this position are unstable
         //~| ERROR expected expression, found `let` statement
+        //~| ERROR `let` expressions are not supported here
 
         () if (((let 0 = 1))) => {}
         //~^ ERROR `let` expressions in this position are unstable
         //~| ERROR expected expression, found `let` statement
+        //~| ERROR `let` expressions are not supported here
 
         () if true && let 0 = 1 => {}
         //~^ ERROR `if let` guards are experimental
@@ -26,16 +28,20 @@ fn _if_let_guard() {
         () if (let 0 = 1) && true => {}
         //~^ ERROR `let` expressions in this position are unstable
         //~| ERROR expected expression, found `let` statement
+        //~| ERROR `let` expressions are not supported here
 
         () if true && (let 0 = 1) => {}
         //~^ ERROR `let` expressions in this position are unstable
         //~| ERROR expected expression, found `let` statement
+        //~| ERROR `let` expressions are not supported here
 
         () if (let 0 = 1) && (let 0 = 1) => {}
         //~^ ERROR `let` expressions in this position are unstable
         //~| ERROR `let` expressions in this position are unstable
         //~| ERROR expected expression, found `let` statement
         //~| ERROR expected expression, found `let` statement
+        //~| ERROR `let` expressions are not supported here
+        //~| ERROR `let` expressions are not supported here
 
         () if let 0 = 1 && let 1 = 2 && (let 2 = 3 && let 3 = 4 && let 4 = 5) => {}
         //~^ ERROR `if let` guards are experimental
@@ -47,6 +53,10 @@ fn _if_let_guard() {
         //~| ERROR expected expression, found `let` statement
         //~| ERROR expected expression, found `let` statement
         //~| ERROR expected expression, found `let` statement
+        //~| ERROR `let` expressions are not supported here
+        //~| ERROR `let` expressions are not supported here
+        //~| ERROR `let` expressions are not supported here
+
 
         () if let Range { start: _, end: _ } = (true..true) && false => {}
         //~^ ERROR `if let` guards are experimental
@@ -68,9 +78,11 @@ fn _macros() {
     use_expr!((let 0 = 1 && 0 == 0));
     //~^ ERROR `let` expressions in this position are unstable
     //~| ERROR expected expression, found `let` statement
+    //~| ERROR `let` expressions are not supported here
     use_expr!((let 0 = 1));
     //~^ ERROR `let` expressions in this position are unstable
     //~| ERROR expected expression, found `let` statement
+    //~| ERROR `let` expressions are not supported here
     match () {
         #[cfg(FALSE)]
         () if let 0 = 1 => {}