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| author | Ryan Scott <ryan.gl.scott@gmail.com> | 2020-11-13 10:56:20 -0500 |
|---|---|---|
| committer | Marge Bot <ben+marge-bot@smart-cactus.org> | 2020-11-15 03:36:21 -0500 |
| commit | 645444af9eb185684c750c95e4740d301352b2b9 (patch) | |
| tree | 6e2e1136560d7e2acf1075c3974a65c18ae10512 /compiler/GHC/HsToCore | |
| parent | d61adb3dace8f52e21f302989182145a0efa103f (diff) | |
| download | haskell-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 'compiler/GHC/HsToCore')
| -rw-r--r-- | compiler/GHC/HsToCore/Foreign/Decl.hs | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/compiler/GHC/HsToCore/Foreign/Decl.hs b/compiler/GHC/HsToCore/Foreign/Decl.hs index c7907682ae..cae1d3f115 100644 --- a/compiler/GHC/HsToCore/Foreign/Decl.hs +++ b/compiler/GHC/HsToCore/Foreign/Decl.hs @@ -316,7 +316,7 @@ dsPrimCall :: Id -> Coercion -> ForeignCall dsPrimCall fn_id co fcall = do let ty = coercionLKind co - (tvs, fun_ty) = tcSplitForAllTyVars ty + (tvs, fun_ty) = tcSplitForAllInvisTyVars ty (arg_tys, io_res_ty) = tcSplitFunTys fun_ty args <- newSysLocalsDs arg_tys -- no FFI levity-polymorphism @@ -489,7 +489,7 @@ dsFExportDynamic id co0 cconv = do where ty = coercionLKind co0 - (tvs,sans_foralls) = tcSplitForAllTyVars ty + (tvs,sans_foralls) = tcSplitForAllInvisTyVars ty ([Scaled arg_mult arg_ty], fn_res_ty) = tcSplitFunTys sans_foralls Just (io_tc, res_ty) = tcSplitIOType_maybe fn_res_ty -- Must have an IO type; hence Just |