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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. |