Move canDeclProvideDefaultImplementationFor() from libIDE into libIndex

include/swift/Index/Index.h

@@ -20,14 +20,6 @@ class ModuleDecl;
 class SourceFile;
 class DeclContext;
 
-// Get decls that the given decl overrides, protocol requirements that it
-// serves as a default implementation of, and optionally (as it is more
-// expensive) protocol requirements it satisfies in a conforming class
-std::vector<ValueDecl*>
-getOverriddenDecls(ValueDecl *VD, bool IncludeProtocolRequirements = true,
-                   bool Transitive = false);
-
-
 namespace index {
 
 void indexDeclContext(DeclContext *DC, IndexDataConsumer &consumer);

include/swift/Index/Utils.h

@@ -0,0 +1,41 @@
+//===--- Utils.h - Index utilities that are generally useful ----*- C++ -*-===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef SWIFT_INDEX_UTILS_H
+#define SWIFT_INDEX_UTILS_H
+
+#include "swift/Basic/LLVM.h"
+#include "llvm/ADT/ArrayRef.h"
+#include "llvm/ADT/SmallVector.h"
+
+namespace swift {
+class ValueDecl;
+
+/// \brief Collect all the protocol requirements that a given declaration can
+///   provide default implementations for. VD is a declaration in extension
+///   declaration. Scratch is the buffer to collect those protocol
+///   requirements.
+///
+/// \returns the slice of Scratch
+ArrayRef<ValueDecl*>
+canDeclProvideDefaultImplementationFor(ValueDecl* VD,
+                                       llvm::SmallVectorImpl<ValueDecl*> &Scratch);
+
+/// \brief Get decls that the given decl overrides, protocol requirements that
+///   it serves as a default implementation of, and optionally protocol
+///   requirements it satisfies in a conforming class
+std::vector<ValueDecl*>
+getOverriddenDecls(ValueDecl *VD, bool IncludeProtocolRequirements = true,
+                   bool Transitive = false);
+
+} // end namespace swift
+#endif // SWIFT_INDEX_UTILS_H