Disallow (->) as a data constructor in "data" declaration (fixes #16999)wip/B16999

4 files changed, 13 insertions, 1 deletions

diff --git a/compiler/parser/RdrHsSyn.hs b/compiler/parser/RdrHsSyn.hs
index a574fbe338..defad0fb51 100644
--- a/compiler/parser/RdrHsSyn.hs
+++ b/compiler/parser/RdrHsSyn.hs
@@ -565,13 +565,15 @@ done.
 tyConToDataCon :: SrcSpan -> RdrName -> Either (SrcSpan, SDoc) (Located RdrName)
 tyConToDataCon loc tc
   | isTcOcc occ || isDataOcc occ
-  , isLexCon (occNameFS occ)
+  , isLexCon cs
+  , cs /= fsLit "->"  -- Fixes #16999
   = return (cL loc (setRdrNameSpace tc srcDataName))
 
   | otherwise
   = Left (loc, msg)
   where
     occ = rdrNameOcc tc
+    cs = occNameFS occ
     msg = text "Not a data constructor:" <+> quotes (ppr tc)
 
 mkPatSynMatchGroup :: Located RdrName
diff --git a/testsuite/tests/parser/should_fail/T16999.hs b/testsuite/tests/parser/should_fail/T16999.hs
new file mode 100644
index 0000000000..d43612d035
--- /dev/null
+++ b/testsuite/tests/parser/should_fail/T16999.hs
@@ -0,0 +1,6 @@
+module T16999 where
+
+data Type
+  = TBool
+  | TInt
+  | (->) Type Type
diff --git a/testsuite/tests/parser/should_fail/T16999.stderr b/testsuite/tests/parser/should_fail/T16999.stderr
new file mode 100644
index 0000000000..f9f1569695
--- /dev/null
+++ b/testsuite/tests/parser/should_fail/T16999.stderr
@@ -0,0 +1,2 @@
+
+T16999.hs:6:5: Not a data constructor: ‘->’
diff --git a/testsuite/tests/parser/should_fail/all.T b/testsuite/tests/parser/should_fail/all.T
index 2fc7f3d326..5b919e1a2d 100644
--- a/testsuite/tests/parser/should_fail/all.T
+++ b/testsuite/tests/parser/should_fail/all.T
@@ -161,3 +161,5 @@ test('patFail006', normal, compile_fail, [''])
 test('patFail007', normal, compile_fail, [''])
 test('patFail008', normal, compile_fail, [''])
 test('patFail009', normal, compile_fail, [''])
+
+test('T16999', normal, compile_fail, [''])