[commit: ghc] master: Document type functions in the Paterson conditions (608e76c)

[git at git.haskell.org]

Repository : ssh://git@git.haskell.org/ghc

On branch  : master
Link       : http://ghc.haskell.org/trac/ghc/changeset/608e76ced1ae2f8a9d2084d3092e37c47480fa91/ghc

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commit 608e76ced1ae2f8a9d2084d3092e37c47480fa91
Author: Simon Peyton Jones <simonpj at microsoft.com>
Date:   Thu Jul 23 12:24:14 2015 +0100

    Document type functions in the Paterson conditions


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608e76ced1ae2f8a9d2084d3092e37c47480fa91
 docs/users_guide/glasgow_exts.xml | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/docs/users_guide/glasgow_exts.xml b/docs/users_guide/glasgow_exts.xml
index 2ec1d4e..9685b1d 100644
--- a/docs/users_guide/glasgow_exts.xml
+++ b/docs/users_guide/glasgow_exts.xml
@@ -5246,7 +5246,12 @@ The Paterson Conditions: for each class constraint <literal>(C t1 ... tn)</liter
 <orderedlist>
 <listitem><para>No type variable has more occurrences in the constraint than in the head</para></listitem>
 <listitem><para>The constraint has fewer constructors and variables (taken together
-      and counting repetitions) than the head</para></listitem>
+      and counting repetitions) than the head
+</para></listitem>
+<listitem><para>The constraint mentions no type functions.
+A type function application can in principle expand to a
+type of arbitrary size, and so are rejected out of hand
+</para></listitem>
 </orderedlist>
 </para></listitem>