[modules] Disallow return statement in module body.

src/parsing/parser-base.h

 // Copyright 2012 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.
 
 #ifndef V8_PARSING_PARSER_BASE_H
 #define V8_PARSING_PARSER_BASE_H
 
 #include "src/ast/ast.h"
 #include "src/ast/scopes.h"
 #include "src/bailout-reason.h"
@@ skipping 4684 matching lines @@
     bool* ok) {
   // ReturnStatement ::
   //   'return' [no line terminator] Expression? ';'
 
   // Consume the return token. It is necessary to do that before
   // reporting any errors on it, because of the way errors are
   // reported (underlining).
   Expect(Token::RETURN, CHECK_OK);
   Scanner::Location loc = scanner()->location();
 
+  switch (GetDeclarationScope()->scope_type()) {
+    case SCRIPT_SCOPE:
+    case EVAL_SCOPE:
+    case MODULE_SCOPE:
+      impl()->ReportMessageAt(loc, MessageTemplate::kIllegalReturn);
+      *ok = false;
+      return impl()->NullStatement();
+    default:
+      break;
+  }
+
   Token::Value tok = peek();
   ExpressionT return_value = impl()->EmptyExpression();
   if (scanner()->HasAnyLineTerminatorBeforeNext() || tok == Token::SEMICOLON ||
       tok == Token::RBRACE || tok == Token::EOS) {
     if (IsSubclassConstructor(function_state_->kind())) {
       return_value = impl()->ThisExpression(loc.beg_pos);
     } else {
       return_value = impl()->GetLiteralUndefined(position());
     }
   } else {
     if (IsSubclassConstructor(function_state_->kind())) {
       // Because of the return code rewriting that happens in case of a subclass
       // constructor we don't want to accept tail calls, therefore we don't set
       // ReturnExprScope to kInsideValidReturnStatement here.
       return_value = ParseExpression(true, CHECK_OK);
     } else {
       ReturnExprScope maybe_allow_tail_calls(
           function_state_, ReturnExprContext::kInsideValidReturnStatement);
       return_value = ParseExpression(true, CHECK_OK);
 
       if (allow_tailcalls() && !is_sloppy(language_mode()) && !is_resumable()) {
         // ES6 14.6.1 Static Semantics: IsInTailPosition
         function_state_->AddImplicitTailCallExpression(return_value);
       }
     }
   }
   ExpectSemicolon(CHECK_OK);
   return_value = impl()->RewriteReturn(return_value, loc.beg_pos);
-
-  DeclarationScope* decl_scope = GetDeclarationScope();
-  if (decl_scope->is_script_scope() || decl_scope->is_eval_scope()) {
-    impl()->ReportMessageAt(loc, MessageTemplate::kIllegalReturn);
-    *ok = false;
-    return impl()->NullStatement();
-  }
   return factory()->NewReturnStatement(return_value, loc.beg_pos);
 }
 
 template <typename Impl>
 typename ParserBase<Impl>::StatementT ParserBase<Impl>::ParseWithStatement(
     ZoneList<const AstRawString*>* labels, bool* ok) {
   // WithStatement ::
   //   'with' '(' Expression ')' Statement
 
   Expect(Token::WITH, CHECK_OK);
@@ skipping 567 matching lines @@
     has_seen_constructor_ = true;
     return;
   }
 }
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_PARSING_PARSER_BASE_H