Auto merge of #41096 - clarcharr:as_bytes_mut, r=alexcrichton

Reduce str transmutes, add mut versions of methods.

When I was working on the various parts involved in #40380 one of the comments I got was the excess of transmutes necessary to make the changes work. This is part of a set of multiple changes I'd like to offer to fix this problem.

I think that having these methods is reasonable because they're already possible via transmutes, and it makes the code that uses them safer. I can also add `pub(crate)` to these methods for now if the libs team would rather not expose them to the public without an RFC.

2 files changed, 3 insertions, 3 deletions

diff --git a/src/libstd/ascii.rs b/src/libstd/ascii.rs
index b3625386209..4e3781ecafa 100644
--- a/src/libstd/ascii.rs
+++ b/src/libstd/ascii.rs
@@ -27,7 +27,6 @@
 #![stable(feature = "rust1", since = "1.0.0")]
 
 use fmt;
-use mem;
 use ops::Range;
 use iter::FusedIterator;
 
@@ -599,12 +598,12 @@ impl AsciiExt for str {
     }
 
     fn make_ascii_uppercase(&mut self) {
-        let me: &mut [u8] = unsafe { mem::transmute(self) };
+        let me = unsafe { self.as_bytes_mut() };
         me.make_ascii_uppercase()
     }
 
     fn make_ascii_lowercase(&mut self) {
-        let me: &mut [u8] = unsafe { mem::transmute(self) };
+        let me = unsafe { self.as_bytes_mut() };
         me.make_ascii_lowercase()
     }
 
diff --git a/src/libstd/lib.rs b/src/libstd/lib.rs
index 064144dcd68..6299a9070ae 100644
--- a/src/libstd/lib.rs
+++ b/src/libstd/lib.rs
@@ -296,6 +296,7 @@
 #![feature(stmt_expr_attributes)]
 #![feature(str_char)]
 #![feature(str_internals)]
+#![feature(str_mut_extras)]
 #![feature(str_utf16)]
 #![feature(test, rustc_private)]
 #![feature(thread_local)]