Strengthen overloading resolution to deal with extension methods #6116
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This does not yet fully solve the problem of overloaded extensions, since the identified overloaded alternatives will still be ambiguous if the first parameter list is the same. But at least we get a notice what extension method was tried.
If resolving with the first parameter list yields a draw, and there are further argument lists following the first one, take these into account as well in order to arrive at a single best alternative. This is particularly useful for extension methods, where we might well have several overloaded extension methods with the same first parameter list.
Use NoPrefix since that way the info of the TermRef is guaranteed to be the info of the Symbol. More tests for overloading behavior of extension methods
FunProto and PolyProto now print without exposing internal names.
Extension methods cannot override normal methods and vice versa.
liufengyun
approved these changes
Mar 20, 2019
| tp.memberBasedOnFlags(name, required = ExtensionMethod) match { | ||
| case mbr: SingleDenotation => qualifies(mbr) | ||
| case mbr => mbr.hasAltWith(qualifies(_)) | ||
| } |
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What is the purpose of the dispatch here? Semantically it seems the same as:
tp.memberBasedOnFlags(name, required = ExtensionMethod).hasAltWith(qualifies(_))Is it for performance? It seems we save several exists check this way.
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Yes, it's for performance. We optimize for the common case where the member is not overloaded.
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If resolving with the first parameter list yields a draw, and there are
further argument lists following the first one, take these into account
as well in order to arrive at a single best alternative.
This is particularly useful for extension methods, where we might
well have several overloaded extension methods with the same first
parameter list.