Resolver trait moved (#652)

Author: tshepang

src/name-resolution.md

@@ -19,8 +19,8 @@ namespaces and therefore can co-exist.
 
 The name resolution in Rust is a two-phase process. In the first phase, which runs
 during macro expansion, we build a tree of modules and resolve imports. Macro
-expansion and name resolution communicate with each other via the `Resolver`
-trait, defined in `librustc_ast`.
+expansion and name resolution communicate with each other via the
+[`Resolver`] trait.
 
 The input to the second phase is the syntax tree, produced by parsing input
 files and expanding macros. This phase produces links from all the names in the
@@ -36,6 +36,7 @@ The name resolution lives in the `librustc_resolve` crate, with the meat in
 `lib.rs` and some helpers or symbol-type specific logic in the other modules.
 
 [`Resolver::resolve_crate`]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_resolve/struct.Resolver.html#method.resolve_crate
+[`Resolver`]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_ast_lowering/trait.Resolver.html
 
 ## Namespaces