Rollup of 4 pull requests

compiler/rustc_lint/src/array_into_iter.rs

@@ -32,7 +32,7 @@ declare_lint! {
     Warn,
     "detects calling `into_iter` on arrays in Rust 2015 and 2018",
     @future_incompatible = FutureIncompatibleInfo {
-        reference: "issue #66145 <https://github.com/rust-lang/rust/issues/66145>",
+        reference: "<https://doc.rust-lang.org/nightly/edition-guide/rust-2021/IntoIterator-for-arrays.html>",
         reason: FutureIncompatibilityReason::EditionSemanticsChange(Edition::Edition2021),
     };
 }

compiler/rustc_lint/src/builtin.rs

@@ -1680,7 +1680,7 @@ declare_lint! {
     Warn,
     "`...` range patterns are deprecated",
     @future_incompatible = FutureIncompatibleInfo {
-        reference: "issue #80165 <https://github.com/rust-lang/rust/issues/80165>",
+        reference: "<https://doc.rust-lang.org/nightly/edition-guide/rust-2021/warnings-promoted-to-error.html>",
         reason: FutureIncompatibilityReason::EditionError(Edition::Edition2021),
     };
 }

compiler/rustc_lint_defs/src/builtin.rs

@@ -1605,7 +1605,7 @@ declare_lint! {
     Warn,
     "suggest using `dyn Trait` for trait objects",
     @future_incompatible = FutureIncompatibleInfo {
-        reference: "issue #80165 <https://github.com/rust-lang/rust/issues/80165>",
+        reference: "<https://doc.rust-lang.org/nightly/edition-guide/rust-2021/warnings-promoted-to-error.html>",
         reason: FutureIncompatibilityReason::EditionError(Edition::Edition2021),
     };
 }
@@ -3247,7 +3247,7 @@ declare_lint! {
     Allow,
     "detects usage of old versions of or-patterns",
     @future_incompatible = FutureIncompatibleInfo {
-        reference: "issue #84869 <https://github.com/rust-lang/rust/issues/84869>",
+        reference: "<https://doc.rust-lang.org/nightly/edition-guide/rust-2021/or-patterns-macro-rules.html>",
         reason: FutureIncompatibilityReason::EditionError(Edition::Edition2021),
     };
 }
@@ -3296,7 +3296,7 @@ declare_lint! {
     "detects the usage of trait methods which are ambiguous with traits added to the \
         prelude in future editions",
     @future_incompatible = FutureIncompatibleInfo {
-        reference: "issue #85684 <https://github.com/rust-lang/rust/issues/85684>",
+        reference: "<https://doc.rust-lang.org/nightly/edition-guide/rust-2021/prelude.html>",
         reason: FutureIncompatibilityReason::EditionError(Edition::Edition2021),
     };
 }
@@ -3331,7 +3331,7 @@ declare_lint! {
     Allow,
     "identifiers that will be parsed as a prefix in Rust 2021",
     @future_incompatible = FutureIncompatibleInfo {
-        reference: "issue #84978 <https://github.com/rust-lang/rust/issues/84978>",
+        reference: "<https://doc.rust-lang.org/nightly/edition-guide/rust-2021/reserving-syntax.html>",
         reason: FutureIncompatibilityReason::EditionError(Edition::Edition2021),
     };
     crate_level_only

compiler/rustc_typeck/src/check/wfcheck.rs

@@ -194,12 +194,13 @@ pub fn check_trait_item(tcx: TyCtxt<'_>, def_id: LocalDefId) {
     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
     let trait_item = tcx.hir().expect_trait_item(hir_id);
 
-    let method_sig = match trait_item.kind {
-        hir::TraitItemKind::Fn(ref sig, _) => Some(sig),
-        _ => None,
+    let (method_sig, span) = match trait_item.kind {
+        hir::TraitItemKind::Fn(ref sig, _) => (Some(sig), trait_item.span),
+        hir::TraitItemKind::Type(_bounds, Some(ty)) => (None, ty.span),
+        _ => (None, trait_item.span),
     };
     check_object_unsafe_self_trait_by_name(tcx, &trait_item);
-    check_associated_item(tcx, trait_item.hir_id(), trait_item.span, method_sig);
+    check_associated_item(tcx, trait_item.hir_id(), span, method_sig);
 }
 
 fn could_be_self(trait_def_id: LocalDefId, ty: &hir::Ty<'_>) -> bool {
@@ -268,12 +269,13 @@ pub fn check_impl_item(tcx: TyCtxt<'_>, def_id: LocalDefId) {
     let hir_id = tcx.hir().local_def_id_to_hir_id(def_id);
     let impl_item = tcx.hir().expect_impl_item(hir_id);
 
-    let method_sig = match impl_item.kind {
-        hir::ImplItemKind::Fn(ref sig, _) => Some(sig),
-        _ => None,
+    let (method_sig, span) = match impl_item.kind {
+        hir::ImplItemKind::Fn(ref sig, _) => (Some(sig), impl_item.span),
+        hir::ImplItemKind::TyAlias(ty) => (None, ty.span),
+        _ => (None, impl_item.span),
     };
 
-    check_associated_item(tcx, impl_item.hir_id(), impl_item.span, method_sig);
+    check_associated_item(tcx, impl_item.hir_id(), span, method_sig);
 }
 
 fn check_param_wf(tcx: TyCtxt<'_>, param: &hir::GenericParam<'_>) {

library/std/src/sys/windows/process.rs

@@ -3,7 +3,6 @@
 #[cfg(test)]
 mod tests;
 
-use crate::borrow::Borrow;
 use crate::cmp;
 use crate::collections::BTreeMap;
 use crate::convert::{TryFrom, TryInto};
@@ -46,6 +45,12 @@ pub struct EnvKey {
     utf16: Vec<u16>,
 }
 
+impl EnvKey {
+    fn new<T: Into<OsString>>(key: T) -> Self {
+        EnvKey::from(key.into())
+    }
+}
+
 // Comparing Windows environment variable keys[1] are behaviourally the
 // composition of two operations[2]:
 //
@@ -100,6 +105,20 @@ impl PartialEq for EnvKey {
         }
     }
 }
+impl PartialOrd<str> for EnvKey {
+    fn partial_cmp(&self, other: &str) -> Option<cmp::Ordering> {
+        Some(self.cmp(&EnvKey::new(other)))
+    }
+}
+impl PartialEq<str> for EnvKey {
+    fn eq(&self, other: &str) -> bool {
+        if self.os_string.len() != other.len() {
+            false
+        } else {
+            self.cmp(&EnvKey::new(other)) == cmp::Ordering::Equal
+        }
+    }
+}
 
 // Environment variable keys should preserve their original case even though
 // they are compared using a caseless string mapping.
@@ -115,9 +134,9 @@ impl From<EnvKey> for OsString {
     }
 }
 
-impl Borrow<OsStr> for EnvKey {
-    fn borrow(&self) -> &OsStr {
-        &self.os_string
+impl From<&OsStr> for EnvKey {
+    fn from(k: &OsStr) -> Self {
+        Self::from(k.to_os_string())
     }
 }
 
@@ -242,7 +261,7 @@ impl Command {
         // to read the *child's* PATH if one is provided. See #15149 for more
         // details.
         let program = maybe_env.as_ref().and_then(|env| {
-            if let Some(v) = env.get(OsStr::new("PATH")) {
+            if let Some(v) = env.get(&EnvKey::new("PATH")) {
                 // Split the value and test each path to see if the
                 // program exists.
                 for path in split_paths(&v) {

library/std/src/sys_common/process.rs

@@ -65,16 +65,18 @@ impl CommandEnv {
 
     // The following functions build up changes
     pub fn set(&mut self, key: &OsStr, value: &OsStr) {
+        let key = EnvKey::from(key);
         self.maybe_saw_path(&key);
-        self.vars.insert(key.to_owned().into(), Some(value.to_owned()));
+        self.vars.insert(key, Some(value.to_owned()));
     }
 
     pub fn remove(&mut self, key: &OsStr) {
+        let key = EnvKey::from(key);
         self.maybe_saw_path(&key);
         if self.clear {
-            self.vars.remove(key);
+            self.vars.remove(&key);
         } else {
-            self.vars.insert(key.to_owned().into(), None);
+            self.vars.insert(key, None);
         }
     }
 
@@ -87,7 +89,7 @@ impl CommandEnv {
         self.saw_path || self.clear
     }
 
-    fn maybe_saw_path(&mut self, key: &OsStr) {
+    fn maybe_saw_path(&mut self, key: &EnvKey) {
         if !self.saw_path && key == "PATH" {
             self.saw_path = true;
         }

src/test/ui/associated-types/defaults-cyclic-fail-1.stderr

@@ -1,14 +1,14 @@
 error[E0275]: overflow evaluating the requirement `<bool as Tr>::B == _`
-  --> $DIR/defaults-cyclic-fail-1.rs:26:5
+  --> $DIR/defaults-cyclic-fail-1.rs:26:14
    |
 LL |     type A = Box<Self::B>;
-   |     ^^^^^^^^^^^^^^^^^^^^^^
+   |              ^^^^^^^^^^^^
 
 error[E0275]: overflow evaluating the requirement `<usize as Tr>::A == _`
-  --> $DIR/defaults-cyclic-fail-1.rs:32:5
+  --> $DIR/defaults-cyclic-fail-1.rs:32:14
    |
 LL |     type B = &'static Self::A;
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |              ^^^^^^^^^^^^^^^^
 
 error: aborting due to 2 previous errors
 

src/test/ui/associated-types/defaults-cyclic-fail-2.stderr

@@ -1,14 +1,14 @@
 error[E0275]: overflow evaluating the requirement `<bool as Tr>::B == _`
-  --> $DIR/defaults-cyclic-fail-2.rs:27:5
+  --> $DIR/defaults-cyclic-fail-2.rs:27:14
    |
 LL |     type A = Box<Self::B>;
-   |     ^^^^^^^^^^^^^^^^^^^^^^
+   |              ^^^^^^^^^^^^
 
 error[E0275]: overflow evaluating the requirement `<usize as Tr>::A == _`
-  --> $DIR/defaults-cyclic-fail-2.rs:33:5
+  --> $DIR/defaults-cyclic-fail-2.rs:33:14
    |
 LL |     type B = &'static Self::A;
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |              ^^^^^^^^^^^^^^^^
 
 error: aborting due to 2 previous errors
 

src/test/ui/const-generics/min_const_generics/const-expression-suggest-missing-braces.stderr

@@ -139,7 +139,7 @@ LL |     foo::<BAR + BAR>();
    |
    = note: `#[warn(bare_trait_objects)]` on by default
    = warning: this is accepted in the current edition (Rust 2015) but is a hard error in Rust 2021!
-   = note: for more information, see issue #80165 <https://github.com/rust-lang/rust/issues/80165>
+   = note: for more information, see <https://doc.rust-lang.org/nightly/edition-guide/rust-2021/warnings-promoted-to-error.html>
 
 error[E0747]: type provided when a constant was expected
   --> $DIR/const-expression-suggest-missing-braces.rs:11:11

src/test/ui/dyn-keyword/dyn-2018-edition-lint.stderr

@@ -10,7 +10,7 @@ note: the lint level is defined here
 LL | #[deny(bare_trait_objects)]
    |        ^^^^^^^^^^^^^^^^^^
    = warning: this is accepted in the current edition (Rust 2018) but is a hard error in Rust 2021!
-   = note: for more information, see issue #80165 <https://github.com/rust-lang/rust/issues/80165>
+   = note: for more information, see <https://doc.rust-lang.org/nightly/edition-guide/rust-2021/warnings-promoted-to-error.html>
 
 error: trait objects without an explicit `dyn` are deprecated
   --> $DIR/dyn-2018-edition-lint.rs:4:35
@@ -19,7 +19,7 @@ LL | fn function(x: &SomeTrait, y: Box<SomeTrait>) {
    |                                   ^^^^^^^^^ help: use `dyn`: `dyn SomeTrait`
    |
    = warning: this is accepted in the current edition (Rust 2018) but is a hard error in Rust 2021!
-   = note: for more information, see issue #80165 <https://github.com/rust-lang/rust/issues/80165>
+   = note: for more information, see <https://doc.rust-lang.org/nightly/edition-guide/rust-2021/warnings-promoted-to-error.html>
 
 error: trait objects without an explicit `dyn` are deprecated
   --> $DIR/dyn-2018-edition-lint.rs:9:14
@@ -28,7 +28,7 @@ LL |     let _x: &SomeTrait = todo!();
    |              ^^^^^^^^^ help: use `dyn`: `dyn SomeTrait`
    |
    = warning: this is accepted in the current edition (Rust 2018) but is a hard error in Rust 2021!
-   = note: for more information, see issue #80165 <https://github.com/rust-lang/rust/issues/80165>
+   = note: for more information, see <https://doc.rust-lang.org/nightly/edition-guide/rust-2021/warnings-promoted-to-error.html>
 
 error: aborting due to 3 previous errors
 

src/test/ui/generic-associated-types/gat-trait-path-parenthesised-args.stderr

@@ -18,7 +18,7 @@ LL | fn foo<'a>(arg: Box<dyn X<Y('a) = &'a ()>>) {}
    |
    = note: `#[warn(bare_trait_objects)]` on by default
    = warning: this is accepted in the current edition (Rust 2015) but is a hard error in Rust 2021!
-   = note: for more information, see issue #80165 <https://github.com/rust-lang/rust/issues/80165>
+   = note: for more information, see <https://doc.rust-lang.org/nightly/edition-guide/rust-2021/warnings-promoted-to-error.html>
 
 error[E0107]: this associated type takes 1 lifetime argument but 0 lifetime arguments were supplied
   --> $DIR/gat-trait-path-parenthesised-args.rs:7:27

src/test/ui/generic-associated-types/projection-bound-cycle-generic.stderr

@@ -1,11 +1,11 @@
 error[E0275]: overflow evaluating the requirement `<T as Foo>::Item: Sized`
-  --> $DIR/projection-bound-cycle-generic.rs:44:5
+  --> $DIR/projection-bound-cycle-generic.rs:44:18
    |
 LL | struct OnlySized<T> where T: Sized { f: T }
    |                  - required by this bound in `OnlySized`
 ...
 LL |     type Assoc = OnlySized<<T as Foo>::Item>;
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: aborting due to previous error
 

src/test/ui/generic-associated-types/projection-bound-cycle.stderr

@@ -1,11 +1,11 @@
 error[E0275]: overflow evaluating the requirement `<T as Foo>::Item: Sized`
-  --> $DIR/projection-bound-cycle.rs:46:5
+  --> $DIR/projection-bound-cycle.rs:46:18
    |
 LL | struct OnlySized<T> where T: Sized { f: T }
    |                  - required by this bound in `OnlySized`
 ...
 LL |     type Assoc = OnlySized<<T as Foo>::Item>;
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: aborting due to previous error
 

src/test/ui/issues/issue-21946.stderr

@@ -1,8 +1,8 @@
 error[E0275]: overflow evaluating the requirement `<FooStruct as Foo>::A == _`
-  --> $DIR/issue-21946.rs:8:5
+  --> $DIR/issue-21946.rs:8:14
    |
 LL |     type A = <FooStruct as Foo>::A;
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |              ^^^^^^^^^^^^^^^^^^^^^
 
 error: aborting due to previous error
 

src/test/ui/issues/issue-23122-1.stderr

@@ -1,8 +1,8 @@
 error[E0275]: overflow evaluating the requirement `<GetNext<T> as Next>::Next == _`
-  --> $DIR/issue-23122-1.rs:10:5
+  --> $DIR/issue-23122-1.rs:10:17
    |
 LL |     type Next = <GetNext<T> as Next>::Next;
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: aborting due to previous error
 

src/test/ui/issues/issue-23122-2.stderr

@@ -1,8 +1,8 @@
 error[E0275]: overflow evaluating the requirement `<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<T as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next: Sized`
-  --> $DIR/issue-23122-2.rs:9:5
+  --> $DIR/issue-23122-2.rs:9:17
    |
 LL |     type Next = <GetNext<T::Next> as Next>::Next;
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = help: consider adding a `#![recursion_limit="256"]` attribute to your crate (`issue_23122_2`)
 note: required because of the requirements on the impl of `Next` for `GetNext<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<T as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next as Next>::Next>`

src/test/ui/issues/issue-86756.stderr

@@ -22,7 +22,7 @@ LL |     eq::<dyn, Foo>
    |
    = note: `#[warn(bare_trait_objects)]` on by default
    = warning: this is accepted in the current edition (Rust 2015) but is a hard error in Rust 2021!
-   = note: for more information, see issue #80165 <https://github.com/rust-lang/rust/issues/80165>
+   = note: for more information, see <https://doc.rust-lang.org/nightly/edition-guide/rust-2021/warnings-promoted-to-error.html>
 
 error[E0107]: missing generics for trait `Foo`
   --> $DIR/issue-86756.rs:5:15

src/test/ui/iterators/into-iter-on-arrays-2018.stderr

@@ -6,7 +6,7 @@ LL |     let _: Iter<'_, i32> = array.into_iter();
    |
    = note: `#[warn(array_into_iter)]` on by default
    = warning: this changes meaning in Rust 2021
-   = note: for more information, see issue #66145 <https://github.com/rust-lang/rust/issues/66145>
+   = note: for more information, see <https://doc.rust-lang.org/nightly/edition-guide/rust-2021/IntoIterator-for-arrays.html>
 help: use `.iter()` instead of `.into_iter()` to avoid ambiguity
    |
 LL |     let _: Iter<'_, i32> = array.iter();
@@ -23,7 +23,7 @@ LL |     let _: Iter<'_, i32> = Box::new(array).into_iter();
    |                                            ^^^^^^^^^
    |
    = warning: this changes meaning in Rust 2021
-   = note: for more information, see issue #66145 <https://github.com/rust-lang/rust/issues/66145>
+   = note: for more information, see <https://doc.rust-lang.org/nightly/edition-guide/rust-2021/IntoIterator-for-arrays.html>
 help: use `.iter()` instead of `.into_iter()` to avoid ambiguity
    |
 LL |     let _: Iter<'_, i32> = Box::new(array).iter();
@@ -40,7 +40,7 @@ LL |     for _ in [1, 2, 3].into_iter() {}
    |                        ^^^^^^^^^
    |
    = warning: this changes meaning in Rust 2021
-   = note: for more information, see issue #66145 <https://github.com/rust-lang/rust/issues/66145>
+   = note: for more information, see <https://doc.rust-lang.org/nightly/edition-guide/rust-2021/IntoIterator-for-arrays.html>
 help: use `.iter()` instead of `.into_iter()` to avoid ambiguity
    |
 LL |     for _ in [1, 2, 3].iter() {}