Rollup merge of #99573 - tbodt:stabilize-backtrace, r=yaahc

Stabilize backtrace

This PR stabilizes the std::backtrace module. As of #99431, the std::Error::backtrace item has been removed, and so the rest of the backtrace feature is set to be stabilized.

Previous discussion can be found in #72981, #3156.

Stabilized API summary:
```rust
pub mod std {
    pub mod backtrace {
        pub struct Backtrace { }
        pub enum BacktraceStatus {
            Unsupported,
            Disabled,
            Captured,
        }
        impl fmt::Debug for Backtrace {}
        impl Backtrace {
            pub fn capture() -> Backtrace;
            pub fn force_capture() -> Backtrace;
            pub const fn disabled() -> Backtrace;
            pub fn status(&self) -> BacktraceStatus;
        }
        impl fmt::Display for Backtrace {}
    }
}
```

`@yaahc`

compiler/rustc_errors/src/lib.rs

@@ -4,7 +4,6 @@
 
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/nightly-rustc/")]
 #![feature(drain_filter)]
-#![feature(backtrace)]
 #![feature(if_let_guard)]
 #![cfg_attr(bootstrap, feature(let_chains))]
 #![feature(let_else)]

compiler/rustc_middle/src/lib.rs

@@ -26,7 +26,6 @@
 #![feature(allocator_api)]
 #![feature(array_windows)]
 #![feature(assert_matches)]
-#![feature(backtrace)]
 #![feature(box_patterns)]
 #![feature(core_intrinsics)]
 #![feature(discriminant_kind)]

library/std/src/backtrace.rs

@@ -9,12 +9,6 @@
 //! implementing `std::error::Error`) to get a causal chain of where an error
 //! was generated.
 //!
-//! > **Note**: this module is unstable and is designed in [RFC 2504], and you
-//! > can learn more about its status in the [tracking issue].
-//!
-//! [RFC 2504]: https://github.com/rust-lang/rfcs/blob/master/text/2504-fix-error.md
-//! [tracking issue]: https://github.com/rust-lang/rust/issues/53487
-//!
 //! ## Accuracy
 //!
 //! Backtraces are attempted to be as accurate as possible, but no guarantees
@@ -64,7 +58,7 @@
 //! `RUST_LIB_BACKTRACE` or `RUST_BACKTRACE` at runtime might not actually change
 //! how backtraces are captured.
 
-#![unstable(feature = "backtrace", issue = "53487")]
+#![stable(feature = "backtrace", since = "1.65.0")]
 
 #[cfg(test)]
 mod tests;
@@ -110,6 +104,7 @@ use crate::vec::Vec;
 /// previous point in time. In some instances the `Backtrace` type may
 /// internally be empty due to configuration. For more information see
 /// `Backtrace::capture`.
+#[stable(feature = "backtrace", since = "1.65.0")]
 #[must_use]
 pub struct Backtrace {
     inner: Inner,
@@ -117,6 +112,7 @@ pub struct Backtrace {
 
 /// The current status of a backtrace, indicating whether it was captured or
 /// whether it is empty for some other reason.
+#[stable(feature = "backtrace", since = "1.65.0")]
 #[non_exhaustive]
 #[derive(Debug, PartialEq, Eq)]
 pub enum BacktraceStatus {
@@ -174,6 +170,7 @@ enum BytesOrWide {
     Wide(Vec<u16>),
 }
 
+#[stable(feature = "backtrace", since = "1.65.0")]
 impl fmt::Debug for Backtrace {
     fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
         let capture = match &self.inner {
@@ -200,6 +197,7 @@ impl fmt::Debug for Backtrace {
     }
 }
 
+#[unstable(feature = "backtrace_frames", issue = "79676")]
 impl fmt::Debug for BacktraceFrame {
     fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
         let mut dbg = fmt.debug_list();
@@ -288,6 +286,7 @@ impl Backtrace {
     ///
     /// To forcibly capture a backtrace regardless of environment variables, use
     /// the `Backtrace::force_capture` function.
+    #[stable(feature = "backtrace", since = "1.65.0")]
     #[inline(never)] // want to make sure there's a frame here to remove
     pub fn capture() -> Backtrace {
         if !Backtrace::enabled() {
@@ -306,6 +305,7 @@ impl Backtrace {
     /// Note that capturing a backtrace can be an expensive operation on some
     /// platforms, so this should be used with caution in performance-sensitive
     /// parts of code.
+    #[stable(feature = "backtrace", since = "1.65.0")]
     #[inline(never)] // want to make sure there's a frame here to remove
     pub fn force_capture() -> Backtrace {
         Backtrace::create(Backtrace::force_capture as usize)
@@ -313,6 +313,8 @@ impl Backtrace {
 
     /// Forcibly captures a disabled backtrace, regardless of environment
     /// variable configuration.
+    #[stable(feature = "backtrace", since = "1.65.0")]
+    #[rustc_const_stable(feature = "backtrace", since = "1.65.0")]
     pub const fn disabled() -> Backtrace {
         Backtrace { inner: Inner::Disabled }
     }
@@ -356,6 +358,7 @@ impl Backtrace {
     /// Returns the status of this backtrace, indicating whether this backtrace
     /// request was unsupported, disabled, or a stack trace was actually
     /// captured.
+    #[stable(feature = "backtrace", since = "1.65.0")]
     #[must_use]
     pub fn status(&self) -> BacktraceStatus {
         match self.inner {
@@ -375,6 +378,7 @@ impl<'a> Backtrace {
     }
 }
 
+#[stable(feature = "backtrace", since = "1.65.0")]
 impl fmt::Display for Backtrace {
     fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
         let capture = match &self.inner {

library/std/src/error.rs

@@ -1454,7 +1454,6 @@ impl<E> Report<E> {
     ///
     /// ```rust
     /// #![feature(error_reporter)]
-    /// #![feature(backtrace)]
     /// #![feature(provide_any)]
     /// #![feature(error_generic_member_access)]
     /// # use std::error::Error;

src/test/run-make-fulldeps/issue-47551/eh_frame-terminator.rs

@@ -1,6 +1,5 @@
 // run-pass
 
-#![feature(backtrace)]
 #[derive(Clone, Copy)]
 struct Foo {
     array: [u64; 10240],

src/test/ui/backtrace-apple-no-dsymutil.rs

@@ -4,8 +4,6 @@
 // compile-flags:-g -Csplit-debuginfo=unpacked
 // only-macos
 
-#![feature(backtrace)]
-
 use std::process::Command;
 use std::str;
 

src/test/ui/std-backtrace.rs

@@ -7,8 +7,6 @@
 // compile-flags:-g
 // compile-flags:-Cstrip=none
 
-#![feature(backtrace)]
-
 use std::env;
 use std::process::Command;
 use std::str;