fix: ref match uses unified type

[A4-Tacks]

Example

struct S<T>(T);
fn foo<T>(s: &mut S<T>) {}
fn main() {
    let mut ssss = S(2u32);
    foo($0);
}

Before this PR

st S(…) S(T) []
st &mut S(…) [type]
lc ssss S<u32> [local]

After this PR

st S(…) S(T) []
st &mut S(…) [type]
lc ssss S<u32> [local]
lc &mut ssss [type+local]