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Rollup merge of rust-lang#111072 - Urgau:check-cfg-new-syntax, r=petr…
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…ochenkov

Add new simpler and more explicit syntax for check-cfg

<details>
<summary>
Old proposition (before the MCP)
</summary>

This PR adds a new simpler and more explicit syntax for check-cfg. It consist of two new form:
 - `exhaustive(names, values)`
 - `configure(name, "value1", "value2", ... "valueN")`

The preview forms `names(...)` and `values(...)` have implicit meaning that are not strait-forward. In particular `values(foo)`&`values(bar)` and `names(foo, bar)` are not equivalent which has created [some confusions](rust-lang#98080).

Also the `names()` and `values()` form are not clear either and again created some confusions where peoples believed that `values()`&`values(foo)` could be reduced to just `values(foo)`.

To fix that the two new forms are made to be explicit and simpler. See the table of correspondence:
  - `names()` -> `exhaustive(names)`
  - `values()` -> `exhaustive(values)`
  - `names(foo)` -> `exhaustive(names)`&`configure(foo)`
  - `values(foo)` -> `configure(foo)`
  - `values(feat, "foo", "bar")` -> `configure(feat, "foo", "bar")`
  - `values(foo)`&`values(bar)` -> `configure(foo, bar)`
  - `names()`&`values()`&`values(my_cfg)` -> `exhaustive(names, values)`&`configure(my_cfg)`

Another benefits of the new syntax is that it allow for further options (like conditional checking for --cfg, currently always on) without syntax change.

The two previous forms are deprecated and will be removed once cargo and beta rustc have the necessary support.

</details>

This PR is the first part of the implementation of [MCP636 - Simplify and improve explicitness of the check-cfg syntax](rust-lang/compiler-team#636).

## New `cfg` form

It introduces the new [`cfg` form](rust-lang/compiler-team#636) and deprecate the other two:
```
rustc --check-cfg 'cfg(name1, ..., nameN, values("value1", "value2", ... "valueN"))'
```

## Default built-in names and values

It also changes the default for the built-in names and values checking.

 - Built-in values checking would always be activated as long as a `--check-cfg` argument is present
 - Built-in names checking would always be activated as long as a `--check-cfg` argument is present **unless** if any `cfg(any())` arg is passed

~~**Note: depends on rust-lang#111068 but is reviewable (last two commits)!**~~

Resolve rust-lang/compiler-team#636

r? `@petrochenkov`
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@matthiaskrgr
matthiaskrgr authored Oct 17, 2023
2 parents 93e62a2 + fc78d78 commit ce40742
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Showing 72 changed files with 1,017 additions and 216 deletions.
139 changes: 132 additions & 7 deletions compiler/rustc_interface/src/interface.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -125,8 +125,13 @@ pub fn parse_cfgspecs(
/// Converts strings provided as `--check-cfg [specs]` into a `CheckCfg`.
pub fn parse_check_cfg(handler: &EarlyErrorHandler, specs: Vec<String>) -> CheckCfg {
rustc_span::create_default_session_if_not_set_then(move |_| {
let mut check_cfg = CheckCfg::default();
// If any --check-cfg is passed then exhaustive_values and exhaustive_names
// are enabled by default.
let exhaustive_names = !specs.is_empty();
let exhaustive_values = !specs.is_empty();
let mut check_cfg = CheckCfg { exhaustive_names, exhaustive_values, ..CheckCfg::default() };

let mut old_syntax = None;
for s in specs {
let sess = ParseSess::with_silent_emitter(Some(format!(
"this error occurred on the command line: `--check-cfg={s}`"
Expand All @@ -142,18 +147,21 @@ pub fn parse_check_cfg(handler: &EarlyErrorHandler, specs: Vec<String>) -> Check
};
}

let expected_error = || {
error!(
"expected `names(name1, name2, ... nameN)` or \
`values(name, \"value1\", \"value2\", ... \"valueN\")`"
)
};
let expected_error =
|| error!("expected `cfg(name, values(\"value1\", \"value2\", ... \"valueN\"))`");

match maybe_new_parser_from_source_str(&sess, filename, s.to_string()) {
Ok(mut parser) => match parser.parse_meta_item() {
Ok(meta_item) if parser.token == token::Eof => {
if let Some(args) = meta_item.meta_item_list() {
if meta_item.has_name(sym::names) {
// defaults are flipped for the old syntax
if old_syntax == None {
check_cfg.exhaustive_names = false;
check_cfg.exhaustive_values = false;
}
old_syntax = Some(true);

check_cfg.exhaustive_names = true;
for arg in args {
if arg.is_word() && arg.ident().is_some() {
Expand All @@ -167,6 +175,13 @@ pub fn parse_check_cfg(handler: &EarlyErrorHandler, specs: Vec<String>) -> Check
}
}
} else if meta_item.has_name(sym::values) {
// defaults are flipped for the old syntax
if old_syntax == None {
check_cfg.exhaustive_names = false;
check_cfg.exhaustive_values = false;
}
old_syntax = Some(true);

if let Some((name, values)) = args.split_first() {
if name.is_word() && name.ident().is_some() {
let ident = name.ident().expect("multi-segment cfg key");
Expand Down Expand Up @@ -216,6 +231,116 @@ pub fn parse_check_cfg(handler: &EarlyErrorHandler, specs: Vec<String>) -> Check
} else {
expected_error();
}
} else if meta_item.has_name(sym::cfg) {
old_syntax = Some(false);

let mut names = Vec::new();
let mut values: FxHashSet<_> = Default::default();

let mut any_specified = false;
let mut values_specified = false;
let mut values_any_specified = false;

for arg in args {
if arg.is_word() && let Some(ident) = arg.ident() {
if values_specified {
error!("`cfg()` names cannot be after values");
}
names.push(ident);
} else if arg.has_name(sym::any)
&& let Some(args) = arg.meta_item_list()
{
if any_specified {
error!("`any()` cannot be specified multiple times");
}
any_specified = true;
if !args.is_empty() {
error!("`any()` must be empty");
}
} else if arg.has_name(sym::values)
&& let Some(args) = arg.meta_item_list()
{
if names.is_empty() {
error!(
"`values()` cannot be specified before the names"
);
} else if values_specified {
error!(
"`values()` cannot be specified multiple times"
);
}
values_specified = true;

for arg in args {
if let Some(LitKind::Str(s, _)) =
arg.lit().map(|lit| &lit.kind)
{
values.insert(Some(s.to_string()));
} else if arg.has_name(sym::any)
&& let Some(args) = arg.meta_item_list()
{
if values_any_specified {
error!(
"`any()` in `values()` cannot be specified multiple times"
);
}
values_any_specified = true;
if !args.is_empty() {
error!("`any()` must be empty");
}
} else {
error!(
"`values()` arguments must be string literals or `any()`"
);
}
}
} else {
error!(
"`cfg()` arguments must be simple identifiers, `any()` or `values(...)`"
);
}
}

if values.is_empty() && !values_any_specified && !any_specified {
values.insert(None);
} else if !values.is_empty() && values_any_specified {
error!(
"`values()` arguments cannot specify string literals and `any()` at the same time"
);
}

if any_specified {
if !names.is_empty()
|| !values.is_empty()
|| values_any_specified
{
error!("`cfg(any())` can only be provided in isolation");
}

check_cfg.exhaustive_names = false;
} else {
for name in names {
check_cfg
.expecteds
.entry(name.to_string())
.and_modify(|v| match v {
ExpectedValues::Some(v)
if !values_any_specified =>
{
v.extend(values.clone())
}
ExpectedValues::Some(_) => *v = ExpectedValues::Any,
ExpectedValues::Any => {}
})
.or_insert_with(|| {
if values_any_specified {
ExpectedValues::Any
} else {
ExpectedValues::Some(values.clone())
}
});
}
}
} else {
expected_error();
}
Expand Down
1 change: 1 addition & 0 deletions compiler/rustc_interface/src/lib.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -3,6 +3,7 @@
#![feature(internal_output_capture)]
#![feature(thread_spawn_unchecked)]
#![feature(lazy_cell)]
#![feature(let_chains)]
#![feature(try_blocks)]
#![recursion_limit = "256"]
#![allow(rustc::potential_query_instability)]
Expand Down
4 changes: 2 additions & 2 deletions src/doc/rustdoc/src/unstable-features.md
View file
Original file line number Diff line number Diff line change
Expand Up @@ -628,10 +628,10 @@ Using this flag looks like this:

```bash
$ rustdoc src/lib.rs -Z unstable-options \
--check-cfg='names()' --check-cfg='values(feature, "foo", "bar")'
--check-cfg='cfg(feature, values("foo", "bar"))'
```

The example above check every well known names (`target_os`, `doc`, `test`, ... via `names()`)
The example above check every well known names and values (`target_os`, `doc`, `test`, ...)
and check the values of `feature`: `foo` and `bar`.

### `--generate-link-to-definition`: Generate links on types in source code
Expand Down
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