Add initial support for anyref as an opaque type (#2294)

Another round of trying to push upstream things from my fork.

This PR only adds support for anyref itself as an opaque type. It does NOT implement the full [reference types proposal](https://github.com/WebAssembly/reference-types/blob/master/proposals/reference-types/Overview.md)--so no table.get/set/grow/etc or ref.null, ref.func, etc.

Figured it was easier to review and merge as we go, especially if I did something fundamentally wrong.

***

I did put it under the `--enable-reference-types` flag as I imagine that even though this PR doesn't complete the full feature set, it probably is the right home. Lmk if not.

I'll also be adding a few github comments to places I want to point out/question.

1 files changed, 2 insertions, 0 deletions

diff --git a/src/wasm/wasm-validator.cpp b/src/wasm/wasm-validator.cpp
index 8eb3341de..339ad6f68 100644
--- a/src/wasm/wasm-validator.cpp
+++ b/src/wasm/wasm-validator.cpp
@@ -1134,6 +1134,7 @@ void FunctionValidator::validateMemBytes(uint8_t bytes,
       shouldBeEqual(
         bytes, uint8_t(16), curr, "expected v128 operation to touch 16 bytes");
       break;
+    case anyref: // anyref cannot be stored in memory
     case exnref: // exnref cannot be stored in memory
     case none:
       WASM_UNREACHABLE();
@@ -1788,6 +1789,7 @@ void FunctionValidator::validateAlignment(
     case v128:
     case unreachable:
       break;
+    case anyref: // anyref cannot be stored in memory
     case exnref: // exnref cannot be stored in memory
     case none:
       WASM_UNREACHABLE();