Fast path for processing some obligations in the new solver

compiler/rustc_next_trait_solver/src/delegate.rs

@@ -3,6 +3,8 @@ use std::ops::Deref;
 use rustc_type_ir::solve::{Certainty, Goal, NoSolution};
 use rustc_type_ir::{self as ty, InferCtxtLike, Interner, TypeFoldable};
 
+use crate::solve::HasChanged;
+
 pub trait SolverDelegate: Deref<Target = Self::Infcx> + Sized {
     type Infcx: InferCtxtLike<Interner = Self::Interner>;
     type Interner: Interner;
@@ -17,6 +19,12 @@ pub trait SolverDelegate: Deref<Target = Self::Infcx> + Sized {
     where
         V: TypeFoldable<Self::Interner>;
 
+    fn compute_goal_fast_path(
+        &self,
+        goal: Goal<Self::Interner, <Self::Interner as Interner>::Predicate>,
+        span: <Self::Interner as Interner>::Span,
+    ) -> Option<HasChanged>;
+
     fn fresh_var_for_kind_with_span(
         &self,
         arg: <Self::Interner as Interner>::GenericArg,