Rollup merge of rust-lang#51807 - newpavlov:deprecate_str_slice, r=alexcrichton

Deprecation of str::slice_unchecked(_mut)

Closes rust-lang#51715

I am not sure if 1.28.0 or 1.29.0 should be used for deprecation version, for now it's 1.28.0.

Additionally I've replaced `slice_unchecked` uses with `get_unchecked`. The only places where this method is still used are `src/liballoc/tests/str.rs` and `src/liballoc/tests/str.rs`.

Author: kennytm

src/liballoc/str.rs

@@ -268,11 +268,11 @@ impl str {
         let mut result = String::new();
         let mut last_end = 0;
         for (start, part) in self.match_indices(from) {
-            result.push_str(unsafe { self.slice_unchecked(last_end, start) });
+            result.push_str(unsafe { self.get_unchecked(last_end..start) });
             result.push_str(to);
             last_end = start + part.len();
         }
-        result.push_str(unsafe { self.slice_unchecked(last_end, self.len()) });
+        result.push_str(unsafe { self.get_unchecked(last_end..self.len()) });
         result
     }
 
@@ -309,11 +309,11 @@ impl str {
         let mut result = String::with_capacity(32);
         let mut last_end = 0;
         for (start, part) in self.match_indices(pat).take(count) {
-            result.push_str(unsafe { self.slice_unchecked(last_end, start) });
+            result.push_str(unsafe { self.get_unchecked(last_end..start) });
             result.push_str(to);
             last_end = start + part.len();
         }
-        result.push_str(unsafe { self.slice_unchecked(last_end, self.len()) });
+        result.push_str(unsafe { self.get_unchecked(last_end..self.len()) });
         result
     }
 

src/liballoc/string.rs

@@ -1222,7 +1222,7 @@ impl String {
 
         while idx < len {
             let ch = unsafe {
-                self.slice_unchecked(idx, len).chars().next().unwrap()
+                self.get_unchecked(idx..len).chars().next().unwrap()
             };
             let ch_len = ch.len_utf8();
 

src/liballoc/tests/str.rs

@@ -177,9 +177,9 @@ fn test_join_for_different_lengths_with_long_separator() {
 
 #[test]
 fn test_unsafe_slice() {
-    assert_eq!("ab", unsafe {"abc".slice_unchecked(0, 2)});
-    assert_eq!("bc", unsafe {"abc".slice_unchecked(1, 3)});
-    assert_eq!("", unsafe {"abc".slice_unchecked(1, 1)});
+    assert_eq!("ab", unsafe {"abc".get_unchecked(0..2)});
+    assert_eq!("bc", unsafe {"abc".get_unchecked(1..3)});
+    assert_eq!("", unsafe {"abc".get_unchecked(1..1)});
     fn a_million_letter_a() -> String {
         let mut i = 0;
         let mut rs = String::new();
@@ -200,7 +200,7 @@ fn test_unsafe_slice() {
     }
     let letters = a_million_letter_a();
     assert_eq!(half_a_million_letter_a(),
-        unsafe { letters.slice_unchecked(0, 500000)});
+        unsafe { letters.get_unchecked(0..500000)});
 }
 
 #[test]

src/libcore/str/mod.rs

@@ -1055,7 +1055,7 @@ impl<'a, P: Pattern<'a>> SplitInternal<'a, P> {
         if !self.finished && (self.allow_trailing_empty || self.end - self.start > 0) {
             self.finished = true;
             unsafe {
-                let string = self.matcher.haystack().slice_unchecked(self.start, self.end);
+                let string = self.matcher.haystack().get_unchecked(self.start..self.end);
                 Some(string)
             }
         } else {
@@ -1070,7 +1070,7 @@ impl<'a, P: Pattern<'a>> SplitInternal<'a, P> {
         let haystack = self.matcher.haystack();
         match self.matcher.next_match() {
             Some((a, b)) => unsafe {
-                let elt = haystack.slice_unchecked(self.start, a);
+                let elt = haystack.get_unchecked(self.start..a);
                 self.start = b;
                 Some(elt)
             },
@@ -1095,13 +1095,13 @@ impl<'a, P: Pattern<'a>> SplitInternal<'a, P> {
         let haystack = self.matcher.haystack();
         match self.matcher.next_match_back() {
             Some((a, b)) => unsafe {
-                let elt = haystack.slice_unchecked(b, self.end);
+                let elt = haystack.get_unchecked(b..self.end);
                 self.end = a;
                 Some(elt)
             },
             None => unsafe {
                 self.finished = true;
-                Some(haystack.slice_unchecked(self.start, self.end))
+                Some(haystack.get_unchecked(self.start..self.end))
             },
         }
     }
@@ -1222,7 +1222,7 @@ impl<'a, P: Pattern<'a>> MatchIndicesInternal<'a, P> {
     #[inline]
     fn next(&mut self) -> Option<(usize, &'a str)> {
         self.0.next_match().map(|(start, end)| unsafe {
-            (start, self.0.haystack().slice_unchecked(start, end))
+            (start, self.0.haystack().get_unchecked(start..end))
         })
     }
 
@@ -1231,7 +1231,7 @@ impl<'a, P: Pattern<'a>> MatchIndicesInternal<'a, P> {
         where P::Searcher: ReverseSearcher<'a>
     {
         self.0.next_match_back().map(|(start, end)| unsafe {
-            (start, self.0.haystack().slice_unchecked(start, end))
+            (start, self.0.haystack().get_unchecked(start..end))
         })
     }
 }
@@ -1274,7 +1274,7 @@ impl<'a, P: Pattern<'a>> MatchesInternal<'a, P> {
     fn next(&mut self) -> Option<&'a str> {
         self.0.next_match().map(|(a, b)| unsafe {
             // Indices are known to be on utf8 boundaries
-            self.0.haystack().slice_unchecked(a, b)
+            self.0.haystack().get_unchecked(a..b)
         })
     }
 
@@ -1284,7 +1284,7 @@ impl<'a, P: Pattern<'a>> MatchesInternal<'a, P> {
     {
         self.0.next_match_back().map(|(a, b)| unsafe {
             // Indices are known to be on utf8 boundaries
-            self.0.haystack().slice_unchecked(a, b)
+            self.0.haystack().get_unchecked(a..b)
         })
     }
 }
@@ -2453,6 +2453,7 @@ impl str {
     /// }
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
+    #[rustc_deprecated(since = "1.29.0", reason = "use `get_unchecked(begin..end)` instead")]
     #[inline]
     pub unsafe fn slice_unchecked(&self, begin: usize, end: usize) -> &str {
         (begin..end).get_unchecked(self)
@@ -2483,6 +2484,7 @@ impl str {
     /// * `begin` and `end` must be byte positions within the string slice.
     /// * `begin` and `end` must lie on UTF-8 sequence boundaries.
     #[stable(feature = "str_slice_mut", since = "1.5.0")]
+    #[rustc_deprecated(since = "1.29.0", reason = "use `get_unchecked_mut(begin..end)` instead")]
     #[inline]
     pub unsafe fn slice_mut_unchecked(&mut self, begin: usize, end: usize) -> &mut str {
         (begin..end).get_unchecked_mut(self)
@@ -2524,8 +2526,8 @@ impl str {
         // is_char_boundary checks that the index is in [0, .len()]
         if self.is_char_boundary(mid) {
             unsafe {
-                (self.slice_unchecked(0, mid),
-                 self.slice_unchecked(mid, self.len()))
+                (self.get_unchecked(0..mid),
+                 self.get_unchecked(mid..self.len()))
             }
         } else {
             slice_error_fail(self, 0, mid)
@@ -3702,7 +3704,7 @@ impl str {
         }
         unsafe {
             // Searcher is known to return valid indices
-            self.slice_unchecked(i, j)
+            self.get_unchecked(i..j)
         }
     }
 
@@ -3741,7 +3743,7 @@ impl str {
         }
         unsafe {
             // Searcher is known to return valid indices
-            self.slice_unchecked(i, self.len())
+            self.get_unchecked(i..self.len())
         }
     }
 
@@ -3788,7 +3790,7 @@ impl str {
         }
         unsafe {
             // Searcher is known to return valid indices
-            self.slice_unchecked(0, j)
+            self.get_unchecked(0..j)
         }
     }
 

src/libcore/str/pattern.rs

@@ -354,7 +354,7 @@ unsafe impl<'a> ReverseSearcher<'a> for CharSearcher<'a> {
     #[inline]
     fn next_back(&mut self) -> SearchStep {
         let old_finger = self.finger_back;
-        let slice = unsafe { self.haystack.slice_unchecked(self.finger, old_finger) };
+        let slice = unsafe { self.haystack.get_unchecked(self.finger..old_finger) };
         let mut iter = slice.chars();
         let old_len = iter.iter.len();
         if let Some(ch) = iter.next_back() {