Update paths in comments.

Author: jonathanCogan

library/alloc/src/slice.rs

@@ -653,7 +653,7 @@ impl [u8] {
 ///
 /// ```error
 /// error[E0207]: the type parameter `T` is not constrained by the impl trait, self type, or predica
-///    --> src/alloc/slice.rs:608:6
+///    --> library/alloc/src/slice.rs:608:6
 ///     |
 /// 608 | impl<T: Clone, V: Borrow<[T]>> Concat for [V] {
 ///     |      ^ unconstrained type parameter

library/core/src/lib.rs

@@ -39,7 +39,7 @@
 //!    called. The `lang` attribute is called `eh_personality`.
 
 // Since core defines many fundamental lang items, all tests live in a
-// separate crate, libcoretest, to avoid bizarre issues.
+// separate crate, libcoretest (library/core/tests), to avoid bizarre issues.
 //
 // Here we explicitly #[cfg]-out this whole crate when testing. If we don't do
 // this, both the generated test artifact and the linked libtest (which

library/core/tests/str.rs

@@ -1 +1 @@
-// All `str` tests live in alloc/tests
+// All `str` tests live in library/alloc/tests/str.rs