[full-codegen] Introduce NestedStatement subclass for class literals.

This fixes a bug where returning from a class literal inside
a try-finally didn't restore the context properly when
entering the finally clause.

BUG=v8:4965
LOG=n

Review-Url: https://codereview.chromium.org/1952633002
Cr-Commit-Position: refs/heads/master@{#36021}

src/full-codegen/full-codegen.cc

@@ -1469,6 +1469,7 @@ void FullCodeGenerator::VisitClassLiteral(ClassLiteral* lit) {
   Comment cmnt(masm_, "[ ClassLiteral");
 
   {
+    NestedClassLiteral nested_class_literal(this, lit);
     EnterBlockScopeIfNeeded block_scope_state(
         this, lit->scope(), lit->EntryId(), lit->DeclsId(), lit->ExitId());
 

src/full-codegen/full-codegen.h

@@ -211,6 +211,23 @@ class FullCodeGenerator: public AstVisitor {
     }
   };
 
+  // A class literal expression
+  class NestedClassLiteral : public NestedStatement {
+   public:
+    NestedClassLiteral(FullCodeGenerator* codegen, ClassLiteral* lit)
+        : NestedStatement(codegen),
+          needs_context_(lit->scope() != nullptr &&
+                         lit->scope()->NeedsContext()) {}
+
+    NestedStatement* Exit(int* context_length) override {
+      if (needs_context_) ++(*context_length);
+      return previous_;
+    }
+
+   private:
+    const bool needs_context_;
+  };
+
   class DeferredCommands {
    public:
     enum Command { kReturn, kThrow, kBreak, kContinue };

test/mjsunit/es6/classes.js

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-// Flags: --allow-natives-syntax
+// Flags: --allow-natives-syntax --harmony-do-expressions
 
 (function TestBasics() {
   var C = class C {}
@@ -994,3 +994,55 @@ function testClassRestrictedProperties(C) {
   testClassRestrictedProperties(
       class extends Class { constructor() { super(); } });
 })();
+
+
+(function testReturnFromClassLiteral() {
+
+  function usingDoExpressionInBody() {
+    let x = 42;
+    let dummy = function() {x};
+    try {
+      class C {
+        dummy() {C}
+        [do {return}]() {}
+      };
+    } finally {
+      return x;
+    }
+  }
+  assertEquals(42, usingDoExpressionInBody());
+
+  function usingDoExpressionInExtends() {
+    let x = 42;
+    let dummy = function() {x};
+    try {
+      class C extends (do {return}) { dummy() {C} };
+    } finally {
+      return x;
+    }
+  }
+  assertEquals(42, usingDoExpressionInExtends());
+
+  function usingYieldInBody() {
+    function* foo() {
+      class C {
+        [yield]() {}
+      }
+    }
+    var g = foo();
+    g.next();
+    return g.return(42).value;
+  }
+  assertEquals(42, usingYieldInBody());
+
+  function usingYieldInExtends() {
+    function* foo() {
+      class C extends (yield) {};
+    }
+    var g = foo();
+    g.next();
+    return g.return(42).value;
+  }
+  assertEquals(42, usingYieldInExtends());
+
+})();