Don't try default args when there are ambiguous implicits #19647
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mbovel
commented
Feb 8, 2024
mbovel
commented
Feb 8, 2024
mbovel
commented
Feb 8, 2024
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| val propFail = propagatedFailure(args) | ||
| val firstAmbiguous = args.tpes.find(_.isInstanceOf[AmbiguousImplicits]) | ||
| def firstError = args.tpes.find(_.isError) |
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Now traversing args twice in the worst case, but I think the readability gain is worth it.
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Note: as before, I am only checking for AmbiguousImplicits. Should TooUnspecific fall in the same case? I am asking because both are considered ambiguous here:
Before this commit, the logic in `class Typer` / `def adapt1` / `def addImplicitArgs` was to try default arguments if *any* argument had an implicit search error that was not an ambiguous implicits error. This commit changes the logic to try default arguments only if *all* arguments' implicit search errors are not ambiguous implicits error. The rational is that if there is any ambiguous implicits error, it's not worth trying default arguments because this cannot solve the ambiguity. Instead, we report the first ambiguous implicits error directly.
smarter
reviewed
Mar 25, 2024
| val propFail = propagatedFailure(args) | ||
| val firstAmbiguous = args.tpes.find(_.isInstanceOf[AmbiguousImplicits]) | ||
| def firstError = args.tpes.find(_.isError) | ||
| val propFail = firstAmbiguous.orElse(firstError).getOrElse(NoType) |
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So the previous logic preferred non-ambiguity errors over ambiguity errors, and this PR changes it to prefer ambiguity errors over non-ambiguity errors, but since ambiguity is no longer special after https://dotty.epfl.ch/docs/reference/changed-features/implicit-resolution.html, perhaps we could just report the first error found? /cc @odersky
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Superseded by #20261. |
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Fixes #19414.