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| author | Matthieu Sozeau | 2018-11-28 17:10:02 +0100 |
|---|---|---|
| committer | Matthieu Sozeau | 2018-11-28 17:10:02 +0100 |
| commit | 320f8c4503293b37c852548e4d19ff4dd1c191cb (patch) | |
| tree | 9d306d01b8ef00d8b87615259ea09fa82b568ad8 /doc | |
| parent | 2e68697327f6f8a7f365ba3474a3f1a04ca4a621 (diff) | |
| parent | 23fcb09d934bf77fe58f232d2c246a81fc76591f (diff) | |
Merge PR #9015: [Typeclasses] Warn when RHS of `:>` is not a class
Diffstat (limited to 'doc')
| -rw-r--r-- | doc/sphinx/addendum/type-classes.rst | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/doc/sphinx/addendum/type-classes.rst b/doc/sphinx/addendum/type-classes.rst index 15a55d9e72..882798205b 100644 --- a/doc/sphinx/addendum/type-classes.rst +++ b/doc/sphinx/addendum/type-classes.rst @@ -260,6 +260,12 @@ preorder can be used instead. This is very similar to the coercion mechanism of ``Structure`` declarations. The implementation simply declares each projection as an instance. +.. warn:: Ignored instance declaration for “@ident”: “@term” is not a class + + Using this ``:>`` syntax with a right-hand-side that is not itself a Class + has no effect (apart from emitting this warning). In particular, is does not + declare a coercion. + One can also declare existing objects or structure projections using the Existing Instance command to achieve the same effect. |