Remove the now-unused GenericSignatureBuilder::updateRequirementSource().

Author: DougGregor

include/swift/AST/GenericSignatureBuilder.h

@@ -169,14 +169,6 @@ class GenericSignatureBuilder {
   GenericSignatureBuilder(const GenericSignatureBuilder &) = delete;
   GenericSignatureBuilder &operator=(const GenericSignatureBuilder &) = delete;
 
-  /// Update an existing constraint source reference when another constraint
-  /// source was found to produce the same constraint. Only the better
-  /// constraint source will be kept.
-  ///
-  /// \returns true if the new constraint source was better, false otherwise.
-  bool updateRequirementSource(const RequirementSource *&existingSource,
-                               const RequirementSource *newSource);
-
   /// Retrieve the constraint source conformance for the superclass constraint
   /// of the given potential archetype (if present) to the given protocol.
   ///

lib/AST/GenericSignatureBuilder.cpp

@@ -814,22 +814,6 @@ bool EquivalenceClass::isConformanceSatisfiedBySuperclass(
   return false;
 }
 
-bool GenericSignatureBuilder::updateRequirementSource(
-                                      const RequirementSource *&existingSource,
-                                      const RequirementSource *newSource) {
-  if (int result = newSource->compare(existingSource)) {
-    if (result < 0) {
-      existingSource = newSource;
-      return true;
-    }
-
-    return false;
-  }
-
-  assert(existingSource == newSource && "incomparable requirement sources");
-  return false;
-}
-
 const RequirementSource *GenericSignatureBuilder::resolveSuperConformance(
                       GenericSignatureBuilder::PotentialArchetype *pa,
                       ProtocolDecl *proto) {