[wasm] throw in case of assignment to module parameters

src/asmjs/typing-asm.cc

Index: src/asmjs/typing-asm.cc
diff --git a/src/asmjs/typing-asm.cc b/src/asmjs/typing-asm.cc
index f3a4ad82ce9e2856654c770f794cec6e2657f0f0..01db88aa94ad0acdab6a9d776a97fcf0084a9357 100644
--- a/src/asmjs/typing-asm.cc
+++ b/src/asmjs/typing-asm.cc
@@ -675,6 +675,9 @@ void AsmTyper::VisitAssignment(Assignment* expr) {
     }
     expected_type_ = target_type;
     Variable* var = proxy->var();
+    if (!in_function_ && var->IsParameter()) {
+      FAIL(expr, "assignment to module parameter");
+    }
     VariableInfo* info = GetVariableInfo(var);
     if (info == nullptr || info->type == nullptr) {
       if (var->mode() == TEMPORARY) {