[Git][ghc/ghc][wip/soulomoon/suggest-UnliftedNewtypes-unlifted-data-family-25593] 2 commits: update comment

[Patrick (@soulomoon)]

Patrick pushed to branch wip/soulomoon/suggest-UnliftedNewtypes-unlifted-data-family-25593 at Glasgow Haskell Compiler / GHC


Commits:
6ff397a2 by Patrick at 2025-01-05T16:30:00+08:00
update comment

- - - - -
4c83df3b by Patrick at 2025-01-05T17:09:56+08:00
Change UnliftedNewtypesUnassociatedFamilyFail to UnliftedNewtypesUnassociatedFamilyInfer.

- - - - -


4 changed files:

- compiler/GHC/Tc/TyCl/Instance.hs
- + testsuite/tests/typecheck/should_compile/UnliftedNewtypesUnassociatedFamilyInfer.hs
- testsuite/tests/typecheck/should_compile/all.T
- testsuite/tests/typecheck/should_fail/all.T


Changes:

=====================================
compiler/GHC/Tc/TyCl/Instance.hs
=====================================
@@ -945,10 +945,11 @@ tcDataFamInstHeader mb_clsinfo skol_info fam_tc hs_outer_bndrs fixity
                   -- Add constraints from the result signature
                   ; res_kind <- tc_kind_sig m_ksig
 
-                  -- Do not add constraints from the data constructors
-                  -- See Note [Kind inference for data family instances]
-
                   -- Add constraints from the data constructors
+                  -- Fix #25611
+                  -- But becareful about the GADT style case,
+                  -- do not unify LHS's kind with RHS's kind,
+                  -- See Note [Kind inference for data family instances]
                   ; kcConDecls new_or_data res_kind hs_cons
 
 


=====================================
testsuite/tests/typecheck/should_compile/UnliftedNewtypesUnassociatedFamilyInfer.hs
=====================================
@@ -0,0 +1,29 @@
+{-# LANGUAGE UnliftedNewtypes #-}
+{-# LANGUAGE DataKinds #-}
+{-# LANGUAGE TypeFamilies #-}
+{-# LANGUAGE PolyKinds #-}
+{-# LANGUAGE MagicHash #-}
+{-# LANGUAGE UnboxedTuples #-}
+{-# LANGUAGE GADTs #-}
+
+module UnliftedNewtypesUnassociatedFamily where
+
+import GHC.Int (Int(I#))
+import GHC.Word (Word(W#))
+import GHC.Exts (Int#,Word#)
+import GHC.Exts (TYPE,RuntimeRep(IntRep,WordRep,TupleRep))
+
+data family DF :: TYPE (r :: RuntimeRep)
+
+-- it used to be failed: see #18891 and !4419
+-- See Note [Kind inference for data family instances]
+-- in GHC.Tc.TyCl.Instance
+-- but succ now see #25611
+newtype instance DF = MkDF1a Int#
+newtype instance DF = MkDF2a Word#
+newtype instance DF = MkDF3a (# Int#, Word# #)
+
+go = 1
+  where
+    x :: DF @IntRep
+    x = MkDF1a 3#


=====================================
testsuite/tests/typecheck/should_compile/all.T
=====================================
@@ -696,6 +696,7 @@ test('T505', normal, compile, [''])
 test('T12928', normal, compile, [''])
 test('UnliftedNewtypesGnd', normal, compile, [''])
 test('UnliftedNewtypesUnassociatedFamily', normal, compile, [''])
+test('UnliftedNewtypesUnassociatedFamilyInfer', normal, compile, [''])
 test('UnliftedNewtypesUnifySig', normal, compile, [''])
 test('UnliftedNewtypesForall', normal, compile, [''])
 test('UnlifNewUnify', normal, compile, [''])


=====================================
testsuite/tests/typecheck/should_fail/all.T
=====================================
@@ -552,7 +552,6 @@ test('UnliftedNewtypesConstraintFamily', normal, compile_fail, [''])
 test('UnliftedNewtypesMismatchedKind', normal, compile_fail, [''])
 test('UnliftedNewtypesMismatchedKindRecord', normal, compile_fail, [''])
 test('UnliftedNewtypesMultiFieldGadt', normal, compile_fail, [''])
-test('UnliftedNewtypesUnassociatedFamilyFail', normal, compile_fail, [''])
 test('T13834', normal, compile_fail, [''])
 test('T17077', normal, compile_fail, [''])
 test('T16512a', normal, compile_fail, [''])



View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/ef44934cc8de1b5ff84e63e8eaa3085c8620463f...4c83df3b0f784d27afcef9ccc28a9e3ef461f129

-- 
View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/ef44934cc8de1b5ff84e63e8eaa3085c8620463f...4c83df3b0f784d27afcef9ccc28a9e3ef461f129
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