Assertion failed in wasm-as when casting to externref

[hgruniaux]

The following WAT code:

(module
    (func (param eqref) (result externref)
        (ref.cast externref (local.get 0))))

crash the assembler with the following message:

Assertion failed: isRef() (/src/src/wasm/wasm-type.cpp: getHeapType: 930)

The problem is the cast to externref. The assembler should probably print an error message.

The crash was reproduced on the main branch (commit 22c28bd).

[kripken]

Thanks @hgruniaux , I opened #6741 with a fix.