8 files changed, 19 insertions, 25 deletions
diff --git a/src/passes/Print.cpp b/src/passes/Print.cpp
index 23590ebd5..371d83962 100644
--- a/src/passes/Print.cpp
+++ b/src/passes/Print.cpp
@@ -1786,8 +1786,6 @@ struct PrintExpressionContents
   void visitBrOnCast(BrOnCast* curr) {
     printMedium(o, "br_on_cast ");
     printName(curr->name, o);
-    o << " ";
-    printHeapTypeName(o, curr->getCastType().getHeapType());
   }
   void visitRttCanon(RttCanon* curr) {
     printMedium(o, "rtt.canon ");
diff --git a/src/wasm-builder.h b/src/wasm-builder.h
index 6716bca20..516d1cc15 100644
--- a/src/wasm-builder.h
+++ b/src/wasm-builder.h
@@ -709,11 +709,9 @@ public:
     ret->finalize();
     return ret;
   }
-  BrOnCast*
-  makeBrOnCast(Name name, HeapType heapType, Expression* ref, Expression* rtt) {
+  BrOnCast* makeBrOnCast(Name name, Expression* ref, Expression* rtt) {
     auto* ret = wasm.allocator.alloc<BrOnCast>();
     ret->name = name;
-    ret->castType = Type(heapType, Nullable);
     ret->ref = ref;
     ret->rtt = rtt;
     ret->finalize();
diff --git a/src/wasm-delegations-fields.h b/src/wasm-delegations-fields.h
index a39a8b7af..b0be5844c 100644
--- a/src/wasm-delegations-fields.h
+++ b/src/wasm-delegations-fields.h
@@ -591,7 +591,6 @@ switch (DELEGATE_ID) {
   case Expression::Id::BrOnCastId: {
     DELEGATE_START(BrOnCast);
     DELEGATE_FIELD_SCOPE_NAME_USE(BrOnCast, name);
-    DELEGATE_FIELD_TYPE(BrOnCast, castType);
     DELEGATE_FIELD_CHILD(BrOnCast, rtt);
     DELEGATE_FIELD_CHILD(BrOnCast, ref);
     DELEGATE_END(BrOnCast);
diff --git a/src/wasm.h b/src/wasm.h
index 094233b5c..041f7b49b 100644
--- a/src/wasm.h
+++ b/src/wasm.h
@@ -1386,9 +1386,6 @@ public:
   BrOnCast(MixedArena& allocator) {}
 
   Name name;
-  // The cast type cannot be inferred from rtt if rtt is unreachable, so we must
-  // store it explicitly.
-  Type castType;
   Expression* ref;
   Expression* rtt;
 
diff --git a/src/wasm/wasm-binary.cpp b/src/wasm/wasm-binary.cpp
index 398ef9cb5..4a82c84a9 100644
--- a/src/wasm/wasm-binary.cpp
+++ b/src/wasm/wasm-binary.cpp
@@ -5835,7 +5835,7 @@ bool WasmBinaryBuilder::maybeVisitBrOnCast(Expression*& out, uint32_t code) {
     throwError("bad rtt for br_on_cast");
   }
   auto* ref = popNonVoidExpression();
-  out = Builder(wasm).makeBrOnCast(name, rtt->type.getHeapType(), ref, rtt);
+  out = Builder(wasm).makeBrOnCast(name, ref, rtt);
   return true;
 }
 
diff --git a/src/wasm/wasm-s-parser.cpp b/src/wasm/wasm-s-parser.cpp
index 5dec22eb3..9cf2f3be9 100644
--- a/src/wasm/wasm-s-parser.cpp
+++ b/src/wasm/wasm-s-parser.cpp
@@ -2132,11 +2132,16 @@ Expression* SExpressionWasmBuilder::makeRefCast(Element& s) {
 
 Expression* SExpressionWasmBuilder::makeBrOnCast(Element& s) {
   auto name = getLabel(*s[1]);
-  auto heapType = parseHeapType(*s[2]);
-  auto* ref = parseExpression(*s[3]);
-  auto* rtt = parseExpression(*s[4]);
-  validateHeapTypeUsingChild(rtt, heapType, s);
-  return Builder(wasm).makeBrOnCast(name, heapType, ref, rtt);
+  auto* ref = parseExpression(*s[2]);
+  auto* rtt = parseExpression(*s[3]);
+  Builder builder(wasm);
+  if (rtt->type == Type::unreachable) {
+    // An unreachable rtt is not supported: the text format does 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.
+    return builder.makeSequence(builder.makeDrop(ref), rtt);
+  }
+  return builder.makeBrOnCast(name, ref, rtt);
 }
 
 Expression* SExpressionWasmBuilder::makeRttCanon(Element& s) {
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) {
diff --git a/src/wasm/wasm.cpp b/src/wasm/wasm.cpp
index 690c96f67..1e4ff6e3e 100644
--- a/src/wasm/wasm.cpp
+++ b/src/wasm/wasm.cpp
@@ -939,7 +939,7 @@ void BrOnCast::finalize() {
   }
 }
 
-Type BrOnCast::getCastType() { return castType; }
+Type BrOnCast::getCastType() { return Type(rtt->type.getHeapType(), Nullable); }
 
 void RttCanon::finalize() {
   // Nothing to do - the type must have been set already during construction.