Touch up PR 293

Author: dtolnay

Cargo.toml

@@ -16,6 +16,10 @@ default = ["std"]
 std = []
 
 [dependencies]
+# On compilers older than 1.65, features=["backtrace"] may be used to enable
+# backtraces via the `backtrace` crate. This feature has no effect on 1.65+
+# besides bringing in an unused dependency, as `std::backtrace` is always
+# preferred.
 backtrace = { version = "0.3.51", optional = true }
 
 [dev-dependencies]

README.md

@@ -75,10 +75,10 @@ anyhow = "1.0"
   }
   ```
 
-- If using Rust ≥ 1.65 or `features = ["backtrace"]`, a backtrace is captured
-  and printed with the error if the underlying error type does not already
-  provide its own. In order to see backtraces, they must be enabled through the
-  environment variables described in [`std::backtrace`]:
+- If using Rust ≥ 1.65, a backtrace is captured and printed with the error if
+  the underlying error type does not already provide its own. In order to see
+  backtraces, they must be enabled through the environment variables described
+  in [`std::backtrace`]:
 
   - If you want panics and errors to both have backtraces, set
     `RUST_BACKTRACE=1`;

src/error.rs

@@ -363,17 +363,17 @@ impl Error {
     ///
     /// # Stability
     ///
-    /// Standard library backtraces are only available when using Rust ≥ 1.65.
-    /// On older compilers, this function is only available if the crate's
+    /// Standard library backtraces are only available when using Rust ≥
+    /// 1.65. On older compilers, this function is only available if the crate's
     /// "backtrace" feature is enabled, and will use the `backtrace` crate as
-    /// the underlying backtrace implementation.
+    /// the underlying backtrace implementation. The return type of this
+    /// function on old compilers is `&(impl Debug + Display)`.
     ///
     /// ```toml
     /// [dependencies]
     /// anyhow = { version = "1.0", features = ["backtrace"] }
     /// ```
     #[cfg(any(std_backtrace, feature = "backtrace"))]
-    #[cfg_attr(doc_cfg, doc(cfg(any(nightly, feature = "backtrace"))))]
     pub fn backtrace(&self) -> &impl_backtrace!() {
         unsafe { ErrorImpl::backtrace(self.inner.by_ref()) }
     }

src/lib.rs

@@ -128,10 +128,10 @@
 //!   # ;
 //!   ```
 //!
-//! - If using Rust ≥ 1.65 or `features = ["backtrace"]`, a backtrace is captured
-//!   and printed with the error if the underlying error type does not already
-//!   provide its own. In order to see backtraces, they must be enabled through the
-//!   environment variables described in [`std::backtrace`]:
+//! - If using Rust ≥ 1.65, a backtrace is captured and printed with the
+//!   error if the underlying error type does not already provide its own. In
+//!   order to see backtraces, they must be enabled through the environment
+//!   variables described in [`std::backtrace`]:
 //!
 //!   - If you want panics and errors to both have backtraces, set
 //!     `RUST_BACKTRACE=1`;