Common scope for function's in{}, out(result){} and body{}

[Nick Treleaven via Digitalmars-d]

On 12/09/2014 07:41, Ilya Yaroshenko wrote:
> auto functionName(Range1, Range2)(Range1 r1, Ranger2)
> scope  {
>      import std.range; //imports are allowed
>      enum MaxLength = 1024; //enums are allowed
>      immutable A = [0.123, 0.456, 0.789]; // immutable and const are
> allowed
>      bool isOdd (uint i) {return i%2;}
>
>      static assert(isInputRange!Range1,
>          Range1.stringof!~" is not InputRange");
>
>      int i; //Error, mutable data disallowed.
>      immutable length = r1.length; //Error, can't use function parameters.
> }
> in {
>     assert(!r1.empty); // we already know that r1 is InputRange and
> function have local imports!
>
>   // can use std.range, MaxLength, A, isOdd
> }

I like this idea, I've wanted something like it to share an expression 
used in a template constraint with the function body - I suggest that 
constraints can use symbols defined in the 'scope' block too. As well as 
making template and contract code more DRY, it may also allow us to 
further reduce global imports where they are only used in template 
constraints.