Propagate switch statement value for 'eval'

This patch changes the switch scope desugaring to create blocks which
propagate their 'return value' for eval.

BUG=v8:4399
R=adamk
LOG=Y

Review URL: https://codereview.chromium.org/1309303006

Cr-Commit-Position: refs/heads/master@{#30454}

src/parser.cc

@@ -2987,7 +2987,7 @@ Statement* Parser::ParseSwitchStatement(ZoneList<const AstRawString*>* labels,
   // }
 
   Block* switch_block =
-      factory()->NewBlock(NULL, 2, true, RelocInfo::kNoPosition);
+      factory()->NewBlock(NULL, 2, false, RelocInfo::kNoPosition);
   int switch_pos = peek_position();
 
   Expect(Token::SWITCH, CHECK_OK);
@@ -3004,8 +3004,17 @@ Statement* Parser::ParseSwitchStatement(ZoneList<const AstRawString*>* labels,
       factory()->NewExpressionStatement(tag_assign, RelocInfo::kNoPosition);
   switch_block->AddStatement(tag_statement, zone());
 
+  // make statement: undefined;
+  // This is needed so the tag isn't returned as the value, in case the switch
+  // statements don't have a value.
+  switch_block->AddStatement(
+      factory()->NewExpressionStatement(
+          factory()->NewUndefinedLiteral(RelocInfo::kNoPosition),
+          RelocInfo::kNoPosition),
+      zone());
+
   Block* cases_block =
-      factory()->NewBlock(NULL, 1, true, RelocInfo::kNoPosition);
+      factory()->NewBlock(NULL, 1, false, RelocInfo::kNoPosition);
   Scope* cases_scope = NewScope(scope_, BLOCK_SCOPE);
   cases_scope->SetNonlinear();
 

test/cctest/test-ast-expression-visitor.cc

@@ -303,6 +303,7 @@ TEST(VisitSwitchStatment) {
         CHECK_VAR(.switch_tag, DEFAULT_TYPE);
         CHECK_EXPR(Literal, DEFAULT_TYPE);
       }
+      CHECK_EXPR(Literal, DEFAULT_TYPE);
       CHECK_VAR(.switch_tag, DEFAULT_TYPE);
       CHECK_EXPR(Literal, DEFAULT_TYPE);
     }

test/mjsunit/regress/regress-4399.js

+// Copyright 2015 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Test that switch has the appropriate 'eval' value
+
+assertEquals("foo", eval('switch(1) { case 1: "foo" }'));
+assertEquals("foo", eval('{ switch(1) { case 1: "foo" } }'));
+assertEquals("foo", eval('switch(1) { case 1: { "foo" } }'));
+assertEquals("foo", eval('switch(1) { case 1: "foo"; break; case 2: "bar"; break }'));
+assertEquals("bar", eval('switch(2) { case 1: "foo"; break; case 2: "bar"; break }'));
+assertEquals("bar", eval('switch(1) { case 1: "foo"; case 2: "bar"; break }'));
+
+// The tag is not the value, if there's no value
+
+assertEquals(undefined, eval('switch (1) {}'));
+assertEquals(undefined, eval('switch (1) { case 1: {} }'));