1 files changed, 88 insertions, 0 deletions
diff --git a/clang-tools-extra/clang-tidy/utils/UsingInserter.cpp b/clang-tools-extra/clang-tidy/utils/UsingInserter.cpp
new file mode 100644
index 00000000000..c0746afc9ab
--- /dev/null
+++ b/clang-tools-extra/clang-tidy/utils/UsingInserter.cpp
@@ -0,0 +1,88 @@
+//===---------- UsingInserter.cpp - clang-tidy ----------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "UsingInserter.h"
+
+#include "ASTUtils.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/ASTMatchers/ASTMatchers.h"
+#include "clang/Lex/Lexer.h"
+
+namespace clang {
+namespace tidy {
+namespace utils {
+
+using namespace ast_matchers;
+
+static StringRef getUnqualifiedName(StringRef QualifiedName) {
+  size_t LastSeparatorPos = QualifiedName.rfind("::");
+  if (LastSeparatorPos == StringRef::npos)
+    return QualifiedName;
+  return QualifiedName.drop_front(LastSeparatorPos + 2);
+}
+
+UsingInserter::UsingInserter(const SourceManager &SourceMgr)
+    : SourceMgr(SourceMgr) {}
+
+Optional<FixItHint> UsingInserter::createUsingDeclaration(
+    ASTContext &Context, const Stmt &Statement, StringRef QualifiedName) {
+  StringRef UnqualifiedName = getUnqualifiedName(QualifiedName);
+  const FunctionDecl *Function = getSurroundingFunction(Context, Statement);
+  if (!Function)
+    return None;
+
+  if (AddedUsing.count(std::make_pair(Function, QualifiedName.str())) != 0)
+    return None;
+
+  SourceLocation InsertLoc = Lexer::getLocForEndOfToken(
+      Function->getBody()->getLocStart(), 0, SourceMgr, Context.getLangOpts());
+
+  // Only use using declarations in the main file, not in includes.
+  if (SourceMgr.getFileID(InsertLoc) != SourceMgr.getMainFileID())
+    return None;
+
+  // FIXME: This declaration could be masked. Investigate if
+  // there is a way to avoid using Sema.
+  bool AlreadyHasUsingDecl =
+      !match(stmt(hasAncestor(decl(has(usingDecl(hasAnyUsingShadowDecl(
+                 hasTargetDecl(hasName(QualifiedName.str())))))))),
+             Statement, Context)
+           .empty();
+  if (AlreadyHasUsingDecl) {
+    AddedUsing.emplace(NameInFunction(Function, QualifiedName.str()));
+    return None;
+  }
+  // Find conflicting declarations and references.
+  auto ConflictingDecl = namedDecl(hasName(UnqualifiedName));
+  bool HasConflictingDeclaration =
+      !match(findAll(ConflictingDecl), *Function, Context).empty();
+  bool HasConflictingDeclRef =
+      !match(findAll(declRefExpr(to(ConflictingDecl))), *Function, Context)
+           .empty();
+  if (HasConflictingDeclaration || HasConflictingDeclRef)
+    return None;
+
+  std::string Declaration = (llvm::Twine("\nusing ") + QualifiedName + ";").str();
+
+  AddedUsing.emplace(std::make_pair(Function, QualifiedName.str()));
+  return FixItHint::CreateInsertion(InsertLoc, Declaration);
+}
+
+StringRef UsingInserter::getShortName(ASTContext &Context,
+                                      const Stmt &Statement,
+                                      StringRef QualifiedName) {
+  const FunctionDecl *Function = getSurroundingFunction(Context, Statement);
+  if (AddedUsing.count(NameInFunction(Function, QualifiedName.str())) != 0)
+    return getUnqualifiedName(QualifiedName);
+  return QualifiedName;
+}
+
+} // namespace utils
+} // namespace tidy
+} // namespace clang