Fix incorrect rest element type inside contextually typed parameter #47909
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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, becausecheckMode
is going to haveCheckMode.RestBindingElement
set, 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.