Creating a &'static HeaderName

[zesterer]

Hi,

The Header trait requires a name function that returns a &'static HeaderName. However, none of the methods used to construct a HeaderName are marked const (and so cannot be used to create a regular static, either explicitly or via promotion of a local temporary), so there appears to only be two possible ways to write a valid implementation of Header::name:

1) Box and then leak a HeaderName on every call

2) Set up a lazy_static (or equivalent via new primitives like LazyCell) that uses internal mutability to lazily initiate a HeaderName

Both of these approaches are undesirable for fairly clear reasons, the first especially, which leads me to the question:

What is the intended approach when implementing this trait?

Or, alternatively, would it be possible to do one of the following? 1) Make some of the methods used to create `HeaderName` `const` (as is the case for `HeaderValue`) 2) Have `Header::name` return `Cow<'static, HeaderName>`

[seanmonstar]

The expected options are:

• Use an existing constant.
• Create a lazy static one.
• Eventually use const fns in http.

[zesterer]

Unfortunately, only the lazy_static route is available to me right now. I guess it'll have to do.