ast, cgen: fix as cast with call expr (fix #19453)

[yuyi98]

This PR fix as cast with call expr (fix #19453).

• Fix as cast with call expr.
• Add test.

type Numbers = int | string

struct Values {
	value Numbers
}

struct Wrapper {
	element []Values
mut:
	index int
}

fn (mut instance Wrapper) get() Values {
	println('Gets called')
	return instance.element[0]
}

fn main() {
	mut wrapper := Wrapper{
		element: [
			Values{
				value: 1
			},
			Values{
				value: '2'
			},
		]
	}
	println(wrapper.get().value as int)
}

PS D:\Test\v\tt1> v run .
Gets called
1

[spytheman]

The linux and macos failures are fixed on master (just rebase), the windows one may need local fixes though.

[yuyi98]

OK, I'll try to fix it.

[spytheman]

Good work.