[modules] Never do lazy parsing in modules.

If we want to allow this in the future, we must force context-allocation for all
variables that are declared at the module level but not MODULE-allocated.

R=adamk@chromium.org
BUG=v8:1569

Review-Url: https://codereview.chromium.org/2373573003
Cr-Commit-Position: refs/heads/master@{#39745}

src/parsing/parser.cc

@@ -768,6 +768,10 @@ FunctionLiteral* Parser::DoParseProgram(ParseInfo* info) {
     } else if (info->is_module()) {
       DCHECK_EQ(outer, info->script_scope());
       outer = NewModuleScope(info->script_scope());
+      // Never do lazy parsing in modules.  If we want to support this in the
+      // future, we must force context-allocation for all variables that are
+      // declared at the module level but not MODULE-allocated.
+      parsing_mode = PARSE_EAGERLY;
     }
 
     DeclarationScope* scope = outer->AsDeclarationScope();

test/mjsunit/modules-preparse.js

+// Copyright 2016 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.
+//
+// MODULE
+// Flags: --min-preparse-length=0
+
+let foo = 42;
+function testFoo(x) { assertEquals(x, foo); }
+testFoo(42);
+foo++;
+testFoo(43);