enable `rust_2018_idioms` for doctests

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

12 files changed, 54 insertions, 35 deletions

diff --git a/compiler/rustc_ast_lowering/src/lib.rs b/compiler/rustc_ast_lowering/src/lib.rs
index d07355a4154..8a511d8b5fb 100644
--- a/compiler/rustc_ast_lowering/src/lib.rs
+++ b/compiler/rustc_ast_lowering/src/lib.rs
@@ -1474,6 +1474,8 @@ 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
     /// }
@@ -1481,13 +1483,13 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
     ///
     /// 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 --git a/compiler/rustc_builtin_macros/src/deriving/generic/mod.rs b/compiler/rustc_builtin_macros/src/deriving/generic/mod.rs
index e5a00331588..caced3d6447 100644
--- a/compiler/rustc_builtin_macros/src/deriving/generic/mod.rs
+++ b/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 --git a/compiler/rustc_graphviz/src/lib.rs b/compiler/rustc_graphviz/src/lib.rs
index b70a55e8953..5d86d895817 100644
--- a/compiler/rustc_graphviz/src/lib.rs
+++ b/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 --git a/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs b/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs
index 48214b899a4..b956ed50073 100644
--- a/compiler/rustc_hir_analysis/src/check/compare_impl_item.rs
+++ b/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 --git a/compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs b/compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs
index 1c496f867a0..f17caba5787 100644
--- a/compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs
+++ b/compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs
@@ -1913,7 +1913,7 @@ 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 --git a/compiler/rustc_infer/src/infer/error_reporting/need_type_info.rs b/compiler/rustc_infer/src/infer/error_reporting/need_type_info.rs
index 58e3159a4e2..5000b0139df 100644
--- a/compiler/rustc_infer/src/infer/error_reporting/need_type_info.rs
+++ b/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 --git a/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/different_lifetimes.rs b/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/different_lifetimes.rs
index da0271a345e..1a60bab18db 100644
--- a/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/different_lifetimes.rs
+++ b/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 --git a/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/find_anon_type.rs b/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/find_anon_type.rs
index fec04af2313..0df417d0950 100644
--- a/compiler/rustc_infer/src/infer/error_reporting/nice_region_error/find_anon_type.rs
+++ b/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 --git a/compiler/rustc_infer/src/infer/outlives/test_type_match.rs b/compiler/rustc_infer/src/infer/outlives/test_type_match.rs
index 01f900f050e..75ce0f83fd6 100644
--- a/compiler/rustc_infer/src/infer/outlives/test_type_match.rs
+++ b/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 --git a/compiler/rustc_infer/src/infer/outlives/verify.rs b/compiler/rustc_infer/src/infer/outlives/verify.rs
index e1cb53bc71d..4b59059010f 100644
--- a/compiler/rustc_infer/src/infer/outlives/verify.rs
+++ b/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 --git a/compiler/rustc_infer/src/infer/region_constraints/mod.rs b/compiler/rustc_infer/src/infer/region_constraints/mod.rs
index 6692cd1d389..c7a307b89e4 100644
--- a/compiler/rustc_infer/src/infer/region_constraints/mod.rs
+++ b/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 --git a/compiler/rustc_lint_defs/src/builtin.rs b/compiler/rustc_lint_defs/src/builtin.rs
index b223b8c137a..814513cbd6d 100644
--- a/compiler/rustc_lint_defs/src/builtin.rs
+++ b/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