typeof map

[cal]

Is it by design that the code below does not compile?
import std.algorithm, std.range;

void main() {
   typeof(iota(10).map!(a=>a)) x = iota(10).map!(a=>a);   
}

Error message (DMD git-latest on DPaste):
Error: constructor f755.main.MapResult!(__lambda2, 
Result).MapResult.this (Result input) is not callable using 
argument types (MapResult!(__lambda4, Result))
Error: cannot implicitly convert expression (map(iota(10))) of 
type MapResult!(__lambda4, Result) to Result