[clang-tidy] Add modernize-use-default-member-init check

Summary: Fixes PR18858

Reviewers: alexfh, hokein, aaron.ballman

Subscribers: JDevlieghere, Eugene.Zelenko, Prazek, mgorny, cfe-commits, modocache

Differential Revision: https://reviews.llvm.org/D26750

llvm-svn: 290202

clang-tools-extra/clang-tidy/modernize/CMakeLists.txt

@@ -16,6 +16,7 @@ add_clang_library(clangTidyModernizeModule
   ShrinkToFitCheck.cpp
   UseAutoCheck.cpp
   UseBoolLiteralsCheck.cpp
+  UseDefaultMemberInitCheck.cpp
   UseEmplaceCheck.cpp
   UseEqualsDefaultCheck.cpp
   UseEqualsDeleteCheck.cpp

clang-tools-extra/clang-tidy/modernize/ModernizeTidyModule.cpp

@@ -22,6 +22,7 @@
 #include "ShrinkToFitCheck.h"
 #include "UseAutoCheck.h"
 #include "UseBoolLiteralsCheck.h"
+#include "UseDefaultMemberInitCheck.h"
 #include "UseEmplaceCheck.h"
 #include "UseEqualsDefaultCheck.h"
 #include "UseEqualsDeleteCheck.h"
@@ -56,6 +57,8 @@ class ModernizeModule : public ClangTidyModule {
     CheckFactories.registerCheck<UseAutoCheck>("modernize-use-auto");
     CheckFactories.registerCheck<UseBoolLiteralsCheck>(
         "modernize-use-bool-literals");
+    CheckFactories.registerCheck<UseDefaultMemberInitCheck>(
+        "modernize-use-default-member-init");
     CheckFactories.registerCheck<UseEmplaceCheck>("modernize-use-emplace");
     CheckFactories.registerCheck<UseEqualsDefaultCheck>("modernize-use-equals-default");
     CheckFactories.registerCheck<UseEqualsDeleteCheck>(

clang-tools-extra/clang-tidy/modernize/UseDefaultMemberInitCheck.cpp

@@ -0,0 +1,241 @@
+//===--- UseDefaultMemberInitCheck.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 "UseDefaultMemberInitCheck.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/Lex/Lexer.h"
+
+using namespace clang::ast_matchers;
+
+namespace clang {
+namespace tidy {
+namespace modernize {
+
+static StringRef getValueOfValueInit(const QualType InitType) {
+  switch (InitType->getScalarTypeKind()) {
+  case Type::STK_CPointer:
+  case Type::STK_BlockPointer:
+  case Type::STK_ObjCObjectPointer:
+  case Type::STK_MemberPointer:
+    return "nullptr";
+
+  case Type::STK_Bool:
+    return "false";
+
+  case Type::STK_Integral:
+    switch (InitType->getAs<BuiltinType>()->getKind()) {
+    case BuiltinType::Char_U:
+    case BuiltinType::UChar:
+    case BuiltinType::Char_S:
+    case BuiltinType::SChar:
+      return "'\\0'";
+    case BuiltinType::WChar_U:
+    case BuiltinType::WChar_S:
+      return "L'\\0'";
+    case BuiltinType::Char16:
+      return "u'\\0'";
+    case BuiltinType::Char32:
+      return "U'\\0'";
+    default:
+      return "0";
+    }
+
+  case Type::STK_Floating:
+    switch (InitType->getAs<BuiltinType>()->getKind()) {
+    case BuiltinType::Half:
+    case BuiltinType::Float:
+      return "0.0f";
+    default:
+      return "0.0";
+    }
+
+  case Type::STK_FloatingComplex:
+  case Type::STK_IntegralComplex:
+    return getValueOfValueInit(
+        InitType->getAs<ComplexType>()->getElementType());
+  }
+  llvm_unreachable("Invalid scalar type kind");
+}
+
+static bool isZero(const Expr *E) {
+  switch (E->getStmtClass()) {
+  case Stmt::CXXNullPtrLiteralExprClass:
+  case Stmt::ImplicitValueInitExprClass:
+    return true;
+  case Stmt::InitListExprClass:
+    return cast<InitListExpr>(E)->getNumInits() == 0;
+  case Stmt::CharacterLiteralClass:
+    return !cast<CharacterLiteral>(E)->getValue();
+  case Stmt::CXXBoolLiteralExprClass:
+    return !cast<CXXBoolLiteralExpr>(E)->getValue();
+  case Stmt::IntegerLiteralClass:
+    return !cast<IntegerLiteral>(E)->getValue();
+  case Stmt::FloatingLiteralClass: {
+    llvm::APFloat Value = cast<FloatingLiteral>(E)->getValue();
+    return Value.isZero() && !Value.isNegative();
+  }
+  default:
+    return false;
+  }
+}
+
+static const Expr *ignoreUnaryPlus(const Expr *E) {
+  auto *UnaryOp = dyn_cast<UnaryOperator>(E);
+  if (UnaryOp && UnaryOp->getOpcode() == UO_Plus)
+    return UnaryOp->getSubExpr();
+  return E;
+}
+
+static const Expr *getInitializer(const Expr *E) {
+  auto *InitList = dyn_cast<InitListExpr>(E);
+  if (InitList && InitList->getNumInits() == 1)
+    return InitList->getInit(0);
+  return E;
+}
+
+static bool sameValue(const Expr *E1, const Expr *E2) {
+  E1 = ignoreUnaryPlus(getInitializer(E1->IgnoreParenImpCasts()));
+  E2 = ignoreUnaryPlus(getInitializer(E2->IgnoreParenImpCasts()));
+
+  if (isZero(E1) && isZero(E2))
+    return true;
+
+  if (E1->getStmtClass() != E2->getStmtClass())
+    return false;
+
+  switch (E1->getStmtClass()) {
+  case Stmt::UnaryOperatorClass:
+    return sameValue(cast<UnaryOperator>(E1)->getSubExpr(),
+                     cast<UnaryOperator>(E2)->getSubExpr());
+  case Stmt::CharacterLiteralClass:
+    return cast<CharacterLiteral>(E1)->getValue() ==
+           cast<CharacterLiteral>(E2)->getValue();
+  case Stmt::CXXBoolLiteralExprClass:
+    return cast<CXXBoolLiteralExpr>(E1)->getValue() ==
+           cast<CXXBoolLiteralExpr>(E2)->getValue();
+  case Stmt::IntegerLiteralClass:
+    return cast<IntegerLiteral>(E1)->getValue() ==
+           cast<IntegerLiteral>(E2)->getValue();
+  case Stmt::FloatingLiteralClass:
+    return cast<FloatingLiteral>(E1)->getValue().bitwiseIsEqual(
+        cast<FloatingLiteral>(E2)->getValue());
+  case Stmt::StringLiteralClass:
+    return cast<StringLiteral>(E1)->getString() ==
+           cast<StringLiteral>(E2)->getString();
+  case Stmt::DeclRefExprClass:
+    return cast<DeclRefExpr>(E1)->getDecl() == cast<DeclRefExpr>(E2)->getDecl();
+  default:
+    return false;
+  }
+}
+
+UseDefaultMemberInitCheck::UseDefaultMemberInitCheck(StringRef Name,
+                                                     ClangTidyContext *Context)
+    : ClangTidyCheck(Name, Context),
+      UseAssignment(Options.get("UseAssignment", 0) != 0) {}
+
+void UseDefaultMemberInitCheck::storeOptions(
+    ClangTidyOptions::OptionMap &Opts) {
+  Options.store(Opts, "UseAssignment", UseAssignment);
+}
+
+AST_MATCHER(FieldDecl, hasInClassInitializer) {
+  return Node.hasInClassInitializer();
+}
+
+void UseDefaultMemberInitCheck::registerMatchers(MatchFinder *Finder) {
+  if (!getLangOpts().CPlusPlus11)
+    return;
+
+  auto Init =
+      anyOf(stringLiteral(), characterLiteral(), integerLiteral(),
+            unaryOperator(anyOf(hasOperatorName("+"), hasOperatorName("-")),
+                          hasUnaryOperand(integerLiteral())),
+            floatLiteral(),
+            unaryOperator(anyOf(hasOperatorName("+"), hasOperatorName("-")),
+                          hasUnaryOperand(floatLiteral())),
+            cxxBoolLiteral(), cxxNullPtrLiteralExpr(), implicitValueInitExpr(),
+            declRefExpr());
+
+  Finder->addMatcher(
+      cxxConstructorDecl(
+          isDefaultConstructor(), unless(isInstantiated()),
+          forEachConstructorInitializer(allOf(
+              forField(unless(anyOf(isBitField(), hasInClassInitializer()))),
+              cxxCtorInitializer(isWritten(),
+                                 withInitializer(ignoringImplicit(Init)))
+                  .bind("default")))),
+      this);
+
+  Finder->addMatcher(
+      cxxConstructorDecl(
+          unless(ast_matchers::isTemplateInstantiation()),
+          forEachConstructorInitializer(
+              allOf(forField(hasInClassInitializer()),
+                    cxxCtorInitializer(isWritten(),
+                                       withInitializer(ignoringImplicit(Init)))
+                        .bind("existing")))),
+      this);
+}
+
+void UseDefaultMemberInitCheck::check(const MatchFinder::MatchResult &Result) {
+  if (const auto *Default =
+          Result.Nodes.getNodeAs<CXXCtorInitializer>("default"))
+    checkDefaultInit(Result, Default);
+  else if (const auto *Existing =
+               Result.Nodes.getNodeAs<CXXCtorInitializer>("existing"))
+    checkExistingInit(Result, Existing);
+  else
+    llvm_unreachable("Bad Callback. No node provided.");
+}
+
+void UseDefaultMemberInitCheck::checkDefaultInit(
+    const MatchFinder::MatchResult &Result, const CXXCtorInitializer *Init) {
+  const FieldDecl *Field = Init->getMember();
+
+  SourceLocation FieldEnd =
+      Lexer::getLocForEndOfToken(Field->getSourceRange().getEnd(), 0,
+                                 *Result.SourceManager, getLangOpts());
+  SourceLocation LParenEnd = Lexer::getLocForEndOfToken(
+      Init->getLParenLoc(), 0, *Result.SourceManager, getLangOpts());
+  CharSourceRange InitRange =
+      CharSourceRange::getCharRange(LParenEnd, Init->getRParenLoc());
+
+  auto Diag =
+      diag(Field->getLocation(), "use default member initializer for %0")
+      << Field
+      << FixItHint::CreateInsertion(FieldEnd, UseAssignment ? " = " : "{")
+      << FixItHint::CreateInsertionFromRange(FieldEnd, InitRange);
+
+  if (UseAssignment && isa<ImplicitValueInitExpr>(Init->getInit()))
+    Diag << FixItHint::CreateInsertion(
+        FieldEnd, getValueOfValueInit(Init->getInit()->getType()));
+
+  if (!UseAssignment)
+    Diag << FixItHint::CreateInsertion(FieldEnd, "}");
+
+  Diag << FixItHint::CreateRemoval(Init->getSourceRange());
+}
+
+void UseDefaultMemberInitCheck::checkExistingInit(
+    const MatchFinder::MatchResult &Result, const CXXCtorInitializer *Init) {
+  const FieldDecl *Field = Init->getMember();
+
+  if (!sameValue(Field->getInClassInitializer(), Init->getInit()))
+    return;
+
+  diag(Init->getSourceLocation(), "member initializer for %0 is redundant")
+      << Field
+      << FixItHint::CreateRemoval(Init->getSourceRange());
+}
+
+} // namespace modernize
+} // namespace tidy
+} // namespace clang

clang-tools-extra/clang-tidy/modernize/UseDefaultMemberInitCheck.h

@@ -0,0 +1,45 @@
+//===--- UseDefaultMemberInitCheck.h - clang-tidy----------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MODERNIZE_USE_DEFAULT_MEMBER_INIT_H
+#define LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MODERNIZE_USE_DEFAULT_MEMBER_INIT_H
+
+#include "../ClangTidy.h"
+
+namespace clang {
+namespace tidy {
+namespace modernize {
+
+/// Convert a default constructor's member initializers into default member
+/// initializers.  Remove member initializers that are the same as a default
+/// member initializer.
+///
+/// For the user-facing documentation see:
+/// http://clang.llvm.org/extra/clang-tidy/checks/modernize-use-default-member-init.html
+class UseDefaultMemberInitCheck : public ClangTidyCheck {
+public:
+  UseDefaultMemberInitCheck(StringRef Name, ClangTidyContext *Context);
+  void storeOptions(ClangTidyOptions::OptionMap &Opts) override;
+  void registerMatchers(ast_matchers::MatchFinder *Finder) override;
+  void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
+
+private:
+  void checkDefaultInit(const ast_matchers::MatchFinder::MatchResult &Result,
+                        const CXXCtorInitializer *Init);
+  void checkExistingInit(const ast_matchers::MatchFinder::MatchResult &Result,
+                         const CXXCtorInitializer *Init);
+
+  const bool UseAssignment;
+};
+
+} // namespace modernize
+} // namespace tidy
+} // namespace clang
+
+#endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_MODERNIZE_USE_DEFAULT_MEMBER_INIT_H

clang-tools-extra/docs/ReleaseNotes.rst

@@ -108,6 +108,12 @@ Improvements to clang-tidy
 
 - The modernize-use-default check has been renamed to `modernize-use-equals-default
   <http://clang.llvm.org/extra/clang-tidy/checks/modernize-use-equals-default.html>`_.
+
+- New `modernize-use-default-member-init
+  <http://clang.llvm.org/extra/clang-tidy/checks/modernize-use-default-member-init.html>`_ check
+
+  Converts a default constructor's member initializers into default member initializers.
+  Removes member initializers that are the same as a default member initializer.
 
 - New `modernize-use-equals-delete
   <http://clang.llvm.org/extra/clang-tidy/checks/modernize-use-equals-delete.html>`_ check

clang-tools-extra/docs/clang-tidy/checks/list.rst

@@ -110,6 +110,7 @@ Clang-Tidy Checks
    modernize-shrink-to-fit
    modernize-use-auto
    modernize-use-bool-literals
+   modernize-use-default-member-init
    modernize-use-emplace
    modernize-use-equals-default
    modernize-use-equals-delete

clang-tools-extra/docs/clang-tidy/checks/modernize-use-default-member-init.rst

@@ -0,0 +1,49 @@
+.. title:: clang-tidy - modernize-use-default-member-init
+
+modernize-use-default-member-init
+=================================
+
+This check converts a default constructor's member initializers into the new
+default member initializers in C++11. Other member initializers that match the
+default member initializer are removed. This can reduce repeated code or allow
+use of '= default'.
+
+.. code-block:: c++
+
+  struct A {
+    A() : i(5), j(10.0) {}
+    A(int i) : i(i), j(10.0) {}
+    int i;
+    double j;
+  };
+
+  // becomes
+
+  struct A {
+    A() {}
+    A(int i) : i(i) {}
+    int i{5};
+    double j{10.0};
+  };
+
+.. note::
+  Only converts member initializers for built-in types, enums, and pointers.
+  The `readability-redundant-member-init` check will remove redundant member
+  initializers for classes.
+
+Options
+-------
+
+.. option:: UseAssignment
+
+   If this option is set to non-zero (default is `0`), the check will initialise
+   members with an assignment. For example:
+
+.. code-block:: c++
+
+  struct A {
+    A() {}
+    A(int i) : i(i) {}
+    int i = 5;
+    double j = 10.0;
+  };