[Issue 20298] New: Passing field alias to alias predicate doesn't work, predicate needs explicit instantiation

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=20298

          Issue ID: 20298
           Summary: Passing field alias to alias predicate doesn't work,
                    predicate needs explicit instantiation
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Keywords: rejects-valid
          Severity: normal
          Priority: P3
         Component: dmd
          Assignee: nobody at puremagic.com
          Reporter: dlang-bugzilla at thecybershadow.net

///////////// test.d /////////////
struct S
{
    int i;
    alias field = i;

    int fun(alias pred)() const
    {
        // Doesn't work:
        //return pred(field);

        // Works:
        alias ipred = pred!int;
        return ipred(field);
    }

    alias fun1 = fun!(i => i + 1);
}
//////////////////////////////////

Error is:

test.d(9,14): Error: template `test.S.__lambda5` cannot deduce function from
argument types `!()(const(int)) const`, candidates are:
test.d(16,20):        `__lambda5`
test.d(16,15): Error: template instance `test.S.fun!((i) => i + 1)` error
instantiating

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