Fix signatures involving WildcardTypes #12240
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A `WildcardType` never appears in the type of a tree, but it can appear in an expected type and because TypeComparer checks if `tp1.signature consistentParams tp2.signature`, we can end up calling `sigName` on a `WildcardType`. Before this commit, the result was either a custom type name or the upper-bound of the wildcard, but both of these options means that `consistentParams` could return false in situations where the two method types would in fact match. We fix this by always returning `tpnme.Uninstantiated`, meaning that `consistentParams` will always allow a wildcard to match any other type. This does not cause any over-approximation because the TypeComparer will always check that the actual types match after checking that the signatures match. Also use tpnme.ERROR instead of tpnme.Wildcard for ErrorType and NoType to make it easier to spot their usage. Fixes scala#11481.
anatoliykmetyuk
approved these changes
Apr 28, 2021
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A
WildcardTypenever appears in the type of a tree, but it can appearin an expected type and because TypeComparer checks if
tp1.signature consistentParams tp2.signature, we can end up callingsigNameon aWildcardType.Before this commit, the result was either a custom type name or the
upper-bound of the wildcard, but both of these options means that
consistentParamscould return false in situations where the two methodtypes would in fact match. We fix this by always returning
tpnme.Uninstantiated, meaning thatconsistentParamswill alwaysallow a wildcard to match any other type. This does not cause any
over-approximation because the TypeComparer will always check that the
actual types match after checking that the signatures match.
Also use tpnme.ERROR instead of tpnme.Wildcard for ErrorType and NoType
to make it easier to spot their usage.
Fixes #11481.