[Wasm GC] Parse text field names even of types that end up canonicalized together (#3647)

Names of structurally identical types end up "collapsed" together after the
types are canonicalized, but with this PR we can properly read content that
has structurally identical types with different names.

2 files changed, 21 insertions, 16 deletions

diff --git a/src/wasm-s-parser.h b/src/wasm-s-parser.h
index 9fb9d4389..6ccc7c36c 100644
--- a/src/wasm-s-parser.h
+++ b/src/wasm-s-parser.h
@@ -137,6 +137,14 @@ class SExpressionWasmBuilder {
   std::map<Name, Signature> functionSignatures;
   std::unordered_map<cashew::IString, Index> debugInfoFileIndices;
 
+  // Maps type indexes to a mapping of field index => name. This is not the same
+  // as the field names stored on the wasm object, as that maps types after
+  // their canonicalization. Canonicalization loses information, which means
+  // that structurally identical types cannot have different names. However,
+  // while parsing the text format we keep this mapping of type indexes to names
+  // which does allow reading such content.
+  std::unordered_map<size_t, std::unordered_map<Index, Name>> fieldNames;
+
 public:
   // Assumes control of and modifies the input.
   SExpressionWasmBuilder(Module& wasm, Element& module, IRProfile profile);
@@ -272,7 +280,7 @@ private:
   Expression* makeRttCanon(Element& s);
   Expression* makeRttSub(Element& s);
   Expression* makeStructNew(Element& s, bool default_);
-  Index getStructIndex(const HeapType& type, Element& s);
+  Index getStructIndex(Element& type, Element& field);
   Expression* makeStructGet(Element& s, bool signed_ = false);
   Expression* makeStructSet(Element& s);
   Expression* makeArrayNew(Element& s, bool default_);
diff --git a/src/wasm/wasm-s-parser.cpp b/src/wasm/wasm-s-parser.cpp
index 0b0f3f407..3baf19063 100644
--- a/src/wasm/wasm-s-parser.cpp
+++ b/src/wasm/wasm-s-parser.cpp
@@ -786,10 +786,6 @@ void SExpressionWasmBuilder::preParseHeapTypes(Element& module) {
                      builder.getTempTupleType(results));
   };
 
-  // Maps type indexes to a mapping of field index => name. We store the data
-  // here while parsing as types have not been created yet.
-  std::unordered_map<size_t, std::unordered_map<Index, Name>> fieldNames;
-
   // Parses a field, and notes the name if one is found.
   auto parseField = [&](Element* elem, Name& name) {
     Mutability mutable_ = Immutable;
@@ -2610,27 +2606,28 @@ Expression* SExpressionWasmBuilder::makeStructNew(Element& s, bool default_) {
   return Builder(wasm).makeStructNew(rtt, operands);
 }
 
-Index SExpressionWasmBuilder::getStructIndex(const HeapType& type, Element& s) {
-  if (s.dollared()) {
-    auto name = s.str();
-    auto struct_ = type.getStruct();
+Index SExpressionWasmBuilder::getStructIndex(Element& type, Element& field) {
+  if (field.dollared()) {
+    auto name = field.str();
+    auto index = typeIndices[type.str().str];
+    auto struct_ = types[index].getStruct();
     auto& fields = struct_.fields;
-    const auto& fieldNames = wasm.typeNames[type].fieldNames;
+    const auto& names = fieldNames[index];
     for (Index i = 0; i < fields.size(); i++) {
-      auto it = fieldNames.find(i);
-      if (it != fieldNames.end() && it->second == name) {
+      auto it = names.find(i);
+      if (it != names.end() && it->second == name) {
         return i;
       }
     }
-    throw ParseException("bad struct field name", s.line, s.col);
+    throw ParseException("bad struct field name", field.line, field.col);
   }
   // this is a numeric index
-  return atoi(s.c_str());
+  return atoi(field.c_str());
 }
 
 Expression* SExpressionWasmBuilder::makeStructGet(Element& s, bool signed_) {
   auto heapType = parseHeapType(*s[1]);
-  auto index = getStructIndex(heapType, *s[2]);
+  auto index = getStructIndex(*s[1], *s[2]);
   auto type = heapType.getStruct().fields[index].type;
   auto ref = parseExpression(*s[3]);
   validateHeapTypeUsingChild(ref, heapType, s);
@@ -2639,7 +2636,7 @@ Expression* SExpressionWasmBuilder::makeStructGet(Element& s, bool signed_) {
 
 Expression* SExpressionWasmBuilder::makeStructSet(Element& s) {
   auto heapType = parseHeapType(*s[1]);
-  auto index = getStructIndex(heapType, *s[2]);
+  auto index = getStructIndex(*s[1], *s[2]);
   auto ref = parseExpression(*s[3]);
   validateHeapTypeUsingChild(ref, heapType, s);
   auto value = parseExpression(*s[4]);