Bug 19531 – Function pointers should be allowed as template arguments

Function pointers should be allowed as template arguments.

If you need to pass a function pointer, which is a runtime value, by value to a template function, you can pass it as an argument to the function instead of the template: void foo(T)(T fn) if (is(T == delegate)) { fn(); } foo(() => writeln("hi")); If you need to expose a function as a symbol to a template to be used at compile time, you can pass it as a symbol argument to the template. The parameter is declared as "alias fn" instead of just "fn": void foo(alias fn)() { fn(); } foo!(() => writeln("hi")); If you need to expose a function pointer to a template, you can do that by exposing a variable that holds that function pointer to the template as a symbol: void foo(alias fn)() { fn(); } void bar() { writeln("bar"); } auto functionPointer = &bar; foo!functionPointer(); Most of the time, you can make things work the way you want just by omitting &.