Mapped and indexed access type fixes #17455
Merged
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This PR adds some missing checks related to indexed access types and mapped types. In particular, for an indexed access
T[K]
the PR ensures that we always check thatK
is assignable tokeyof T
. This check was previously not performed whenT
is a generic mapped type.Fixes #17238. This PR supercedes #17336, but keeps the tests from that PR.