harmony-scoping: Disallow cross-script assignment to const

R=rossberg@chromium.org
BUG=v8:2198
LOG=N

Review URL: https://codereview.chromium.org/745963002

Cr-Commit-Position: refs/heads/master@{#25468}

src/hydrogen.cc

@@ -6556,6 +6556,9 @@ void HOptimizedGraphBuilder::HandleGlobalVariableAssignment(
         global->native_context()->script_context_table());
     ScriptContextTable::LookupResult lookup;
     if (ScriptContextTable::Lookup(script_contexts, var->name(), &lookup)) {
+      if (lookup.mode == CONST) {
+        return Bailout(kNonInitializerAssignmentToConst);
+      }
       Handle<Context> script_context =
           ScriptContextTable::GetContext(script_contexts, lookup.context_index);
       HStoreNamedField* instr = Add<HStoreNamedField>(

test/cctest/test-decls.cc

@@ -1136,3 +1136,26 @@ TEST(CrossScriptStoreICs) {
                   Number::New(CcTest::isolate(), 20));
   }
 }
+
+
+TEST(CrossScriptAssignmentToConst) {
+  i::FLAG_harmony_scoping = true;
+  i::FLAG_allow_natives_syntax = true;
+
+  HandleScope handle_scope(CcTest::isolate());
+
+  {
+    SimpleContext context;
+
+    context.Check("function f() { x = 27; }", EXPECT_RESULT,
+                  Undefined(CcTest::isolate()));
+    context.Check("'use strict';const x = 1; x", EXPECT_RESULT,
+                  Number::New(CcTest::isolate(), 1));
+    context.Check("f();", EXPECT_EXCEPTION);
+    context.Check("x", EXPECT_RESULT, Number::New(CcTest::isolate(), 1));
+    context.Check("f();", EXPECT_EXCEPTION);
+    context.Check("x", EXPECT_RESULT, Number::New(CcTest::isolate(), 1));
+    context.Check("%OptimizeFunctionOnNextCall(f);f();", EXPECT_EXCEPTION);
+    context.Check("x", EXPECT_RESULT, Number::New(CcTest::isolate(), 1));
+  }
+}