[GC] Update br_on_cast: the text format also no longer has a heap type (#3523)

As a result, we cannot handle a br_on_cast with an unreachable RTT. The
binary format solves the problem by ignoring unreachable code, and this makes
the text format do the same.

A nice benefit of this is that we can remove the castType extra field.

1 files changed, 6 insertions, 9 deletions

diff --git a/src/wasm/wasm-validator.cpp b/src/wasm/wasm-validator.cpp
index 8def0e529..c6d0d9fe7 100644
--- a/src/wasm/wasm-validator.cpp
+++ b/src/wasm/wasm-validator.cpp
@@ -2215,15 +2215,12 @@ void FunctionValidator::visitBrOnCast(BrOnCast* curr) {
     shouldBeTrue(
       curr->ref->type.isRef(), curr, "br_on_cast ref must have ref type");
   }
-  if (curr->rtt->type != Type::unreachable) {
-    shouldBeTrue(
-      curr->rtt->type.isRtt(), curr, "br_on_cast rtt must have rtt type");
-    shouldBeEqual(curr->rtt->type.getHeapType(),
-                  curr->castType.getHeapType(),
-                  curr,
-                  "br_on_cast rtt must have the proper heap type");
-    noteBreak(curr->name, curr->castType, curr);
-  }
+  // Note that an unreachable rtt is not supported: the text and binary formats
+  // do not provide the type, so if it's unreachable we should not even create
+  // a br_on_cast in such a case, as we'd have no idea what it casts to.
+  shouldBeTrue(
+    curr->rtt->type.isRtt(), curr, "br_on_cast rtt must have rtt type");
+  noteBreak(curr->name, curr->getCastType(), curr);
 }
 
 void FunctionValidator::visitRttCanon(RttCanon* curr) {