[wasm][asm.js] Forbid function declaration replacing variable declaration.

BUG=673240
R=titzer@chromium.org

Review-Url: https://codereview.chromium.org/2568773002
Cr-Commit-Position: refs/heads/master@{#41638}

src/asmjs/asm-typer.cc

@@ -945,6 +945,10 @@ AsmType* AsmTyper::ExportType(VariableProxy* fun_export) {
     FAIL(fun_export, "Module export is not an asm.js function.");
   }
 
+  if (!fun_export->var()->is_function()) {
+    FAIL(fun_export, "Module exports must be function declarations.");
+  }
+
   return type;
 }
 

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

@@ -672,11 +672,16 @@ TEST(ErrorsInModuleExport) {
       {"return {'a': f()}", "must be an asm.js function name"},
       {"return {'a': f}", "Undefined identifier in asm.js module export"},
       {"function v() { a(); } return {b: d2s}", "Missing definition for forw"},
-      {"return {b: d2s, 'a': d2s_tbl}", "cannot export function tables"},
-      {"return {b: d2s, 'a': min}", "cannot export standard library"},
-      {"return {b: d2s, 'a': ffi}", "cannot export foreign functions"},
-      {"return {b: d2s, 'a': f()}", "must be an asm.js function name"},
-      {"return {b: d2s, 'a': f}", "Undefined identifier in asm.js module"},
+      {"function v() {} return {b: v, 'a': d2s_tbl}",
+       "cannot export function tables"},
+      {"function v() {} return {b: v, 'a': min}",
+       "cannot export standard library"},
+      {"function v() {} return {b: v, 'a': ffi}",
+       "cannot export foreign functions"},
+      {"function v() {} return {b: v, 'a': f()}",
+       "must be an asm.js function name"},
+      {"function v() {} return {b: v, 'a': f}",
+       "Undefined identifier in asm.js module"},
   };
 
   auto d2s_tbl = [](Zone* zone) -> iw::AsmType* {
@@ -687,17 +692,10 @@ TEST(ErrorsInModuleExport) {
     return ret;
   };
 
-  auto d2s = [](Zone* zone) -> iw::AsmType* {
-    auto* ret = iw::AsmType::Function(zone, iw::AsmType::Signed());
-    ret->AsFunctionType()->AddArgument(iw::AsmType::Double());
-    return ret;
-  };
-
   for (size_t ii = 0; ii < arraysize(kTests); ++ii) {
     const auto* test = kTests + ii;
     if (!ValidationOf(Export(test->module_export))
              ->WithGlobal(DynamicGlobal("d2s_tbl"), d2s_tbl)
-             ->WithGlobal(DynamicGlobal("d2s"), d2s)
              ->WithImport(DynamicGlobal("min"), iw::AsmTyper::kMathMin)
              ->WithImport(DynamicGlobal("ffi"), iw::AsmTyper::kFFI)
              ->WithGlobal(DynamicGlobal("I"), iw::AsmType::Int())

test/mjsunit/asm/asm-validation.js

@@ -363,3 +363,14 @@ function assertValidAsm(func) {
   assertFalse(%IsAsmWasmCode(Module));
   assertEquals(43, m.foo(3));
 })();
+
+(function TestVarHidesExport() {
+  function Module() {
+    "use asm";
+    var foo;
+    function foo() {}
+    return foo;
+  }
+  Module();
+  assertFalse(%IsAsmWasmCode(Module));
+})();