Bug 7864 – Structs with class members can't be sorted

This compiles with 2.058, but not with the latest head (which I assume is the same as 2.059 beta) import std.algorithm; import std.string; class C { string str; this(string str) { this.str = str; } override int opCmp(Object o) const { auto rhs = cast(C)o; assert(rhs); return cmp(str, rhs.str); } } struct S { C c; this(C c) { this.c = c; } int opCmp(S rhs) const { if(c < rhs.c) return -1; if(c > rhs.c) return 1; return 0; } int opCmp(const ref S rhs) const { if(c < rhs.c) return -1; if(c > rhs.c) return 1; return 0; } } void main() { S[] stuff; sort(stuff); } /home/jmdavis/dmd2/linux/bin/../../src/phobos/std/algorithm.d(6802): Error: static assert "Invalid predicate passed to sort: a < b" q.d(52): instantiated from here: sort!("a < b",cast(SwapStrategy)0,S[]) The same occurs if you use a SysTime instead of C, so the problem occurs whether the class is directly or indirectly insed of S. This strikes me as being similar to issue# 7808 (though not identical). That was fixed however, and this isn't.

(In reply to comment #0) > This compiles with 2.058, but not with the latest head (which I assume is the > same as 2.059 beta) > [snip] > > /home/jmdavis/dmd2/linux/bin/../../src/phobos/std/algorithm.d(6802): Error: > static assert "Invalid predicate passed to sort: a < b" > q.d(52): instantiated from here: sort!("a < b",cast(SwapStrategy)0,S[]) This is wrong opCmp overload problem, not compiler regression. If you change opCmp signatures to: int opCmp(const S rhs) const int opCmp(const ref S rhs) const // may work in general or: int opCmp(const S rhs) const // may work in general if S allows lvalue copying or: int opCmp(S rhs) const // In this case, sorted elements is always mutable so it works or: int opCmp(const ref S rhs) const // In this case, current std.algorithm.sort implementation only requires // lvalue comparison, so it works) Then you can compile it. > The same occurs if you use a SysTime instead of C, so the problem occurs > whether the class is directly or indirectly insed of S. This strikes me as > being similar to issue# 7808 (though not identical). That was fixed however, > and this isn't. Bug 7808 was alias this type resolution problem. There is no matter.

(In reply to comment #1) > If you change opCmp signatures to: > > int opCmp(const S rhs) const > int opCmp(const ref S rhs) const > // may work in general Maybe one opCmp is enough in general: struct S { C c; int opCmp()(const auto ref S rhs) const { if (c < rhs.c) return -1; if (c > rhs.c) return 1; return 0; } }