Re: Working with ranges: mismatched function return type inference

[pineapple via Digitalmars-d-learn]

On Tuesday, 11 October 2016 at 07:55:36 UTC, orip wrote:
I get "Error: mismatched function return type inference" errors 
with choosing the return type for functions that work on ranges 
using, e.g, std.algorithm or std.range functions, but have 
different behavior based on runtime values. The return type is 
always a range with the same underlying type.

Here's an example:

auto foo(int[] ints) {
  import std.range;
  if (ints.length > 10) {
    return chain(ints[0..5], ints[8..$]);
  } else {
    //return ints; // Error: mismatched function return type 
inference of int[] and Result
    return chain(ints[0..0], ints[0..$]); // This workaround 
compiles
  }
}

Is there a compatible return type that can be used, or some 
other workaround?
I couldn't find one when searching for the error or looking at 
the phobos source code.

Thanks! orip

Rewrite `return chain(ints[0..5], ints[8..$]);` as `return 
ints[0..5] ~ ints[8..$];`

The `chain` function doesn't return an array, it returns a 
lazily-evaluated sequence of an entirely different type from 
`int[]`.