[Issue 18969] New: 'need this for <function>' when passing field or method as template parameter

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=18969

          Issue ID: 18969
           Summary: 'need this for <function>' when passing field or
                    method as template parameter
           Product: D
           Version: D2
          Hardware: x86
                OS: Windows
            Status: NEW
          Severity: enhancement
          Priority: P1
         Component: dmd
          Assignee: nobody at puremagic.com
          Reporter: simen.kjaras at gmail.com

Consider this code:

class C { int n; }

void fun(alias fn)() {}

unittest {
    C c = new C();
    fun!(c.n)();
}

Error message:
foo.d(7): Error: need this for fun of type pure nothrow @nogc @safe void()

What's actually needed here is for fun to get a context pointer, either to the
unittest block or to the instance of C.

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