Question and user story examples for the `time` crate

[xFrednet]

Hey everyone watching this repo. I'm currently working on the basic framework to implement a stable interface. Currently, I'm mostly working with the rust reference, but feel like this isn't ideal when it comes to macro and attribute representations among other things.

To get a feel, what lint authors and library implementors would actually like to have, I would like to collect user storied. Therefore, I would like to select user stories. Would everyone be okay with collecting them in this repo as issues? I believe this is the best place we currently have for something like this. :upside_down_face:

[jhpratt]

Here's a list of lints I could plausibly see myself writing for time as it currently exists:

• using doc-hidden methods, excluding expansion from time macros
• assuming the type of EncodedConfig cannot change (i.e. using u128 or integer literal as a const generic)
• construction of a type with a statically known invalid value (i.e. Time::from_hms(25, 0, 0))
• manual construction when constant is available (i.e. Duration::new(0, 0))
• format description containing components that will always error (for the type provided)
• known invalid format description (e.g. invalid syntax)
• use of iso8601::Config outside of const context (it's useless)
• call of modifier::X::default() in a const context when #![no_implicit_prelude] is enabled (behavior explicitly not guaranteed)

Happy to provide further explanation on any/all of these as needed. I don't believe the level of a warning is in any way relevant to the design.

[xFrednet]

Thank you for the response! Most of these seam pretty straightforward and would be covered by only having the reference representation. Could you maybe elaborate on these two points:

• format description containing components that will always error (for the type provided)

• known invalid format description (e.g. invalid syntax)

A code snipped you would like to lint would be nice. (I haven't worked with the crate yet.) Besides that, do you have any lint ideas that interact with attributes or macros?

[jhpratt]

format description containing components that will always error (for the type provided)

let fd = time::macros::format_description!("[year]");
UtcOffset::UTC.format(fd);
//~^ ERROR `UtcOffset` does not provide the `[year]` component
//~^^ NOTE this method call will always fail

known invalid format description (e.g. invalid syntax)

Any (unescaped) opening bracket has to be closed:

let _ = time::format_description::parse("[");
//~^ ERROR invalid format description
//~^^ NOTE this function call will always fail

This will fail at compile time if you use the macro. I would like to lint the statically known runtime case as well (ignoring the fact that the macro should be suggested).

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In theory I would like to be able to know which components are present in a runtime format description, but that would be far more involved. It's certainly not something I would want/need to be present initially.

[jhpratt]

Here's an interesting one: I would like to know whether the crate being analyzed is a binary or a library. This is because a library fundamentally cannot uphold the guarantees that this unsafe fn requires.