Auto merge of rust-lang#34762 - creativcoder:slice-ext, r=alexcrichton

extend lifetime on binary_search_by_key of SliceExt trait

Fixes rust-lang#34683.

src/libcollections/slice.rs

@@ -973,8 +973,8 @@ impl<T> [T] {
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
     #[inline]
-    pub fn binary_search_by<F>(&self, f: F) -> Result<usize, usize>
-        where F: FnMut(&T) -> Ordering
+    pub fn binary_search_by<'a, F>(&'a self, f: F) -> Result<usize, usize>
+        where F: FnMut(&'a T) -> Ordering
     {
         core_slice::SliceExt::binary_search_by(self, f)
     }
@@ -1009,8 +1009,8 @@ impl<T> [T] {
     /// ```
     #[stable(feature = "slice_binary_search_by_key", since = "1.10.0")]
     #[inline]
-    pub fn binary_search_by_key<B, F>(&self, b: &B, f: F) -> Result<usize, usize>
-        where F: FnMut(&T) -> B,
+    pub fn binary_search_by_key<'a, B, F>(&'a self, b: &B, f: F) -> Result<usize, usize>
+        where F: FnMut(&'a T) -> B,
               B: Ord
     {
         core_slice::SliceExt::binary_search_by_key(self, b, f)

src/libcore/slice.rs

@@ -105,11 +105,11 @@ pub trait SliceExt {
     fn binary_search(&self, x: &Self::Item) -> Result<usize, usize>
         where Self::Item: Ord;
     #[stable(feature = "core", since = "1.6.0")]
-    fn binary_search_by<F>(&self, f: F) -> Result<usize, usize>
-        where F: FnMut(&Self::Item) -> Ordering;
+    fn binary_search_by<'a, F>(&'a self, f: F) -> Result<usize, usize>
+        where F: FnMut(&'a Self::Item) -> Ordering;
     #[stable(feature = "slice_binary_search_by_key", since = "1.10.0")]
-    fn binary_search_by_key<B, F>(&self, b: &B, f: F) -> Result<usize, usize>
-        where F: FnMut(&Self::Item) -> B,
+    fn binary_search_by_key<'a, B, F>(&'a self, b: &B, f: F) -> Result<usize, usize>
+        where F: FnMut(&'a Self::Item) -> B,
               B: Ord;
     #[stable(feature = "core", since = "1.6.0")]
     fn len(&self) -> usize;
@@ -301,8 +301,8 @@ impl<T> SliceExt for [T] {
         self as *const [T] as *const T
     }
 
-    fn binary_search_by<F>(&self, mut f: F) -> Result<usize, usize> where
-        F: FnMut(&T) -> Ordering
+    fn binary_search_by<'a, F>(&'a self, mut f: F) -> Result<usize, usize>
+        where F: FnMut(&'a T) -> Ordering
     {
         let mut base = 0usize;
         let mut s = self;
@@ -514,8 +514,8 @@ impl<T> SliceExt for [T] {
     }
 
     #[inline]
-    fn binary_search_by_key<B, F>(&self, b: &B, mut f: F) -> Result<usize, usize>
-        where F: FnMut(&Self::Item) -> B,
+    fn binary_search_by_key<'a, B, F>(&'a self, b: &B, mut f: F) -> Result<usize, usize>
+        where F: FnMut(&'a Self::Item) -> B,
               B: Ord
     {
         self.binary_search_by(|k| f(k).cmp(b))

src/test/run-pass/slice_binary_search.rs

@@ -0,0 +1,29 @@
+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// Test binary_search_by_key lifetime. Issue #34683
+
+#[derive(Debug)]
+struct Assignment {
+    topic: String,
+    partition: i32,
+}
+
+fn main() {
+    let xs = vec![
+        Assignment { topic: "abc".into(), partition: 1 },
+        Assignment { topic: "def".into(), partition: 2 },
+        Assignment { topic: "ghi".into(), partition: 3 },
+    ];
+
+    let key: &str = "def";
+    let r = xs.binary_search_by_key(&key, |e| &e.topic);
+    assert_eq!(Ok(1), r.map(|i| i));
+}