expression and the type declaration is parsed as an array type declaration.
To resolve the ambiguity, embed the constraint in an
<a href="#Interface_types">interface</a> or use a trailing comma:
</p>

<pre>
type T[P interface{*C}] …
type T[P *C,] …
</pre>

<p>
Type parameters may also be declared by the receiver specification

    * This allows having a router for `/cats` and all its *path operations*, while having one of them for `/cats`.
    * Now it doesn't have to be only `/cats/` (with a trailing slash).
    * To use it, declare the path in the *path operation* as the empty string (`""`).
    * PR [#415](https://github.com/tiangolo/fastapi/pull/415) by [@vitalik](https://github.com/vitalik).