`MacArgs` is an enum with three variants: `Empty`, `Delimited`, and `Eq`. It's
used in two ways:
- For representing attribute macro arguments (e.g. in `AttrItem`), where all
three variants are used.
- For representing function-like macros (e.g. in `MacCall` and `MacroDef`),
where only the `Delimited` variant is used.
In other words, `MacArgs` is used in two quite different places due to them
having partial overlap. I find this makes the code hard to read. It also leads
to various unreachable code paths, and allows invalid values (such as
accidentally using `MacArgs::Empty` in a `MacCall`).
This commit splits `MacArgs` in two:
- `DelimArgs` is a new struct just for the "delimited arguments" case. It is
now used in `MacCall` and `MacroDef`.
- `AttrArgs` is a renaming of the old `MacArgs` enum for the attribute macro
case. Its `Delimited` variant now contains a `DelimArgs`.
Various other related things are renamed as well.
These changes make the code clearer, avoids several unreachable paths, and
disallows the invalid values.
It's not clear why it was done, and apparently it's no longer necessary now.
Such additions are unpredictable for early doc link resolution and would force us to collect all doc links from all external traits.
`Res::SelfTy` currently has two `Option`s. When the second one is `Some`
the first one is never consulted. So we can split it into two variants,
`Res::SelfTyParam` and `Res::SelfTyAlias`, reducing the size of `Res`
from 24 bytes to 12. This then shrinks `hir::Path` and
`hir::PathSegment`, which are the HIR types that take up the most space.
`rustc_data_structures::thin_vec::ThinVec` looks like this:
```
pub struct ThinVec<T>(Option<Box<Vec<T>>>);
```
It's just a zero word if the vector is empty, but requires two
allocations if it is non-empty. So it's only usable in cases where the
vector is empty most of the time.
This commit removes it in favour of `thin_vec::ThinVec`, which is also
word-sized, but stores the length and capacity in the same allocation as
the elements. It's good in a wider variety of situation, e.g. in enum
variants where the vector is usually/always non-empty.
The commit also:
- Sorts some `Cargo.toml` dependency lists, to make additions easier.
- Sorts some `use` item lists, to make additions easier.
- Changes `clean_trait_ref_with_bindings` to take a
`ThinVec<TypeBinding>` rather than a `&[TypeBinding]`, because this
avoid some unnecessary allocations.
rustdoc: Censor certain complex unevaluated const exprs
Fixes#97933.
This is more of a hotfix for the aforementioned issue. By that, I mean that my proposed patch is
not the best solution but one that does not change as much existing code.
It treats symptoms rather than the root cause.
This PR “censors” certain complex unevaluated constant expressions like `match`es, blocks, function calls, struct literals etc. by pretty-printing them as `_` / `{ _ }` (number and string literals, paths and `()` are still printed as one would expect).
Resorting to this placeholder is preferable to printing the full expression verbatim since
they can be quite large and verbose resulting in an unreadable mess in the generated documentation.
Further, mindlessly printing the const would leak private and `doc(hidden)` struct fields (#97933), at least in the current
stable & nightly implementations which rely on `span_to_snippet` (!) and `rustc_hir_pretty::id_to_string`.
The censoring of _verbose_ expressions is probably going to stay longer term.
However, in regards to private and `doc(hidden)` struct fields, I have a more proper fix in mind
which I have already partially implemented locally and for which I am going to open a separate PR sometime soon.
For that, I was already in contact with `@GuillaumeGomez.`
The proper fix involves rustdoc not falling back on pretty-printing unevaluated consts so easily (what this PR is concerned about)
and instead preferring to print evaluated consts which contain more information allowing it to selectively hide private and `doc(hidden)` fields, create hyperlinks etc. generally making the output more granular and precise (compared to the brutal `_` placeholder).
Unfortunately, I was a bit too late and the issue just hit stable (1.62).
Should this be backported to beta or even a potential 1.62.1?
r? `@GuillaumeGomez`
And likewise for the `Const::val` method.
Because its type is called `ConstKind`. Also `val` is a confusing name
because `ConstKind` is an enum with seven variants, one of which is
called `Value`. Also, this gives consistency with `TyS` and `PredicateS`
which have `kind` fields.
The commit also renames a few `Const` variables from `val` to `c`, to
avoid confusion with the `ConstKind::Value` variant.
Lifetime variance fixes for rustdoc
#97287 migrates rustc to a `Ty` type that is invariant over its lifetime `'tcx`, so I need to fix a bunch of places that assume that `Ty<'a>` and `Ty<'b>` can be unified by shortening both to some common lifetime.
This is doable, since everything is already `'tcx`, so all this PR does is be a bit more explicit that elided lifetimes are actually `'tcx`.
Split out from #97287 so the rustdoc team can review independently.
Only crate root def-ids don't have a parent, and in majority of cases the argument of `DefIdTree::parent` cannot be a crate root.
So we now panic by default in `parent` and introduce a new non-panicing function `opt_parent` for cases where the argument can be a crate root.
Same applies to `local_parent`/`opt_local_parent`.
