Represent ref.as_{func,data,i31} with RefCast (#5413)

These operations are deprecated and directly representable as casts, so remove
their opcodes in the internal IR and parse them as casts instead. For now, add
logic to the printing and binary writing of RefCast to continue emitting the
legacy instructions to minimize test changes. The few test changes necessary are
because it is no longer valid to perform a ref.as_func on values outside the
func type hierarchy now that ref.as_func is subject to the ref.cast validation
rules.

RefAsExternInternalize, RefAsExternExternalize, and RefAsNonNull are left
unmodified. A future PR may remove RefAsNonNull as well, since it is also
expressible with casts.

1 files changed, 4 insertions, 17 deletions

diff --git a/test/binaryen.js/expressions.js b/test/binaryen.js/expressions.js
index ee55ee90b..c9111c9b4 100644
--- a/test/binaryen.js/expressions.js
+++ b/test/binaryen.js/expressions.js
@@ -1450,6 +1450,7 @@ console.log("# RefAs");
 
   var op = binaryen.Operations.RefAsNonNull;
   var value = module.local.get(1, binaryen.anyref);
+  var externref = module.local.get(3, binaryen.externref);
   const theRefAs = binaryen.RefAs(module.ref.as_non_null(value));
   assert(theRefAs instanceof binaryen.RefAs);
   assert(theRefAs instanceof binaryen.Expression);
@@ -1457,9 +1458,9 @@ console.log("# RefAs");
   assert(theRefAs.value === value);
   assert(theRefAs.type !== binaryen.i32); // TODO: === (ref any)
 
-  theRefAs.op = op = binaryen.Operations.RefAsFunc;
+  theRefAs.op = op = binaryen.Operations.RefAsExternExternalize;
   assert(theRefAs.op === op);
-  theRefAs.op = op = binaryen.Operations.RefAsNull;
+  theRefAs.op = op = binaryen.Operations.RefAsNonNull;
   theRefAs.value = value = module.local.get(2, binaryen.anyref);
   assert(theRefAs.value === value);
   theRefAs.type = binaryen.f64;
@@ -1473,21 +1474,7 @@ console.log("# RefAs");
     "(ref.as_non_null\n (local.get $2)\n)\n"
   );
 
-  assert(
-    binaryen.RefAs(module.ref.as_func(value)).toText()
-    ==
-    "(ref.as_func\n (local.get $2)\n)\n"
-  );
-  assert(
-    binaryen.RefAs(module.ref.as_data(value)).toText()
-    ==
-    "(ref.as_data\n (local.get $2)\n)\n"
-  );
-  assert(
-    binaryen.RefAs(module.ref.as_i31(value)).toText()
-    ==
-    "(ref.as_i31\n (local.get $2)\n)\n"
-  );
+  // TODO: extern.externalize and extern.internalize
 
   module.dispose();
 })();