Preserve Function HeapTypes (#3952)

When using nominal types, func.ref of two functions with identical signatures
but different HeapTypes will yield different types. To preserve these semantics,
Functions need to track their HeapTypes, not just their Signatures.

This PR replaces the Signature field in Function with a HeapType field and adds
new utility methods to make it almost as simple to update and query the function
HeapType as it was to update and query the Function Signature.

1 files changed, 2 insertions, 2 deletions

diff --git a/src/ir/module-utils.h b/src/ir/module-utils.h
index 9c9f5cbfb..2cbab414b 100644
--- a/src/ir/module-utils.h
+++ b/src/ir/module-utils.h
@@ -33,7 +33,7 @@ namespace ModuleUtils {
 inline Function* copyFunction(Function* func, Module& out) {
   auto* ret = new Function();
   ret->name = func->name;
-  ret->sig = func->sig;
+  ret->type = func->type;
   ret->vars = func->vars;
   ret->localNames = func->localNames;
   ret->localIndices = func->localIndices;
@@ -526,7 +526,7 @@ inline void collectHeapTypes(Module& wasm,
   // Collect info from functions in parallel.
   ModuleUtils::ParallelFunctionAnalysis<Counts, InsertOrderedMap> analysis(
     wasm, [&](Function* func, Counts& counts) {
-      counts.note(func->sig);
+      counts.note(func->type);
       for (auto type : func->vars) {
         counts.note(type);
       }