Rather than adding `get_unused_rule` to the `TTMacroExpander` trait, put
it on the concrete `MacroRulesMacroExpander`, and downcast to that type
via `Any` in order to call it.
Suggested-by: Vadim Petrochenkov <vadim.petrochenkov@gmail.com>
The MBE parser checks rules at initial parse time to see if their RHS
has `compile_error!` in it, and returns a list of rule indexes and LHS
spans that don't map to `compile_error!`, for use in unused macro rule
checking.
Instead, have the unused macro rule reporting ask the macro for the rule
to report, and let the macro check at that time. That avoids checking
rules unless they're unused.
In the process, refactor the data structure used to store macro rules,
to group the LHS and RHS (and LHS span) of each rule together, and
refactor the unused rule tracking to only track rule indexes.
This ends up being a net simplification, and reduction in code size.
It collects data about macro expansions and prints them in a table after
expansion finishes. It's very useful for detecting macro bloat,
especially for proc macros.
Details:
- It measures code snippets by pretty-printing them and then measuring
lines and bytes. This required a bunch of additional pretty-printing
plumbing, in `rustc_ast_pretty` and `rustc_expand`.
- The measurement is done in `MacroExpander::expand_invoc`.
- The measurements are stored in `ExtCtxt::macro_stats`.
So they match the order of the parts in the source code, e.g.:
```
struct Foo<T, U> { t: T, u: U }
<-><----> <------------>
/ | \
ident generics variant_data
```
I'm removing empty identifiers everywhere, because in practice they
always mean "no identifier" rather than "empty identifier". (An empty
identifier is impossible.) It's better to use `Option` to mean "no
identifier" because you then can't forget about the "no identifier"
possibility.
Some specifics:
- When testing an attribute for a single name, the commit uses the
`has_name` method.
- When testing an attribute for multiple names, the commit uses the new
`has_any_name` method.
- When using `match` on an attribute, the match arms now have `Some` on
them.
In the tests, we now avoid printing empty identifiers by not printing
the identifier in the `error:` line at all, instead letting the carets
point out the problem.
It bugs me when variables of type `Ident` are called `name`. It leads to
silly things like `name.name`. `Ident` variables should be called
`ident`, and `name` should be used for variables of type `Symbol`.
This commit improves things by by doing `s/name/ident/` on a bunch of
`Ident` variables. Not all of them, but a decent chunk.
`ast::Item` has an `ident` field.
- It's always non-empty for these item kinds: `ExternCrate`, `Static`,
`Const`, `Fn`, `Mod`, `TyAlias`, `Enum`, `Struct`, `Union`,
`Trait`, `TraitAlias`, `MacroDef`, `Delegation`.
- It's always empty for these item kinds: `Use`, `ForeignMod`,
`GlobalAsm`, `Impl`, `MacCall`, `DelegationMac`.
There is a similar story for `AssocItemKind` and `ForeignItemKind`.
Some sites that handle items check for an empty ident, some don't. This
is a very C-like way of doing things, but this is Rust, we have sum
types, we can do this properly and never forget to check for the
exceptional case and never YOLO possibly empty identifiers (or possibly
dummy spans) around and hope that things will work out.
The commit is large but it's mostly obvious plumbing work. Some notable
things.
- `ast::Item` got 8 bytes bigger. This could be avoided by boxing the
fields within some of the `ast::ItemKind` variants (specifically:
`Struct`, `Union`, `Enum`). I might do that in a follow-up; this
commit is big enough already.
- For the visitors: `FnKind` no longer needs an `ident` field because
the `Fn` within how has one.
- In the parser, the `ItemInfo` typedef is no longer needed. It was used
in various places to return an `Ident` alongside an `ItemKind`, but
now the `Ident` (if present) is within the `ItemKind`.
- In a few places I renamed identifier variables called `name` (or
`foo_name`) as `ident` (or `foo_ident`), to better match the type, and
because `name` is normally used for `Symbol`s. It's confusing to see
something like `foo_name.name`.
This involves replacing `nt_pretty_printing_compatibility_hack` with
`stream_pretty_printing_compatibility_hack`.
The handling of statements in `transcribe` is slightly different to
other nonterminal kinds, due to the lack of `from_ast` implementation
for empty statements.
Notable test changes:
- `tests/ui/proc-macro/expand-to-derive.rs`: the diff looks large but
the only difference is the insertion of a single invisible-delimited
group around a metavar.
`rustc_span::symbol` defines some things that are re-exported from
`rustc_span`, such as `Symbol` and `sym`. But it doesn't re-export some
closely related things such as `Ident` and `kw`. So you can do `use
rustc_span::{Symbol, sym}` but you have to do `use
rustc_span::symbol::{Ident, kw}`, which is inconsistent for no good
reason.
This commit re-exports `Ident`, `kw`, and `MacroRulesNormalizedIdent`,
and changes many `rustc_span::symbol::` qualifiers in `compiler/` to
`rustc_span::`. This is a 200+ net line of code reduction, mostly
because many files with two `use rustc_span` items can be reduced to
one.
Fundamentally, we have *three* disjoint categories of functions:
1. const-stable functions
2. private/unstable functions that are meant to be callable from const-stable functions
3. functions that can make use of unstable const features
This PR implements the following system:
- `#[rustc_const_stable]` puts functions in the first category. It may only be applied to `#[stable]` functions.
- `#[rustc_const_unstable]` by default puts functions in the third category. The new attribute `#[rustc_const_stable_indirect]` can be added to such a function to move it into the second category.
- `const fn` without a const stability marker are in the second category if they are still unstable. They automatically inherit the feature gate for regular calls, it can now also be used for const-calls.
Also, several holes in recursive const stability checking are being closed.
There's still one potential hole that is hard to avoid, which is when MIR
building automatically inserts calls to a particular function in stable
functions -- which happens in the panic machinery. Those need to *not* be
`rustc_const_unstable` (or manually get a `rustc_const_stable_indirect`) to be
sure they follow recursive const stability. But that's a fairly rare and special
case so IMO it's fine.
The net effect of this is that a `#[unstable]` or unmarked function can be
constified simply by marking it as `const fn`, and it will then be
const-callable from stable `const fn` and subject to recursive const stability
requirements. If it is publicly reachable (which implies it cannot be unmarked),
it will be const-unstable under the same feature gate. Only if the function ever
becomes `#[stable]` does it need a `#[rustc_const_unstable]` or
`#[rustc_const_stable]` marker to decide if this should also imply
const-stability.
Adding `#[rustc_const_unstable]` is only needed for (a) functions that need to
use unstable const lang features (including intrinsics), or (b) `#[stable]`
functions that are not yet intended to be const-stable. Adding
`#[rustc_const_stable]` is only needed for functions that are actually meant to
be directly callable from stable const code. `#[rustc_const_stable_indirect]` is
used to mark intrinsics as const-callable and for `#[rustc_const_unstable]`
functions that are actually called from other, exposed-on-stable `const fn`. No
other attributes are required.
Fixup Windows verbatim paths when used with the `include!` macro
On Windows, the following code can fail if the `OUT_DIR` environment variable is a [verbatim path](https://doc.rust-lang.org/std/path/enum.Prefix.html) (i.e. begins with `\\?\`):
```rust
include!(concat!(env!("OUT_DIR"), "/src/repro.rs"));
```
This is because verbatim paths treat `/` literally, as if it were just another character in the file name.
The good news is that the standard library already has code to fix this. We can simply use `components` to normalize the path so it works as intended.
When using `concat!` to join paths, the Unix path separator (`/`) is often used. This breaks on Windows if the base path is a verbatim path (i.e. starts with `\\?\`).
delegation: Implement glob delegation
Support delegating to all trait methods in one go.
Overriding globs with explicit definitions is also supported.
The implementation is generally based on the design from https://github.com/rust-lang/rfcs/pull/3530#issuecomment-2020869823, but unlike with list delegation in https://github.com/rust-lang/rust/pull/123413 we cannot expand glob delegation eagerly.
We have to enqueue it into the queue of unexpanded macros (most other macros are processed this way too), and then a glob delegation waits in that queue until its trait path is resolved, and enough code expands to generate the identifier list produced from the glob.
Glob delegation is only allowed in impls, and can only point to traits.
Supporting it in other places gives very little practical benefit, but significantly raises the implementation complexity.
Part of https://github.com/rust-lang/rust/issues/118212.
We still check for the `rental`/`allsorts-rental` crates. But now if
they are detected we just emit a fatal error, instead of emitting a
warning and providing alternative behaviour.
The original "hack" implementing alternative behaviour was added
in #73345.
The lint was added in #83127.
The tracking issue is #83125.
The direct motivation for the change is that providing the alternative
behaviour is interfering with #125174 and follow-on work.
