Auto merge of #106621 - ozkanonur:enable-elided-lifetimes-for-doctests, r=Mark-Simulacrum

enable `rust_2018_idioms` lint group for doctests

With this change, `rust_2018_idioms` lint group will be enabled for compiler/libstd doctests.

Resolves #106086
Resolves #99144

Signed-off-by: ozkanonur <work@onurozkan.dev>

Author: bors

Diff for: compiler/rustc_ast_lowering/src/lib.rs

@@ -1477,20 +1477,22 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
     /// Given a function definition like:
     ///
     /// ```rust
+    /// use std::fmt::Debug;
+    ///
     /// fn test<'a, T: Debug>(x: &'a T) -> impl Debug + 'a {
     ///     x
     /// }
     /// ```
     ///
     /// we will create a TAIT definition in the HIR like
     ///
-    /// ```
+    /// ```rust,ignore (pseudo-Rust)
     /// type TestReturn<'a, T, 'x> = impl Debug + 'x
     /// ```
     ///
     /// and return a type like `TestReturn<'static, T, 'a>`, so that the function looks like:
     ///
-    /// ```rust
+    /// ```rust,ignore (pseudo-Rust)
     /// fn test<'a, T: Debug>(x: &'a T) -> TestReturn<'static, T, 'a>
     /// ```
     ///

Diff for: compiler/rustc_builtin_macros/src/deriving/generic/mod.rs

@@ -1038,7 +1038,7 @@ impl<'a> MethodDef<'a> {
     /// `&self.x` because that might cause an unaligned ref. So for any trait
     /// method that takes a reference, we use a local block to force a copy.
     /// This requires that the field impl `Copy`.
-    /// ```
+    /// ```rust,ignore (example)
     /// # struct A { x: u8, y: u8 }
     /// impl PartialEq for A {
     ///     fn eq(&self, other: &A) -> bool {

Diff for: compiler/rustc_graphviz/src/lib.rs

@@ -167,7 +167,7 @@
 //!     fn node_label(&self, n: &Nd) -> dot::LabelText<'_> {
 //!         dot::LabelText::LabelStr(self.nodes[*n].into())
 //!     }
-//!     fn edge_label<'b>(&'b self, _: &Ed) -> dot::LabelText<'b> {
+//!     fn edge_label(&self, _: &Ed<'_>) -> dot::LabelText<'_> {
 //!         dot::LabelText::LabelStr("&sube;".into())
 //!     }
 //! }
@@ -177,8 +177,8 @@
 //!     type Edge = Ed<'a>;
 //!     fn nodes(&self) -> dot::Nodes<'a,Nd> { (0..self.nodes.len()).collect() }
 //!     fn edges(&'a self) -> dot::Edges<'a,Ed<'a>> { self.edges.iter().collect() }
-//!     fn source(&self, e: &Ed) -> Nd { let & &(s,_) = e; s }
-//!     fn target(&self, e: &Ed) -> Nd { let & &(_,t) = e; t }
+//!     fn source(&self, e: &Ed<'_>) -> Nd { let & &(s,_) = e; s }
+//!     fn target(&self, e: &Ed<'_>) -> Nd { let & &(_,t) = e; t }
 //! }
 //!
 //! # pub fn main() { render_to(&mut Vec::new()) }
@@ -226,11 +226,11 @@
 //!     fn node_id(&'a self, n: &Nd<'a>) -> dot::Id<'a> {
 //!         dot::Id::new(format!("N{}", n.0)).unwrap()
 //!     }
-//!     fn node_label<'b>(&'b self, n: &Nd<'b>) -> dot::LabelText<'b> {
+//!     fn node_label(&self, n: &Nd<'_>) -> dot::LabelText<'_> {
 //!         let &(i, _) = n;
 //!         dot::LabelText::LabelStr(self.nodes[i].into())
 //!     }
-//!     fn edge_label<'b>(&'b self, _: &Ed<'b>) -> dot::LabelText<'b> {
+//!     fn edge_label(&self, _: &Ed<'_>) -> dot::LabelText<'_> {
 //!         dot::LabelText::LabelStr("&sube;".into())
 //!     }
 //! }

Diff for: compiler/rustc_hir_analysis/src/check/compare_impl_item.rs

@@ -60,19 +60,21 @@ pub(super) fn compare_impl_method<'tcx>(
     };
 }
 
-/// This function is best explained by example. Consider a trait:
+/// This function is best explained by example. Consider a trait with it's implementation:
 ///
-///     trait Trait<'t, T> {
-///         // `trait_m`
-///         fn method<'a, M>(t: &'t T, m: &'a M) -> Self;
-///     }
+/// ```rust
+/// trait Trait<'t, T> {
+///     // `trait_m`
+///     fn method<'a, M>(t: &'t T, m: &'a M) -> Self;
+/// }
 ///
-/// And an impl:
+/// struct Foo;
 ///
-///     impl<'i, 'j, U> Trait<'j, &'i U> for Foo {
-///          // `impl_m`
-///          fn method<'b, N>(t: &'j &'i U, m: &'b N) -> Foo;
-///     }
+/// impl<'i, 'j, U> Trait<'j, &'i U> for Foo {
+///     // `impl_m`
+///     fn method<'b, N>(t: &'j &'i U, m: &'b N) -> Foo { Foo }
+/// }
+/// ```
 ///
 /// We wish to decide if those two method types are compatible.
 /// For this we have to show that, assuming the bounds of the impl hold, the
@@ -82,7 +84,9 @@ pub(super) fn compare_impl_method<'tcx>(
 /// type parameters to impl type parameters. This is taken from the
 /// impl trait reference:
 ///
-///     trait_to_impl_substs = {'t => 'j, T => &'i U, Self => Foo}
+/// ```rust,ignore (pseudo-Rust)
+/// trait_to_impl_substs = {'t => 'j, T => &'i U, Self => Foo}
+/// ```
 ///
 /// We create a mapping `dummy_substs` that maps from the impl type
 /// parameters to fresh types and regions. For type parameters,
@@ -91,13 +95,17 @@ pub(super) fn compare_impl_method<'tcx>(
 /// regions (Note: but only early-bound regions, i.e., those
 /// declared on the impl or used in type parameter bounds).
 ///
-///     impl_to_placeholder_substs = {'i => 'i0, U => U0, N => N0 }
+/// ```rust,ignore (pseudo-Rust)
+/// impl_to_placeholder_substs = {'i => 'i0, U => U0, N => N0 }
+/// ```
 ///
 /// Now we can apply `placeholder_substs` to the type of the impl method
 /// to yield a new function type in terms of our fresh, placeholder
 /// types:
 ///
-///     <'b> fn(t: &'i0 U0, m: &'b) -> Foo
+/// ```rust,ignore (pseudo-Rust)
+/// <'b> fn(t: &'i0 U0, m: &'b) -> Foo
+/// ```
 ///
 /// We now want to extract and substitute the type of the *trait*
 /// method and compare it. To do so, we must create a compound
@@ -106,11 +114,15 @@ pub(super) fn compare_impl_method<'tcx>(
 /// type parameters. We extend the mapping to also include
 /// the method parameters.
 ///
-///     trait_to_placeholder_substs = { T => &'i0 U0, Self => Foo, M => N0 }
+/// ```rust,ignore (pseudo-Rust)
+/// trait_to_placeholder_substs = { T => &'i0 U0, Self => Foo, M => N0 }
+/// ```
 ///
 /// Applying this to the trait method type yields:
 ///
-///     <'a> fn(t: &'i0 U0, m: &'a) -> Foo
+/// ```rust,ignore (pseudo-Rust)
+/// <'a> fn(t: &'i0 U0, m: &'a) -> Foo
+/// ```
 ///
 /// This type is also the same but the name of the bound region (`'a`
 /// vs `'b`). However, the normal subtyping rules on fn types handle
@@ -1163,7 +1175,7 @@ fn compare_self_type<'tcx>(
 /// as the number of generics on the respective assoc item in the trait definition.
 ///
 /// For example this code emits the errors in the following code:
-/// ```
+/// ```rust,compile_fail
 /// trait Trait {
 ///     fn foo();
 ///     type Assoc<T>;
@@ -1547,7 +1559,7 @@ fn compare_synthetic_generics<'tcx>(
 /// the same kind as the respective generic parameter in the trait def.
 ///
 /// For example all 4 errors in the following code are emitted here:
-/// ```
+/// ```rust,ignore (pseudo-Rust)
 /// trait Foo {
 ///     fn foo<const N: u8>();
 ///     type bar<const N: u8>;

Diff for: compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs

@@ -1923,7 +1923,7 @@ fn is_late_bound_map(
     /// handles cycle detection as we go through the query system.
     ///
     /// This is necessary in the first place for the following case:
-    /// ```
+    /// ```rust,ignore (pseudo-Rust)
     /// type Alias<'a, T> = <T as Trait<'a>>::Assoc;
     /// fn foo<'a>(_: Alias<'a, ()>) -> Alias<'a, ()> { ... }
     /// ```

Diff for: compiler/rustc_infer/src/infer/error_reporting/need_type_info.rs

@@ -31,7 +31,7 @@ pub enum TypeAnnotationNeeded {
     /// ```
     E0282,
     /// An implementation cannot be chosen unambiguously because of lack of information.
-    /// ```compile_fail,E0283
+    /// ```compile_fail,E0790
     /// let _ = Default::default();
     /// ```
     E0283,

Diff for: compiler/rustc_infer/src/infer/error_reporting/nice_region_error/different_lifetimes.rs

@@ -21,7 +21,7 @@ impl<'a, 'tcx> NiceRegionError<'a, 'tcx> {
     ///
     /// Consider a case where we have
     ///
-    /// ```compile_fail,E0623
+    /// ```compile_fail
     /// fn foo(x: &mut Vec<&u8>, y: &u8) {
     ///     x.push(y);
     /// }

Diff for: compiler/rustc_infer/src/infer/error_reporting/nice_region_error/find_anon_type.rs

@@ -14,7 +14,7 @@ use rustc_middle::ty::{self, Region, TyCtxt};
 /// br - the bound region corresponding to the above region which is of type `BrAnon(_)`
 ///
 /// # Example
-/// ```compile_fail,E0623
+/// ```compile_fail
 /// fn foo(x: &mut Vec<&u8>, y: &u8)
 ///    { x.push(y); }
 /// ```

Diff for: compiler/rustc_infer/src/infer/outlives/test_type_match.rs

@@ -13,9 +13,11 @@ use crate::infer::region_constraints::VerifyIfEq;
 
 /// Given a "verify-if-eq" type test like:
 ///
-///     exists<'a...> {
-///         verify_if_eq(some_type, bound_region)
-///     }
+/// ```rust,ignore (pseudo-Rust)
+/// exists<'a...> {
+///     verify_if_eq(some_type, bound_region)
+/// }
+/// ```
 ///
 /// and the type `test_ty` that the type test is being tested against,
 /// returns:

Diff for: compiler/rustc_infer/src/infer/outlives/verify.rs

@@ -277,7 +277,7 @@ impl<'cx, 'tcx> VerifyBoundCx<'cx, 'tcx> {
     ///
     /// It will not, however, work for higher-ranked bounds like:
     ///
-    /// ```compile_fail,E0311
+    /// ```ignore(this does compile today, previously was marked as `compile_fail,E0311`)
     /// trait Foo<'a, 'b>
     /// where for<'x> <Self as Foo<'x, 'b>>::Bar: 'x
     /// {

Diff for: compiler/rustc_infer/src/infer/region_constraints/mod.rs

@@ -217,7 +217,7 @@ pub enum VerifyBound<'tcx> {
 /// and supplies a bound if it ended up being relevant. It's used in situations
 /// like this:
 ///
-/// ```rust
+/// ```rust,ignore (pseudo-Rust)
 /// fn foo<'a, 'b, T: SomeTrait<'a>>
 /// where
 ///    <T as SomeTrait<'a>>::Item: 'b
@@ -232,7 +232,7 @@ pub enum VerifyBound<'tcx> {
 /// In the [`VerifyBound`], this struct is enclosed in `Binder` to account
 /// for cases like
 ///
-/// ```rust
+/// ```rust,ignore (pseudo-Rust)
 /// where for<'a> <T as SomeTrait<'a>::Item: 'a
 /// ```
 ///

Diff for: compiler/rustc_lint_defs/src/builtin.rs

@@ -333,6 +333,7 @@ declare_lint! {
     ///
     /// ```rust,compile_fail
     /// #![deny(unused_extern_crates)]
+    /// #![deny(warnings)]
     /// extern crate proc_macro;
     /// ```
     ///
@@ -1667,6 +1668,7 @@ declare_lint! {
     ///
     /// ```rust,compile_fail
     /// #![deny(elided_lifetimes_in_paths)]
+    /// #![deny(warnings)]
     /// struct Foo<'a> {
     ///     x: &'a u32
     /// }
@@ -2158,6 +2160,7 @@ declare_lint! {
     /// ```rust,compile_fail
     /// # #![allow(unused)]
     /// #![deny(explicit_outlives_requirements)]
+    /// #![deny(warnings)]
     ///
     /// struct SharedRef<'a, T>
     /// where

Diff for: library/alloc/src/borrow.rs

@@ -115,7 +115,7 @@ where
 /// ```
 /// use std::borrow::Cow;
 ///
-/// fn abs_all(input: &mut Cow<[i32]>) {
+/// fn abs_all(input: &mut Cow<'_, [i32]>) {
 ///     for i in 0..input.len() {
 ///         let v = input[i];
 ///         if v < 0 {
@@ -145,7 +145,7 @@ where
 /// ```
 /// use std::borrow::Cow;
 ///
-/// struct Items<'a, X: 'a> where [X]: ToOwned<Owned = Vec<X>> {
+/// struct Items<'a, X> where [X]: ToOwned<Owned = Vec<X>> {
 ///     values: Cow<'a, [X]>,
 /// }
 ///
@@ -267,7 +267,7 @@ impl<B: ?Sized + ToOwned> Cow<'_, B> {
     ///
     /// assert_eq!(
     ///   cow,
-    ///   Cow::Owned(String::from("FOO")) as Cow<str>
+    ///   Cow::Owned(String::from("FOO")) as Cow<'_, str>
     /// );
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
@@ -311,7 +311,7 @@ impl<B: ?Sized + ToOwned> Cow<'_, B> {
     /// use std::borrow::Cow;
     ///
     /// let s = "Hello world!";
-    /// let cow: Cow<str> = Cow::Owned(String::from(s));
+    /// let cow: Cow<'_, str> = Cow::Owned(String::from(s));
     ///
     /// assert_eq!(
     ///   cow.into_owned(),

Diff for: library/alloc/src/fmt.rs

@@ -363,7 +363,7 @@
 //! # use std::fmt;
 //! # struct Foo; // our custom type
 //! # impl fmt::Display for Foo {
-//! fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+//! fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 //! # write!(f, "testing, testing")
 //! # } }
 //! ```
@@ -399,7 +399,7 @@
 //! }
 //!
 //! impl fmt::Display for Vector2D {
-//!     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+//!     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 //!         // The `f` value implements the `Write` trait, which is what the
 //!         // write! macro is expecting. Note that this formatting ignores the
 //!         // various flags provided to format strings.
@@ -410,7 +410,7 @@
 //! // Different traits allow different forms of output of a type. The meaning
 //! // of this format is to print the magnitude of a vector.
 //! impl fmt::Binary for Vector2D {
-//!     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+//!     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 //!         let magnitude = (self.x * self.x + self.y * self.y) as f64;
 //!         let magnitude = magnitude.sqrt();
 //!
@@ -517,7 +517,7 @@
 //! let mut some_writer = io::stdout();
 //! write!(&mut some_writer, "{}", format_args!("print with a {}", "macro"));
 //!
-//! fn my_fmt_fn(args: fmt::Arguments) {
+//! fn my_fmt_fn(args: fmt::Arguments<'_>) {
 //!     write!(&mut io::stdout(), "{args}");
 //! }
 //! my_fmt_fn(format_args!(", or a {} too", "function"));

Diff for: library/alloc/src/rc.rs

@@ -2039,7 +2039,7 @@ where
     /// ```rust
     /// # use std::rc::Rc;
     /// # use std::borrow::Cow;
-    /// let cow: Cow<str> = Cow::Borrowed("eggplant");
+    /// let cow: Cow<'_, str> = Cow::Borrowed("eggplant");
     /// let shared: Rc<str> = Rc::from(cow);
     /// assert_eq!("eggplant", &shared[..]);
     /// ```

Diff for: library/alloc/src/string.rs

@@ -2741,7 +2741,7 @@ impl<'a> From<Cow<'a, str>> for String {
     /// ```
     /// # use std::borrow::Cow;
     /// // If the string is not owned...
-    /// let cow: Cow<str> = Cow::Borrowed("eggplant");
+    /// let cow: Cow<'_, str> = Cow::Borrowed("eggplant");
     /// // It will allocate on the heap and copy the string.
     /// let owned: String = String::from(cow);
     /// assert_eq!(&owned[..], "eggplant");

Diff for: library/alloc/src/sync.rs

@@ -2768,7 +2768,7 @@ where
     /// ```rust
     /// # use std::sync::Arc;
     /// # use std::borrow::Cow;
-    /// let cow: Cow<str> = Cow::Borrowed("eggplant");
+    /// let cow: Cow<'_, str> = Cow::Borrowed("eggplant");
     /// let shared: Arc<str> = Arc::from(cow);
     /// assert_eq!("eggplant", &shared[..]);
     /// ```

Diff for: library/alloc/src/vec/drain.rs

@@ -16,7 +16,7 @@ use super::Vec;
 ///
 /// ```
 /// let mut v = vec![0, 1, 2];
-/// let iter: std::vec::Drain<_> = v.drain(..);
+/// let iter: std::vec::Drain<'_, _> = v.drain(..);
 /// ```
 #[stable(feature = "drain", since = "1.6.0")]
 pub struct Drain<

Diff for: library/alloc/src/vec/drain_filter.rs

@@ -16,7 +16,7 @@ use super::Vec;
 /// #![feature(drain_filter)]
 ///
 /// let mut v = vec![0, 1, 2];
-/// let iter: std::vec::DrainFilter<_, _> = v.drain_filter(|x| *x % 2 == 0);
+/// let iter: std::vec::DrainFilter<'_, _, _> = v.drain_filter(|x| *x % 2 == 0);
 /// ```
 #[unstable(feature = "drain_filter", reason = "recently added", issue = "43244")]
 #[derive(Debug)]

Diff for: library/alloc/src/vec/mod.rs

@@ -3142,8 +3142,8 @@ where
     ///
     /// ```
     /// # use std::borrow::Cow;
-    /// let o: Cow<[i32]> = Cow::Owned(vec![1, 2, 3]);
-    /// let b: Cow<[i32]> = Cow::Borrowed(&[1, 2, 3]);
+    /// let o: Cow<'_, [i32]> = Cow::Owned(vec![1, 2, 3]);
+    /// let b: Cow<'_, [i32]> = Cow::Borrowed(&[1, 2, 3]);
     /// assert_eq!(Vec::from(o), Vec::from(b));
     /// ```
     fn from(s: Cow<'a, [T]>) -> Vec<T> {