Auto merge of #69796 - Centril:rollup-xg85jmx, r=Centril

Rollup of 9 pull requests

Successful merges:

 - #67741 (When encountering an Item in a pat context, point at the item def)
 - #68985 (Parse & reject postfix operators after casts)
 - #69656 (Use .next() instead of .nth(0) on iterators.)
 - #69680 (rustc_expand: Factor out `Annotatable::into_tokens` to a separate method)
 - #69690 (test(pattern): add tests for combinations of pattern features)
 - #69706 (Use subslice patterns in slice methods)
 - #69727 (Avoid using `unwrap()` in suggestions)
 - #69754 (Update deprecation version to 1.42 for Error::description)
 - #69782 (Don't redundantly repeat field names (clippy::redundant_field_names))

Failed merges:

r? @ghost

src/liballoc/collections/linked_list.rs

@@ -959,7 +959,7 @@ impl<T> LinkedList<T> {
         let it = self.head;
         let old_len = self.len;
 
-        DrainFilter { list: self, it: it, pred: filter, idx: 0, old_len: old_len }
+        DrainFilter { list: self, it, pred: filter, idx: 0, old_len }
     }
 }
 

src/liballoc/vec.rs

@@ -1659,7 +1659,7 @@ struct SetLenOnDrop<'a> {
 impl<'a> SetLenOnDrop<'a> {
     #[inline]
     fn new(len: &'a mut usize) -> Self {
-        SetLenOnDrop { local_len: *len, len: len }
+        SetLenOnDrop { local_len: *len, len }
     }
 
     #[inline]

src/libcore/slice/mod.rs

@@ -103,7 +103,7 @@ impl<T> [T] {
     #[stable(feature = "rust1", since = "1.0.0")]
     #[inline]
     pub fn first(&self) -> Option<&T> {
-        self.get(0)
+        if let [first, ..] = self { Some(first) } else { None }
     }
 
     /// Returns a mutable pointer to the first element of the slice, or `None` if it is empty.
@@ -121,7 +121,7 @@ impl<T> [T] {
     #[stable(feature = "rust1", since = "1.0.0")]
     #[inline]
     pub fn first_mut(&mut self) -> Option<&mut T> {
-        self.get_mut(0)
+        if let [first, ..] = self { Some(first) } else { None }
     }
 
     /// Returns the first and all the rest of the elements of the slice, or `None` if it is empty.
@@ -139,7 +139,7 @@ impl<T> [T] {
     #[stable(feature = "slice_splits", since = "1.5.0")]
     #[inline]
     pub fn split_first(&self) -> Option<(&T, &[T])> {
-        if self.is_empty() { None } else { Some((&self[0], &self[1..])) }
+        if let [first, tail @ ..] = self { Some((first, tail)) } else { None }
     }
 
     /// Returns the first and all the rest of the elements of the slice, or `None` if it is empty.
@@ -159,12 +159,7 @@ impl<T> [T] {
     #[stable(feature = "slice_splits", since = "1.5.0")]
     #[inline]
     pub fn split_first_mut(&mut self) -> Option<(&mut T, &mut [T])> {
-        if self.is_empty() {
-            None
-        } else {
-            let split = self.split_at_mut(1);
-            Some((&mut split.0[0], split.1))
-        }
+        if let [first, tail @ ..] = self { Some((first, tail)) } else { None }
     }
 
     /// Returns the last and all the rest of the elements of the slice, or `None` if it is empty.
@@ -182,8 +177,7 @@ impl<T> [T] {
     #[stable(feature = "slice_splits", since = "1.5.0")]
     #[inline]
     pub fn split_last(&self) -> Option<(&T, &[T])> {
-        let len = self.len();
-        if len == 0 { None } else { Some((&self[len - 1], &self[..(len - 1)])) }
+        if let [init @ .., last] = self { Some((last, init)) } else { None }
     }
 
     /// Returns the last and all the rest of the elements of the slice, or `None` if it is empty.
@@ -203,13 +197,7 @@ impl<T> [T] {
     #[stable(feature = "slice_splits", since = "1.5.0")]
     #[inline]
     pub fn split_last_mut(&mut self) -> Option<(&mut T, &mut [T])> {
-        let len = self.len();
-        if len == 0 {
-            None
-        } else {
-            let split = self.split_at_mut(len - 1);
-            Some((&mut split.1[0], split.0))
-        }
+        if let [init @ .., last] = self { Some((last, init)) } else { None }
     }
 
     /// Returns the last element of the slice, or `None` if it is empty.
@@ -226,8 +214,7 @@ impl<T> [T] {
     #[stable(feature = "rust1", since = "1.0.0")]
     #[inline]
     pub fn last(&self) -> Option<&T> {
-        let last_idx = self.len().checked_sub(1)?;
-        self.get(last_idx)
+        if let [.., last] = self { Some(last) } else { None }
     }
 
     /// Returns a mutable pointer to the last item in the slice.
@@ -245,8 +232,7 @@ impl<T> [T] {
     #[stable(feature = "rust1", since = "1.0.0")]
     #[inline]
     pub fn last_mut(&mut self) -> Option<&mut T> {
-        let last_idx = self.len().checked_sub(1)?;
-        self.get_mut(last_idx)
+        if let [.., last] = self { Some(last) } else { None }
     }
 
     /// Returns a reference to an element or subslice depending on the type of

src/libproc_macro/diagnostic.rs

@@ -55,13 +55,15 @@ pub struct Diagnostic {
 }
 
 macro_rules! diagnostic_child_methods {
-    ($spanned:ident, $regular:ident, $level:expr) => (
+    ($spanned:ident, $regular:ident, $level:expr) => {
         /// Adds a new child diagnostic message to `self` with the level
         /// identified by this method's name with the given `spans` and
         /// `message`.
         #[unstable(feature = "proc_macro_diagnostic", issue = "54140")]
         pub fn $spanned<S, T>(mut self, spans: S, message: T) -> Diagnostic
-            where S: MultiSpan, T: Into<String>
+        where
+            S: MultiSpan,
+            T: Into<String>,
         {
             self.children.push(Diagnostic::spanned(spans, $level, message));
             self
@@ -74,7 +76,7 @@ macro_rules! diagnostic_child_methods {
             self.children.push(Diagnostic::new($level, message));
             self
         }
-    )
+    };
 }
 
 /// Iterator over the children diagnostics of a `Diagnostic`.
@@ -96,7 +98,7 @@ impl Diagnostic {
     /// Creates a new diagnostic with the given `level` and `message`.
     #[unstable(feature = "proc_macro_diagnostic", issue = "54140")]
     pub fn new<T: Into<String>>(level: Level, message: T) -> Diagnostic {
-        Diagnostic { level: level, message: message.into(), spans: vec![], children: vec![] }
+        Diagnostic { level, message: message.into(), spans: vec![], children: vec![] }
     }
 
     /// Creates a new diagnostic with the given `level` and `message` pointing to
@@ -107,12 +109,7 @@ impl Diagnostic {
         S: MultiSpan,
         T: Into<String>,
     {
-        Diagnostic {
-            level: level,
-            message: message.into(),
-            spans: spans.into_spans(),
-            children: vec![],
-        }
+        Diagnostic { level, message: message.into(), spans: spans.into_spans(), children: vec![] }
     }
 
     diagnostic_child_methods!(span_error, error, Level::Error);

src/librustc/hir/map/definitions.rs

@@ -192,7 +192,7 @@ impl DefPath {
             }
         }
         data.reverse();
-        DefPath { data: data, krate: krate }
+        DefPath { data, krate }
     }
 
     /// Returns a string representation of the `DefPath` without

src/librustc/mir/mod.rs

@@ -1446,7 +1446,7 @@ impl<'tcx> Debug for TerminatorKind<'tcx> {
         match successor_count {
             0 => Ok(()),
 
-            1 => write!(fmt, " -> {:?}", self.successors().nth(0).unwrap()),
+            1 => write!(fmt, " -> {:?}", self.successors().next().unwrap()),
 
             _ => {
                 write!(fmt, " -> [")?;

src/librustc/mir/mono.rs

@@ -258,7 +258,7 @@ pub enum Visibility {
 
 impl<'tcx> CodegenUnit<'tcx> {
     pub fn new(name: Symbol) -> CodegenUnit<'tcx> {
-        CodegenUnit { name: name, items: Default::default(), size_estimate: None }
+        CodegenUnit { name, items: Default::default(), size_estimate: None }
     }
 
     pub fn name(&self) -> Symbol {

src/librustc/traits/structural_impls.rs

@@ -532,9 +532,9 @@ impl<'a, 'tcx> Lift<'tcx> for traits::Vtable<'a, ()> {
                 nested,
             }) => tcx.lift(&substs).map(|substs| {
                 traits::VtableGenerator(traits::VtableGeneratorData {
-                    generator_def_id: generator_def_id,
-                    substs: substs,
-                    nested: nested,
+                    generator_def_id,
+                    substs,
+                    nested,
                 })
             }),
             traits::VtableClosure(traits::VtableClosureData { closure_def_id, substs, nested }) => {

src/librustc/ty/context.rs

@@ -2256,22 +2256,22 @@ impl<'tcx> TyCtxt<'tcx> {
 
     #[inline]
     pub fn mk_mut_ref(self, r: Region<'tcx>, ty: Ty<'tcx>) -> Ty<'tcx> {
-        self.mk_ref(r, TypeAndMut { ty: ty, mutbl: hir::Mutability::Mut })
+        self.mk_ref(r, TypeAndMut { ty, mutbl: hir::Mutability::Mut })
     }
 
     #[inline]
     pub fn mk_imm_ref(self, r: Region<'tcx>, ty: Ty<'tcx>) -> Ty<'tcx> {
-        self.mk_ref(r, TypeAndMut { ty: ty, mutbl: hir::Mutability::Not })
+        self.mk_ref(r, TypeAndMut { ty, mutbl: hir::Mutability::Not })
     }
 
     #[inline]
     pub fn mk_mut_ptr(self, ty: Ty<'tcx>) -> Ty<'tcx> {
-        self.mk_ptr(TypeAndMut { ty: ty, mutbl: hir::Mutability::Mut })
+        self.mk_ptr(TypeAndMut { ty, mutbl: hir::Mutability::Mut })
     }
 
     #[inline]
     pub fn mk_imm_ptr(self, ty: Ty<'tcx>) -> Ty<'tcx> {
-        self.mk_ptr(TypeAndMut { ty: ty, mutbl: hir::Mutability::Not })
+        self.mk_ptr(TypeAndMut { ty, mutbl: hir::Mutability::Not })
     }
 
     #[inline]
@@ -2393,7 +2393,7 @@ impl<'tcx> TyCtxt<'tcx> {
 
     #[inline]
     pub fn mk_ty_param(self, index: u32, name: Symbol) -> Ty<'tcx> {
-        self.mk_ty(Param(ParamTy { index, name: name }))
+        self.mk_ty(Param(ParamTy { index, name }))
     }
 
     #[inline]

src/librustc/ty/instance.rs

@@ -241,7 +241,7 @@ impl<'tcx> Instance<'tcx> {
             def_id,
             substs
         );
-        Instance { def: InstanceDef::Item(def_id), substs: substs }
+        Instance { def: InstanceDef::Item(def_id), substs }
     }
 
     pub fn mono(tcx: TyCtxt<'tcx>, def_id: DefId) -> Instance<'tcx> {

src/librustc/ty/mod.rs

@@ -370,7 +370,7 @@ pub trait DefIdTree: Copy {
 
 impl<'tcx> DefIdTree for TyCtxt<'tcx> {
     fn parent(self, id: DefId) -> Option<DefId> {
-        self.def_key(id).parent.map(|index| DefId { index: index, ..id })
+        self.def_key(id).parent.map(|index| DefId { index, ..id })
     }
 }
 
@@ -2227,7 +2227,7 @@ impl ReprOptions {
         if !tcx.consider_optimizing(|| format!("Reorder fields of {:?}", tcx.def_path_str(did))) {
             flags.insert(ReprFlags::IS_LINEAR);
         }
-        ReprOptions { int: size, align: max_align, pack: min_pack, flags: flags }
+        ReprOptions { int: size, align: max_align, pack: min_pack, flags }
     }
 
     #[inline]

src/librustc/ty/normalize_erasing_regions.rs

@@ -34,10 +34,7 @@ impl<'tcx> TyCtxt<'tcx> {
         if !value.has_projections() {
             value
         } else {
-            value.fold_with(&mut NormalizeAfterErasingRegionsFolder {
-                tcx: self,
-                param_env: param_env,
-            })
+            value.fold_with(&mut NormalizeAfterErasingRegionsFolder { tcx: self, param_env })
         }
     }
 

src/librustc/ty/relate.rs

@@ -287,7 +287,7 @@ impl<'tcx> Relate<'tcx> for ty::TraitRef<'tcx> {
             Err(TypeError::Traits(expected_found(relation, &a.def_id, &b.def_id)))
         } else {
             let substs = relate_substs(relation, None, a.substs, b.substs)?;
-            Ok(ty::TraitRef { def_id: a.def_id, substs: substs })
+            Ok(ty::TraitRef { def_id: a.def_id, substs })
         }
     }
 }
@@ -303,7 +303,7 @@ impl<'tcx> Relate<'tcx> for ty::ExistentialTraitRef<'tcx> {
             Err(TypeError::Traits(expected_found(relation, &a.def_id, &b.def_id)))
         } else {
             let substs = relate_substs(relation, None, a.substs, b.substs)?;
-            Ok(ty::ExistentialTraitRef { def_id: a.def_id, substs: substs })
+            Ok(ty::ExistentialTraitRef { def_id: a.def_id, substs })
         }
     }
 }

src/librustc/ty/sty.rs

@@ -1193,7 +1193,7 @@ pub struct ParamTy {
 
 impl<'tcx> ParamTy {
     pub fn new(index: u32, name: Symbol) -> ParamTy {
-        ParamTy { index, name: name }
+        ParamTy { index, name }
     }
 
     pub fn for_self() -> ParamTy {

src/librustc/ty/util.rs

@@ -357,7 +357,7 @@ impl<'tcx> TyCtxt<'tcx> {
         let mut dtor_did = None;
         let ty = self.type_of(adt_did);
         self.for_each_relevant_impl(drop_trait, ty, |impl_did| {
-            if let Some(item) = self.associated_items(impl_did).in_definition_order().nth(0) {
+            if let Some(item) = self.associated_items(impl_did).in_definition_order().next() {
                 if validate(self, impl_did).is_ok() {
                     dtor_did = Some(item.def_id);
                 }

src/librustc_builtin_macros/deriving/generic/mod.rs

@@ -482,7 +482,7 @@ impl<'a> TraitDef<'a> {
                         })
                         .cloned(),
                 );
-                push(Annotatable::Item(P(ast::Item { attrs: attrs, ..(*newitem).clone() })))
+                push(Annotatable::Item(P(ast::Item { attrs, ..(*newitem).clone() })))
             }
             _ => {
                 // Non-Item derive is an error, but it should have been

src/librustc_codegen_llvm/abi.rs

@@ -148,7 +148,7 @@ impl LlvmType for CastTarget {
             .prefix
             .iter()
             .flat_map(|option_kind| {
-                option_kind.map(|kind| Reg { kind: kind, size: self.prefix_chunk }.llvm_type(cx))
+                option_kind.map(|kind| Reg { kind, size: self.prefix_chunk }.llvm_type(cx))
             })
             .chain((0..rest_count).map(|_| rest_ll_unit))
             .collect();

src/librustc_expand/base.rs

@@ -4,7 +4,7 @@ use rustc_ast::ast::{self, Attribute, Name, NodeId, PatKind};
 use rustc_ast::mut_visit::{self, MutVisitor};
 use rustc_ast::ptr::P;
 use rustc_ast::token;
-use rustc_ast::tokenstream::{self, TokenStream};
+use rustc_ast::tokenstream::{self, TokenStream, TokenTree};
 use rustc_ast::visit::{AssocCtxt, Visitor};
 use rustc_attr::{self as attr, Deprecation, HasAttrs, Stability};
 use rustc_data_structures::fx::FxHashMap;
@@ -118,6 +118,31 @@ impl Annotatable {
         }
     }
 
+    crate fn into_tokens(self) -> TokenStream {
+        // `Annotatable` can be converted into tokens directly, but we
+        // are packing it into a nonterminal as a piece of AST to make
+        // the produced token stream look nicer in pretty-printed form.
+        let nt = match self {
+            Annotatable::Item(item) => token::NtItem(item),
+            Annotatable::TraitItem(item) | Annotatable::ImplItem(item) => {
+                token::NtItem(P(item.and_then(ast::AssocItem::into_item)))
+            }
+            Annotatable::ForeignItem(item) => {
+                token::NtItem(P(item.and_then(ast::ForeignItem::into_item)))
+            }
+            Annotatable::Stmt(stmt) => token::NtStmt(stmt.into_inner()),
+            Annotatable::Expr(expr) => token::NtExpr(expr),
+            Annotatable::Arm(..)
+            | Annotatable::Field(..)
+            | Annotatable::FieldPat(..)
+            | Annotatable::GenericParam(..)
+            | Annotatable::Param(..)
+            | Annotatable::StructField(..)
+            | Annotatable::Variant(..) => panic!("unexpected annotatable"),
+        };
+        TokenTree::token(token::Interpolated(Lrc::new(nt)), DUMMY_SP).into()
+    }
+
     pub fn expect_item(self) -> P<ast::Item> {
         match self {
             Annotatable::Item(i) => i,