Rollup merge of rust-lang#123501 - Urgau:stabilize-check-cfg, r=petrochenkov

Stabilize checking of cfgs at compile-time: `--check-cfg` option

This PR stabilize the `--check-cfg` CLI option of `rustc` (and `rustdoc`) 🎉.

In particular this PR does two things:
  1. it makes the `--check-cfg` option stable
  2. and it moves the documentation to the stable books

FCP: rust-lang#82450 (comment)

Resolves rust-lang#82450

`@rustbot` labels +S-blocked +F-check-cfg
r? `@petrochenkov`

Author: matthiaskrgr

compiler/rustc_lint/src/context/diagnostics/check_cfg.rs

@@ -168,7 +168,7 @@ pub(super) fn unexpected_cfg_name(
         diag.note("see <https://doc.rust-lang.org/nightly/cargo/reference/unstable.html#check-cfg> for more information about checking conditional configuration");
     } else {
         diag.help(format!("to expect this configuration use `--check-cfg={inst}`"));
-        diag.note("see <https://doc.rust-lang.org/nightly/unstable-book/compiler-flags/check-cfg.html> for more information about checking conditional configuration");
+        diag.note("see <https://doc.rust-lang.org/nightly/rustc/check-cfg.html> for more information about checking conditional configuration");
     }
 }
 
@@ -272,6 +272,6 @@ pub(super) fn unexpected_cfg_value(
         if !is_cfg_a_well_know_name {
             diag.help(format!("to expect this configuration use `--check-cfg={inst}`"));
         }
-        diag.note("see <https://doc.rust-lang.org/nightly/unstable-book/compiler-flags/check-cfg.html> for more information about checking conditional configuration");
+        diag.note("see <https://doc.rust-lang.org/nightly/rustc/check-cfg.html> for more information about checking conditional configuration");
     }
 }

compiler/rustc_session/src/config.rs

@@ -1373,7 +1373,7 @@ pub fn rustc_short_optgroups() -> Vec<RustcOptGroup> {
         opt::flag_s("h", "help", "Display this message"),
         opt::multi_s("", "cfg", "Configure the compilation environment.
                              SPEC supports the syntax `NAME[=\"VALUE\"]`.", "SPEC"),
-        opt::multi("", "check-cfg", "Provide list of valid cfg options for checking", "SPEC"),
+        opt::multi_s("", "check-cfg", "Provide list of expected cfgs for checking", "SPEC"),
         opt::multi_s(
             "L",
             "",

compiler/rustc_session/src/config/cfg.rs

@@ -257,7 +257,7 @@ impl CheckCfg {
         // `tests/ui/check-cfg/well-known-values.rs` (in order to test the
         // expected values of the new config) and bless the all directory.
         //
-        // Don't forget to update `src/doc/unstable-book/src/compiler-flags/check-cfg.md`
+        // Don't forget to update `src/doc/rustc/src/check-cfg.md`
         // in the unstable book as well!
 
         ins!(sym::debug_assertions, no_values);

src/doc/rustc/src/SUMMARY.md

@@ -77,6 +77,7 @@
 - [Profile-guided Optimization](profile-guided-optimization.md)
 - [Instrumentation-based Code Coverage](instrument-coverage.md)
 - [Linker-plugin-based LTO](linker-plugin-lto.md)
+- [Checking conditional configurations](check-cfg.md)
 - [Exploit Mitigations](exploit-mitigations.md)
 - [Symbol Mangling](symbol-mangling/index.md)
     - [v0 Symbol Format](symbol-mangling/v0.md)

src/doc/unstable-book/src/compiler-flags/check-cfg.md renamed to src/doc/rustc/src/check-cfg.md

@@ -1,10 +1,4 @@
-# `check-cfg`
-
-The tracking issue for this feature is: [#82450](https://github.com/rust-lang/rust/issues/82450).
-
-------------------------
-
-This feature enables checking of conditional configuration.
+# Checking conditional configurations
 
 `rustc` accepts the `--check-cfg` option, which specifies whether to check conditions and how to
 check them. The `--check-cfg` option takes a value, called the _check cfg specification_.

src/doc/rustc/src/command-line-arguments.md

@@ -18,6 +18,16 @@ The value can either be a single identifier or two identifiers separated by `=`.
 For examples, `--cfg 'verbose'` or `--cfg 'feature="serde"'`. These correspond
 to `#[cfg(verbose)]` and `#[cfg(feature = "serde")]` respectively.
 
+<a id="option-check-cfg"></a>
+## `--check-cfg`: enables checking conditional configurations
+
+This flag will enable checking conditional configurations.
+Refer to the [Checking conditional configurations](check-cfg.md) of this book
+for further details and explanation.
+
+For examples, `--check-cfg 'cfg(verbose)'` or `--check-cfg 'cfg(feature, values("serde"))'`.
+These correspond to `#[cfg(verbose)]` and `#[cfg(feature = "serde")]` respectively.
+
 <a id="option-l-search-path"></a>
 ## `-L`: add a directory to the library search path
 

src/doc/rustdoc/src/command-line-arguments.md

@@ -131,6 +131,20 @@ This flag accepts the same values as `rustc --cfg`, and uses it to configure
 compilation. The example above uses `feature`, but any of the `cfg` values
 are acceptable.
 
+## `--check-cfg`: check configuration flags
+
+This flag accepts the same values as `rustc --check-cfg`, and uses it to
+check configuration flags.
+
+Using this flag looks like this:
+
+```bash
+$ rustdoc src/lib.rs --check-cfg='cfg(my_cfg, values("foo", "bar"))'
+```
+
+The example above check every well known names and values (`target_os`, `doc`, `test`, ...)
+and check the values of `my_cfg`: `foo` and `bar`.
+
 ## `--extern`: specify a dependency's location
 
 Using this flag looks like this:

src/doc/rustdoc/src/unstable-features.md

@@ -618,22 +618,6 @@ crate being documented (`foobar`) and a path to output the calls
 To scrape examples from test code, e.g. functions marked `#[test]`, then
 add the `--scrape-tests` flag.
 
-### `--check-cfg`: check configuration flags
-
- * Tracking issue: [#82450](https://github.com/rust-lang/rust/issues/82450)
-
-This flag accepts the same values as `rustc --check-cfg`, and uses it to check configuration flags.
-
-Using this flag looks like this:
-
-```bash
-$ rustdoc src/lib.rs -Z unstable-options \
-    --check-cfg='cfg(feature, values("foo", "bar"))'
-```
-
-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
 
  * Tracking issue: [#89095](https://github.com/rust-lang/rust/issues/89095)

src/librustdoc/doctest.rs

@@ -60,11 +60,8 @@ pub(crate) fn generate_args_file(file_path: &Path, options: &RustdocOptions) ->
     for cfg in &options.cfgs {
         content.push(format!("--cfg={cfg}"));
     }
-    if !options.check_cfgs.is_empty() {
-        content.push("-Zunstable-options".to_string());
-        for check_cfg in &options.check_cfgs {
-            content.push(format!("--check-cfg={check_cfg}"));
-        }
+    for check_cfg in &options.check_cfgs {
+        content.push(format!("--check-cfg={check_cfg}"));
     }
 
     for lib_str in &options.lib_strs {

src/librustdoc/lib.rs

@@ -242,7 +242,7 @@ fn opts() -> Vec<RustcOptGroup> {
             o.optmulti("L", "library-path", "directory to add to crate search path", "DIR")
         }),
         stable("cfg", |o| o.optmulti("", "cfg", "pass a --cfg to rustc", "")),
-        unstable("check-cfg", |o| o.optmulti("", "check-cfg", "pass a --check-cfg to rustc", "")),
+        stable("check-cfg", |o| o.optmulti("", "check-cfg", "pass a --check-cfg to rustc", "")),
         stable("extern", |o| o.optmulti("", "extern", "pass an --extern to rustc", "NAME[=PATH]")),
         unstable("extern-html-root-url", |o| {
             o.optmulti(