[6.0][CSBindings] Optional object type variable should be connected to the optional #73983
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… optional If both sides of an `OptionalObject` constraint are un-inferred, their binding sets need to correctly reflect adjacency - a type variable that represents optional would get "object" as an adjacency through its potential binding (the binding is - "object" wrapped in a single level of optional) and "object" type variable needs to get its parent optional type variable added to its adjacency list explicitly. Without this it would be possible to prematurely pick "object" before its parent optional type variable. Resolves: swiftlang#73207 Resolves: rdar://126960579 (cherry picked from commit d7a0628)
If the contextual type propagated into the optional chain mismatches with the inner type formed from its member references and that inner type is a result of some fix, let's consider that un-salvageable and avoid producing additional "ignore contextual type" fixes which only lead to subpar solutions. (cherry picked from commit 243cc16)
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@swift-ci please test |
hborla
approved these changes
May 29, 2024
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Cherry-pick of #73960
Explanation:
Fixes a recent regression in for-in lookup type-checking.
If both sides of an
OptionalObjectconstraint are un-inferred, theirbinding sets need to correctly reflect adjacency - a type variable
that represents optional would get "object" as an adjacency through
its potential binding (the binding is - "object" wrapped in a single
level of optional) and "object" type variable needs to get its parent
optional type variable added to its adjacency list explicitly.
Without this it would be possible to prematurely pick "object" before
its parent optional type variable.
Scope: One known situation where this comes up is for-in loop where the pattern has an explicit contextual type.
Main Branch PRs: [CSBindings] Optional object type variable should be connected to the optional #73960
Resolves: (type checker) regression on main in subtyping rules for tuple labels #73207
Resolves: rdar://126960579
Risk: Low
Reviewed By: @hborla
Testing: Added new test-cases to the test suite