Bug 4582 – distinct field names constraint for std.typecons.Tuple

It's better to put guards as template constraints at the std.typecons.Tuple, so erroneous Tuple template instantiations fail at the instantiation point, giving a more useful error message in the user code instead giving an error inside the std.typecons module (this is one of the main purposes of template constraints). This code guards against duplicated field names: private template Iota(int stop) { // this is useful in general static if (stop <= 0) alias TypeTuple!() Iota; else alias TypeTuple!(Iota!(stop-1), stop-1) Iota; } private bool distinctFieldNames(T...)() { enum int tlen = T.length; // can't move this below, probably DMD bug foreach (i1; Iota!(tlen)) static if (is(typeof(T[i1]) : string)) foreach (i2; Iota!(tlen)) static if (i1 != i2 && is(typeof(T[i2]) : string)) if (T[i1] == T[i2]) return false; return true; } // ............... struct Tuple(T...) if (distinctFieldNames!(T)()) {

Excellent.

Thank you. But I think some tests/benchmarks may be done to make sure this extra test doesn't slow down too much the compilation of programs that define many tuple types.

Commits pushed to master at https://github.com/dlang/phobos https://github.com/dlang/phobos/commit/4e8fa84ba227b2ff4662b2e2fcdeca57074bc2fd Fix Issue 4582 - distinct field names constraint for std.typecons.Tuple https://github.com/dlang/phobos/commit/f24da9d895b6be51c0b1d196eb0c9d0e67f81dc1 Merge pull request #5725 from RazvanN7/Issue_4582 Fix Issue 4582 - distinct field names constraint for std.typecons.Tuple merged-on-behalf-of: MetaLang <[email protected]>

Commits pushed to stable at https://github.com/dlang/phobos https://github.com/dlang/phobos/commit/4e8fa84ba227b2ff4662b2e2fcdeca57074bc2fd Fix Issue 4582 - distinct field names constraint for std.typecons.Tuple https://github.com/dlang/phobos/commit/f24da9d895b6be51c0b1d196eb0c9d0e67f81dc1 Merge pull request #5725 from RazvanN7/Issue_4582