macros 1.1: future proofing and cleanup
This PR
- uses the macro namespace for custom derives (instead of a dedicated custom derive namespace),
- relaxes the shadowing rules for `#[macro_use]`-imported custom derives to match the shadowing rules for ordinary `#[macro_use]`-imported macros, and
- treats custom derive `extern crate`s like empty modules so that we can eventually allow, for example, `extern crate serde_derive; use serde_derive::Serialize;` backwards compatibly.
r? @alexcrichton
Avoid many CrateConfig clones.
This commit changes `ExtCtx::cfg()` so it returns a `CrateConfig`
reference instead of a clone. As a result, it also changes all of the
`cfg()` callsites to explicitly clone... except one, because the commit
also changes `macro_parser::parse()` to take `&CrateConfig`. This is
good, because that function can be hot, and `CrateConfig` is expensive
to clone.
This change almost halves the number of heap allocations done by rustc
for `html5ever` in rustc-benchmarks suite, which makes compilation 1.20x
faster.
r? @nrc
Clarify the positions of the lexer and parser
The lexer and parser use unclear names to indicate their positions in the
source code. I propose the following renamings.
Lexer:
```
pos -> next_pos # it's actually the next pos!
last_pos -> pos # it's actually the current pos!
curr -> ch # the current char
curr_is -> ch_is # tests the current char
col (unchanged) # the current column
```
parser
```
- last_span -> prev_span # the previous token's span
- last_token_kind -> prev_token_kind # the previous token's kind
- LastTokenKind -> PrevTokenKind # ditto (but the type)
- token (unchanged) # the current token
- span (unchanged) # the current span
```
Things to note:
- This proposal removes all uses of "last", which is an unclear word because it
could mean (a) previous, (b) final, or (c) most recent, i.e. current.
- The "current" things (ch, col, token, span) consistently lack a prefix. The
"previous" and "next" things consistently have a prefix.
This commit changes `ExtCtx::cfg()` so it returns a `CrateConfig`
reference instead of a clone. As a result, it also changes all of the
`cfg()` callsites to explicitly clone... except one, because the commit
also changes `macro_parser::parse()` to take `&CrateConfig`. This is
good, because that function can be hot, and `CrateConfig` is expensive
to clone.
This change almost halves the number of heap allocations done by rustc
for `html5ever` in rustc-benchmarks suite, which makes compilation 1.20x
faster.
macros: clean up scopes of expanded `#[macro_use]` imports
This PR changes the scope of macro-expanded `#[macro_use]` imports to match that of unexpanded `#[macro_use]` imports. For example, this would be allowed:
```rust
example!();
macro_rules! m { () => { #[macro_use(example)] extern crate example_crate; } }
m!();
```
This PR also enforces the full shadowing restrictions from RFC 1560 on `#[macro_use]` imports (currently, we only enforce the weakened restrictions from #36767).
This is a [breaking-change], but I believe it is highly unlikely to cause breakage in practice.
r? @nrc
This commit blanket renames the `rustc_macro` infrastructure to `proc_macro`,
which reflects the general consensus of #35900. A follow up PR to Cargo will be
required to purge the `rustc-macro` name as well.
Enforce the shadowing restrictions from RFC 1560 for today's macros
This PR enforces a weakened version of the shadowing restrictions from RFC 1560. More specifically,
- If a macro expansion contains a `macro_rules!` macro definition that is used outside of the expansion, the defined macro may not shadow an existing macro.
- If a macro expansion contains a `#[macro_use] extern crate` macro import that is used outside of the expansion, the imported macro may not shadow an existing macro.
This is a [breaking-change]. For example,
```rust
macro_rules! m { () => {} }
macro_rules! n { () => {
macro_rules! m { () => {} } //< This shadows an existing macro.
m!(); //< This is inside the expansion that generated `m`'s definition, so it is OK.
} }
n!();
m!(); //< This use of `m` is outside the expansion, so it causes the shadowing to be an error.
```
r? @nrc
This applies the HIR changes from the previous commits to the AST, and
is thus a syntax-[breaking-change]
Renames `PatKind::Vec` to `PatKind::Slice`, since these are called slice
patterns, not vec patterns. Renames `TyKind::Vec`, which represents the
type `[T]`, to `TyKind::Slice`. Renames `TyKind::FixedLengthVec` to
`TyKind::Array`.
This commit alters the expansion order of custom macros-1.1 style `#[derive]`
modes. Instead of left-to-right the expansion now happens in three categories,
each of which is internally left-to-right:
* Old-style custom derive (`#[derive_Foo]`) is expanded
* New-style custom derive (macros 1.1) is expanded
* Built in derive modes are expanded
This gives built in derive modes maximal knowledge about the struct that's being
expanded and also avoids pesky issues like exposing `#[structural_match]` or
`#[rustc_copy_clone_marker]`.
cc #35900
I am using `ThinAttributes` rather than a vector for attributes
attached to generics, since I expect almost all lifetime and types
parameters to not carry any attributes.
Adds a `ProcMacro` form of syntax extension
This commit adds syntax extension forms matching the types for procedural macros 2.0 (RFC #1566), these still require the usual syntax extension boiler plate, but this is a first step towards proper implementation and should be useful for macros 1.1 stuff too.
Supports both attribute-like and function-like macros.
Note that RFC #1566 has not been accepted yet, but I think there is consensus that we want to head in vaguely that direction and so this PR will be useful in any case. It is also fairly easy to undo and does not break any existing programs.
This is related to #35957 in that I hope it can be used in the implementation of macros 1.1, however, there is no direct overlap and is more of a complement than a competing proposal. There is still a fair bit of work to do before the two can be combined.
r? @jseyfried
cc @alexcrichton, @cgswords, @eddyb, @aturon
Assign node ids during macro expansion
After this PR,
- The `ExtCtxt` can access `resolve`'s `Resolver` through the trait object `ext::base::Resolver`.
- The `Resolver` trait object can load macros and replaces today's `MacroLoader` trait object.
- The macro expander uses the `Resolver` trait object to resolve macro invocations.
- The macro expander assigns node ids and builds the `Resolver`'s `macros_at_scope` map.
- This is groundwork for merging import resolution and expansion.
- Performance of expansion together with node id assignment improves by ~5%.
**EDIT:** Since Github is reordering the commits, here is `git log`:
- b54e1e399741579612f13e2df98a25ea9447989d: Differentiate between monotonic and non-monotonic expansion and only assign node ids during monotonic expansion.
- 78c00398780db6f59ebf43e765fa9368dad436d2: Expand generated test harnesses and macro registries.
- f3c2dca3539e6edc745f9c91898cb97d281865c1: Remove scope placeholders from the crate root.
- c86c8d41a26b2037e80c9fd028a59313a78b3a66: Perform node id assignment and `macros_at_scope` construction during the `InvocationCollector` and `PlaceholderExpander` folds.
- 72a636975fc5d0bb4af45af7bdd97987cc722a6a: Move macro resolution into `librustc_resolve`.
- 20b43b23230ce063ccf99a4841d85790ad311bdf: Rewrite the unit tests in `ext/expand.rs` as a `compile-fail` test.
- a9821e1658240bb2c056f260a4b6bc9789301fae: Refactor `ExtCtxt` to use a `Resolver` instead of a `MacroLoader`.
- 60440b226d2f70bdae803443ff7ad2e2af2c9b10: Refactor `noop_fold_stmt_kind` out of `noop_fold_stmt`.
- 50f94f6c95c944f08c4af264f48260e42efefd47: Avoid needless reexpansions.
r? @nrc
Improve shallow `Clone` deriving
`Copy` unions now support `#[derive(Clone)]`.
Less code is generated for `#[derive(Clone, Copy)]`.
+
Unions now support `#[derive(Eq)]`.
Less code is generated for `#[derive(Eq)]`.
---
Example of code reduction:
```
enum E {
A { a: u8, b: u16 },
B { c: [u8; 100] },
}
```
Before:
```
fn clone(&self) -> E {
match (&*self,) {
(&E::A { a: ref __self_0, b: ref __self_1 },) => {
::std::clone::assert_receiver_is_clone(&(*__self_0));
::std::clone::assert_receiver_is_clone(&(*__self_1));
*self
}
(&E::B { c: ref __self_0 },) => {
::std::clone::assert_receiver_is_clone(&(*__self_0));
*self
}
}
}
```
After:
```
fn clone(&self) -> E {
{
let _: ::std::clone::AssertParamIsClone<u8>;
let _: ::std::clone::AssertParamIsClone<u16>;
let _: ::std::clone::AssertParamIsClone<[u8; 100]>;
*self
}
}
```
All the matches are removed, bound assertions are more lightweight.
`let _: Checker<CheckMe>;`, unlike `checker(&check_me);`, doesn't have to be translated by rustc_trans and then inlined by LLVM, it doesn't even exist in MIR, this means faster compilation.
---
Union impls are generated like this:
```
union U {
a: u8,
b: u16,
c: [u8; 100],
}
```
```
fn clone(&self) -> U {
{
let _: ::std::clone::AssertParamIsCopy<Self>;
*self
}
}
```
Fixes https://github.com/rust-lang/rust/issues/36043
cc @durka
r? @alexcrichton
Point macros 1.1 errors to the input item
Moved from https://github.com/alexcrichton/rust/pull/6 to continue discussion. Fixes#36218.
Before:
```rust
error[E0106]: missing lifetime specifier
--> src/main.rs:10:10
|
10 | #[derive(Serialize, Deserialize)]
| ^ expected lifetime parameter
error[E0038]: the trait `T` cannot be made into an object
--> src/main.rs:15:15
|
15 | #[derive(Serialize, Deserialize)]
| ^^^^^^^^^^ the trait `T` cannot be made into an object
```
After:
```rust
error[E0106]: missing lifetime specifier
--> src/main.rs:11:1
|
11 | struct A {
| ^ expected lifetime parameter
error[E0038]: the trait `T` cannot be made into an object
--> src/main.rs:16:1
|
16 | struct B<'a> {
| ^ the trait `T` cannot be made into an object
```
Before:
```rust
error[E0106]: missing lifetime specifier
--> src/main.rs:10:10
|
10 | #[derive(Serialize, Deserialize)]
| ^ expected lifetime parameter
error[E0038]: the trait `T` cannot be made into an object
--> src/main.rs:15:15
|
15 | #[derive(Serialize, Deserialize)]
| ^^^^^^^^^^ the trait `T` cannot be made into an object
```
After:
```rust
error[E0106]: missing lifetime specifier
--> src/main.rs:11:1
|
11 | struct A {
| ^ expected lifetime parameter
error[E0038]: the trait `T` cannot be made into an object
--> src/main.rs:16:1
|
16 | struct B<'a> {
| ^ the trait `T` cannot be made into an object
```
This commit is an implementation of [RFC 1681] which adds support to the
compiler for first-class user-define custom `#[derive]` modes with a far more
stable API than plugins have today.
[RFC 1681]: https://github.com/rust-lang/rfcs/blob/master/text/1681-macros-1.1.md
The main features added by this commit are:
* A new `rustc-macro` crate-type. This crate type represents one which will
provide custom `derive` implementations and perhaps eventually flower into the
implementation of macros 2.0 as well.
* A new `rustc_macro` crate in the standard distribution. This crate will
provide the runtime interface between macro crates and the compiler. The API
here is particularly conservative right now but has quite a bit of room to
expand into any manner of APIs required by macro authors.
* The ability to load new derive modes through the `#[macro_use]` annotations on
other crates.
All support added here is gated behind the `rustc_macro` feature gate, both for
the library support (the `rustc_macro` crate) as well as the language features.
There are a few minor differences from the implementation outlined in the RFC,
such as the `rustc_macro` crate being available as a dylib and all symbols are
`dlsym`'d directly instead of having a shim compiled. These should only affect
the implementation, however, not the public interface.
This commit also ended up touching a lot of code related to `#[derive]`, making
a few notable changes:
* Recognized derive attributes are no longer desugared to `derive_Foo`. Wasn't
sure how to keep this behavior and *not* expose it to custom derive.
* Derive attributes no longer have access to unstable features by default, they
have to opt in on a granular level.
* The `derive(Copy,Clone)` optimization is now done through another "obscure
attribute" which is just intended to ferry along in the compiler that such an
optimization is possible. The `derive(PartialEq,Eq)` optimization was also
updated to do something similar.
---
One part of this PR which needs to be improved before stabilizing are the errors
and exact interfaces here. The error messages are relatively poor quality and
there are surprising spects of this such as `#[derive(PartialEq, Eq, MyTrait)]`
not working by default. The custom attributes added by the compiler end up
becoming unstable again when going through a custom impl.
Hopefully though this is enough to start allowing experimentation on crates.io!
syntax-[breaking-change]
