[commit: ghc] master: Clarify promotion rules for newtypes in the documentation (6290c7b)
Simon Peyton Jones <[email protected]>
| Newsgroups | gmane.comp.lang.haskell.cvs.ghc |
|---|---|
| Message-ID | <[email protected]> |
Repository : ssh://darcs.haskell.org//srv/darcs/ghc On branch : master http://hackage.haskell.org/trac/ghc/changeset/6290c7bd0941dc2ae02df200d903d35ca825c4aa >--------------------------------------------------------------- commit 6290c7bd0941dc2ae02df200d903d35ca825c4aa Author: Simon Peyton Jones <[email protected]> Date: Fri Dec 21 09:14:19 2012 +0000 Clarify promotion rules for newtypes in the documentation >--------------------------------------------------------------- docs/users_guide/glasgow_exts.xml | 7 ++++--- 1 files changed, 4 insertions(+), 3 deletions(-) diff --git a/docs/users_guide/glasgow_exts.xml b/docs/users_guide/glasgow_exts.xml index c7b695c..7898677 100644 --- a/docs/users_guide/glasgow_exts.xml +++ b/docs/users_guide/glasgow_exts.xml @@ -5528,7 +5528,10 @@ kinds have sort <literal>BOX</literal>. <para> The following restrictions apply to promotion: <itemizedlist> - <listitem><para>We only promote datatypes whose kinds are of the form + <listitem><para>We promote <literal>data</literal> types and <literal>newtypes</literal>, + but not type synonyms, or type/data families (<xref linkend="type-families"/>). + </para></listitem> + <listitem><para>We only promote types whose kinds are of the form <literal>* -> ... -> * -> *</literal>. In particular, we do not promote higher-kinded datatypes such as <literal>data Fix f = In (f (Fix f))</literal>, or datatypes whose kinds involve promoted types such as @@ -5537,8 +5540,6 @@ The following restrictions apply to promotion: polymorphic, involve constraints, mention type or data families, or involve types that are not promotable. </para></listitem> - <listitem><para>We do not promote data family instances (<xref linkend="data-families"/>). - </para></listitem> </itemizedlist> </para> </sect2>