Bug 19220 – multiSort and SortedRange.groupBy do not play together

std.algorithm.multiSort returns a SortedRange which in turn has a groupBy method. Usage of this method does not actually compile when sorting by more than one predicate. Example repro (online here: https://run.dlang.io/is/mQGAvD): import std.stdio; import std.algorithm; void main() { auto records = [ Record(10, 10), Record(12, 1), Record(30, 12), Record(10, 10), ]; { // Works: auto groups = records.multiSort!(`a.x < b.x`).groupBy; writeln(groups); } { // Doesn't work: auto groups = records.multiSort!(`a.x < b.x`, `a.y < b.y`).groupBy; writeln(groups); } } struct Record { int x; int y; } SortedRange.groupBy apparently delegates the work to chunkBy which chokes on the predicate defined by multiSort: /dlang/dmd-beta/linux/bin64/../../src/phobos/std/algorithm/iteration.d(1821): Error: static assert: "chunkBy expects either a binary predicate or a unary predicate on range elements of type: Record" /dlang/dmd-beta/linux/bin64/../../src/phobos/std/algorithm/iteration.d(1896): instantiated from here: ChunkByImplIsUnary!(__lambda1, Record[]) /dlang/dmd-beta/linux/bin64/../../src/phobos/std/algorithm/iteration.d(2110): instantiated from here: ChunkByImpl!(__lambda1, Record[]) /dlang/dmd-beta/linux/bin64/../../src/phobos/std/range/package.d(10730): instantiated from here: chunkBy!((a, b) => !predFun(a, b) && !predFun(b, a), Record[]) onlineapp.d(21): instantiated from here: groupBy!() Commenting out the "doesn't work" section demonstrates that multiSort's predicate works fine as long there's a single original predicate.

Compiles & runs sucessfully with 2.091.0