Loosen

Declares a derive-like function attr macro which creates another wrap-like function with single tuple-loosened argument, retrieved from the former function.

Upon call, the loosened function propagates the call with the flattened input tuple as arguments to the original function.

Example

```

[loose]

fn fa(a: A, b: B) {}

// normal call fa(A, B);

// loose call let args = (A, B); fa_loose(args); // ie. instead of two arguments, // there is only a single tuple argument

// usage in mappings (0..10) .map(|| (A, B)) .map(faloose) .collect::>(); ```

Note

This is a draft and is my first try on proc-macros. I suggested this as an rfc before realising a proc macro would suffice: https://github.com/rust-lang/rfcs/issues/2667