Fix incorrect rest element type inside contextually typed parameter #47909
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typescript-bot added Author: Team For Milestone Bug 
RyanCavanaugh approved these changes Feb 15, 2022
| @typescript-bot cherry-pick this to release-4.6 |
| Heya @RyanCavanaugh, I've started to run the task to cherry-pick this into |
| Hey @RyanCavanaugh, I've opened #47912 for you. |
typescript-bot pushed a commit to typescript-bot/TypeScript that referenced this pull request Feb 15, 2022
weswigham approved these changes Feb 15, 2022
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Fixes #47865.
When pushing down the instantiated contextual type from a parameter to its binding elements (i.e. a parameter that is a binding pattern), we relied on storing this parameter type in our type cache (
symbolLinks.type), and retrieving this cached type when computing the type of its binding elements (inassignBindingElementTypes). However, if the binding element is a rest binding element, as of #47337 we skip looking for its parent type in the cache, becausecheckModeis going to haveCheckMode.RestBindingElementset, and we compute the wrong (uninstantiated) type for the parent.This fix makes it so we explicitly pass the parent type in
assignBindingElementTypes, avoiding the need to rely on getting the cached type.