Minor fixes in binary type name emitting (#4239)

Add an assert on not emitting a null name (which would cause
a crash a few lines down on trying to read its bytes). I hit that
when writing a buggy pass that updated field names.

Also fix the case of a type not having a name but some of its
fields having names. We can't test that atm since our text
format requires types to have names anyhow, so this is a
fix for a possible future where we do allow parsing non-named
types.

1 files changed, 3 insertions, 2 deletions

diff --git a/src/wasm/wasm-binary.cpp b/src/wasm/wasm-binary.cpp
index 9aa18f270..70bc738f6 100644
--- a/src/wasm/wasm-binary.cpp
+++ b/src/wasm/wasm-binary.cpp
@@ -770,7 +770,7 @@ void WasmBinaryWriter::writeNames() {
     std::vector<HeapType> namedTypes;
     for (auto& kv : typeIndices) {
       auto type = kv.first;
-      if (wasm->typeNames.count(type)) {
+      if (wasm->typeNames.count(type) && wasm->typeNames[type].name.is()) {
         namedTypes.push_back(type);
       }
     }
@@ -906,7 +906,7 @@ void WasmBinaryWriter::writeNames() {
     std::vector<HeapType> relevantTypes;
     for (auto& type : types) {
       if (type.isStruct() && wasm->typeNames.count(type) &&
-          !wasm->typeNames.at(type).fieldNames.empty()) {
+          !wasm->typeNames[type].fieldNames.empty()) {
         relevantTypes.push_back(type);
       }
     }
@@ -1194,6 +1194,7 @@ static int decodeHexNibble(char ch) {
 }
 
 void WasmBinaryWriter::writeEscapedName(const char* name) {
+  assert(name);
   if (!strpbrk(name, "\\")) {
     writeInlineString(name);
     return;