Rely on docs.rs to define --cfg=docsrs by default

Author: dtolnay

Cargo.toml

@@ -23,4 +23,4 @@ doc-scrape-examples = false
 
 [package.metadata.docs.rs]
 targets = ["x86_64-unknown-linux-gnu"]
-rustdoc-args = ["--cfg", "doc_cfg", "--generate-link-to-definition"]
+rustdoc-args = ["--generate-link-to-definition"]

build.rs

@@ -11,7 +11,6 @@ fn main() {
     };
 
     if compiler >= 80 {
-        println!("cargo:rustc-check-cfg=cfg(doc_cfg)");
         println!("cargo:rustc-check-cfg=cfg(no_alloc_crate)");
         println!("cargo:rustc-check-cfg=cfg(no_const_vec_new)");
         println!("cargo:rustc-check-cfg=cfg(no_exhaustive_int_match)");

src/error.rs

@@ -26,7 +26,7 @@ pub(crate) enum Position {
 }
 
 #[cfg(feature = "std")]
-#[cfg_attr(doc_cfg, doc(cfg(feature = "std")))]
+#[cfg_attr(docsrs, doc(cfg(feature = "std")))]
 impl std::error::Error for Error {}
 
 impl Display for Error {

src/lib.rs

@@ -61,7 +61,7 @@
 //! [Specifying Dependencies]: https://doc.rust-lang.org/cargo/reference/specifying-dependencies.html
 
 #![doc(html_root_url = "https://docs.rs/semver/1.0.23")]
-#![cfg_attr(doc_cfg, feature(doc_cfg))]
+#![cfg_attr(docsrs, feature(doc_cfg))]
 #![cfg_attr(all(not(feature = "std"), not(no_alloc_crate)), no_std)]
 #![cfg_attr(not(no_unsafe_op_in_unsafe_fn_lint), deny(unsafe_op_in_unsafe_fn))]
 #![cfg_attr(no_unsafe_op_in_unsafe_fn_lint, allow(unused_unsafe))]