add additional TypeFlags fast paths

compiler/rustc_next_trait_solver/src/canonicalizer.rs

@@ -572,4 +572,8 @@ impl<D: SolverDelegate<Interner = I>, I: Interner> TypeFolder<I> for Canonicaliz
     fn fold_predicate(&mut self, p: I::Predicate) -> I::Predicate {
         if p.flags().intersects(NEEDS_CANONICAL) { p.super_fold_with(self) } else { p }
     }
+
+    fn fold_clauses(&mut self, c: I::Clauses) -> I::Clauses {
+        if c.flags().intersects(NEEDS_CANONICAL) { c.super_fold_with(self) } else { c }
+    }
 }

compiler/rustc_next_trait_solver/src/resolve.rs

@@ -11,7 +11,7 @@ use crate::delegate::SolverDelegate;
 // EAGER RESOLUTION
 
 /// Resolves ty, region, and const vars to their inferred values or their root vars.
-pub struct EagerResolver<'a, D, I = <D as SolverDelegate>::Interner>
+struct EagerResolver<'a, D, I = <D as SolverDelegate>::Interner>
 where
     D: SolverDelegate<Interner = I>,
     I: Interner,
@@ -22,8 +22,20 @@ where
     cache: DelayedMap<I::Ty, I::Ty>,
 }
 
+pub fn eager_resolve_vars<D: SolverDelegate, T: TypeFoldable<D::Interner>>(
+    delegate: &D,
+    value: T,
+) -> T {
+    if value.has_infer() {
+        let mut folder = EagerResolver::new(delegate);
+        value.fold_with(&mut folder)
+    } else {
+        value
+    }
+}
+
 impl<'a, D: SolverDelegate> EagerResolver<'a, D> {
-    pub fn new(delegate: &'a D) -> Self {
+    fn new(delegate: &'a D) -> Self {
         EagerResolver { delegate, cache: Default::default() }
     }
 }
@@ -90,4 +102,8 @@ impl<D: SolverDelegate<Interner = I>, I: Interner> TypeFolder<I> for EagerResolv
     fn fold_predicate(&mut self, p: I::Predicate) -> I::Predicate {
         if p.has_infer() { p.super_fold_with(self) } else { p }
     }
+
+    fn fold_clauses(&mut self, c: I::Clauses) -> I::Clauses {
+        if c.has_infer() { c.super_fold_with(self) } else { c }
+    }
 }

compiler/rustc_next_trait_solver/src/solve/eval_ctxt/canonical.rs

@@ -22,7 +22,7 @@ use tracing::{debug, instrument, trace};
 
 use crate::canonicalizer::Canonicalizer;
 use crate::delegate::SolverDelegate;
-use crate::resolve::EagerResolver;
+use crate::resolve::eager_resolve_vars;
 use crate::solve::eval_ctxt::CurrentGoalKind;
 use crate::solve::{
     CanonicalInput, CanonicalResponse, Certainty, EvalCtxt, ExternalConstraintsData, Goal,
@@ -61,8 +61,7 @@ where
         // so we only canonicalize the lookup table and ignore
         // duplicate entries.
         let opaque_types = self.delegate.clone_opaque_types_lookup_table();
-        let (goal, opaque_types) =
-            (goal, opaque_types).fold_with(&mut EagerResolver::new(self.delegate));
+        let (goal, opaque_types) = eager_resolve_vars(self.delegate, (goal, opaque_types));
 
         let mut orig_values = Default::default();
         let canonical = Canonicalizer::canonicalize_input(
@@ -157,8 +156,8 @@ where
 
         let external_constraints =
             self.compute_external_query_constraints(certainty, normalization_nested_goals);
-        let (var_values, mut external_constraints) = (self.var_values, external_constraints)
-            .fold_with(&mut EagerResolver::new(self.delegate));
+        let (var_values, mut external_constraints) =
+            eager_resolve_vars(self.delegate, (self.var_values, external_constraints));
 
         // Remove any trivial or duplicated region constraints once we've resolved regions
         let mut unique = HashSet::default();
@@ -469,7 +468,7 @@ where
 {
     let var_values = CanonicalVarValues { var_values: delegate.cx().mk_args(var_values) };
     let state = inspect::State { var_values, data };
-    let state = state.fold_with(&mut EagerResolver::new(delegate));
+    let state = eager_resolve_vars(delegate, state);
     Canonicalizer::canonicalize_response(delegate, max_input_universe, &mut vec![], state)
 }
 

compiler/rustc_next_trait_solver/src/solve/eval_ctxt/mod.rs

@@ -848,6 +848,22 @@ where
                     }
                 }
             }
+
+            fn visit_predicate(&mut self, p: I::Predicate) -> Self::Result {
+                if p.has_non_region_infer() || p.has_placeholders() {
+                    p.super_visit_with(self)
+                } else {
+                    ControlFlow::Continue(())
+                }
+            }
+
+            fn visit_clauses(&mut self, c: I::Clauses) -> Self::Result {
+                if c.has_non_region_infer() || c.has_placeholders() {
+                    c.super_visit_with(self)
+                } else {
+                    ControlFlow::Continue(())
+                }
+            }
         }
 
         let mut visitor = ContainsTermOrNotNameable {