[ConstraintSystem] Fix a logic error in computing potential bindings. #17317
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A change was made to attempt to use constraints that we have between type variables to inform potential bindings, such that if we have: $T1 <: $T2 we would use $T1's bindings to add to the bindings of $T2. This is only valid if we're adding bindings where $T1 is the supertype, though, otherwise we could have the constraints: $T1 <: $T2 $T1 <: X imply that $T2 is a supertype of X, which doesn't make sense. Fixes rdar://problem/40810000 (aka https://bugs.swift.org/browse/SR-7875).
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lib/Sema/CSBindings.cpp
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| // to add Supertype bindings based on the relationship between | ||
| // our type variables. | ||
| if (binding.Kind != AllowedBindingKind::Exact | ||
| && binding.Kind != AllowedBindingKind::Supertypes) |
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Only formatting nit - clang-format always leaves operators on at the end of the line, so in this case && wouldn't be moved done.
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Yes, this isn't formatted the same way that our current clang-format rules would format it. I think that's a good thing :).
My recollection is that there was a thread on this not long ago where there was some support for changing the clang-format rule for this since it's often easier to see what's going on when the operators are at the beginning of the continuation line.
We don't, AFAIK, have a rule about clang-formatting all changes, either (if we did, we'd probably make that a git post-receive hook).
Having said all that, we do have a rule that new code should be formatted consistently with surrounding code and in this case this would be an outlier, so I'll add another commit to fix this.
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Interesting, always good to know the background!
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@swift-ci Please test source compatibility |
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@swift-ci Please smoke test |
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@swift-ci Please test source compatibility |
A change was made to attempt to use constraints that we have between
type variables to inform potential bindings, such that if we have:
we would use
$T1's bindings to add to the bindings of$T2. This isonly valid if we're adding bindings where
$T1is the supertype,though, otherwise we could have the constraints:
imply that
$T2is a supertype ofX, which doesn't make sense.Fixes rdar://problem/40810000 (aka https://bugs.swift.org/browse/SR-7875).