[wasm] [asm.js] Don't allow bad return types from a global constant

src/asmjs/asm-typer.cc

Index: src/asmjs/asm-typer.cc
diff --git a/src/asmjs/asm-typer.cc b/src/asmjs/asm-typer.cc
index ddc5911782c155c429079f07498a91fdf12d5354..7b24e524f54173056eb582ff086b5f0989176a5d 100644
--- a/src/asmjs/asm-typer.cc
+++ b/src/asmjs/asm-typer.cc
@@ -2713,6 +2713,10 @@ AsmType* AsmTyper::ReturnTypeAnnotations(ReturnStatement* statement) {
       FAIL(statement, "Identifier in return statement is not const.");
     }
 
+    if (!var_info->type()->IsReturnType()) {
+      FAIL(statement, "Constant in return must be signed, float, or double.");
+    }
+
     return var_info->type();
   }