[Issue 23274] New: [REG2.099] Wrong call resolution (ambiguity) with const and non-const methods

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=23274

          Issue ID: 23274
           Summary: [REG2.099] Wrong call resolution (ambiguity) with
                    const and non-const methods
           Product: D
           Version: D2
          Hardware: All
                OS: All
            Status: NEW
          Severity: regression
          Priority: P1
         Component: dmd
          Assignee: nobody at puremagic.com
          Reporter: johanengelen at weka.io

Testcase:
```
struct A {
  void foo(int delegate(int)) { }

  void foo(int delegate(int) nothrow) const { } // const

  void bug() {
    foo( delegate int(int k) { return 1;} );
  }
}
```

Compilation with dlang2.098 succeeds.
Compilation with dlang2.099 errors with:
```
<source>(7): Error: `example.A.foo` called with argument types `(int
delegate(int k) pure nothrow @nogc @safe)` matches both:
<source>(2):     `example.A.foo(int delegate(int) _param_0)`
and:
<source>(4):     `example.A.foo(int delegate(int) nothrow _param_0) const`
```

Because `bug` is not const, I would expect that only the non-const `foo` is a
candidate. If `nothrow` is removed, indeed that is what is called.

Note: replacing `delegate` with `function` errors on all compilers at least
back to dlang2.071.

--