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/function-utils.h b/src/ir/function-utils.h
index f172240e2..b1654d965 100644
--- a/src/ir/function-utils.h
+++ b/src/ir/function-utils.h
@@ -28,13 +28,13 @@ namespace FunctionUtils {
 // everything but their name (which can't be the same, in the same
 // module!) - same params, vars, body, result, etc.
 inline bool equal(Function* left, Function* right) {
-  if (left->sig != right->sig) {
+  if (left->type != right->type) {
     return false;
   }
   if (left->getNumVars() != right->getNumVars()) {
     return false;
   }
-  for (Index i = left->sig.params.size(); i < left->getNumLocals(); i++) {
+  for (Index i = left->getParams().size(); i < left->getNumLocals(); i++) {
     if (left->getLocalType(i) != right->getLocalType(i)) {
       return false;
     }