Auto merge of #143500 - compiler-errors:characterize-less, r=lcnr

Skip walking into param-env component if it has no placeholder/re-var

Although it only provides a minor perf improvement, it seems like it could matter in more pathological cases.

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

@@ -10,8 +10,8 @@
 use rustc_type_ir::lang_items::TraitSolverLangItem;
 use rustc_type_ir::solve::SizedTraitKind;
 use rustc_type_ir::{
-    self as ty, Interner, TypeFoldable, TypeSuperVisitable, TypeVisitable, TypeVisitableExt as _,
-    TypeVisitor, TypingMode, Upcast as _, elaborate,
+    self as ty, Interner, TypeFlags, TypeFoldable, TypeSuperVisitable, TypeVisitable,
+    TypeVisitableExt as _, TypeVisitor, TypingMode, Upcast as _, elaborate,
 };
 use tracing::{debug, instrument};
 
@@ -132,6 +132,7 @@ fn probe_and_consider_param_env_candidate(
         })
         .enter(|ecx| {
             Self::match_assumption(ecx, goal, assumption, |ecx| {
+                ecx.try_evaluate_added_goals()?;
                 source.set(ecx.characterize_param_env_assumption(goal.param_env, assumption)?);
                 ecx.evaluate_added_goals_and_make_canonical_response(Certainty::Yes)
             })
@@ -1069,8 +1070,10 @@ fn visit_ty(&mut self, ty: I::Ty) -> Self::Result {
             } else {
                 ControlFlow::Continue(())
             }
-        } else {
+        } else if ty.has_type_flags(TypeFlags::HAS_PLACEHOLDER | TypeFlags::HAS_RE_INFER) {
             ty.super_visit_with(self)
+        } else {
+            ControlFlow::Continue(())
         }
     }
 
@@ -1086,8 +1089,10 @@ fn visit_const(&mut self, ct: I::Const) -> Self::Result {
             } else {
                 ControlFlow::Continue(())
             }
-        } else {
+        } else if ct.has_type_flags(TypeFlags::HAS_PLACEHOLDER | TypeFlags::HAS_RE_INFER) {
             ct.super_visit_with(self)
+        } else {
+            ControlFlow::Continue(())
         }
     }