[Asm.js] Prevents assignments to immutables.

test/cctest/asmjs/test-asm-typer.cc

 // 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.
 
 #include <cstring>
 #include <functional>
 #include <iostream>
 #include <memory>
 
 #include "src/asmjs/asm-typer.h"
@@ skipping 1923 matching lines @@
 
   for (size_t ii = 0; ii < arraysize(kTests); ++ii) {
     if (!ValidationOf(Module(kTests[ii]))
              ->FailsWithMessage("Invalid heap access index")) {
       std::cerr << "Test:\n" << kTests[ii];
       CHECK(false);
     }
   }
 }
 
+// This issue was triggered because assignments to immutable symbols (e.g., the
+// module's name, or any of the asm.js' module parameters) was not being
+// handled.
+TEST(B640194) {
+  const char* kTests[] = {
+      "function asm() {\n"
+      "  'use asm';\n"
+      "  function f() {\n"
+      "    asm = 0;\n"
+      "  }\n"
+      "  return f;\n"
+      "}",
+      "function asm(stdlib) {\n"
+      "  'use asm';\n"
+      "  function f() {\n"
+      "    stdlib = 0;\n"
+      "  }\n"
+      "  return f;\n"
+      "}",
+      "function asm(stdlib, foreign) {\n"
+      "  'use asm';\n"
+      "  function f() {\n"
+      "    foreign = 0;\n"
+      "  }\n"
+      "  return f;\n"
+      "}",
+      "function asm(stdlib, foreign, heap) {\n"
+      "  'use asm';\n"
+      "  function f() {\n"
+      "    heap = 0;\n"
+      "  }\n"
+      "  return f;\n"
+      "}",
+      "function asm(stdlib, foreign, heap) {\n"
+      "  'use asm';\n"
+      "  var f = stdlib.Math.fround;\n"
+      "  function f() {\n"
+      "    f = 0;\n"
+      "  }\n"
+      "  return f;\n"
+      "}",
+      "function asm(stdlib, foreign, heap) {\n"
+      "  'use asm';\n"
+      "  var E = stdlib.Math.E;\n"
+      "  function f() {\n"
+      "    E = 0;\n"
+      "  }\n"
+      "  return f;\n"
+      "}",
+  };
+  for (size_t ii = 0; ii < arraysize(kTests); ++ii) {
+    if (!ValidationOf(Module(kTests[ii]))
+             ->FailsWithMessage("Can't assign to immutable symbol")) {
+      std::cerr << "Test:\n" << kTests[ii];
+      CHECK(false);
+    }
+  }
+}
+
 }  // namespace