rollup merge of #20721: japaric/snap

Conflicts:
	src/libcollections/vec.rs
	src/libcore/fmt/mod.rs
	src/librustc/lint/builtin.rs
	src/librustc/session/config.rs
	src/librustc_trans/trans/base.rs
	src/librustc_trans/trans/context.rs
	src/librustc_trans/trans/type_.rs
	src/librustc_typeck/check/_match.rs
	src/librustdoc/html/format.rs
	src/libsyntax/std_inject.rs
	src/libsyntax/util/interner.rs
	src/test/compile-fail/mut-pattern-mismatched.rs

src/libtest/lib.rs

@@ -949,7 +949,7 @@ fn should_sort_failures_before_printing_them() {
 
     st.write_failures().unwrap();
     let s = match st.out {
-        Raw(ref m) => String::from_utf8_lossy(m.index(&FullRange)),
+        Raw(ref m) => String::from_utf8_lossy(&m[]),
         Pretty(_) => unreachable!()
     };