auto fn1 = ( string s ) {
		return s;
	};
auto fn2 = ( string s ) {
		return map!fn1( [""] );
	};
auto idirs = map!fn2( [""] );

The above code fails with the following error message:

foo.d(114): Error: struct foo.main.Map!(fn2,string[]).Map inner struct Map cannot be a field
foo.d(114): Error: struct foo.main.Map!(fn2,string[]).Map inner struct Map cannot be a field