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authorRyan Scott <ryan.gl.scott@gmail.com>2020-11-13 10:56:20 -0500
committerMarge Bot <ben+marge-bot@smart-cactus.org>2020-11-15 03:36:21 -0500
commit645444af9eb185684c750c95e4740d301352b2b9 (patch)
tree6e2e1136560d7e2acf1075c3974a65c18ae10512 /utils
parentd61adb3dace8f52e21f302989182145a0efa103f (diff)
downloadhaskell-645444af9eb185684c750c95e4740d301352b2b9.tar.gz
Use tcSplitForAllInvisTyVars (not tcSplitForAllTyVars) in more places
The use of `tcSplitForAllTyVars` in `tcDataFamInstHeader` was the immediate cause of #18939, and replacing it with a new `tcSplitForAllInvisTyVars` function (which behaves like `tcSplitForAllTyVars` but only splits invisible type variables) fixes the issue. However, this led me to realize that _most_ uses of `tcSplitForAllTyVars` in GHC really ought to be `tcSplitForAllInvisTyVars` instead. While I was in town, I opted to replace most uses of `tcSplitForAllTys` with `tcSplitForAllTysInvis` to reduce the likelihood of such bugs in the future. I say "most uses" above since there is one notable place where we _do_ want to use `tcSplitForAllTyVars`: in `GHC.Tc.Validity.forAllTyErr`, which produces the "`Illegal polymorphic type`" error message if you try to use a higher-rank `forall` without having `RankNTypes` enabled. Here, we really do want to split all `forall`s, not just invisible ones, or we run the risk of giving an inaccurate error message in the newly added `T18939_Fail` test case. I debated at some length whether I wanted to name the new function `tcSplitForAllInvisTyVars` or `tcSplitForAllTyVarsInvisible`, but in the end, I decided that I liked the former better. For consistency's sake, I opted to rename the existing `splitPiTysInvisible` and `splitPiTysInvisibleN` functions to `splitInvisPiTys` and `splitPiTysInvisN`, respectively, so that they use the same naming convention. As a consequence, this ended up requiring a `haddock` submodule bump. Fixes #18939.
Diffstat (limited to 'utils')
m---------utils/haddock0
1 files changed, 0 insertions, 0 deletions
diff --git a/utils/haddock b/utils/haddock
-Subproject ad9cbad7312a64e6757c32bd9488c55ba4f2fec
+Subproject 4d0498d503bd51b7d7626497580232685a2691a