[Static if] Replace overload constraints with static if (comparison.d)

[wilzbach]

Split up of #5145

[JackStouffer]

if (isInputRange!R1 && isInputRange!R2 && isSomeChar!(ElementType!R1) && isSomeChar!(ElementType!R2))

[jmdavis]

Yeah, you have to be very careful with isSomeString in template constraints for range-based functions, because enums pass isSomeString but are not ranges.

[JackStouffer]

this will be true for all inputs, the is some string overload needs to come first

[wilzbach]

if (isInputRange!R1 && isInputRange!R2 && isSomeChar!(ElementType!R1) && isSomeChar!(ElementType!R2))

@JackStouffer :

• I think you meant ... sInputRange!R2 || isSomeChar... ?
• FWIW I just copied the existing overloads to one function. If we change them, wouldn't this be a breaking change?

edit: as CircleCi and the auto-tester showed, it really would be a breaking change...
-> reverted your suggestions

[JackStouffer]

My point was that the isSomeString checks are redundant because all strings are going to be character ranges.

The auto tester errors look like the non-string inputs weren't being sent to the input range code path but instead being sent to the string code path.

[dlang-bot]

Thanks for your pull request, @wilzbach!

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[wilzbach]

My point was that the isSomeString checks are redundant because all strings are going to be character ranges.

Finally came around rebasing this one :)

[wilzbach]

Finally came around rebasing this one :)

... and another rebase. This PR just combines the overloads of cmp into one. It just moves the regarding bodies inside.

[JackStouffer]

Looks good. Go ahead and merge when the CI failures are fixed

[andralex]

I just noticed this is inefficient because at this point it is known that r1 is not empty. Normally you'd need to make a separate PR for that, but let's not let protocol getting in the way of good work. And how about you eliminate the cast - it's a nice conversion:

if (r1.empty) return -int(r2.empty);
if (r2.empty) return 1;

This will fold two calls to r2.empty into one and perhaps generates better code:

immutable e1 = r1.empty, e2 = r2.empty;
if (e1) return -int(e2);
if (e2) return 1;