From 7a90020f167ab016cbfa95decafaa1a54a974bc6 Mon Sep 17 00:00:00 2001
From: Krzysztof Gogolewski <krzysztof.gogolewski@tweag.io>
Date: Wed, 18 Oct 2023 17:01:34 +0200
Subject: [PATCH] docs: fix ScopedTypeVariables example (#24101)

The previous example didn't compile.

Furthermore, it wasn't demonstrating the point properly.
I have changed it to an example which shows that 'a' in the signature
must be the same 'a' as in the instance head.
---
 docs/users_guide/exts/scoped_type_variables.rst | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/docs/users_guide/exts/scoped_type_variables.rst b/docs/users_guide/exts/scoped_type_variables.rst
index ee6a77f32a3..feeb65ecb7f 100644
--- a/docs/users_guide/exts/scoped_type_variables.rst
+++ b/docs/users_guide/exts/scoped_type_variables.rst
@@ -293,11 +293,11 @@ signatures/ of the methods. For example, the following will be accepted without
 explicitly enabling :extension:`ScopedTypeVariables`: ::
 
       class D a where
-        m :: [a] -> a
+        m :: a -> a
 
-      instance D [a] where
+      instance Num a => D [a] where
         m :: [a] -> [a]
-        m = reverse
+        m x = map (*2) x
 
 Note that writing ``m :: [a] -> [a]`` requires the use of the
 :extension:`InstanceSigs` extension.
-- 
GitLab