Add long-distance info for pattern bindings (#18572)

We didn't consider the RHS of a pattern-binding before, which led to
surprising warnings listed in #18572.

As can be seen from the regression test T18572, we get the expected
output now.

3 files changed, 32 insertions, 2 deletions

diff --git a/testsuite/tests/pmcheck/should_compile/T18572.hs b/testsuite/tests/pmcheck/should_compile/T18572.hs
new file mode 100644
index 0000000000..9a37de4813
--- /dev/null
+++ b/testsuite/tests/pmcheck/should_compile/T18572.hs
@@ -0,0 +1,12 @@
+{-# OPTIONS_GHC -Wincomplete-uni-patterns -Wincomplete-patterns -fforce-recomp #-}
+{-# LANGUAGE DataKinds, KindSignatures, GADTs #-}
+
+module T18572 where
+
+True = True
+
+data SBool (b :: Bool) where
+  STrue :: SBool True
+  SFalse :: SBool False
+
+STrue = SFalse
diff --git a/testsuite/tests/pmcheck/should_compile/T18572.stderr b/testsuite/tests/pmcheck/should_compile/T18572.stderr
new file mode 100644
index 0000000000..15d9f7c5b5
--- /dev/null
+++ b/testsuite/tests/pmcheck/should_compile/T18572.stderr
@@ -0,0 +1,16 @@
+
+T18572.hs:12:1: warning: [-Winaccessible-code (in -Wdefault)]
+    • Couldn't match type ‘'False’ with ‘'True’
+      Inaccessible code in
+        a pattern with constructor: STrue :: SBool 'True,
+        in a pattern binding
+    • In the pattern: STrue
+      In a pattern binding: STrue = SFalse
+
+T18572.hs:12:1: warning: [-Woverlapping-patterns (in -Wdefault)]
+    Pattern match is redundant
+    In a pattern binding: STrue = ...
+
+T18572.hs:12:1: warning: [-Wincomplete-uni-patterns]
+    Pattern match(es) are non-exhaustive
+    In a pattern binding: Patterns not matched: SFalse
diff --git a/testsuite/tests/pmcheck/should_compile/all.T b/testsuite/tests/pmcheck/should_compile/all.T
index 51fb76b078..ee69cf176a 100644
--- a/testsuite/tests/pmcheck/should_compile/all.T
+++ b/testsuite/tests/pmcheck/should_compile/all.T
@@ -102,6 +102,8 @@ test('T17234', normal, compile,
      ['-fwarn-incomplete-patterns -fwarn-overlapping-patterns'])
 test('T17248', normal, compile,
      ['-fwarn-incomplete-patterns -fwarn-overlapping-patterns'])
+test('T17340', normal, compile,
+     ['-Wredundant-bang-patterns'])
 test('T17357', expect_broken(17357), compile,
      ['-fwarn-incomplete-patterns -fwarn-overlapping-patterns'])
 test('T17376', normal, compile,
@@ -124,8 +126,8 @@ test('T18478', collect_compiler_stats('bytes allocated',10), compile,
      ['-fwarn-incomplete-patterns -fwarn-overlapping-patterns'])
 test('T18533', normal, compile,
      ['-fwarn-incomplete-patterns -fwarn-overlapping-patterns'])
-test('T17340', normal, compile,
-     ['-Wredundant-bang-patterns'])
+test('T18572', normal, compile,
+     ['-fwarn-incomplete-patterns -fwarn-incomplete-uni-patterns -fwarn-overlapping-patterns'])
 
 # Other tests
 test('pmc001', [], compile,