Use braces in TH case pprint (fixes #20893)

This patch ensures that the pretty printer formats `case` statements
using braces (instead of layout) to remain consistent with the
formatting of other statements (like `do`)

4 files changed, 45 insertions, 1 deletions

diff --git a/libraries/template-haskell/Language/Haskell/TH/Ppr.hs b/libraries/template-haskell/Language/Haskell/TH/Ppr.hs
index 02f38852ac..42d32487c8 100644
--- a/libraries/template-haskell/Language/Haskell/TH/Ppr.hs
+++ b/libraries/template-haskell/Language/Haskell/TH/Ppr.hs
@@ -183,7 +183,7 @@ pprExp i (LetE ds_ e) = parensIf (i > noPrec) $ text "let" <+> pprDecs ds_
 
 pprExp i (CaseE e ms)
  = parensIf (i > noPrec) $ text "case" <+> ppr e <+> text "of"
-                        $$ nest nestDepth (ppr ms)
+                        $$ braces (semiSep ms)
 pprExp i (DoE m ss_) = parensIf (i > noPrec) $
     pprQualifier m <> text "do" <+> pprStms ss_
   where
diff --git a/testsuite/tests/quotes/T20893.hs b/testsuite/tests/quotes/T20893.hs
new file mode 100644
index 0000000000..90f1efb331
--- /dev/null
+++ b/testsuite/tests/quotes/T20893.hs
@@ -0,0 +1,29 @@
+-- #20893
+
+module Main where
+
+import Language.Haskell.TH
+import Language.Haskell.TH.Ppr
+
+main = do
+  runQ t1 >>= p
+  runQ t2 >>= p
+
+t1 = [d| main = do { case 0 of { 0 -> 1 }; putStrLn "pass" } |]
+
+t2 = [d|
+      main = do
+         let day = "mon"
+         let num = case day of
+               "mon" -> 0
+               "tue" -> 1
+               "wed" -> 3
+               "thu" -> 4
+               "fri" -> 5
+               "sat" -> 6
+               "sun" -> 7
+               _ -> 8
+         putStrLn (show day) ++ " is " (show num)
+      |]
+
+p = putStrLn . pprint
diff --git a/testsuite/tests/quotes/T20893.stdout b/testsuite/tests/quotes/T20893.stdout
new file mode 100644
index 0000000000..c08abdd03d
--- /dev/null
+++ b/testsuite/tests/quotes/T20893.stdout
@@ -0,0 +1,14 @@
+main_0 = do {case 0 of
+             {0 -> 1};
+             System.IO.putStrLn "pass"}
+main_0 = do {let {day_1 = "mon"};
+             let {num_2 = case day_1 of
+                          {"mon" -> 0;
+                           "tue" -> 1;
+                           "wed" -> 3;
+                           "thu" -> 4;
+                           "fri" -> 5;
+                           "sat" -> 6;
+                           "sun" -> 7;
+                           _ -> 8}};
+             System.IO.putStrLn (GHC.Show.show day_1) GHC.Base.++ " is " (GHC.Show.show num_2)}
\ No newline at end of file
diff --git a/testsuite/tests/quotes/all.T b/testsuite/tests/quotes/all.T
index e441811111..1d145e8781 100644
--- a/testsuite/tests/quotes/all.T
+++ b/testsuite/tests/quotes/all.T
@@ -39,3 +39,4 @@ test('TH_top_splice', normal, compile_fail, [''])
 test('TTH_top_splice', normal, compile_fail, [''])
 test('TH_double_splice', normal, compile_fail, [''])
 test('T20688', normal, compile, ['-Wimplicit-lift -Werror'])
+test('T20893', normal, compile_and_run, [''])