Rollup merge of rust-lang#103484 - saschanaz:patch-2, r=ehuss

Add `rust` to `let_underscore_lock` example

Currently https://doc.rust-lang.org/beta/rustc/lints/listing/deny-by-default.html#let-underscore-lock has no colored grammar and raw `{{produces}}` command is exposed.

compiler/rustc_lint/src/let_underscore.rs

@@ -57,7 +57,7 @@ declare_lint! {
     /// of at end of scope, which is typically incorrect.
     ///
     /// ### Example
-    /// ```compile_fail
+    /// ```rust,compile_fail
     /// use std::sync::{Arc, Mutex};
     /// use std::thread;
     /// let data = Arc::new(Mutex::new(0));

compiler/rustc_lint/src/opaque_hidden_inferred_bound.rs

@@ -26,19 +26,23 @@ declare_lint! {
     ///
     /// ### Example
     ///
-    /// ```
+    /// ```rust
+    /// trait Duh {}
+    ///
+    /// impl Duh for i32 {}
+    ///
     /// trait Trait {
-    ///     type Assoc: Send;
+    ///     type Assoc: Duh;
     /// }
     ///
     /// struct Struct;
     ///
-    /// impl Trait for Struct {
-    ///     type Assoc = i32;
+    /// impl<F: Duh> Trait for F {
+    ///     type Assoc = F;
     /// }
     ///
     /// fn test() -> impl Trait<Assoc = impl Sized> {
-    ///     Struct
+    ///     42
     /// }
     /// ```
     ///

compiler/rustc_lint_defs/src/builtin.rs

@@ -605,7 +605,7 @@ declare_lint! {
     ///
     /// ### Example
     ///
-    /// ```
+    /// ```rust
     /// #[warn(unused_tuple_struct_fields)]
     /// struct S(i32, i32, i32);
     /// let s = S(1, 2, 3);
@@ -1154,7 +1154,7 @@ declare_lint! {
     ///
     /// ### Example
     ///
-    /// ```compile_fail
+    /// ```rust,compile_fail
     /// #[repr(packed)]
     /// pub struct Foo {
     ///     field1: u64,
@@ -2548,7 +2548,7 @@ declare_lint! {
     ///
     /// ### Example
     ///
-    /// ```compile_fail
+    /// ```rust,compile_fail
     /// # #![allow(unused)]
     /// enum E {
     ///     A,
@@ -3918,7 +3918,7 @@ declare_lint! {
     ///
     /// ### Example
     ///
-    /// ```
+    /// ```rust
     /// #![allow(test_unstable_lint)]
     /// ```
     ///

src/tools/lint-docs/src/lib.rs

@@ -37,10 +37,8 @@ impl Lint {
     }
 
     fn is_ignored(&self) -> bool {
-        self.doc
-            .iter()
-            .filter(|line| line.starts_with("```rust"))
-            .all(|line| line.contains(",ignore"))
+        let blocks: Vec<_> = self.doc.iter().filter(|line| line.starts_with("```rust")).collect();
+        !blocks.is_empty() && blocks.iter().all(|line| line.contains(",ignore"))
     }
 
     /// Checks the doc style of the lint.