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We can handle non-void constraints since !1733, so we can now express the strictness of `-XEmptyCase` just by adding a non-void constraint to the initial Uncovered set. For `case x of {}` we thus check that the Uncovered set `{ x | x /~ ⊥ }` is non-empty. This is conceptually simpler than the plan outlined in #17376, because it talks to the oracle directly. In order for this patch to pass the testsuite, I had to fix handling of newtypes in the pattern-match checker (#17248). Since we use a different code path (well, the main code path) for `-XEmptyCase` now, we apparently also handle #13717 correctly. There's also some dead code that we can get rid off now. `provideEvidence` has been updated to provide output more in line with the old logic, which used `inhabitationCandidates` under the hood. A consequence of the shift away from the `UncoveredPatterns` type is that we don't report reduced type families for empty case matches, because the pretty printer is pure and only knows the match variable's type. Fixes #13717, #17248, #17386
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