Missing validation error

解压 jj.tar.gz，并使用 pkg/dart2wasm/bin/run_wasm.js、jj.mjs 和 jj.wasm 重现 V8 验证错误。比较 wasm-opt 对所示不可达 WAT 序列的处理与 V8 的验证结果，并添加或更新回归测试，使这些工具就该模块是否有效达成一致。

See jj.tar.gz.

Unpack via:

% tar xvzf jj.tar.gz
...

When running with V8 we get a validation error:

% d8 $PWD/pkg/dart2wasm/bin/run_wasm.js  -- $PWD/jj.mjs $PWD/jj.wasm   
run_wasm.js:346: CompileError: WebAssembly.compile(): Compiling function #181:"main" failed: not enough arguments on the stack for drop (need 1, got 0) @+25996
  }
  ^
CompileError: WebAssembly.compile(): Compiling function #181:"main" failed: not enough arguments on the stack for drop (need 1, got 0) @+25996

1 pending unhandled Promise rejection(s) detected.

Though optimizing with wasm-opt works fine and the result runs:

% wasm-opt --enable-gc --enable-reference-types --enable-multivalue --enable-exception-handling --enable-nontrapping-float-to-int --enable-sign-ext --enable-bulk-memory --enable-threads --enable-simd '--no-inline=*<noInline>*' --traps-never-happen -g -Os --gufa -Os -Os jj.wasm -o jj.wasm  
% d8 $PWD/pkg/dart2wasm/bin/run_wasm.js  -- $PWD/jj.mjs $PWD/jj.wasm
%

Is wasm-opt not supposed to issue a validation error here as well? (even though the corresponding code is unreachable)

        local.get $reporter
        drop
        drop
        block $label2
          unreachable
        end
        drop