[Issue 23101] [std.sumtype] canMatch does not account ref

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=23101

--- Comment #3 from João Lourenço <jlourenco5691 at gmail.com> ---
Sorry, correction of the bug report example:
```
SumType!(int, string) st;
st.match!(
  function int*(string _) => assert(0),
  function int*(ref int i) => &i,
);
```

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