Implement RFC 2523, `#[cfg(version(..))]`

1 files changed, 34 insertions, 0 deletions

diff --git a/src/doc/unstable-book/src/language-features/cfg-version.md b/src/doc/unstable-book/src/language-features/cfg-version.md
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+# `cfg_version`
+
+The tracking issue for this feature is: [#64796]
+
+[#64796]: https://github.com/rust-lang/rust/issues/64796
+
+------------------------
+
+The `cfg_version` feature makes it possible to execute different code
+depending on the compiler version.
+
+## Examples
+
+```rust
+#![feature(cfg_version)]
+
+#[cfg(version("1.42"))]
+fn a() {
+    // ...
+}
+
+#[cfg(not(version("1.42")))]
+fn a() {
+    // ...
+}
+
+fn b() {
+    if cfg!(version("1.42")) {
+        // ...
+    } else {
+        // ...
+    }
+}
+```