Fix #2973: Check variances of class parents #4057
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Blaisorblade
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Blaisorblade
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Guess I learned a bit about why this change is annoyingly hard. Trying to comment out some of the calls involved in the spurious error also removes the correct error from the new test.
| case tree: TypeDef => | ||
| checkVariance(sym, tree.pos) | ||
| tree.rhs match { | ||
| case rhs: Template => traverseChildren(rhs) |
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Here traverseChildren sees parents (in the form of a constructor call), but this Traverser ignores terms and only looks at definitions...
| //case tp: ClassInfo => | ||
| // ??? not clear what to do here yet. presumably, it's all checked at local typedefs | ||
| case tp: ClassInfo => | ||
| foldOver(status, tp.classParents) |
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This visit sees the parent classes, but stripped of any annotations!
| case defn: MemberDef if skip => | ||
| ctx.debuglog(s"Skipping variance check of ${sym.showDcl}") | ||
| case tree: TypeDef => | ||
| checkVariance(sym, tree.pos) |
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On tests/pos/Iterable.scala we get an error inside this call (going through tp.classParents), because sym contains the parens but without annotations!
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Closing since this is likely noise — I've a first guess why Martin got stuck on it, and it's not an issue for a beginner like me yet. |
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I'm opening this PR to recover this "lost" fix to a soundness issue (#2973, #3856). Let's see its status.