Auto merge of rust-lang#48476 - Manishearth:rollup, r=Manishearth

Rollup of 12 pull requests

- Successful merges: rust-lang#47933, rust-lang#48072, rust-lang#48083, rust-lang#48123, rust-lang#48157, rust-lang#48219, rust-lang#48221, rust-lang#48245, rust-lang#48429, rust-lang#48436, rust-lang#48438, rust-lang#48472
- Failed merges:

Author: bors

Diff for: src/Cargo.lock

@@ -747,8 +747,8 @@ impl<T> LinkedList<T> {
     /// Creates an iterator which uses a closure to determine if an element should be removed.
     ///
     /// If the closure returns true, then the element is removed and yielded.
-    /// If the closure returns false, it will try again, and call the closure on the next element,
-    /// seeing if it passes the test.
+    /// If the closure returns false, the element will remain in the list and will not be yielded
+    /// by the iterator.
     ///
     /// Note that `drain_filter` lets you mutate every element in the filter closure, regardless of
     /// whether you choose to keep or remove it.

Diff for: src/liballoc/linked_list.rs

@@ -364,7 +364,7 @@ impl String {
     ///
     /// Given that the `String` is empty, this will not allocate any initial
     /// buffer. While that means that this initial operation is very
-    /// inexpensive, but may cause excessive allocation later, when you add
+    /// inexpensive, it may cause excessive allocation later when you add
     /// data. If you have an idea of how much data the `String` will hold,
     /// consider the [`with_capacity`] method to prevent excessive
     /// re-allocation.

Diff for: src/liballoc/string.rs

@@ -1966,8 +1966,8 @@ impl<T> Vec<T> {
     /// Creates an iterator which uses a closure to determine if an element should be removed.
     ///
     /// If the closure returns true, then the element is removed and yielded.
-    /// If the closure returns false, it will try again, and call the closure
-    /// on the next element, seeing if it passes the test.
+    /// If the closure returns false, the element will remain in the vector and will not be yielded
+    /// by the iterator.
     ///
     /// Using this method is equivalent to the following code:
     ///

Diff for: src/liballoc/vec.rs

@@ -1366,9 +1366,9 @@ pub trait Iterator {
     ///
     /// In particular, try to have this call `try_fold()` on the internal parts
     /// from which this iterator is composed.  If multiple calls are needed,
-    /// the `?` operator be convenient for chaining the accumulator value along,
-    /// but beware any invariants that need to be upheld before those early
-    /// returns.  This is a `&mut self` method, so iteration needs to be
+    /// the `?` operator may be convenient for chaining the accumulator value
+    /// along, but beware any invariants that need to be upheld before those
+    /// early returns.  This is a `&mut self` method, so iteration needs to be
     /// resumable after hitting an error here.
     ///
     /// # Examples
@@ -1414,6 +1414,42 @@ pub trait Iterator {
         Try::from_ok(accum)
     }
 
+    /// An iterator method that applies a fallible function to each item in the
+    /// iterator, stopping at the first error and returning that error.
+    ///
+    /// This can also be thought of as the fallible form of [`for_each()`]
+    /// or as the stateless version of [`try_fold()`].
+    ///
+    /// [`for_each()`]: #method.for_each
+    /// [`try_fold()`]: #method.try_fold
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(iterator_try_fold)]
+    /// use std::fs::rename;
+    /// use std::io::{stdout, Write};
+    /// use std::path::Path;
+    ///
+    /// let data = ["no_tea.txt", "stale_bread.json", "torrential_rain.png"];
+    ///
+    /// let res = data.iter().try_for_each(|x| writeln!(stdout(), "{}", x));
+    /// assert!(res.is_ok());
+    ///
+    /// let mut it = data.iter().cloned();
+    /// let res = it.try_for_each(|x| rename(x, Path::new(x).with_extension("old")));
+    /// assert!(res.is_err());
+    /// // It short-circuited, so the remaining items are still in the iterator:
+    /// assert_eq!(it.next(), Some("stale_bread.json"));
+    /// ```
+    #[inline]
+    #[unstable(feature = "iterator_try_fold", issue = "45594")]
+    fn try_for_each<F, R>(&mut self, mut f: F) -> R where
+        Self: Sized, F: FnMut(Self::Item) -> R, R: Try<Ok=()>
+    {
+        self.try_fold((), move |(), x| f(x))
+    }
+
     /// An iterator method that applies a function, producing a single, final value.
     ///
     /// `fold()` takes two arguments: an initial value, and a closure with two
@@ -1532,7 +1568,7 @@ pub trait Iterator {
     fn all<F>(&mut self, mut f: F) -> bool where
         Self: Sized, F: FnMut(Self::Item) -> bool
     {
-        self.try_fold((), move |(), x| {
+        self.try_for_each(move |x| {
             if f(x) { LoopState::Continue(()) }
             else { LoopState::Break(()) }
         }) == LoopState::Continue(())
@@ -1581,7 +1617,7 @@ pub trait Iterator {
         Self: Sized,
         F: FnMut(Self::Item) -> bool
     {
-        self.try_fold((), move |(), x| {
+        self.try_for_each(move |x| {
             if f(x) { LoopState::Break(()) }
             else { LoopState::Continue(()) }
         }) == LoopState::Break(())
@@ -1635,7 +1671,7 @@ pub trait Iterator {
         Self: Sized,
         P: FnMut(&Self::Item) -> bool,
     {
-        self.try_fold((), move |(), x| {
+        self.try_for_each(move |x| {
             if predicate(&x) { LoopState::Break(x) }
             else { LoopState::Continue(()) }
         }).break_value()

Diff for: src/libcore/iter/iterator.rs

@@ -844,6 +844,12 @@ pub mod __internal {
         })
     }
 
+    pub fn in_sess() -> bool
+    {
+        let p = CURRENT_SESS.with(|p| p.get());
+        !p.0.is_null()
+    }
+
     pub fn with_sess<F, R>(f: F) -> R
         where F: FnOnce((&ParseSess, Mark)) -> R
     {

Diff for: src/libproc_macro/lib.rs

@@ -14,7 +14,9 @@ bitflags = "1.0"
 fmt_macros = { path = "../libfmt_macros" }
 graphviz = { path = "../libgraphviz" }
 jobserver = "0.1"
+lazy_static = "1.0.0"
 log = { version = "0.4", features = ["release_max_level_info", "std"] }
+proc_macro = { path = "../libproc_macro" }
 rustc_apfloat = { path = "../librustc_apfloat" }
 rustc_back = { path = "../librustc_back" }
 rustc_const_math = { path = "../librustc_const_math" }

Diff for: src/librustc/Cargo.toml

@@ -60,6 +60,7 @@
 #![feature(never_type)]
 #![feature(non_exhaustive)]
 #![feature(nonzero)]
+#![feature(proc_macro_internals)]
 #![feature(quote)]
 #![feature(refcell_replace_swap)]
 #![feature(rustc_diagnostic_macros)]
@@ -81,6 +82,7 @@ extern crate core;
 extern crate fmt_macros;
 extern crate getopts;
 extern crate graphviz;
+#[macro_use] extern crate lazy_static;
 #[cfg(windows)]
 extern crate libc;
 extern crate rustc_back;
@@ -92,6 +94,7 @@ extern crate rustc_errors as errors;
 #[macro_use] extern crate syntax;
 extern crate syntax_pos;
 extern crate jobserver;
+extern crate proc_macro;
 
 extern crate serialize as rustc_serialize; // used by deriving
 

Diff for: src/librustc/lib.rs

@@ -270,6 +270,19 @@ enum Scope<'a> {
         /// we should use for an early-bound region?
         next_early_index: u32,
 
+        /// Whether or not this binder would serve as the parent
+        /// binder for abstract types introduced within. For example:
+        ///
+        ///     fn foo<'a>() -> impl for<'b> Trait<Item = impl Trait2<'a>>
+        ///
+        /// Here, the abstract types we create for the `impl Trait`
+        /// and `impl Trait2` references will both have the `foo` item
+        /// as their parent. When we get to `impl Trait2`, we find
+        /// that it is nested within the `for<>` binder -- this flag
+        /// allows us to skip that when looking for the parent binder
+        /// of the resulting abstract type.
+        abstract_type_parent: bool,
+
         s: ScopeRef<'a>,
     },
 
@@ -498,6 +511,7 @@ impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> {
                 let scope = Scope::Binder {
                     lifetimes,
                     next_early_index,
+                    abstract_type_parent: true,
                     s: ROOT_SCOPE,
                 };
                 self.with(scope, |old_scope, this| {
@@ -541,6 +555,7 @@ impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> {
                         .collect(),
                     s: self.scope,
                     next_early_index,
+                    abstract_type_parent: false,
                 };
                 self.with(scope, |old_scope, this| {
                     // a bare fn has no bounds, so everything
@@ -614,7 +629,10 @@ impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> {
                     ref generics,
                     ref bounds,
                 } = *exist_ty;
-                let mut index = self.next_early_index();
+
+                // We want to start our early-bound indices at the end of the parent scope,
+                // not including any parent `impl Trait`s.
+                let mut index = self.next_early_index_for_abstract_type();
                 debug!("visit_ty: index = {}", index);
 
                 let mut elision = None;
@@ -638,7 +656,12 @@ impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> {
                         s: self.scope
                     };
                     self.with(scope, |_old_scope, this| {
-                        let scope = Scope::Binder { lifetimes, next_early_index, s: this.scope };
+                        let scope = Scope::Binder {
+                            lifetimes,
+                            next_early_index,
+                            s: this.scope,
+                            abstract_type_parent: false,
+                        };
                         this.with(scope, |_old_scope, this| {
                             this.visit_generics(generics);
                             for bound in bounds {
@@ -647,7 +670,12 @@ impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> {
                         });
                     });
                 } else {
-                    let scope = Scope::Binder { lifetimes, next_early_index, s: self.scope };
+                    let scope = Scope::Binder {
+                        lifetimes,
+                        next_early_index,
+                        s: self.scope,
+                        abstract_type_parent: false,
+                    };
                     self.with(scope, |_old_scope, this| {
                         this.visit_generics(generics);
                         for bound in bounds {
@@ -681,7 +709,12 @@ impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> {
                     .collect();
 
                 let next_early_index = index + generics.ty_params().count() as u32;
-                let scope = Scope::Binder { lifetimes, next_early_index, s: self.scope };
+                let scope = Scope::Binder {
+                    lifetimes,
+                    next_early_index,
+                    s: self.scope,
+                    abstract_type_parent: true,
+                };
                 self.with(scope, |_old_scope, this| {
                     this.visit_generics(generics);
                     for bound in bounds {
@@ -721,7 +754,12 @@ impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> {
                     .collect();
 
                 let next_early_index = index + generics.ty_params().count() as u32;
-                let scope = Scope::Binder { lifetimes, next_early_index, s: self.scope };
+                let scope = Scope::Binder {
+                    lifetimes,
+                    next_early_index,
+                    s: self.scope,
+                    abstract_type_parent: true,
+                };
                 self.with(scope, |_old_scope, this| {
                     this.visit_generics(generics);
                     this.visit_ty(ty);
@@ -792,6 +830,7 @@ impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> {
                                 .collect(),
                             s: self.scope,
                             next_early_index,
+                            abstract_type_parent: false,
                         };
                         let result = self.with(scope, |old_scope, this| {
                             this.check_lifetime_params(old_scope, &bound_generic_params);
@@ -853,6 +892,7 @@ impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> {
                     .collect(),
                 s: self.scope,
                 next_early_index,
+                abstract_type_parent: false,
             };
             self.with(scope, |old_scope, this| {
                 this.check_lifetime_params(old_scope, &trait_ref.bound_generic_params);
@@ -1046,6 +1086,7 @@ fn extract_labels(ctxt: &mut LifetimeContext<'_, '_>, body: &hir::Body) {
                     ref lifetimes,
                     s,
                     next_early_index: _,
+                    abstract_type_parent: _,
                 } => {
                     // FIXME (#24278): non-hygienic comparison
                     if let Some(def) = lifetimes.get(&hir::LifetimeName::Name(label)) {
@@ -1303,32 +1344,49 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
             lifetimes,
             next_early_index,
             s: self.scope,
+            abstract_type_parent: true,
         };
         self.with(scope, move |old_scope, this| {
             this.check_lifetime_params(old_scope, &generics.params);
             this.hack(walk); // FIXME(#37666) workaround in place of `walk(this)`
         });
     }
 
-    /// Returns the next index one would use for an early-bound-region
-    /// if extending the current scope.
-    fn next_early_index(&self) -> u32 {
+    fn next_early_index_helper(&self, only_abstract_type_parent: bool) -> u32 {
         let mut scope = self.scope;
         loop {
             match *scope {
                 Scope::Root => return 0,
 
                 Scope::Binder {
-                    next_early_index, ..
-                } => return next_early_index,
+                    next_early_index,
+                    abstract_type_parent,
+                    ..
+                } if (!only_abstract_type_parent || abstract_type_parent)
+                => return next_early_index,
 
-                Scope::Body { s, .. }
+                Scope::Binder { s, .. }
+                | Scope::Body { s, .. }
                 | Scope::Elision { s, .. }
                 | Scope::ObjectLifetimeDefault { s, .. } => scope = s,
             }
         }
     }
 
+    /// Returns the next index one would use for an early-bound-region
+    /// if extending the current scope.
+    fn next_early_index(&self) -> u32 {
+        self.next_early_index_helper(true)
+    }
+
+    /// Returns the next index one would use for an `impl Trait` that
+    /// is being converted into an `abstract type`. This will be the
+    /// next early index from the enclosing item, for the most
+    /// part. See the `abstract_type_parent` field for more info.
+    fn next_early_index_for_abstract_type(&self) -> u32 {
+        self.next_early_index_helper(false)
+    }
+
     fn resolve_lifetime_ref(&mut self, lifetime_ref: &'tcx hir::Lifetime) {
         debug!("resolve_lifetime_ref(lifetime_ref={:?})", lifetime_ref);
         // Walk up the scope chain, tracking the number of fn scopes
@@ -1353,6 +1411,7 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
                     ref lifetimes,
                     s,
                     next_early_index: _,
+                    abstract_type_parent: _,
                 } => {
                     if let Some(&def) = lifetimes.get(&lifetime_ref.name) {
                         break Some(def.shifted(late_depth));
@@ -2102,6 +2161,7 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
                     ref lifetimes,
                     s,
                     next_early_index: _,
+                    abstract_type_parent: _,
                 } => {
                     if let Some(&def) = lifetimes.get(&lifetime.name) {
                         let node_id = self.tcx.hir.as_local_node_id(def.id().unwrap()).unwrap();