Improve TyCtxt::type_of documentation

Author: GuillaumeGomez

compiler/rustc_middle/src/query/mod.rs

@@ -124,7 +124,10 @@ rustc_queries! {
         separate_provide_extern
     }
 
-    /// Records the type of every item.
+    /// Returns the [`Ty`][rustc_middle::ty::TyS] of the given [`DefId`]. If the [`DefId`] points
+    /// to an alias, it will "skip" this alias to return the aliased type.
+    ///
+    /// [`DefId`]: rustc_hir::def_id::DefId
     query type_of(key: DefId) -> Ty<'tcx> {
         desc { |tcx|
             "{action} `{path}`",