Fix -Woperator-whitespace for consym (part of #19372)

Due to an oversight, the initial specification and implementation of
-Woperator-whitespace focused on varsym exclusively and completely
ignored consym.

This meant that expressions such as "x+ y" would produce a warning,
while "x:+ y" would not.

The specification was corrected in ghc-proposals pull request #404,
and this patch updates the implementation accordingly.

Regression test included.

3 files changed, 31 insertions, 0 deletions

diff --git a/testsuite/tests/parser/should_compile/T19372consym.hs b/testsuite/tests/parser/should_compile/T19372consym.hs
new file mode 100644
index 0000000000..6a8fd14d50
--- /dev/null
+++ b/testsuite/tests/parser/should_compile/T19372consym.hs
@@ -0,0 +1,15 @@
+{-# OPTIONS -Woperator-whitespace #-}
+
+module T19372consym where
+
+import Data.List.NonEmpty
+
+a_suffix      = \x y -> x: y
+a_prefix      = \x y -> x :y
+a_tight_infix = \x y -> x:y
+a_loose_infix = \x y -> x : y   -- Only this one should be without a warning.
+
+b_suffix      = \x y -> x:| y
+b_prefix      = \x y -> x :|y
+b_tight_infix = \x y -> x:|y
+b_loose_infix = \x y -> x :| y  -- Only this one should be without a warning.
diff --git a/testsuite/tests/parser/should_compile/T19372consym.stderr b/testsuite/tests/parser/should_compile/T19372consym.stderr
new file mode 100644
index 0000000000..f2a0998069
--- /dev/null
+++ b/testsuite/tests/parser/should_compile/T19372consym.stderr
@@ -0,0 +1,15 @@
+
+T19372consym.hs:12:26: warning: [GHC-40798] [-Woperator-whitespace]
+    The suffix use of a ‘:|’ might be repurposed as special syntax
+      by a future language extension.
+    Suggested fix: Add whitespace around ‘:|’.
+
+T19372consym.hs:13:27: warning: [GHC-40798] [-Woperator-whitespace]
+    The prefix use of a ‘:|’ might be repurposed as special syntax
+      by a future language extension.
+    Suggested fix: Add whitespace around ‘:|’.
+
+T19372consym.hs:14:26: warning: [GHC-40798] [-Woperator-whitespace]
+    The tight infix use of a ‘:|’ might be repurposed as special syntax
+      by a future language extension.
+    Suggested fix: Add whitespace around ‘:|’.
diff --git a/testsuite/tests/parser/should_compile/all.T b/testsuite/tests/parser/should_compile/all.T
index 53fd222576..5fc2a72566 100644
--- a/testsuite/tests/parser/should_compile/all.T
+++ b/testsuite/tests/parser/should_compile/all.T
@@ -193,3 +193,4 @@ test('T20718',  normal, compile, ['-dsuppress-uniques -ddump-parsed-ast -dkeep-c
 test('T20718b',  normal, compile, ['-dsuppress-uniques -ddump-parsed-ast -dkeep-comments'])
 
 test('T21589', normal, compile, [''])
+test('T19372consym', normal, compile, [''])