Rollup merge of #138632 - clubby789:stabilize-cfg-boolean-lit, r=davidtwco,Urgau,traviscross

Stabilize `cfg_boolean_literals`

Closes #131204
`@rustbot` labels +T-lang +I-lang-nominated
This will end up conflicting with the test in #138293 so whichever doesn't land first will need updating

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# Stabilization Report

## General design

### What is the RFC for this feature and what changes have occurred to the user-facing design since the RFC was finalized?

[RFC 3695](https://github.com/rust-lang/rfcs/pull/3695), none.

### What behavior are we committing to that has been controversial? Summarize the major arguments pro/con.

None

### Are there extensions to this feature that remain unstable? How do we know that we are not accidentally committing to those?

None

## Has a call-for-testing period been conducted? If so, what feedback was received?

Yes; only positive feedback was received.

## Implementation quality

### Summarize the major parts of the implementation and provide links into the code (or to PRs)

Implemented in [#131034](https://github.com/rust-lang/rust/pull/131034).

### Summarize existing test coverage of this feature

- [Basic usage, including `#[cfg()]`, `cfg!()` and `#[cfg_attr()]`](https://github.com/rust-lang/rust/blob/6d71251cf9e40326461f90f8ff9a7024706aea87/tests/ui/cfg/true-false.rs)
- [`--cfg=true/false` on the command line being accessible via `r#true/r#false`](https://github.com/rust-lang/rust/blob/6d71251cf9e40326461f90f8ff9a7024706aea87/tests/ui/cfg/raw-true-false.rs)
- [Interaction with the unstable `#[doc(cfg(..))]` feature](https://github.com/rust-lang/rust/tree/6d71251/tests/rustdoc-ui/cfg-boolean-literal.rs)
- [Denying `--check-cfg=cfg(true/false)`](https://github.com/rust-lang/rust/tree/6d71251/tests/ui/check-cfg/invalid-arguments.rs)
- Ensuring `--cfg false` on the command line doesn't change the meaning of `cfg(false)`: `tests/ui/cfg/cmdline-false.rs`
- Ensuring both `cfg(true)` and `cfg(false)` on the same item result in it being disabled: `tests/ui/cfg/both-true-false.rs`

### What outstanding bugs in the issue tracker involve this feature? Are they stabilization-blocking?

The above mentioned issue; it should not block as it interacts with another unstable feature.

### What FIXMEs are still in the code for that feature and why is it ok to leave them there?

None

### Summarize contributors to the feature by name for recognition and assuredness that people involved in the feature agree with stabilization
- `@clubby789` (RFC)
- `@Urgau` (Implementation in rustc)

### Which tools need to be adjusted to support this feature. Has this work been done?

`rustdoc`'s  unstable`#[doc(cfg(..)]` has been updated to respect it. `cargo` has been updated with a forward compatibility lint to enable supporting it in cargo once stabilized.

## Type system and execution rules

### What updates are needed to the reference/specification? (link to PRs when they exist)

A few lines to be added to the reference for configuration predicates, specified in the RFC.

3 files changed, 5 insertions, 5 deletions

diff --git a/tests/ui/pattern/bindings-after-at/nested-type-ascription-syntactically-invalid.rs b/tests/ui/pattern/bindings-after-at/nested-type-ascription-syntactically-invalid.rs
index 01a978d5557..9582d2729a8 100644
--- a/tests/ui/pattern/bindings-after-at/nested-type-ascription-syntactically-invalid.rs
+++ b/tests/ui/pattern/bindings-after-at/nested-type-ascription-syntactically-invalid.rs
@@ -13,19 +13,19 @@ fn _ok() {
     fn _f(_a @ _b: u8) {} // OK.
 }
 
-#[cfg(FALSE)]
+#[cfg(false)]
 fn case_1() {
     let a: u8 @ b = 0;
     //~^ ERROR expected one of `!`
 }
 
-#[cfg(FALSE)]
+#[cfg(false)]
 fn case_2() {
     let a @ (b: u8);
     //~^ ERROR expected one of `)`
 }
 
-#[cfg(FALSE)]
+#[cfg(false)]
 fn case_3() {
     let a: T1 @ Outer(b: T2);
     //~^ ERROR expected one of `!`
diff --git a/tests/ui/pattern/bindings-after-at/wild-before-at-syntactically-rejected.rs b/tests/ui/pattern/bindings-after-at/wild-before-at-syntactically-rejected.rs
index 50ac0ef2783..c3994d35c42 100644
--- a/tests/ui/pattern/bindings-after-at/wild-before-at-syntactically-rejected.rs
+++ b/tests/ui/pattern/bindings-after-at/wild-before-at-syntactically-rejected.rs
@@ -3,7 +3,7 @@
 
 fn main() {}
 
-#[cfg(FALSE)]
+#[cfg(false)]
 fn wild_before_at_is_bad_syntax() {
     let _ @ a = 0;
     //~^ ERROR pattern on wrong side of `@`
diff --git a/tests/ui/pattern/rest-pat-syntactic.rs b/tests/ui/pattern/rest-pat-syntactic.rs
index 1de29e69b05..59c687bb5a8 100644
--- a/tests/ui/pattern/rest-pat-syntactic.rs
+++ b/tests/ui/pattern/rest-pat-syntactic.rs
@@ -11,7 +11,7 @@ macro_rules! accept_pat {
 
 accept_pat!(..);
 
-#[cfg(FALSE)]
+#[cfg(false)]
 fn rest_patterns() {
     // Top level:
     fn foo(..: u8) {}