Pure higher order functions

[bearophile]

Jonathan M Davis:

> Regardless, the overall situation with purity is improving.

I agree. Someday I hope to see another little improvement in the D type system, to allow code like this to compile without the need of a cast of s2 to string at the end:

string foo(in string s) pure nothrow { // strongly pure
    char[] s2 = s.dup; // dup will become nothrow
    s2[0] = 'A';
    return s2;
}

(alternative design of this feature: this foo returns a char[] but then you are allowed to assign this result to a string).

Seeing the recent large amount of pull requests I am seeing, is someone willing to implement this type system feature?

Bye,
bearophile