2021-07-12 17:45:07 +03:00
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```ucm:hide
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.> builtins.merge
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```
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This is just a simple transcript to regression check an ability
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inference/checking issue.
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```unison
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2021-08-24 21:33:27 +03:00
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structural ability R t where
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2021-07-12 17:45:07 +03:00
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die : () -> x
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near.impl : Nat -> Either () [Nat]
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R.near n = match near.impl n with
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Left e -> die ()
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Right a -> a
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R.near1 region loc = match R.near 42 with
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[loc] -> loc
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ls -> R.die ()
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```
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The issue was that abilities with parameters like this were sometimes
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causing failures like this because the variable in the parameter would
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escape to a scope where it no longer made sense. Then solving would
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fail because the type was invalid.
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The fix was to avoid dropping certain existential variables out of
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scope.
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