[clang-tidy]: Added modernize-replace-disallow-copy-and-assign-macro

Summary:
This check finds macro expansions of `DISALLOW_COPY_AND_ASSIGN(Type)` and
replaces them with a deleted copy constructor and a deleted assignment operator.

Before the `delete` keyword was introduced in C++11 it was common practice to
declare a copy constructor and an assignment operator as a private members. This
effectively makes them unusable to the public API of a class.

With the advent of the `delete` keyword in C++11 we can abandon the
`private` access of the copy constructor and the assignment operator and
delete the methods entirely.

Migration example:

```
lang=dif
class Foo {
  private:
  -  DISALLOW_COPY_AND_ASSIGN(Foo);
  +  Foo(const Foo &) = delete;
  +  const Foo &operator=(const Foo &) = delete;
  };
```

Reviewers: alexfh, hokein, aaron.ballman, njames93

Reviewed By: njames93

Subscribers: Eugene.Zelenko, mgorny, xazax.hun, cfe-commits

Tags: #clang, #clang-tools-extra

Differential Revision: https://reviews.llvm.org/D80531

1 files changed, 90 insertions, 0 deletions

diff --git a/clang-tools-extra/clang-tidy/modernize/ReplaceDisallowCopyAndAssignMacroCheck.cpp b/clang-tools-extra/clang-tidy/modernize/ReplaceDisallowCopyAndAssignMacroCheck.cpp
new file mode 100644
index 0000000..2219a3c
--- /dev/null
+++ b/clang-tools-extra/clang-tidy/modernize/ReplaceDisallowCopyAndAssignMacroCheck.cpp
@@ -0,0 +1,90 @@
+//===--- ReplaceDisallowCopyAndAssignMacroCheck.cpp - clang-tidy ----------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "ReplaceDisallowCopyAndAssignMacroCheck.h"
+#include "clang/Frontend/CompilerInstance.h"
+#include "clang/Lex/MacroArgs.h"
+#include "llvm/Support/FormatVariadic.h"
+
+namespace clang {
+namespace tidy {
+namespace modernize {
+
+namespace {
+
+class ReplaceDisallowCopyAndAssignMacroCallbacks : public PPCallbacks {
+public:
+  explicit ReplaceDisallowCopyAndAssignMacroCallbacks(
+      ReplaceDisallowCopyAndAssignMacroCheck &Check, Preprocessor &PP)
+      : Check(Check), PP(PP) {}
+
+  void MacroExpands(const Token &MacroNameTok, const MacroDefinition &MD,
+                    SourceRange Range, const MacroArgs *Args) override {
+    IdentifierInfo *Info = MacroNameTok.getIdentifierInfo();
+    if (!Info || !Args || Args->getNumMacroArguments() != 1)
+      return;
+    if (Info->getName() != Check.getMacroName())
+      return;
+    // The first argument to the DISALLOW_COPY_AND_ASSIGN macro is exptected to
+    // be the class name.
+    const Token *ClassNameTok = Args->getUnexpArgument(0);
+    if (Args->ArgNeedsPreexpansion(ClassNameTok, PP))
+      // For now we only support simple argument that don't need to be
+      // pre-expanded.
+      return;
+    clang::IdentifierInfo *ClassIdent = ClassNameTok->getIdentifierInfo();
+    if (!ClassIdent)
+      return;
+
+    std::string Replacement = llvm::formatv(
+        R"cpp({0}(const {0} &) = delete;
+const {0} &operator=(const {0} &) = delete{1})cpp",
+        ClassIdent->getName(), shouldAppendSemi(Range) ? ";" : "");
+
+    Check.diag(MacroNameTok.getLocation(),
+               "prefer deleting copy constructor and assignment operator over "
+               "using macro '%0'")
+        << Check.getMacroName()
+        << FixItHint::CreateReplacement(
+               PP.getSourceManager().getExpansionRange(Range), Replacement);
+  }
+
+private:
+  /// \returns \c true if the next token after the given \p MacroLoc is \b not a
+  /// semicolon.
+  bool shouldAppendSemi(SourceRange MacroLoc) {
+    llvm::Optional<Token> Next = Lexer::findNextToken(
+        MacroLoc.getEnd(), PP.getSourceManager(), PP.getLangOpts());
+    return !(Next && Next->is(tok::semi));
+  }
+
+  ReplaceDisallowCopyAndAssignMacroCheck &Check;
+  Preprocessor &PP;
+};
+} // namespace
+
+ReplaceDisallowCopyAndAssignMacroCheck::ReplaceDisallowCopyAndAssignMacroCheck(
+    StringRef Name, ClangTidyContext *Context)
+    : ClangTidyCheck(Name, Context),
+      MacroName(Options.get("MacroName", "DISALLOW_COPY_AND_ASSIGN")) {}
+
+void ReplaceDisallowCopyAndAssignMacroCheck::registerPPCallbacks(
+    const SourceManager &SM, Preprocessor *PP, Preprocessor *ModuleExpanderPP) {
+  PP->addPPCallbacks(
+      ::std::make_unique<ReplaceDisallowCopyAndAssignMacroCallbacks>(
+          *this, *ModuleExpanderPP));
+}
+
+void ReplaceDisallowCopyAndAssignMacroCheck::storeOptions(
+    ClangTidyOptions::OptionMap &Opts) {
+  Options.store(Opts, "MacroName", MacroName);
+}
+
+} // namespace modernize
+} // namespace tidy
+} // namespace clang