diff --git a/compiler/rustc_infer/src/infer/combine.rs b/compiler/rustc_infer/src/infer/combine.rs
index 594e2c6205f85..987380304d222 100644
--- a/compiler/rustc_infer/src/infer/combine.rs
+++ b/compiler/rustc_infer/src/infer/combine.rs
@@ -881,9 +881,7 @@ impl TypeRelation<'tcx> for ConstInferUnifier<'_, 'tcx> {
                     }
                 }
             }
-            ty::Infer(ty::IntVar(_) | ty::FloatVar(_)) => {
-                Ok(t)
-            }
+            ty::Infer(ty::IntVar(_) | ty::FloatVar(_)) => Ok(t),
             _ => relate::super_relate_tys(self, t, t),
         }
     }
diff --git a/compiler/rustc_middle/src/ty/relate.rs b/compiler/rustc_middle/src/ty/relate.rs
index 80dc7d89d187d..ea4e731086fb1 100644
--- a/compiler/rustc_middle/src/ty/relate.rs
+++ b/compiler/rustc_middle/src/ty/relate.rs
@@ -33,6 +33,11 @@ pub trait TypeRelation<'tcx>: Sized {
     /// relation. Just affects error messages.
     fn a_is_expected(&self) -> bool;
 
+    /// Whether we should look into the substs of unevaluated constants
+    /// even if `feature(const_evaluatable_checked)` is active.
+    ///
+    /// This is needed in `combine` to prevent accidentially creating
+    /// infinite types as we abuse `TypeRelation` to walk a type there.
     fn visit_ct_substs(&self) -> bool {
         false
     }