Fix small regression in subtype cache performance #5604
Merged
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Fixes #5514
The root cause is that #5474 added
type_parameter_checker
(a function) as one of the keys of subtype kinds. This function is a nested one, so in fact a new function was created on every call tois_subtype_ignoring_tvars()
causing many thousands parasitic keys created in subtype caches. In addition there are two smaller things listed below.The performance win is around 5%
This PR: