Allow inferred parameter types always, when eta-expanding #18771
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Rather than drawing an exemption based on fully defined types, report the right function arity. This leads eta-expansion to leave off the type, so then the parameter type is inferred. In the test case pos/i18453 this leads to the type var ?A being instantiated to X, rather than ?A & ?B being constrained against X & Y, which leads to ?A being instantiated to X & Y - and then failing to find a Box[X & Y] in scope.
dwijnand
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Seems the previous trick is no longer necessary, so this looks like a nice improvement! |
odersky
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Nov 13, 2023
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Rather than drawing an exemption based on fully defined types, report
the right function arity. This leads eta-expansion to leave off the
type, so then the parameter type is inferred. In the test case
pos/i18453 this leads to the type var ?A being instantiated to X, rather
than ?A & ?B being constrained against X & Y, which leads to ?A being
instantiated to X & Y - and then failing to find a Box[X & Y] in scope.