[Issue 24831] New: IFTI fails for a function template with a default function argument

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=24831

          Issue ID: 24831
           Summary: IFTI fails for a function template with a default
                    function argument
           Product: D
           Version: D2
          Hardware: x86_64
                OS: All
            Status: NEW
          Keywords: rejects-valid
          Severity: normal
          Priority: P1
         Component: dmd
          Assignee: nobody at puremagic.com
          Reporter: maxsamukha at gmail.com

This renders default arguments in generic functions unusable.

void foo(U, T = int)(T v = T.init)
{
}

void main()
{
    foo!int(); // ok
    foo!int("x"); // fail
}

Error: function `foo` is not callable using argument types `(string)`

The second call tries to reuse the previous instantiation instead of creating a
new one. An explicit instantiation works but defeats the purpose of using
default arguments.

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