Wingman: Use awareness of skolems when filtering GADT data constructors #2172
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isovector
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Sep 8, 2021
| matches <- | ||
| liftMaybe $ | ||
| destructionFor | ||
| -- TODO(sandy): This needs a judgment in order to correctly compute |
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maybe it worths to add the link to the issue?
jneira
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Sep 9, 2021
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jneira
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https://en.wikipedia.org/wiki/Thoralf_Skolem force be with you!
…ge-server into skolem-evidence
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I am afraid this needs a rebase |
…ge-server into skolem-evidence
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The test failure in should be: eval (IntLit n) = nusing GADT evidence, but instead we get: eval (IntLit n) = _w0Looks like it didn't learn that the type variable is equal to |
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GHC provides
dataConCannotMatch, which WIngman was using to filter out GADT data constructors which don't typecheck. But GHC doesn't do any reasoning about skolems in this function, so it assumes it can just unify any type variables that are present. This is entirely wrong --- skolems are definitely apart for all of Wingman's purposes.Fixes #2171