Add DOC_INCLUDE lint

Author: jyn514

compiler/rustc_lint_defs/src/lib.rs

@@ -446,6 +446,7 @@ macro_rules! declare_lint {
 macro_rules! declare_tool_lint {
     (
         $(#[$attr:meta])* $vis:vis $tool:ident ::$NAME:ident, $Level: ident, $desc: expr
+        $(, @future_incompatible = FutureIncompatibleInfo { $($field:ident : $val:expr),* $(,)*  }; )?
     ) => (
         $crate::declare_tool_lint!{$(#[$attr])* $vis $tool::$NAME, $Level, $desc, false}
     );

src/doc/rustdoc/src/lints.md

@@ -331,3 +331,15 @@ warning: this URL is not a hyperlink
 3 | /// [http://example.net]
   |      ^^^^^^^^^^^^^^^^^^ help: use an automatic link instead: `<http://example.net>`
 ```
+
+## external_doc
+
+This lint is **nightly-only** and **warns by default**. It detects when
+`#![feature(external_doc)]` is used. This feature is scheduled for removal and will give a hard
+error in a future release.
+
+```rust
+#![feature(external_doc)]
+#[doc(include = "README.md")]
+pub fn foo() {}
+```

src/librustdoc/lint.rs

@@ -64,9 +64,12 @@ where
 }
 
 macro_rules! declare_rustdoc_lint {
-    ($(#[$attr:meta])* $name: ident, $level: ident, $descr: literal $(,)?) => {
+    ($(#[$attr:meta])* $name: ident, $level: ident, $descr: literal
+    $(, @future_incompatible = FutureIncompatibleInfo { $($field:ident : $val:expr),* $(,)*  }; )?
+    $(,)?) => {
         declare_tool_lint! {
             $(#[$attr])* pub rustdoc::$name, $level, $descr
+            $(, @future_incompatible = FutureIncompatibleInfo { $($field : $val),* };)?
         }
     }
 }
@@ -158,6 +161,22 @@ declare_rustdoc_lint! {
     "detects URLs that could be written using only angle brackets"
 }
 
+declare_rustdoc_lint! {
+    /// The `doc_include` lint detects when `#[doc(include = ...)]` is used.
+    /// This feature is scheduled for removal and will give a hard error in a future release.
+    ///
+    /// This is a `rustdoc` only lint, see the documentation in the [rustdoc book].
+    ///
+    /// [rustdoc book]: ../../../rustdoc/lints.html#non_autolinks
+    DOC_INCLUDE,
+    Warn,
+    "detects using `#[doc(include = ...)]`",
+    @future_incompatible = FutureIncompatibleInfo {
+        reference: "issue #44732 <https://github.com/rust-lang/rust/issues/44732>",
+        edition: None,
+    };
+}
+
 crate static RUSTDOC_LINTS: Lazy<Vec<&'static Lint>> = Lazy::new(|| {
     vec![
         BROKEN_INTRA_DOC_LINKS,