Rename rustc_errors dependency in rust 2018 crates
I think this is a better solution than `use rustc_errors as errors` in `lib.rs` and `use crate::errors` in modules.
Related: rust-lang/cargo#5653
cc #58099
r? @Centril
Deduplicate mismatched delimiter errors
Delay unmatched delimiter errors until after the parser has run to deduplicate them when parsing and attempt recovering intelligently.
Second attempt at #54029, follow up to #53949. Fix#31528.
Overhaul `syntax::fold::Folder`.
This PR changes `syntax::fold::Folder` from a functional style
(where most methods take a `T` and produce a new `T`) to a more
imperative style (where most methods take and modify a `&mut T`), and
renames it `syntax::mut_visit::MutVisitor`.
This makes the code faster and more concise.
This commit changes `syntax::fold::Folder` from a functional style
(where most methods take a `T` and produce a new `T`) to a more
imperative style (where most methods take and modify a `&mut T`), and
renames it `syntax::mut_visit::MutVisitor`.
The first benefit is speed. The functional style does not require any
reallocations, due to the use of `P::map` and
`MoveMap::move_{,flat_}map`. However, every field in the AST must be
overwritten; even those fields that are unchanged are overwritten with
the same value. This causes a lot of unnecessary memory writes. The
imperative style reduces instruction counts by 1--3% across a wide range
of workloads, particularly incremental workloads.
The second benefit is conciseness; the imperative style is usually more
concise. E.g. compare the old functional style:
```
fn fold_abc(&mut self, abc: ABC) {
ABC {
a: fold_a(abc.a),
b: fold_b(abc.b),
c: abc.c,
}
}
```
with the imperative style:
```
fn visit_abc(&mut self, ABC { a, b, c: _ }: &mut ABC) {
visit_a(a);
visit_b(b);
}
```
(The reductions get larger in more complex examples.)
Overall, the patch removes over 200 lines of code -- even though the new
code has more comments -- and a lot of the remaining lines have fewer
characters.
Some notes:
- The old style used methods called `fold_*`. The new style mostly uses
methods called `visit_*`, but there are a few methods that map a `T`
to something other than a `T`, which are called `flat_map_*` (`T` maps
to multiple `T`s) or `filter_map_*` (`T` maps to 0 or 1 `T`s).
- `move_map.rs`/`MoveMap`/`move_map`/`move_flat_map` are renamed
`map_in_place.rs`/`MapInPlace`/`map_in_place`/`flat_map_in_place` to
reflect their slightly changed signatures.
- Although this commit renames the `fold` module as `mut_visit`, it
keeps it in the `fold.rs` file, so as not to confuse git. The next
commit will rename the file.
Suggest removing leading left angle brackets.
Fixes#57819.
This PR adds errors and accompanying suggestions as below:
```
bar::<<<<<T as Foo>::Output>();
^^^ help: remove extra angle brackets
```
r? @estebank
This commit extends existing suggestions to move lifetimes before types
in generic arguments to also suggest moving types behind associated type
bindings.
Add suggestion for incorrect field syntax.
Fixes#57684.
This commit adds a suggestion when a `=` character is used when
specifying the value of a field in a struct constructor incorrectly
instead of a `:` character.
r? @estebank
Remove quote_*! macros
This deletes a considerable amount of test cases, some of which we may want to keep. I'm not entirely certain what the primary intent of many of them was; if we should keep them I can attempt to edit each case to continue compiling without the quote_*! macros involved.
Fixes#46849.
Fixes#12265.
Fixes#12266.
Fixes#26994.
r? @Manishearth
Add error for trailing angle brackets.
Fixes#54521.
This PR adds a error (and accompanying machine applicable
suggestion) for trailing angle brackets on function calls with a
turbofish.
r? @estebank
This commit adds a suggestion when a `=` character is used when
specifying the value of a field in a struct constructor incorrectly
instead of a `:` character.
This commit implements a suggestion from @estebank that optimizes the
use of snapshots.
Instead of creating a snapshot for each recursion in `parse_path_segment`
and then replacing `self` with them until the first invocation where if
leading angle brackets are detected, `self` is not replaced and instead the
snapshot is used to inform how parsing should continue.
Now, a snapshot is created in the first invocation that acts as a backup
of the parser state before any generic arguments are parsed (and
therefore, before recursion starts). This backup replaces `self` if after
all parsing of generic arguments has concluded we can determine that
there are leading angle brackets. Parsing can then proceed from the
backup state making use of the now known number of unmatched leading
angle brackets to recover.
This commit extends the trailing `>` detection to also work for paths
such as `Foo::<Bar>>:Baz`.
This involves making the existing check take the token that is expected
to follow the path being checked as a parameter.
Care is taken to ensure that this only happens on the construction of a
whole path segment and not a partial path segment (during recursion).
Through this enhancement, it was also observed that the ordering of
right shift token and greater than tokens was overfitted to the examples
being tested.
In practice, given a sequence of `>` characters: `>>>>>>>>>`
..then they will be split into `>>` eagerly: `>> >> >> >> >`.
..but when a `<` is prepended, then the first `>>` is split:
`<T> > >> >> >> >`
..and then when another `<` is prepended, a right shift is first again:
`Vec<<T>> >> >> >> >`
In the previous commits, a example that had two `<<` characters was
always used and therefore it was incorrectly assumed that `>>` would
always be first - but when there is a single `<`, this is not the case.
