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Richard Eisenberg authored
There were actually two bugs fixed here: 1. candidateQTyVarsOfType needs to be careful that it does not try to zap metavariables from an outer scope as "naughty" quantification candidates. This commit adds a simple check to avoid doing so. 2. We weren't bumping the TcLevel in kcHsKindSig, which was used only for class method sigs. This mistake led to the acceptance of class C a where meth :: forall k. Proxy (a :: k) -> () Note that k is *locally* quantified. This patch fixes the problem by using tcClassSigType, which correctly bumps the level. It's a bit inefficient because tcClassSigType does other work, too, but it would be tedious to repeat much of the code there with only a few changes. This version works well and is simple. And, while updating comments, etc., I noticed that tcRnType was missing a pushTcLevel, leading to #16767, which this patch also fixes, by bumping the level. In the refactoring here, I also use solveEqualities. This initially failed ghci/scripts/T15415, but that was fixed by teaching solveEqualities to respect -XPartialTypeSignatures. This patch also cleans up some Notes around error generation that came up in conversation. Test case: typecheck/should_fail/T16517, ghci/scripts/T16767 (cherry picked from commit a22e51ea)
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