[wasm] Fix validation error for missing return statement in asm.js module.

src/typing-asm.cc

 // 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.
 
 #include "src/v8.h"
 
 #include "src/typing-asm.h"
 
 #include "src/ast/ast.h"
 #include "src/ast/scopes.h"
@@ skipping 109 matching lines @@
       RECURSE(
           VisitWithExpectation(decl->fun(), Type::Any(zone()), "UNREACHABLE"));
       if (!computed_type_->IsFunction()) {
         FAIL(decl->fun(), "function literal expected to be a function");
       }
     }
   }
 
   // Validate exports.
   ReturnStatement* stmt = fun->body()->last()->AsReturnStatement();
+  if (stmt == nullptr) {
+    FAIL(fun->body()->last(), "last statement in module is not a return");
+  }
   RECURSE(VisitWithExpectation(stmt->expression(), Type::Object(),
                                "expected object export"));
 }
 
 
 void AsmTyper::VisitVariableDeclaration(VariableDeclaration* decl) {
   Variable* var = decl->proxy()->var();
   if (var->location() != VariableLocation::PARAMETER) {
     if (GetType(var) == NULL) {
       SetType(var, Type::Any(zone()));
@@ skipping 1309 matching lines @@
 
 
 void AsmTyper::VisitRewritableAssignmentExpression(
     RewritableAssignmentExpression* expr) {
   RECURSE(Visit(expr->expression()));
 }
 
 
 }  // namespace internal
 }  // namespace v8