[GSB] Ensure that term rewriting rules produce correct anchors #14685
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Although we were properly recording rewrite rules like tau_0_1 -> tau_0_0 in the rewrite tree, we were failing to apply them, so tau_0_1 wouldn’t get properly canonicalized. Fix this, and add some assertions to make sure we catch this with our current test suite. Fixes rdar://problem/37469390.
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@swift-ci please test and merge |
…lasses. Instead of representing every same-type constraint we see as a rewrite rule, only record rewrite rules when we merge equivalence classes, and record rules that map the between the anchors of the equivalence classes. This gives us fewer, smaller rewrite rules that (by construction) build correct anchors.
DougGregor
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@swift-ci please smoke test and merge |
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@swift-ci please smoke test and merge |
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@DougGregor this introduced a warning in no-assert builds about the loop only going round once. If you have a preferred suggested way to fix that, I'll raise a PR to do it.
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Rework the way that we form term rewriting rules in the
GenericSignatureBuilder, such that we form rewrite rules only when merging two equivalence classes, in which case we form a rewrite rule from the anchor of one equivalence class to the anchor of the other equivalence class. This produces smaller sets of rewrite rules (by far) and ensures that we always canonicalize to the anchor.While here, fix a problem where we failing to apply rewrite rules like tau_0_1 -> tau_0_0. With both changes in, introduce assertions to make sure we're getting a proper anchor.
Fixes rdar://problem/37469390.