Remove dead find/filter-Constraints functions from the constraint solver

Author: DougGregor

include/swift/Sema/ConstraintSystem.h

@@ -3939,12 +3939,6 @@ class ConstraintSystem {
   /// due to a change.
   ConstraintList &getActiveConstraints() { return ActiveConstraints; }
 
-  void findConstraints(SmallVectorImpl<Constraint *> &found,
-                       llvm::function_ref<bool(const Constraint &)> pred) {
-    filterConstraints(ActiveConstraints, pred, found);
-    filterConstraints(InactiveConstraints, pred, found);
-  }
-
   /// Retrieve the representative of the equivalence class containing
   /// this type variable.
   TypeVariableType *getRepresentative(TypeVariableType *typeVar) const {
@@ -4117,16 +4111,6 @@ class ConstraintSystem {
   /// into the worklist.
   void addTypeVariableConstraintsToWorkList(TypeVariableType *typeVar);
 
-  static void
-  filterConstraints(ConstraintList &constraints,
-                    llvm::function_ref<bool(const Constraint &)> pred,
-                    SmallVectorImpl<Constraint *> &found) {
-    for (auto &constraint : constraints) {
-      if (pred(constraint))
-        found.push_back(&constraint);
-    }
-  }
-
 public:
 
   /// Coerce the given expression to an rvalue, if it isn't already.