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[temp.constr.order] Subsumption is a preorder, not a partial ordering - #9368
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The note says the subsumption relation defines a partial ordering on constraints. By the definition in p1, A && B and B && A subsume each other and are different constraints, so the relation is not antisymmetric: it is a preorder. The partial ordering the note goes on to list uses is the ordering of declarations that p4 and p5 induce from it. Say so.
eisenwave
approved these changes
Oct 25, 2026
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Fixes #9371
Editorial. The note in [temp.constr.order] p2 says "The subsumption relation defines a partial ordering on constraints." It does not: by the definition in p1,
A && BandB && Asubsume each other and are different constraints, so the relation is not antisymmetric. It is a preorder. The partial ordering the note goes on to list uses for is the ordering of declarations that p4 and p5 ("at least as constrained", "more constrained") induce from it, which is a strict partial order.Nothing normative depends on the sentence, since every normative use of subsumption asks for one direction and whether the converse fails. The change rewords the note to say what the relation is and which ordering is used.