Rollup of 9 pull requests

compiler/rustc_builtin_macros/src/standard_library_imports.rs

@@ -2,7 +2,7 @@ use rustc_ast as ast;
 use rustc_expand::base::{ExtCtxt, ResolverExpand};
 use rustc_expand::expand::ExpansionConfig;
 use rustc_session::Session;
-use rustc_span::edition::Edition;
+use rustc_span::edition::Edition::*;
 use rustc_span::hygiene::AstPass;
 use rustc_span::symbol::{kw, sym, Ident, Symbol};
 use rustc_span::DUMMY_SP;
@@ -13,7 +13,7 @@ pub fn inject(
     sess: &Session,
     alt_std_name: Option<Symbol>,
 ) -> ast::Crate {
-    let rust_2018 = sess.parse_sess.edition >= Edition::Edition2018;
+    let edition = sess.parse_sess.edition;
 
     // the first name in this list is the crate name of the crate with the prelude
     let names: &[Symbol] = if sess.contains_name(&krate.attrs, sym::no_core) {
@@ -42,7 +42,11 @@ pub fn inject(
 
     // .rev() to preserve ordering above in combination with insert(0, ...)
     for &name in names.iter().rev() {
-        let ident = if rust_2018 { Ident::new(name, span) } else { Ident::new(name, call_site) };
+        let ident = if edition >= Edition2018 {
+            Ident::new(name, span)
+        } else {
+            Ident::new(name, call_site)
+        };
         krate.items.insert(
             0,
             cx.item(
@@ -58,14 +62,18 @@ pub fn inject(
     // the one with the prelude.
     let name = names[0];
 
-    let import_path = if rust_2018 {
-        [name, sym::prelude, sym::v1].iter().map(|symbol| Ident::new(*symbol, span)).collect()
-    } else {
-        [kw::PathRoot, name, sym::prelude, sym::v1]
-            .iter()
-            .map(|symbol| Ident::new(*symbol, span))
-            .collect()
-    };
+    let root = (edition == Edition2015).then(|| kw::PathRoot);
+
+    let import_path = root
+        .iter()
+        .chain(&[name, sym::prelude])
+        .chain(&[match edition {
+            Edition2015 => sym::rust_2015,
+            Edition2018 => sym::rust_2018,
+            Edition2021 => sym::rust_2021,
+        }])
+        .map(|&symbol| Ident::new(symbol, span))
+        .collect();
 
     let use_item = cx.item(
         span,

compiler/rustc_middle/src/ty/relate.rs

@@ -421,12 +421,14 @@ pub fn super_relate_tys<R: TypeRelation<'tcx>>(
             let t = relation.relate(a_t, b_t)?;
             match relation.relate(sz_a, sz_b) {
                 Ok(sz) => Ok(tcx.mk_ty(ty::Array(t, sz))),
-                // FIXME(#72219) Implement improved diagnostics for mismatched array
-                // length?
-                Err(err) if relation.tcx().lazy_normalization() => Err(err),
                 Err(err) => {
                     // Check whether the lengths are both concrete/known values,
                     // but are unequal, for better diagnostics.
+                    //
+                    // It might seem dubious to eagerly evaluate these constants here,
+                    // we however cannot end up with errors in `Relate` during both
+                    // `type_of` and `predicates_of`. This means that evaluating the
+                    // constants should not cause cycle errors here.
                     let sz_a = sz_a.try_eval_usize(tcx, relation.param_env());
                     let sz_b = sz_b.try_eval_usize(tcx, relation.param_env());
                     match (sz_a, sz_b) {

compiler/rustc_mir/src/interpret/step.rs

@@ -160,7 +160,10 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
         let layout = self.layout_of(src.layout.ty.builtin_deref(true).unwrap().ty)?;
         let (size, align) = (layout.size, layout.align.abi);
         let size = size.checked_mul(count, self).ok_or_else(|| {
-            err_ub_format!("overflow computing total size of `copy_nonoverlapping`")
+            err_ub_format!(
+                "overflow computing total size of `{}`",
+                if nonoverlapping { "copy_nonoverlapping" } else { "copy" }
+            )
         })?;
 
         // Make sure we check both pointers for an access of the total size and aligment,

compiler/rustc_mir/src/lib.rs

@@ -25,7 +25,7 @@ Rust MIR: a lowered representation of Rust.
 #![feature(stmt_expr_attributes)]
 #![feature(trait_alias)]
 #![feature(option_expect_none)]
-#![feature(option_get_or_default)]
+#![feature(option_get_or_insert_default)]
 #![feature(or_patterns)]
 #![feature(once_cell)]
 #![feature(control_flow_enum)]

compiler/rustc_mir/src/transform/coverage/graph.rs

@@ -392,7 +392,8 @@ impl BasicCoverageBlockData {
             }
         }
         let operand = counter_kind.as_operand_id();
-        if let Some(replaced) = self.edge_from_bcbs.get_or_default().insert(from_bcb, counter_kind)
+        if let Some(replaced) =
+            self.edge_from_bcbs.get_or_insert_default().insert(from_bcb, counter_kind)
         {
             Error::from_string(format!(
                 "attempt to set an edge counter more than once; from_bcb: \

compiler/rustc_span/src/edition.rs

@@ -20,7 +20,7 @@ pub enum Edition {
     Edition2015,
     /// The 2018 edition
     Edition2018,
-    /// The 2021 ediiton
+    /// The 2021 edition
     Edition2021,
 }
 

compiler/rustc_span/src/symbol.rs

@@ -958,8 +958,11 @@ symbols! {
         rt,
         rtm_target_feature,
         rust,
+        rust_2015,
         rust_2015_preview,
+        rust_2018,
         rust_2018_preview,
+        rust_2021,
         rust_2021_preview,
         rust_begin_unwind,
         rust_eh_catch_typeinfo,

compiler/rustc_target/src/spec/crt_objects.rs

@@ -108,11 +108,13 @@ pub(super) fn post_mingw() -> CrtObjects {
 }
 
 pub(super) fn pre_wasi_fallback() -> CrtObjects {
+    // Use crt1-command.o instead of crt1.o to enable support for new-style
+    // commands. See https://reviews.llvm.org/D81689 for more info.
     new(&[
-        (LinkOutputKind::DynamicNoPicExe, &["crt1.o"]),
-        (LinkOutputKind::DynamicPicExe, &["crt1.o"]),
-        (LinkOutputKind::StaticNoPicExe, &["crt1.o"]),
-        (LinkOutputKind::StaticPicExe, &["crt1.o"]),
+        (LinkOutputKind::DynamicNoPicExe, &["crt1-command.o"]),
+        (LinkOutputKind::DynamicPicExe, &["crt1-command.o"]),
+        (LinkOutputKind::StaticNoPicExe, &["crt1-command.o"]),
+        (LinkOutputKind::StaticPicExe, &["crt1-command.o"]),
         (LinkOutputKind::WasiReactorExe, &["crt1-reactor.o"]),
     ])
 }

library/core/src/option.rs

@@ -854,55 +854,55 @@ impl<T> Option<T> {
     // Entry-like operations to insert if None and return a reference
     /////////////////////////////////////////////////////////////////////////
 
-    /// Inserts the default value into the option if it is [`None`], then
+    /// Inserts `value` into the option if it is [`None`], then
     /// returns a mutable reference to the contained value.
     ///
     /// # Examples
     ///
     /// ```
-    /// #![feature(option_get_or_default)]
-    ///
     /// let mut x = None;
     ///
     /// {
-    ///     let y: &mut u32 = x.get_or_default();
-    ///     assert_eq!(y, &0);
+    ///     let y: &mut u32 = x.get_or_insert(5);
+    ///     assert_eq!(y, &5);
     ///
     ///     *y = 7;
     /// }
     ///
     /// assert_eq!(x, Some(7));
     /// ```
     #[inline]
-    #[unstable(feature = "option_get_or_default", issue = "82901")]
-    pub fn get_or_default(&mut self) -> &mut T
-    where
-        T: Default,
-    {
-        self.get_or_insert_with(Default::default)
+    #[stable(feature = "option_entry", since = "1.20.0")]
+    pub fn get_or_insert(&mut self, value: T) -> &mut T {
+        self.get_or_insert_with(|| value)
     }
 
-    /// Inserts `value` into the option if it is [`None`], then
+    /// Inserts the default value into the option if it is [`None`], then
     /// returns a mutable reference to the contained value.
     ///
     /// # Examples
     ///
     /// ```
+    /// #![feature(option_get_or_insert_default)]
+    ///
     /// let mut x = None;
     ///
     /// {
-    ///     let y: &mut u32 = x.get_or_insert(5);
-    ///     assert_eq!(y, &5);
+    ///     let y: &mut u32 = x.get_or_insert_default();
+    ///     assert_eq!(y, &0);
     ///
     ///     *y = 7;
     /// }
     ///
     /// assert_eq!(x, Some(7));
     /// ```
     #[inline]
-    #[stable(feature = "option_entry", since = "1.20.0")]
-    pub fn get_or_insert(&mut self, value: T) -> &mut T {
-        self.get_or_insert_with(|| value)
+    #[unstable(feature = "option_get_or_insert_default", issue = "82901")]
+    pub fn get_or_insert_default(&mut self) -> &mut T
+    where
+        T: Default,
+    {
+        self.get_or_insert_with(Default::default)
     }
 
     /// Inserts a value computed from `f` into the option if it is [`None`],

library/core/src/prelude/mod.rs

@@ -1,5 +1,41 @@
 //! The libcore prelude
+//!
+//! This module is intended for users of libcore which do not link to libstd as
+//! well. This module is imported by default when `#![no_std]` is used in the
+//! same manner as the standard library's prelude.
 
 #![stable(feature = "core_prelude", since = "1.4.0")]
 
 pub mod v1;
+
+/// The 2015 version of the core prelude.
+///
+/// See the [module-level documentation](self) for more.
+#[unstable(feature = "prelude_2015", issue = "none")]
+pub mod rust_2015 {
+    #[unstable(feature = "prelude_2015", issue = "none")]
+    #[doc(no_inline)]
+    pub use super::v1::*;
+}
+
+/// The 2018 version of the core prelude.
+///
+/// See the [module-level documentation](self) for more.
+#[unstable(feature = "prelude_2018", issue = "none")]
+pub mod rust_2018 {
+    #[unstable(feature = "prelude_2018", issue = "none")]
+    #[doc(no_inline)]
+    pub use super::v1::*;
+}
+
+/// The 2021 version of the core prelude.
+///
+/// See the [module-level documentation](self) for more.
+#[unstable(feature = "prelude_2021", issue = "none")]
+pub mod rust_2021 {
+    #[unstable(feature = "prelude_2021", issue = "none")]
+    #[doc(no_inline)]
+    pub use super::v1::*;
+
+    // FIXME: Add more things.
+}

library/core/src/prelude/v1.rs

@@ -1,8 +1,6 @@
-//! The core prelude
+//! The first version of the core prelude.
 //!
-//! This module is intended for users of libcore which do not link to libstd as
-//! well. This module is imported by default when `#![no_std]` is used in the
-//! same manner as the standard library's prelude.
+//! See the [module-level documentation](super) for more.
 
 #![stable(feature = "core_prelude", since = "1.4.0")]
 

library/std/src/lib.rs

@@ -302,6 +302,7 @@
 #![feature(panic_internals)]
 #![feature(panic_unwind)]
 #![feature(pin_static_ref)]
+#![feature(prelude_2021)]
 #![feature(prelude_import)]
 #![feature(ptr_internals)]
 #![feature(raw)]

library/std/src/prelude/mod.rs

@@ -84,3 +84,37 @@
 #![stable(feature = "rust1", since = "1.0.0")]
 
 pub mod v1;
+
+/// The 2015 version of the prelude of The Rust Standard Library.
+///
+/// See the [module-level documentation](self) for more.
+#[unstable(feature = "prelude_2015", issue = "none")]
+pub mod rust_2015 {
+    #[unstable(feature = "prelude_2015", issue = "none")]
+    #[doc(no_inline)]
+    pub use super::v1::*;
+}
+
+/// The 2018 version of the prelude of The Rust Standard Library.
+///
+/// See the [module-level documentation](self) for more.
+#[unstable(feature = "prelude_2018", issue = "none")]
+pub mod rust_2018 {
+    #[unstable(feature = "prelude_2018", issue = "none")]
+    #[doc(no_inline)]
+    pub use super::v1::*;
+}
+
+/// The 2021 version of the prelude of The Rust Standard Library.
+///
+/// See the [module-level documentation](self) for more.
+#[unstable(feature = "prelude_2021", issue = "none")]
+pub mod rust_2021 {
+    #[unstable(feature = "prelude_2021", issue = "none")]
+    #[doc(no_inline)]
+    pub use super::v1::*;
+
+    #[unstable(feature = "prelude_2021", issue = "none")]
+    #[doc(no_inline)]
+    pub use core::prelude::rust_2021::*;
+}

library/std/src/prelude/v1.rs

@@ -1,6 +1,6 @@
 //! The first version of the prelude of The Rust Standard Library.
 //!
-//! See the [module-level documentation](../index.html) for more.
+//! See the [module-level documentation](super) for more.
 
 #![stable(feature = "rust1", since = "1.0.0")]
 

library/std/src/sys/unix/ext/process.rs

@@ -62,9 +62,14 @@ pub trait CommandExt: Sealed {
     /// `fork`. This primarily means that any modifications made to memory on
     /// behalf of this closure will **not** be visible to the parent process.
     /// This is often a very constrained environment where normal operations
-    /// like `malloc` or acquiring a mutex are not guaranteed to work (due to
+    /// like `malloc`, accessing environment variables through [`std::env`]
+    /// or acquiring a mutex are not guaranteed to work (due to
     /// other threads perhaps still running when the `fork` was run).
     ///
+    /// For further details refer to the [POSIX fork() specification]
+    /// and the equivalent documentation for any targeted
+    /// platform, especially the requirements around *async-signal-safety*.
+    ///
     /// This also means that all resources such as file descriptors and
     /// memory-mapped regions got duplicated. It is your responsibility to make
     /// sure that the closure does not violate library invariants by making
@@ -73,6 +78,10 @@ pub trait CommandExt: Sealed {
     /// When this closure is run, aspects such as the stdio file descriptors and
     /// working directory have successfully been changed, so output to these
     /// locations may not appear where intended.
+    ///
+    /// [POSIX fork() specification]:
+    ///     https://pubs.opengroup.org/onlinepubs/9699919799/functions/fork.html
+    /// [`std::env`]: mod@crate::env
     #[stable(feature = "process_pre_exec", since = "1.34.0")]
     unsafe fn pre_exec<F>(&mut self, f: F) -> &mut process::Command
     where

library/std/src/sys/unix/process/process_unix.rs

@@ -1,6 +1,7 @@
 use crate::convert::TryInto;
 use crate::fmt;
 use crate::io::{self, Error, ErrorKind};
+use crate::mem;
 use crate::ptr;
 use crate::sys;
 use crate::sys::cvt;
@@ -45,15 +46,14 @@ impl Command {
         //
         // Note that as soon as we're done with the fork there's no need to hold
         // a lock any more because the parent won't do anything and the child is
-        // in its own process.
-        let result = unsafe {
-            let _env_lock = sys::os::env_lock();
-            cvt(libc::fork())?
-        };
+        // in its own process. Thus the parent drops the lock guard while the child
+        // forgets it to avoid unlocking it on a new thread, which would be invalid.
+        let (env_lock, result) = unsafe { (sys::os::env_lock(), cvt(libc::fork())?) };
 
         let pid = unsafe {
             match result {
                 0 => {
+                    mem::forget(env_lock);
                     drop(input);
                     let Err(err) = self.do_exec(theirs, envp.as_ref());
                     let errno = err.raw_os_error().unwrap_or(libc::EINVAL) as u32;
@@ -74,7 +74,10 @@ impl Command {
                     rtassert!(output.write(&bytes).is_ok());
                     libc::_exit(1)
                 }
-                n => n,
+                n => {
+                    drop(env_lock);
+                    n
+                }
             }
         };