[Parser] Parse br_on_cast{_fail} input annotations (#6198)

And validate in IRBuilder both that the input annotation is valid and that the
input matches it.

1 files changed, 10 insertions, 2 deletions

diff --git a/src/wasm/wasm-ir-builder.cpp b/src/wasm/wasm-ir-builder.cpp
index 3cfe0ea30..43a989c6e 100644
--- a/src/wasm/wasm-ir-builder.cpp
+++ b/src/wasm/wasm-ir-builder.cpp
@@ -1420,12 +1420,20 @@ Result<> IRBuilder::makeRefCast(Type type) {
   return Ok{};
 }
 
-Result<> IRBuilder::makeBrOn(Index label, BrOnOp op, Type castType) {
+Result<> IRBuilder::makeBrOn(Index label, BrOnOp op, Type in, Type out) {
   BrOn curr;
   CHECK_ERR(visitBrOn(&curr));
+  if (out != Type::none) {
+    if (!Type::isSubType(out, in)) {
+      return Err{"output type is not a subtype of the input type"};
+    }
+    if (!Type::isSubType(curr.ref->type, in)) {
+      return Err{"expected input to match input type annotation"};
+    }
+  }
   auto name = getLabelName(label);
   CHECK_ERR(name);
-  push(builder.makeBrOn(op, *name, curr.ref, castType));
+  push(builder.makeBrOn(op, *name, curr.ref, out));
   return Ok{};
 }