pretty-printer: Properly parenthesise LastStmt

After ApplicatveDo strips the last `return` during renaming, the pretty
printer has to restore it. However, if the return was followed by `$`,
the dollar was stripped too and not restored.

For example, the last stamement in:

```
  foo = do
    x <- ...
    ...
    return $ f x
```

would be printed as:

```
    return f x
```

This commit preserved the dolar, so it becomes:

```
    return $ f x
```

3 files changed, 19 insertions, 0 deletions

diff --git a/testsuite/tests/ado/ado009.hs b/testsuite/tests/ado/ado009.hs
new file mode 100644
index 0000000000..876a4fba90
--- /dev/null
+++ b/testsuite/tests/ado/ado009.hs
@@ -0,0 +1,10 @@
+{-# LANGUAGE ApplicativeDo #-}
+{-# OPTIONS_GHC -ddump-rn -dsuppress-uniques #-}
+
+module Test where
+
+-- Make sure the $ stripped from the last stmt is printed
+q :: IO ()
+q = do
+  a <- return ()
+  return $ (\_ -> ()) a
diff --git a/testsuite/tests/ado/ado009.stderr b/testsuite/tests/ado/ado009.stderr
new file mode 100644
index 0000000000..19a5defd4c
--- /dev/null
+++ b/testsuite/tests/ado/ado009.stderr
@@ -0,0 +1,8 @@
+
+==================== Renamer ====================
+Test.q :: IO ()
+Test.q
+  = do a <- return ()
+       return $ (\ _ -> ()) a
+
+
diff --git a/testsuite/tests/ado/all.T b/testsuite/tests/ado/all.T
index 634aae2314..11a9f4d6c8 100644
--- a/testsuite/tests/ado/all.T
+++ b/testsuite/tests/ado/all.T
@@ -6,6 +6,7 @@ test('ado005', normal, compile_fail, [''])
 test('ado006', normal, compile, [''])
 test('ado007', normal, compile, [''])
 test('ado008', normal, compile, [''])
+test('ado009', normal, compile, [''])
 test('T11607', normal, compile_and_run, [''])
 test('ado-optimal', normal, compile_and_run, [''])
 test('T12490', normal, compile, [''])