Explain how to evaluate an obligation

Author: mejrs

compiler/rustc_trait_selection/src/infer.rs

@@ -69,9 +69,15 @@ impl<'tcx> InferCtxt<'tcx> {
     /// .must_apply_modulo_regions();
     /// ```
     ///
-    /// In most cases you should instead create an [Obligation](traits::Obligation)
-    /// and check whether it holds, because it properly handles higher ranked traits
-    /// and it is more convenient and safer when your `params` are inside a `Binder`.
+    /// In most cases you should instead create an [Obligation] and check whether
+    ///  it holds via [`evaluate_obligation`] or one of its helper functions like
+    /// [`predicate_must_hold_modulo_regions`], because it properly handles higher ranked traits
+    /// and it is more convenient and safer when your `params` are inside a [`Binder`].
+    ///
+    /// [Obligation]: traits::Obligation
+    /// [`evaluate_obligation`]: crate::traits::query::evaluate_obligation::InferCtxtExt::evaluate_obligation
+    /// [`predicate_must_hold_modulo_regions`]: crate::traits::query::evaluate_obligation::InferCtxtExt::predicate_must_hold_modulo_regions
+    /// [`Binder`]: ty::Binder
     #[instrument(level = "debug", skip(self, params), ret)]
     fn type_implements_trait(
         &self,