Reject lack of "use asm" marker in asm typer.

test/cctest/test-asm-validator.cc

Index: test/cctest/test-asm-validator.cc
diff --git a/test/cctest/test-asm-validator.cc b/test/cctest/test-asm-validator.cc
index 3e6bcd305a2f1f73bb99663978d42bf57daa6e77..7f3b1194ff6e19dbe0f7ea2748165e63dd77e78b 100644
--- a/test/cctest/test-asm-validator.cc
+++ b/test/cctest/test-asm-validator.cc
@@ -309,6 +309,52 @@ TEST(ValidateMinimum) {
 }
 
 
+TEST(MissingUseAsm) {
+  const char test_function[] =
+      "function foo() {\n"
+      "  function bar() {}\n"
+      "  return { bar: bar };\n"
+      "}\n";
+  v8::V8::Initialize();
+  HandleAndZoneScope handles;
+  Zone* zone = handles.main_zone();
+  ZoneVector<ExpressionTypeEntry> types(zone);
+  CHECK_EQ("asm: line 1: missing \"use asm\"\n",
+           Validate(zone, test_function, &types));
+}
+
+
+TEST(WrongUseAsm) {
+  const char test_function[] =
+      "function foo() {\n"
+      "  \"use wasm\"\n"
+      "  function bar() {}\n"
+      "  return { bar: bar };\n"
+      "}\n";
+  v8::V8::Initialize();
+  HandleAndZoneScope handles;
+  Zone* zone = handles.main_zone();
+  ZoneVector<ExpressionTypeEntry> types(zone);
+  CHECK_EQ("asm: line 1: missing \"use asm\"\n",
+           Validate(zone, test_function, &types));
+}
+
+
+TEST(MissingReturnExports) {

[aseemgarg, 2016/01/08 22:30:56]

Is this correct? Although useless, it is not clear from the spec that there has
to be a return (see the validate module section in asmjs spec). Basically for
empty module it is not clear do we write an empty return statement or no return
statement.

[bradn, 2016/01/09 01:05:53]

Actually it does seem to require a ValidateExports of the return (which I assume
requires one to exist).
I was adding this due to:
https://codereview.chromium.org/1564313003/
And the fuzzer bug that prompted it.

But now that I look at the spec, I notice that it allows for export of a single
function. I'm not sure I've ever seen a module like that before, but I will need
to look into handling that case.
I'll defer that to a future CL, as this test is still valid.

+  const char test_function[] =
+      "function foo() {\n"
+      "  \"use asm\"\n"
+      "  function bar() {}\n"
+      "}\n";
+  v8::V8::Initialize();
+  HandleAndZoneScope handles;
+  Zone* zone = handles.main_zone();
+  ZoneVector<ExpressionTypeEntry> types(zone);
+  CHECK_EQ("asm: line 2: last statement in module is not a return\n",
+           Validate(zone, test_function, &types));
+}
+
+
 #define HARNESS_STDLIB()                 \
   "var Infinity = stdlib.Infinity;\n"    \
   "var NaN = stdlib.NaN;\n"              \