Fix Show derivation in the presence of RebindableSyntax/OverloadedStrings

Summary:
To fix this issue, we simply disable `RebindableSyntax` whenever we rename
the code generated from a deriving clause.

Fixes #12688.

Test Plan: make test TEST=T12688

Reviewers: simonpj, austin, bgamari

Reviewed By: simonpj, bgamari

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2591

GHC Trac Issues: #12688

2 files changed, 16 insertions, 0 deletions

diff --git a/testsuite/tests/deriving/should_compile/T12688.hs b/testsuite/tests/deriving/should_compile/T12688.hs
new file mode 100644
index 0000000000..0735a81138
--- /dev/null
+++ b/testsuite/tests/deriving/should_compile/T12688.hs
@@ -0,0 +1,15 @@
+{-# LANGUAGE RebindableSyntax, OverloadedStrings #-}
+module T12688 where
+
+import Prelude (String,Show(..))
+
+newtype Text = Text String
+
+fromString :: String -> Text
+fromString = Text
+
+x :: Text
+x = "x"
+
+newtype Foo = Foo ()
+  deriving (Show)
diff --git a/testsuite/tests/deriving/should_compile/all.T b/testsuite/tests/deriving/should_compile/all.T
index 26312df3e9..bd1f07abe6 100644
--- a/testsuite/tests/deriving/should_compile/all.T
+++ b/testsuite/tests/deriving/should_compile/all.T
@@ -76,3 +76,4 @@ test('T12245', normal, compile, [''])
 test('T12399', normal, compile, [''])
 test('T12583', normal, compile, [''])
 test('T12616', normal, compile, [''])
+test('T12688', normal, compile, [''])