Instead just use `pprust::path_to_string(..)` where needed.
This has two benefits:
a) The AST definition is now independent of printing it.
(Therefore we get closer to extracting a data-crate.)
b) Debugging should be easier as program flow is clearer.
There's not really any reason to not have the visibility default to
inherited, and this saves us the trouble of checking everywhere for
whether we have a visibility or not.
This means that callers can pass in a closure like
`|buf| some_function(..., &mut buf)` and pass in arbitrary arguments to
that function without complicating the trait definition. We also keep
the impl for str and String, since it's useful to be able to just pass
in "" or format!("{}"...) results in some cases.
This changes Print's definition to take self, instead of &self, because
otherwise FnOnce cannot be called directly. We could instead take FnMut
or even Fn, but that seems like it'd merely complicate matters -- most
of the time, the FnOnce does not constrain us at all anyway. If it does,
a custom Print impl for &'_ SomeStruct is not all that painful.
This introduces a WithFormatter abstraction that permits one-time
fmt::Display on an arbitrary closure, created via `display_fn`. This
allows us to prevent allocation while still using functions instead of
structs, which are a bit unwieldy to thread arguments through as they
can't easily call each other (and are generally a bit opaque).
The eventual goal here is likely to move us off of the formatting
infrastructure entirely in favor of something more structured, but this
is a good step to move us in that direction as it makes, for example,
passing a context describing current state to the formatting impl much
easier.
Fix confusion in theme picker functions
To reproduce the bug currently: click on the theme picker button twice (to show it then hide it). Then click anywhere else: the dropdown menu appears again.
The problem was coming from a confusion of what the `hideThemeButtonState` and `showThemeButtonState` were supposed to do. I switched their codes and updated the `switchThemeButtonState` function. It now works as expected.
r? @kinnison
These impls prevent ergonomic use of the config (e.g., forcing us to use
RefCell) despite all usecases for these structs only using their Display
impls once.
