scoped_refptr implicit conversion cleanup tool.

tools/clang/rewrite_scoped_refptr/RewriteScopedRefptr.cpp

+// Copyright (c) 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+//
+// This implements a Clang tool to rewrite all instances of
+// scoped_refptr<T>'s implicit cast to T (operator T*) to an explicit call to
+// the .get() method.
+
+#include <algorithm>
+#include <memory>
+#include <string>
+
+#include "clang/AST/ASTContext.h"
+#include "clang/ASTMatchers/ASTMatchers.h"
+#include "clang/ASTMatchers/ASTMatchersMacros.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/Basic/SourceManager.h"
+#include "clang/Frontend/FrontendActions.h"
+#include "clang/Lex/Lexer.h"
+#include "clang/Tooling/CommonOptionsParser.h"
+#include "clang/Tooling/Refactoring.h"
+#include "clang/Tooling/Tooling.h"
+#include "llvm/Support/CommandLine.h"
+
+using namespace clang::ast_matchers;
+using clang::tooling::CommonOptionsParser;
+using clang::tooling::Replacement;
+using clang::tooling::Replacements;
+using llvm::StringRef;
+
+namespace clang {
+namespace ast_matchers {
+
+const internal::VariadicDynCastAllOfMatcher<Decl, CXXConversionDecl>
+    conversionDecl;
+
+AST_MATCHER(QualType, isBoolean) {
+  return Node->isBooleanType();
+}
+
+}  // namespace ast_matchers
+}  // namespace clang
+
+namespace {
+
+// Returns true if expr needs to be put in parens (eg: when it is an operator
+// syntactically).
+bool NeedsParens(const clang::Expr* expr) {
+  if (llvm::dyn_cast<clang::UnaryOperator>(expr) ||
+      llvm::dyn_cast<clang::BinaryOperator>(expr) ||
+      llvm::dyn_cast<clang::ConditionalOperator>(expr)) {
+    return true;
+  }
+  if (const clang::CXXOperatorCallExpr* op =

[mdempsky, 2014/08/07 22:25:10]

Might be worth adding a comment explaining that this test is checking for
operator overloading, except for foo(...) and foo[...] expressions that don't
need parentheses.

[dcheng, 2014/08/07 23:11:21]

Done.

+          llvm::dyn_cast<clang::CXXOperatorCallExpr>(expr)) {
+    return op->getOperator() != clang::OO_Call &&
+           op->getOperator() != clang::OO_Subscript;
+  }
+  return false;
+}
+
+class GetRewriterCallback : public MatchFinder::MatchCallback {
+ public:
+  explicit GetRewriterCallback(Replacements* replacements)
+      : replacements_(replacements) {}
+  virtual void run(const MatchFinder::MatchResult& result) override;
+
+ private:
+  Replacements* const replacements_;
+};
+
+void GetRewriterCallback::run(const MatchFinder::MatchResult& result) {
+  const clang::CXXMemberCallExpr* const implicit_call =
+      result.Nodes.getNodeAs<clang::CXXMemberCallExpr>("call");
+  const clang::Expr* arg = result.Nodes.getNodeAs<clang::Expr>("arg");
+
+  if (!implicit_call || !arg)
+    return;
+
+  clang::CharSourceRange range = clang::CharSourceRange::getTokenRange(
+      result.SourceManager->getSpellingLoc(arg->getLocStart()),
+      result.SourceManager->getSpellingLoc(arg->getLocEnd()));
+  if (!range.isValid())
+    return;  // TODO(rsleevi): Log an error?
+
+  // Handle cases where an implicit cast is being done by dereferencing a
+  // pointer to a scoped_refptr<> (sadly, it happens...)
+  //
+  // This rewrites both "*foo" and "*(foo)" as "foo->get()".
+  if (const clang::UnaryOperator* op =
+          llvm::dyn_cast<clang::UnaryOperator>(arg)) {
+    if (op->getOpcode() == clang::UO_Deref) {
+      const clang::Expr* const sub_expr =
+          op->getSubExpr()->IgnoreParenImpCasts();
+      clang::CharSourceRange sub_expr_range =
+          clang::CharSourceRange::getTokenRange(
+              result.SourceManager->getSpellingLoc(sub_expr->getLocStart()),
+              result.SourceManager->getSpellingLoc(sub_expr->getLocEnd()));
+      if (!sub_expr_range.isValid())
+        return;  // TODO(rsleevi): Log an error?
+      std::string inner_text = clang::Lexer::getSourceText(
+          sub_expr_range, *result.SourceManager, result.Context->getLangOpts());
+      if (inner_text.empty())
+        return;  // TODO(rsleevi): Log an error?
+
+      if (NeedsParens(sub_expr)) {
+        inner_text.insert(0, "(");
+        inner_text.append(")");
+      }
+      inner_text.append("->get()");
+      replacements_->insert(
+          Replacement(*result.SourceManager, range, inner_text));
+      return;
+    }
+  }
+
+  std::string text = clang::Lexer::getSourceText(
+      range, *result.SourceManager, result.Context->getLangOpts());
+  if (text.empty())
+    return;  // TODO(rsleevi): Log an error?
+
+  // Unwrap any temporaries - for example, custom iterators that return
+  // scoped_refptr<T> as part of operator*. Any such iterators should also
+  // be declaring a scoped_refptr<T>* operator->, per C++03 24.4.1.1 (Table 72)
+  if (const clang::CXXBindTemporaryExpr* op =
+          llvm::dyn_cast<clang::CXXBindTemporaryExpr>(arg)) {
+    arg = op->getSubExpr();
+  }
+
+  // Handle iterators (which are operator* calls, followed by implicit
+  // conversions) by rewriting *it as it->get()
+  if (const clang::CXXOperatorCallExpr* op =
+          llvm::dyn_cast<clang::CXXOperatorCallExpr>(arg)) {
+    if (op->getOperator() == clang::OO_Star) {
+      text.erase(0, 1);
+      text.append("->get()");

[mdempsky, 2014/08/07 22:25:10]

Is it possible we'll NeedParens() here?  E.g., I think "**x" should be rewritten
as "(*x)->get()" instead of "*x->get()", but I don't know if that can actually
happen.

[dcheng, 2014/08/07 23:11:21]

Added a comment per our discussion.

+      replacements_->insert(Replacement(*result.SourceManager, range, text));
+      return;
+    }
+  }
+
+  // The only remaining calls should be non-dereferencing calls (eg: member
+  // calls), so a simple ".get()" appending should suffice.
+  if (NeedsParens(arg)) {
+    text.insert(0, "(");
+    text.append(")");
+  }
+  text.append(".get()");
+  replacements_->insert(Replacement(*result.SourceManager, range, text));
+}
+
+}  // namespace
+
+static llvm::cl::extrahelp common_help(CommonOptionsParser::HelpMessage);
+
+int main(int argc, const char* argv[]) {
+  llvm::cl::OptionCategory category("Remove scoped_refptr conversions");
+  CommonOptionsParser options(argc, argv, category);
+  clang::tooling::ClangTool tool(options.getCompilations(),
+                                 options.getSourcePathList());
+
+  MatchFinder match_finder;
+
+  // Finds all calls to conversion operator member function. This catches calls
+  // to "operator T*", "operator Testable", and "operator bool" equally.
+  StatementMatcher overloaded_call_matcher = memberCallExpr(
+      thisPointerType(recordDecl(isSameOrDerivedFrom("::scoped_refptr"),
+                                 isTemplateInstantiation())),
+      callee(conversionDecl()),
+      on(id("arg", expr())));
+
+  // This catches both user-defined conversions (eg: "operator bool") and
+  // standard conversion sequence (C++03 13.3.3.1.1), such as converting a
+  // pointer to a bool.
+  StatementMatcher implicit_to_bool =
+      implicitCastExpr(hasImplicitDestinationType(isBoolean()));
+
+  // Avoid converting calls to of "operator Testable" -> "bool" and calls of
+  // "operator T*" -> "bool".
+  StatementMatcher bool_conversion_matcher = hasParent(expr(
+      anyOf(expr(implicit_to_bool), expr(hasParent(expr(implicit_to_bool))))));
+
+  // Find all calls to an operator overload that do NOT (ultimately) result in
+  // being cast to a bool - eg: where it's being converted to T* and rewrite
+  // them to add a call to get().
+  //
+  // All bool conversions will be handled with the Testable trick, but that
+  // can only be used once "operator T*" is removed, since otherwise it leaves
+  // the call ambiguous.
+  Replacements get_replacements;
+  GetRewriterCallback get_callback(&get_replacements);
+  match_finder.addMatcher(id("call", expr(overloaded_call_matcher)),
+                          &get_callback);
+
+#if 0
+  // Finds all temporary scoped_refptr<T>'s being assigned to a T*. Note that
+  // this will result in two callbacks--both the above callback to append get()
+  // and this callback will match.
+  match_finder.addMatcher(
+      id("var",
+         varDecl(hasInitializer(ignoringImpCasts(
+                     id("call", expr(overloaded_call_matcher)))),
+                 hasType(pointerType()))),
+      &callback);
+  match_finder.addMatcher(
+      binaryOperator(
+          hasOperatorName("="),
+          hasLHS(declRefExpr(to(id("var", varDecl(hasType(pointerType())))))),
+          hasRHS(ignoringParenImpCasts(
+              id("call", expr(overloaded_call_matcher))))),
+      &callback);
+#endif
+
+  std::unique_ptr<clang::tooling::FrontendActionFactory> factory =
+      clang::tooling::newFrontendActionFactory(&match_finder);
+  int result = tool.run(factory.get());
+  if (result != 0)
+    return result;
+
+  // Serialization format is documented in tools/clang/scripts/run_tool.py
+  llvm::outs() << "==== BEGIN EDITS ====\n";
+  for (const auto& r : get_replacements) {
+    std::string replacement_text = r.getReplacementText().str();
+    std::replace(replacement_text.begin(), replacement_text.end(), '\n', '\0');
+    llvm::outs() << "r:" << r.getFilePath() << ":" << r.getOffset() << ":"
+                 << r.getLength() << ":" << replacement_text << "\n";
+  }
+  llvm::outs() << "==== END EDITS ====\n";
+
+  return 0;
+}