Description

Casting an option-of-sumtype field with as SumType (i.e. ?Type as Type, where Type is a sumtype) generates C that accesses the sumtype-variant members (._main__Type, ._typ) directly on the _option_main__Type option wrapper, instead of first unwrapping the option's .data. The C compiler then rejects it because the option wrapper struct has no such members.

A plain sumtype as cast (no option) compiles correctly, isolating the fault to the ?SumType as SumType case.

V version: V 0.5.1, current master (3690f882f)
OS/Backend: reproduced on macOS arm64; originally reported on Linux/cc.

Reproducer

module main

type Type = TypeBasic | TypeFunc

struct TypeBasic {
	name string
}

struct TypeFunc {
	variadic_type ?Type
}

fn f(tf TypeFunc) Type {
	return tf.variadic_type as Type
}

fn main() {
	tf := TypeFunc{
		variadic_type: Type(TypeBasic{name: 'v'})
	}
	println(f(tf))
}

Compile with:

v file.v

Current behavior

error: no member named '_main__Type' in 'struct _option_main__Type'
  return *(main__Type*)builtin____as_cast((tf.variadic_type)._main__Type, (tf.variadic_type)._typ, 116);
error: no member named '_typ' in 'struct _option_main__Type'

The as Type cast emits (tf.variadic_type)._main__Type / (tf.variadic_type)._typ, but tf.variadic_type has type _option_main__Type (the option wrapper) — the option must be unwrapped (.data) before the sumtype-variant access.

Expected behavior

The option should be unwrapped before the sumtype as cast, so the program compiles.

Notes

• Reported via the bugs.vlang.io crash reporter. Original instance: iris/checker.v, sym.type.variadic_type as Type where variadic_type is ?Type and Type is a sumtype (also surfaced as expected expression before '}' token in some report variants).