[commit: ghc] master: Report better suggestion for GADT data constructor (97032ed)
git at git.haskell.org
git at git.haskell.org
Fri Mar 15 19:06:43 UTC 2019
Repository : ssh://git@git.haskell.org/ghc
On branch : master
Link : http://ghc.haskell.org/trac/ghc/changeset/97032ed9b2594c8939cab776ff871051d6dba30a/ghc
>---------------------------------------------------------------
commit 97032ed9b2594c8939cab776ff871051d6dba30a
Author: Simon Peyton Jones <simonpj at microsoft.com>
Date: Wed Mar 13 13:27:22 2019 +0000
Report better suggestion for GADT data constructor
This addresses issue #16427. An easy fix.
>---------------------------------------------------------------
97032ed9b2594c8939cab776ff871051d6dba30a
compiler/typecheck/TcTyClsDecls.hs | 22 +++++++++-------------
testsuite/tests/gadt/T12087.stderr | 8 ++++----
testsuite/tests/gadt/T16427.hs | 5 +++++
testsuite/tests/gadt/T16427.stderr | 7 +++++++
testsuite/tests/gadt/all.T | 1 +
5 files changed, 26 insertions(+), 17 deletions(-)
diff --git a/compiler/typecheck/TcTyClsDecls.hs b/compiler/typecheck/TcTyClsDecls.hs
index a3e39ad..1ac12b0 100644
--- a/compiler/typecheck/TcTyClsDecls.hs
+++ b/compiler/typecheck/TcTyClsDecls.hs
@@ -3021,9 +3021,8 @@ checkValidDataCon dflags existential_ok tc con
, ppr orig_res_ty <+> dcolon <+> ppr (tcTypeKind orig_res_ty)])
- ; checkTc (isJust (tcMatchTy res_ty_tmpl
- orig_res_ty))
- (badDataConTyCon con res_ty_tmpl orig_res_ty)
+ ; checkTc (isJust (tcMatchTy res_ty_tmpl orig_res_ty))
+ (badDataConTyCon con res_ty_tmpl)
-- Note that checkTc aborts if it finds an error. This is
-- critical to avoid panicking when we call dataConUserType
-- on an un-rejiggable datacon!
@@ -3745,9 +3744,9 @@ noClassTyVarErr clas fam_tc
, text "mentions none of the type or kind variables of the class" <+>
quotes (ppr clas <+> hsep (map ppr (classTyVars clas)))]
-badDataConTyCon :: DataCon -> Type -> Type -> SDoc
-badDataConTyCon data_con res_ty_tmpl actual_res_ty
- | ASSERT( all isTyVar actual_ex_tvs )
+badDataConTyCon :: DataCon -> Type -> SDoc
+badDataConTyCon data_con res_ty_tmpl
+ | ASSERT( all isTyVar tvs )
tcIsForAllTy actual_res_ty
= nested_foralls_contexts_suggestion
| isJust (tcSplitPredFunTy_maybe actual_res_ty)
@@ -3757,6 +3756,8 @@ badDataConTyCon data_con res_ty_tmpl actual_res_ty
text "returns type" <+> quotes (ppr actual_res_ty))
2 (text "instead of an instance of its parent type" <+> quotes (ppr res_ty_tmpl))
where
+ actual_res_ty = dataConOrigResTy data_con
+
-- This suggestion is useful for suggesting how to correct code like what
-- was reported in #12087:
--
@@ -3786,13 +3787,8 @@ badDataConTyCon data_con res_ty_tmpl actual_res_ty
-- underneath the nested foralls and contexts.
-- 3) Smash together the type variables and class predicates from 1) and
-- 2), and prepend them to the rho type from 2).
- actual_ex_tvs = dataConExTyCoVars data_con
- actual_theta = dataConTheta data_con
- (actual_res_tvs, actual_res_theta, actual_res_rho)
- = tcSplitNestedSigmaTys actual_res_ty
- suggested_ty = mkSpecForAllTys (actual_ex_tvs ++ actual_res_tvs) $
- mkPhiTy (actual_theta ++ actual_res_theta)
- actual_res_rho
+ (tvs, theta, rho) = tcSplitNestedSigmaTys (dataConUserType data_con)
+ suggested_ty = mkSpecSigmaTy tvs theta rho
badGadtDecl :: Name -> SDoc
badGadtDecl tc_name
diff --git a/testsuite/tests/gadt/T12087.stderr b/testsuite/tests/gadt/T12087.stderr
index 03f2465..0039e98 100644
--- a/testsuite/tests/gadt/T12087.stderr
+++ b/testsuite/tests/gadt/T12087.stderr
@@ -9,27 +9,27 @@ T12087.hs:6:3: error:
T12087.hs:9:3: error:
• GADT constructor type signature cannot contain nested ‘forall’s or contexts
Suggestion: instead use this type signature:
- MkF2 :: forall a. (Ord a, Eq a) => F2 a
+ MkF2 :: forall a. (Ord a, Eq a) => a -> F2 a
• In the definition of data constructor ‘MkF2’
In the data type declaration for ‘F2’
T12087.hs:12:3: error:
• GADT constructor type signature cannot contain nested ‘forall’s or contexts
Suggestion: instead use this type signature:
- MkF3 :: forall a b. (Eq a, Eq b) => b -> F3 a
+ MkF3 :: forall a b. (Eq a, Eq b) => a -> b -> F3 a
• In the definition of data constructor ‘MkF3’
In the data type declaration for ‘F3’
T12087.hs:15:3: error:
• GADT constructor type signature cannot contain nested ‘forall’s or contexts
Suggestion: instead use this type signature:
- MkF4 :: forall a b. (Eq a, Eq b) => b -> F4 a
+ MkF4 :: forall a b. (Eq a, Eq b) => a -> b -> F4 a
• In the definition of data constructor ‘MkF4’
In the data type declaration for ‘F4’
T12087.hs:18:3: error:
• GADT constructor type signature cannot contain nested ‘forall’s or contexts
Suggestion: instead use this type signature:
- MkF5 :: forall a b. a -> Int -> Int -> b -> F5 a
+ MkF5 :: forall a b. Int -> Int -> a -> Int -> Int -> b -> F5 a
• In the definition of data constructor ‘MkF5’
In the data type declaration for ‘F5’
diff --git a/testsuite/tests/gadt/T16427.hs b/testsuite/tests/gadt/T16427.hs
new file mode 100644
index 0000000..3bcbb7a
--- /dev/null
+++ b/testsuite/tests/gadt/T16427.hs
@@ -0,0 +1,5 @@
+{-# LANGUAGE RankNTypes, GADTs #-}
+
+module T16427 where
+
+data D where C :: Int -> forall b . b -> D
diff --git a/testsuite/tests/gadt/T16427.stderr b/testsuite/tests/gadt/T16427.stderr
new file mode 100644
index 0000000..1c80190
--- /dev/null
+++ b/testsuite/tests/gadt/T16427.stderr
@@ -0,0 +1,7 @@
+
+T16427.hs:5:14: error:
+ • GADT constructor type signature cannot contain nested ‘forall’s or contexts
+ Suggestion: instead use this type signature:
+ C :: forall b. Int -> b -> D
+ • In the definition of data constructor ‘C’
+ In the data type declaration for ‘D’
diff --git a/testsuite/tests/gadt/all.T b/testsuite/tests/gadt/all.T
index 86a9b0c..bffb34a 100644
--- a/testsuite/tests/gadt/all.T
+++ b/testsuite/tests/gadt/all.T
@@ -119,3 +119,4 @@ test('T14719', normal, compile_fail, ['-fdiagnostics-show-caret'])
test('T14808', normal, compile, [''])
test('T15009', normal, compile, [''])
test('T15558', normal, compile, [''])
+test('T16427', normal, compile_fail, [''])
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