Add assignability rules for when the target is a conditional type#27932
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Add assignability rules for when the target is a conditional type#27932weswigham wants to merge 4 commits intomicrosoft:mainmicrosoft/TypeScript:mainfrom weswigham:infer-conditional-class-thisweswigham/TypeScript:infer-conditional-class-thisCopy head branch name to clipboard
weswigham wants to merge 4 commits into
microsoft:mainmicrosoft/TypeScript:mainfrom
weswigham:infer-conditional-class-thisweswigham/TypeScript:infer-conditional-class-thisCopy head branch name to clipboard
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When you write:
By instantiated are you referring to the instantiation of the infer parameters? Would it be possible to write a small example that shows the difference between the proposed behaviour, and the behaviour if you only consider the uninstantiated true constraint (as opposed to the intersection)? I have a hard time translating the rules into concrete examples, so it would be greatly appreciated! |
This was referenced Dec 4, 2018
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Does this address the unsoundness in #26945? |
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This experiment is pretty old, so I'm going to close it to reduce the number of open PRs. |
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Inspired by looking into #27014
Fixes #26933
Steals from #27589
This adds assignability rules for relating types when the target is a conditional type. We only check for conditional type target assignability when:
neverGiven these circumstances, a type is assignable to the conditional in question if
true(yet hasinfertypes, preventing simplification) and it is assignable to the intersection of the instantiated constraint of thetruebranch and the uninstantiated constraint (this allows for "independent" infer types to not interfere with true branch assignability, whilst still preserving the assignment-blocking part of the existential-like behavior of theinfertypes).