Auto merge of #2856 - RalfJung:rustup, r=RalfJung

Rustup

Author: bors

rust-version

@@ -1 +1 @@
-f65615f02d22b85e9205f2716ab36182d34bab2b
+70540d51275086ce1a4cb12e9d96a97134df792e

src/concurrency/data_race.rs

@@ -48,7 +48,7 @@ use std::{
 
 use rustc_ast::Mutability;
 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
-use rustc_index::vec::{Idx, IndexVec};
+use rustc_index::{Idx, IndexVec};
 use rustc_middle::mir;
 use rustc_span::Span;
 use rustc_target::abi::{Align, Size};

src/concurrency/init_once.rs

@@ -1,7 +1,7 @@
 use std::collections::VecDeque;
 use std::num::NonZeroU32;
 
-use rustc_index::vec::Idx;
+use rustc_index::Idx;
 
 use super::sync::EvalContextExtPriv as _;
 use super::thread::MachineCallback;

src/concurrency/sync.rs

@@ -5,7 +5,7 @@ use std::ops::Not;
 use log::trace;
 
 use rustc_data_structures::fx::FxHashMap;
-use rustc_index::vec::{Idx, IndexVec};
+use rustc_index::{Idx, IndexVec};
 
 use super::init_once::InitOnce;
 use super::vector_clock::VClock;

src/concurrency/thread.rs

@@ -10,7 +10,7 @@ use log::trace;
 
 use rustc_data_structures::fx::FxHashMap;
 use rustc_hir::def_id::DefId;
-use rustc_index::vec::{Idx, IndexVec};
+use rustc_index::{Idx, IndexVec};
 use rustc_middle::mir::Mutability;
 use rustc_middle::ty::layout::TyAndLayout;
 use rustc_span::Span;
@@ -603,10 +603,11 @@ impl<'mir, 'tcx: 'mir> ThreadManager<'mir, 'tcx> {
         // this allows us to have a deterministic scheduler.
         for thread in self.threads.indices() {
             match self.timeout_callbacks.entry(thread) {
-                Entry::Occupied(entry) =>
+                Entry::Occupied(entry) => {
                     if entry.get().call_time.get_wait_time(clock) == Duration::new(0, 0) {
                         return Some((thread, entry.remove().callback));
-                    },
+                    }
+                }
                 Entry::Vacant(_) => {}
             }
         }

src/concurrency/vector_clock.rs

@@ -1,4 +1,4 @@
-use rustc_index::vec::Idx;
+use rustc_index::Idx;
 use rustc_span::{Span, SpanData, DUMMY_SP};
 use smallvec::SmallVec;
 use std::{

tests/pass/tree-borrows/read-only-from-mut.rs

@@ -0,0 +1,39 @@
+//@compile-flags: -Zmiri-tree-borrows
+
+fn main() {
+    aliasing_read_only_mutable_refs();
+    string_as_mut_ptr();
+}
+
+// Tree Borrows has no issue with several mutable references existing
+// at the same time, as long as they are used only immutably.
+// I.e. multiple Reserved can coexist.
+pub fn aliasing_read_only_mutable_refs() {
+    unsafe {
+        let base = &mut 42u64;
+        let r1 = &mut *(base as *mut u64);
+        let r2 = &mut *(base as *mut u64);
+        let _l = *r1;
+        let _l = *r2;
+    }
+}
+
+pub fn string_as_mut_ptr() {
+    // This errors in Stacked Borrows since as_mut_ptr restricts the provenance,
+    // but with Tree Borrows it should work.
+    unsafe {
+        let mut s = String::from("hello");
+        s.reserve(1); // make the `str` that `s` derefs to not cover the entire `s`.
+
+        // Prevent automatically dropping the String's data
+        let mut s = mem::ManuallyDrop::new(s);
+
+        let ptr = s.as_mut_ptr();
+        let len = s.len();
+        let capacity = s.capacity();
+
+        let s = String::from_raw_parts(ptr, len, capacity);
+
+        assert_eq!(String::from("hello"), s);
+    }
+}