1 files changed, 113 insertions, 0 deletions
diff --git a/lib/Tooling/Core/Lookup.cpp b/lib/Tooling/Core/Lookup.cpp
new file mode 100644
index 000000000000..697eeb46ce41
--- /dev/null
+++ b/lib/Tooling/Core/Lookup.cpp
@@ -0,0 +1,113 @@
+//===--- Lookup.cpp - Framework for clang refactoring tools ---------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+//  This file defines helper methods for clang tools performing name lookup.
+//
+//===----------------------------------------------------------------------===//
+
+#include "clang/Tooling/Core/Lookup.h"
+#include "clang/AST/Decl.h"
+using namespace clang;
+using namespace clang::tooling;
+
+static bool isInsideDifferentNamespaceWithSameName(const DeclContext *DeclA,
+                                                   const DeclContext *DeclB) {
+  while (true) {
+    // Look past non-namespaces on DeclA.
+    while (DeclA && !isa<NamespaceDecl>(DeclA))
+      DeclA = DeclA->getParent();
+
+    // Look past non-namespaces on DeclB.
+    while (DeclB && !isa<NamespaceDecl>(DeclB))
+      DeclB = DeclB->getParent();
+
+    // We hit the root, no namespace collision.
+    if (!DeclA || !DeclB)
+      return false;
+
+    // Literally the same namespace, not a collision.
+    if (DeclA == DeclB)
+      return false;
+
+    // Now check the names. If they match we have a different namespace with the
+    // same name.
+    if (cast<NamespaceDecl>(DeclA)->getDeclName() ==
+        cast<NamespaceDecl>(DeclB)->getDeclName())
+      return true;
+
+    DeclA = DeclA->getParent();
+    DeclB = DeclB->getParent();
+  }
+}
+
+static StringRef getBestNamespaceSubstr(const DeclContext *DeclA,
+                                        StringRef NewName,
+                                        bool HadLeadingColonColon) {
+  while (true) {
+    while (DeclA && !isa<NamespaceDecl>(DeclA))
+      DeclA = DeclA->getParent();
+
+    // Fully qualified it is! Leave :: in place if it's there already.
+    if (!DeclA)
+      return HadLeadingColonColon ? NewName : NewName.substr(2);
+
+    // Otherwise strip off redundant namespace qualifications from the new name.
+    // We use the fully qualified name of the namespace and remove that part
+    // from NewName if it has an identical prefix.
+    std::string NS =
+        "::" + cast<NamespaceDecl>(DeclA)->getQualifiedNameAsString() + "::";
+    if (NewName.startswith(NS))
+      return NewName.substr(NS.size());
+
+    // No match yet. Strip of a namespace from the end of the chain and try
+    // again. This allows to get optimal qualifications even if the old and new
+    // decl only share common namespaces at a higher level.
+    DeclA = DeclA->getParent();
+  }
+}
+
+/// Check if the name specifier begins with a written "::".
+static bool isFullyQualified(const NestedNameSpecifier *NNS) {
+  while (NNS) {
+    if (NNS->getKind() == NestedNameSpecifier::Global)
+      return true;
+    NNS = NNS->getPrefix();
+  }
+  return false;
+}
+
+std::string tooling::replaceNestedName(const NestedNameSpecifier *Use,
+                                       const DeclContext *UseContext,
+                                       const NamedDecl *FromDecl,
+                                       StringRef ReplacementString) {
+  assert(ReplacementString.startswith("::") &&
+         "Expected fully-qualified name!");
+
+  // We can do a raw name replacement when we are not inside the namespace for
+  // the original function and it is not in the global namespace.  The
+  // assumption is that outside the original namespace we must have a using
+  // statement that makes this work out and that other parts of this refactor
+  // will automatically fix using statements to point to the new function
+  const bool class_name_only = !Use;
+  const bool in_global_namespace =
+      isa<TranslationUnitDecl>(FromDecl->getDeclContext());
+  if (class_name_only && !in_global_namespace &&
+      !isInsideDifferentNamespaceWithSameName(FromDecl->getDeclContext(),
+                                              UseContext)) {
+    auto Pos = ReplacementString.rfind("::");
+    return Pos != StringRef::npos ? ReplacementString.substr(Pos + 2)
+                                  : ReplacementString;
+  }
+  // We did not match this because of a using statement, so we will need to
+  // figure out how good a namespace match we have with our destination type.
+  // We work backwards (from most specific possible namespace to least
+  // specific).
+  return getBestNamespaceSubstr(UseContext, ReplacementString,
+                                isFullyQualified(Use));
+}