Bug 21521 – Cannot state ref return for delegates and function pointers

Currently, the grammar does not allow `ref` to occur in the rhs of IsExpression and parameter types. There is no way to express that a function requires its function pointer/delegate parameter to return by reference without using a helper alias: void f(ref int delegate() dg) { static assert(!__traits(isRef, dg)); // fails, dg is ref, not its return } void f(int delegate() ref dg) // invalid syntax: found `ref` when expecting { } Same for testing whether DG is a fp or delegate returning by ref: is(DG : ref int delegate()) // invalid syntax is(DG : int delegate() ref) // invalid syntax Workaround: alias RefFunctionPointer(T, Args...) = ref T function(Args); alias RefDelegate(T, Args...) = ref T delegate(Args); The workaround has severe limitations such as attributes and parameter storage classes.

*** This issue has been marked as a duplicate of issue 2753 ***