Bug 1638446 - Change wasm start function to not pre-declare a valid r…

…ef.func index. r=lth

This was omitted from the original upstream spec-tests that changed validation to treat
the whole module environment as pre-declaring ref.func indices, and added after our
commit landed.

Differential Revision: https://phabricator.services.mozilla.com/D75989

js/src/jit-test/tests/wasm/gc/ref-func.js

@@ -105,8 +105,8 @@ assertEq(validFuncRefText('(global funcref (ref.func $referenced))', 'anyref') i
 // reference function can be forward declared via export
 assertEq(validFuncRefText('(export "referenced" (func $referenced))', 'anyref') instanceof WebAssembly.Instance, true);
 
-// reference function can be forward declared via start
-assertEq(validFuncRefText('(start $referenced)', 'anyref') instanceof WebAssembly.Instance, true);
+// reference function cannot be forward declared via start
+assertErrorMessage(() => validFuncRefText('(start $referenced)', 'anyref'), WebAssembly.CompileError, /function index is not declared in a section before the code section/);
 
 // Tests not expressible in the text format.
 

js/src/wasm/WasmValidate.cpp

@@ -2563,8 +2563,6 @@ static bool DecodeStartSection(Decoder& d, ModuleEnvironment* env) {
     return d.fail("unknown start function");
   }
 
-  env->validForRefFunc.setBit(funcIndex);
-
   const FuncType& funcType = *env->funcTypes[funcIndex];
   if (funcType.results().length() > 0) {
     return d.fail("start function must not return anything");