Rollup of 14 pull requests

Cargo.lock

@@ -4405,6 +4405,7 @@ dependencies = [
  "rustc_hir_pretty",
  "rustc_index",
  "rustc_infer",
+ "rustc_lint",
  "rustc_macros",
  "rustc_middle",
  "rustc_session",

compiler/rustc_arena/src/lib.rs

@@ -635,7 +635,7 @@ pub macro which_arena_for_type {
 }
 
 #[rustc_macro_transparency = "semitransparent"]
-pub macro declare_arena([], [$($a:tt $name:ident: $ty:ty,)*], $tcx:lifetime) {
+pub macro declare_arena([$($a:tt $name:ident: $ty:ty,)*], $tcx:lifetime) {
     #[derive(Default)]
     pub struct Arena<$tcx> {
         pub dropless: $crate::DroplessArena,

compiler/rustc_ast_lowering/src/lib.rs

@@ -84,7 +84,7 @@ mod path;
 
 const HIR_ID_COUNTER_LOCKED: u32 = 0xFFFFFFFF;
 
-rustc_hir::arena_types!(rustc_arena::declare_arena, [], 'tcx);
+rustc_hir::arena_types!(rustc_arena::declare_arena, 'tcx);
 
 struct LoweringContext<'a, 'hir: 'a> {
     /// Used to assign IDs to HIR nodes that do not directly correspond to AST nodes.

compiler/rustc_data_structures/src/functor.rs

@@ -26,7 +26,7 @@ impl<T> IdFunctor for Box<T> {
             // inverse of `Box::assume_init()` and should be safe.
             let mut raw: Box<mem::MaybeUninit<T>> = Box::from_raw(raw.cast());
             // SAFETY: Write the mapped value back into the `Box`.
-            ptr::write(raw.as_mut_ptr(), f(value));
+            raw.write(f(value));
             // SAFETY: We just initialized `raw`.
             raw.assume_init()
         }

compiler/rustc_hir/src/arena.rs

@@ -9,8 +9,8 @@
 /// where `T` is the type listed. These impls will appear in the implement_ty_decoder! macro.
 #[macro_export]
 macro_rules! arena_types {
-    ($macro:path, $args:tt, $tcx:lifetime) => (
-        $macro!($args, [
+    ($macro:path, $tcx:lifetime) => (
+        $macro!([
             // HIR types
             [few] hir_krate: rustc_hir::Crate<$tcx>,
             [] arm: rustc_hir::Arm<$tcx>,

compiler/rustc_lint/src/lib.rs

@@ -62,6 +62,8 @@ mod traits;
 mod types;
 mod unused;
 
+pub use array_into_iter::ARRAY_INTO_ITER;
+
 use rustc_ast as ast;
 use rustc_hir as hir;
 use rustc_hir::def_id::LocalDefId;

compiler/rustc_middle/src/arena.rs

@@ -9,8 +9,8 @@
 /// listed. These impls will appear in the implement_ty_decoder! macro.
 #[macro_export]
 macro_rules! arena_types {
-    ($macro:path, $args:tt, $tcx:lifetime) => (
-        $macro!($args, [
+    ($macro:path, $tcx:lifetime) => (
+        $macro!([
             [] layouts: rustc_target::abi::Layout,
             // AdtDef are interned and compared by address
             [] adt_def: rustc_middle::ty::AdtDef,
@@ -109,4 +109,4 @@ macro_rules! arena_types {
     )
 }
 
-arena_types!(rustc_arena::declare_arena, [], 'tcx);
+arena_types!(rustc_arena::declare_arena, 'tcx);

compiler/rustc_middle/src/ty/codec.rs

@@ -437,15 +437,15 @@ macro_rules! impl_arena_allocatable_decoder {
 }
 
 macro_rules! impl_arena_allocatable_decoders {
-    ([], [$($a:tt $name:ident: $ty:ty,)*], $tcx:lifetime) => {
+    ([$($a:tt $name:ident: $ty:ty,)*], $tcx:lifetime) => {
         $(
             impl_arena_allocatable_decoder!($a [[$name: $ty], $tcx]);
         )*
     }
 }
 
-rustc_hir::arena_types!(impl_arena_allocatable_decoders, [], 'tcx);
-arena_types!(impl_arena_allocatable_decoders, [], 'tcx);
+rustc_hir::arena_types!(impl_arena_allocatable_decoders, 'tcx);
+arena_types!(impl_arena_allocatable_decoders, 'tcx);
 
 #[macro_export]
 macro_rules! implement_ty_decoder {

compiler/rustc_parse/src/parser/expr.rs

@@ -41,7 +41,7 @@ macro_rules! maybe_whole_expr {
                     let path = path.clone();
                     $p.bump();
                     return Ok($p.mk_expr(
-                        $p.token.span,
+                        $p.prev_token.span,
                         ExprKind::Path(None, path),
                         AttrVec::new(),
                     ));
@@ -50,7 +50,7 @@ macro_rules! maybe_whole_expr {
                     let block = block.clone();
                     $p.bump();
                     return Ok($p.mk_expr(
-                        $p.token.span,
+                        $p.prev_token.span,
                         ExprKind::Block(block, None),
                         AttrVec::new(),
                     ));

compiler/rustc_typeck/Cargo.toml

@@ -26,3 +26,4 @@ rustc_index = { path = "../rustc_index" }
 rustc_infer = { path = "../rustc_infer" }
 rustc_trait_selection = { path = "../rustc_trait_selection" }
 rustc_ty_utils = { path = "../rustc_ty_utils" }
+rustc_lint = { path = "../rustc_lint" }

compiler/rustc_typeck/src/check/fn_ctxt/_impl.rs

@@ -914,7 +914,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             });
 
         if result.is_ok() {
-            self.maybe_lint_bare_trait(qpath, hir_id);
+            self.maybe_lint_bare_trait(qpath, hir_id, span);
             self.register_wf_obligation(ty.into(), qself.span, traits::WellFormed(None));
         }
 
@@ -927,18 +927,23 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         )
     }
 
-    fn maybe_lint_bare_trait(&self, qpath: &QPath<'_>, hir_id: hir::HirId) {
+    fn maybe_lint_bare_trait(&self, qpath: &QPath<'_>, hir_id: hir::HirId, span: Span) {
         if let QPath::TypeRelative(self_ty, _) = qpath {
             if let TyKind::TraitObject([poly_trait_ref, ..], _, TraitObjectSyntax::None) =
                 self_ty.kind
             {
                 let msg = "trait objects without an explicit `dyn` are deprecated";
                 let (sugg, app) = match self.tcx.sess.source_map().span_to_snippet(self_ty.span) {
                     Ok(s) if poly_trait_ref.trait_ref.path.is_global() => {
-                        (format!("<dyn ({})>", s), Applicability::MachineApplicable)
+                        (format!("dyn ({})", s), Applicability::MachineApplicable)
                     }
-                    Ok(s) => (format!("<dyn {}>", s), Applicability::MachineApplicable),
-                    Err(_) => ("<dyn <type>>".to_string(), Applicability::HasPlaceholders),
+                    Ok(s) => (format!("dyn {}", s), Applicability::MachineApplicable),
+                    Err(_) => ("dyn <type>".to_string(), Applicability::HasPlaceholders),
+                };
+                // Wrap in `<..>` if it isn't already.
+                let sugg = match self.tcx.sess.source_map().span_to_snippet(span) {
+                    Ok(s) if s.starts_with('<') => sugg,
+                    _ => format!("<{}>", sugg),
                 };
                 let replace = String::from("use `dyn`");
                 if self.sess().edition() >= Edition::Edition2021 {

compiler/rustc_typeck/src/check/method/prelude2021.rs

@@ -5,9 +5,9 @@ use rustc_ast::Mutability;
 use rustc_errors::Applicability;
 use rustc_hir as hir;
 use rustc_middle::ty::subst::InternalSubsts;
-use rustc_middle::ty::{Adt, Ref, Ty};
+use rustc_middle::ty::{Adt, Array, Ref, Ty};
 use rustc_session::lint::builtin::RUST_2021_PRELUDE_COLLISIONS;
-use rustc_span::symbol::kw::Underscore;
+use rustc_span::symbol::kw::{Empty, Underscore};
 use rustc_span::symbol::{sym, Ident};
 use rustc_span::Span;
 use rustc_trait_selection::infer::InferCtxtExt;
@@ -38,10 +38,20 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             return;
         }
 
-        // These are the method names that were added to prelude in Rust 2021
-        if !matches!(segment.ident.name, sym::try_into) {
-            return;
-        }
+        let prelude_or_array_lint = match segment.ident.name {
+            // `try_into` was added to the prelude in Rust 2021.
+            sym::try_into => RUST_2021_PRELUDE_COLLISIONS,
+            // `into_iter` wasn't added to the prelude,
+            // but `[T; N].into_iter()` doesn't resolve to IntoIterator::into_iter
+            // before Rust 2021, which results in the same problem.
+            // It is only a problem for arrays.
+            sym::into_iter if let Array(..) = self_ty.kind() => {
+                // In this case, it wasn't really a prelude addition that was the problem.
+                // Instead, the problem is that the array-into_iter hack will no longer apply in Rust 2021.
+                rustc_lint::ARRAY_INTO_ITER
+            }
+            _ => return,
+        };
 
         // No need to lint if method came from std/core, as that will now be in the prelude
         if matches!(self.tcx.crate_name(pick.item.def_id.krate), sym::std | sym::core) {
@@ -69,7 +79,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             // Inherent impls only require not relying on autoref and autoderef in order to
             // ensure that the trait implementation won't be used
             self.tcx.struct_span_lint_hir(
-                RUST_2021_PRELUDE_COLLISIONS,
+                prelude_or_array_lint,
                 self_expr.hir_id,
                 self_expr.span,
                 |lint| {
@@ -130,7 +140,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             // trait implementations require full disambiguation to not clash with the new prelude
             // additions (i.e. convert from dot-call to fully-qualified call)
             self.tcx.struct_span_lint_hir(
-                RUST_2021_PRELUDE_COLLISIONS,
+                prelude_or_array_lint,
                 call_expr.hir_id,
                 call_expr.span,
                 |lint| {
@@ -239,47 +249,58 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             let trait_path = self.trait_path_or_bare_name(span, expr_id, pick.item.container.id());
             let trait_generics = self.tcx.generics_of(pick.item.container.id());
 
-            let parameter_count = trait_generics.count() - (trait_generics.has_self as usize);
-            let trait_name = if parameter_count == 0 {
-                trait_path
-            } else {
-                format!(
-                    "{}<{}>",
-                    trait_path,
-                    std::iter::repeat("_").take(parameter_count).collect::<Vec<_>>().join(", ")
-                )
-            };
+            let trait_name =
+                if trait_generics.params.len() <= trait_generics.has_self as usize {
+                    trait_path
+                } else {
+                    let counts = trait_generics.own_counts();
+                    format!(
+                        "{}<{}>",
+                        trait_path,
+                        std::iter::repeat("'_")
+                            .take(counts.lifetimes)
+                            .chain(std::iter::repeat("_").take(
+                                counts.types + counts.consts - trait_generics.has_self as usize
+                            ))
+                            .collect::<Vec<_>>()
+                            .join(", ")
+                    )
+                };
 
             let mut lint = lint.build(&format!(
                 "trait-associated function `{}` will become ambiguous in Rust 2021",
                 method_name.name
             ));
 
-            let self_ty_name = self
+            let mut self_ty_name = self
                 .sess()
                 .source_map()
                 .span_to_snippet(self_ty_span)
                 .unwrap_or_else(|_| self_ty.to_string());
 
-            let self_ty_generics_count = match self_ty.kind() {
-                // Get the number of generics the self type has (if an Adt) unless we can determine that
-                // the user has written the self type with generics already which we (naively) do by looking
-                // for a "<" in `self_ty_name`.
-                Adt(def, _) if !self_ty_name.contains('<') => self.tcx.generics_of(def.did).count(),
-                _ => 0,
-            };
-            let self_ty_generics = if self_ty_generics_count > 0 {
-                format!("<{}>", vec!["_"; self_ty_generics_count].join(", "))
-            } else {
-                String::new()
-            };
+            // Get the number of generics the self type has (if an Adt) unless we can determine that
+            // the user has written the self type with generics already which we (naively) do by looking
+            // for a "<" in `self_ty_name`.
+            if !self_ty_name.contains('<') {
+                if let Adt(def, _) = self_ty.kind() {
+                    let generics = self.tcx.generics_of(def.did);
+                    if !generics.params.is_empty() {
+                        let counts = generics.own_counts();
+                        self_ty_name += &format!(
+                            "<{}>",
+                            std::iter::repeat("'_")
+                                .take(counts.lifetimes)
+                                .chain(std::iter::repeat("_").take(counts.types + counts.consts))
+                                .collect::<Vec<_>>()
+                                .join(", ")
+                        );
+                    }
+                }
+            }
             lint.span_suggestion(
                 span,
                 "disambiguate the associated function",
-                format!(
-                    "<{}{} as {}>::{}",
-                    self_ty_name, self_ty_generics, trait_name, method_name.name,
-                ),
+                format!("<{} as {}>::{}", self_ty_name, trait_name, method_name.name,),
                 Applicability::MachineApplicable,
             );
 
@@ -322,7 +343,12 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             .filter_map(|item| if item.ident.name != Underscore { Some(item.ident) } else { None })
             .next();
         if let Some(any_id) = any_id {
-            return Some(format!("{}", any_id));
+            if any_id.name == Empty {
+                // Glob import, so just use its name.
+                return None;
+            } else {
+                return Some(format!("{}", any_id));
+            }
         }
 
         // All that is left is `_`! We need to use the full path. It doesn't matter which one we pick,

library/core/src/time.rs

@@ -2,14 +2,21 @@
 
 //! Temporal quantification.
 //!
-//! Example:
+//! # Examples:
+//!
+//! There are multiple ways to create a new [`Duration`]:
 //!
 //! ```
-//! use std::time::Duration;
+//! # use std::time::Duration;
+//! let five_seconds = Duration::from_secs(5);
+//! assert_eq!(five_seconds, Duration::from_millis(5_000));
+//! assert_eq!(five_seconds, Duration::from_micros(5_000_000));
+//! assert_eq!(five_seconds, Duration::from_nanos(5_000_000_000));
 //!
-//! let five_seconds = Duration::new(5, 0);
-//! // both declarations are equivalent
-//! assert_eq!(Duration::new(5, 0), Duration::from_secs(5));
+//! let ten_seconds = Duration::from_secs(10);
+//! let seven_nanos = Duration::from_nanos(7);
+//! let total = ten_seconds + seven_nanos;
+//! assert_eq!(total, Duration::new(10, 7));
 //! ```
 
 use crate::fmt;

library/std/src/env.rs

@@ -616,6 +616,9 @@ pub fn temp_dir() -> PathBuf {
 /// return the path of the symbolic link and other platforms will return the
 /// path of the symbolic link’s target.
 ///
+/// If the executable is renamed while it is running, platforms may return the
+/// path at the time it was loaded instead of the new path.
+///
 /// # Errors
 ///
 /// Acquiring the path of the current executable is a platform-specific operation

library/std/src/time.rs

@@ -1,13 +1,32 @@
 //! Temporal quantification.
 //!
-//! Example:
+//! # Examples:
 //!
+//! There are multiple ways to create a new [`Duration`]:
+//!
+//! ```
+//! # use std::time::Duration;
+//! let five_seconds = Duration::from_secs(5);
+//! assert_eq!(five_seconds, Duration::from_millis(5_000));
+//! assert_eq!(five_seconds, Duration::from_micros(5_000_000));
+//! assert_eq!(five_seconds, Duration::from_nanos(5_000_000_000));
+//!
+//! let ten_seconds = Duration::from_secs(10);
+//! let seven_nanos = Duration::from_nanos(7);
+//! let total = ten_seconds + seven_nanos;
+//! assert_eq!(total, Duration::new(10, 7));
 //! ```
-//! use std::time::Duration;
 //!
-//! let five_seconds = Duration::new(5, 0);
-//! // both declarations are equivalent
-//! assert_eq!(Duration::new(5, 0), Duration::from_secs(5));
+//! Using [`Instant`] to calculate how long a function took to run:
+//!
+//! ```ignore (incomplete)
+//! let now = Instant::now();
+//!
+//! // Calling a slow function, it may take a while
+//! slow_function();
+//!
+//! let elapsed_time = now.elapsed();
+//! println!("Running slow_function() took {} seconds.", elapsed_time.as_secs());
 //! ```
 
 #![stable(feature = "time", since = "1.3.0")]
@@ -26,7 +45,7 @@ use crate::sys_common::FromInner;
 pub use core::time::Duration;
 
 /// A measurement of a monotonically nondecreasing clock.
-/// Opaque and useful only with `Duration`.
+/// Opaque and useful only with [`Duration`].
 ///
 /// Instants are always guaranteed to be no less than any previously measured
 /// instant when created, and are often useful for tasks such as measuring