Fix Trac #9815

Dot-dot record-wildcard notation is simply illegal for constructors
without any named fields, but that was neither documented nor checked.
This patch does so

- Make the check in RnPat
- Add test T9815
- Fix CmmLayoutStack which was using the illegal form (!)
- Document in user manual

3 files changed, 11 insertions, 0 deletions

diff --git a/testsuite/tests/rename/should_fail/T9815.hs b/testsuite/tests/rename/should_fail/T9815.hs
new file mode 100644
index 0000000000..7d7ae6616e
--- /dev/null
+++ b/testsuite/tests/rename/should_fail/T9815.hs
@@ -0,0 +1,6 @@
+{-# LANGUAGE RecordWildCards #-}
+module T9815 where
+
+newtype N = N Int deriving (Show)
+
+foo = print N{..}
diff --git a/testsuite/tests/rename/should_fail/T9815.stderr b/testsuite/tests/rename/should_fail/T9815.stderr
new file mode 100644
index 0000000000..99f16b624d
--- /dev/null
+++ b/testsuite/tests/rename/should_fail/T9815.stderr
@@ -0,0 +1,4 @@
+
+T9815.hs:6:13:
+    Illegal `..' notation for constructor ‘N’
+      The constructor has no labelled fields
diff --git a/testsuite/tests/rename/should_fail/all.T b/testsuite/tests/rename/should_fail/all.T
index f2664dc2bf..56d0f87fb9 100644
--- a/testsuite/tests/rename/should_fail/all.T
+++ b/testsuite/tests/rename/should_fail/all.T
@@ -119,3 +119,4 @@ test('T9177', normal, compile_fail, [''])
 test('T9436', normal, compile_fail, [''])
 test('T9437', normal, compile_fail, [''])
 test('T9077', normal, compile_fail, [''])
+test('T9815', normal, compile_fail, [''])