Generics: type mismatch with multi-range types

[mratsim]

In the Generics type mismatch series #7432 and #7446

type HexChars = range['0'..'9'] or range['A'..'F'] or range['a'..'f']

proc foo(x: HexChars) = discard

let a = '0'

foo(a)

Error: type mismatch: got <char>
but expected one of:
proc foo(x: HexChars)

expression: foo(a)

I'm not sure range can be used like that but there should be an error message "you cannot combine Generics with ranges" in case it's not supposed to work like that.