Don't warn about variable-free strict pattern bindings

See Trac #13646 and the new
Note [Pattern bindings that bind no variables]

3 files changed, 20 insertions, 1 deletions

diff --git a/testsuite/tests/rename/should_compile/T13646.hs b/testsuite/tests/rename/should_compile/T13646.hs
new file mode 100644
index 0000000000..d2d82797ae
--- /dev/null
+++ b/testsuite/tests/rename/should_compile/T13646.hs
@@ -0,0 +1,15 @@
+{-# OPTIONS_GHC -Wall #-}
+{-# LANGUAGE BangPatterns #-}
+
+module T13646 where
+
+import Control.Exception
+
+foo :: IO ()
+foo = do let !() = assert False ()
+             -- Should not give a warning
+
+         let () = assert False ()
+             -- Should give a warning
+
+         pure ()
diff --git a/testsuite/tests/rename/should_compile/T13646.stderr b/testsuite/tests/rename/should_compile/T13646.stderr
new file mode 100644
index 0000000000..ad23c444c9
--- /dev/null
+++ b/testsuite/tests/rename/should_compile/T13646.stderr
@@ -0,0 +1,3 @@
+
+T13646.hs:12:14: warning: [-Wunused-pattern-binds (in -Wextra, -Wunused-binds)]
+    This pattern-binding binds no variables: () = assert False ()
diff --git a/testsuite/tests/rename/should_compile/all.T b/testsuite/tests/rename/should_compile/all.T
index f6b71fda3b..e7ad719278 100644
--- a/testsuite/tests/rename/should_compile/all.T
+++ b/testsuite/tests/rename/should_compile/all.T
@@ -27,7 +27,7 @@ test('rn034', normal, compile, [''])
 test('rn035', normal, compile, [''])
 test('rn036', normal, compile, [''])
 test('rn037', normal, compile, [''])
-	
+
 # Missing:
 # test('rn038', normal, compile, [''])
 
@@ -150,3 +150,4 @@ test('T12533', normal, compile, [''])
 test('T12597', normal, compile, [''])
 test('T12548', normal, compile, [''])
 test('T13132', normal, compile, [''])
+test('T13646', normal, compile, [''])