[ImportVerilog] Union type in call

[jpienaar]

Getting a error: 'func.call' op operand type mismatch: expected operand type '!moore.union<..., A, ...>', but provided 'A'.

[fabianschuiki]

That's an interesting catch @jpienaar. Usually, Slang's type checking inserts explicit conversion AST nodes where necessary. It might not do this for unions though, since there's technically no conversion happening. We may have to pass the actual type of the call's argument to convertRvalueExpression:

https://github.com/llvm/circt/blob/main/lib/Conversion/ImportVerilog/Expressions.cpp#L753

This might also have changed in newer Slang versions. There is an open PR to bump Slang to version 8, which might resolve this by having Slang produce a conversion AST node.