[clang-tidy] Add check 'readability-redundant-member-init'

Summary: The check emits a warning if a member-initializer calls the member's default constructor with no arguments.

Reviewers: sbenza, alexfh, aaron.ballman

Subscribers: modocache, mgorny, Eugene.Zelenko, etienneb, Prazek, hokein, cfe-commits, beanz

Differential Revision: https://reviews.llvm.org/D24339

llvm-svn: 284742

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

@@ -16,6 +16,7 @@ add_clang_library(clangTidyReadabilityModule
   NonConstParameterCheck.cpp
   ReadabilityTidyModule.cpp
   RedundantControlFlowCheck.cpp
+  RedundantMemberInitCheck.cpp
   RedundantStringCStrCheck.cpp
   RedundantSmartptrGetCheck.cpp
   RedundantStringInitCheck.cpp

clang-tools-extra/clang-tidy/readability/ReadabilityTidyModule.cpp

@@ -23,6 +23,7 @@
 #include "NamedParameterCheck.h"
 #include "NonConstParameterCheck.h"
 #include "RedundantControlFlowCheck.h"
+#include "RedundantMemberInitCheck.h"
 #include "RedundantSmartptrGetCheck.h"
 #include "RedundantStringCStrCheck.h"
 #include "RedundantStringInitCheck.h"
@@ -57,6 +58,8 @@ public:
         "readability-inconsistent-declaration-parameter-name");
     CheckFactories.registerCheck<MisplacedArrayIndexCheck>(
         "readability-misplaced-array-index");
+    CheckFactories.registerCheck<RedundantMemberInitCheck>(
+        "readability-redundant-member-init");
     CheckFactories.registerCheck<StaticDefinitionInAnonymousNamespaceCheck>(
         "readability-static-definition-in-anonymous-namespace");
     CheckFactories.registerCheck<readability::NamedParameterCheck>(

clang-tools-extra/clang-tidy/readability/RedundantMemberInitCheck.cpp

@@ -0,0 +1,65 @@
+//===--- RedundantMemberInitCheck.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 "RedundantMemberInitCheck.h"
+#include "clang/AST/ASTContext.h"
+#include "clang/ASTMatchers/ASTMatchFinder.h"
+#include "clang/Lex/Lexer.h"
+#include "../utils/Matchers.h"
+#include <algorithm>
+
+using namespace clang::ast_matchers;
+using namespace clang::tidy::matchers;
+
+namespace clang {
+namespace tidy {
+namespace readability {
+
+void RedundantMemberInitCheck::registerMatchers(MatchFinder *Finder) {
+  auto Construct =
+      cxxConstructExpr(
+          hasDeclaration(cxxConstructorDecl(hasParent(
+              cxxRecordDecl(unless(isTriviallyDefaultConstructible()))))))
+          .bind("construct");
+
+  Finder->addMatcher(
+      cxxConstructorDecl(
+          unless(isDelegatingConstructor()),
+          ofClass(unless(
+              anyOf(isUnion(), ast_matchers::isTemplateInstantiation()))),
+          forEachConstructorInitializer(
+              cxxCtorInitializer(isWritten(),
+                                 withInitializer(ignoringImplicit(Construct)),
+                                 unless(forField(hasType(isConstQualified()))))
+                  .bind("init"))),
+      this);
+}
+
+void RedundantMemberInitCheck::check(const MatchFinder::MatchResult &Result) {
+  const auto *Init = Result.Nodes.getNodeAs<CXXCtorInitializer>("init");
+  const auto *Construct = Result.Nodes.getNodeAs<CXXConstructExpr>("construct");
+
+  if (Construct->getNumArgs() == 0 ||
+      Construct->getArg(0)->isDefaultArgument()) {
+    if (Init->isAnyMemberInitializer()) {
+      diag(Init->getSourceLocation(), "initializer for member %0 is redundant")
+          << Init->getMember()
+          << FixItHint::CreateRemoval(Init->getSourceRange());
+    } else {
+      diag(Init->getSourceLocation(),
+           "initializer for base class %0 is redundant")
+          << Init->getTypeSourceInfo()->getType()
+          << FixItHint::CreateRemoval(Init->getSourceRange());
+    }
+  }
+}
+
+} // namespace readability
+} // namespace tidy
+} // namespace clang

clang-tools-extra/clang-tidy/readability/RedundantMemberInitCheck.h

@@ -0,0 +1,36 @@
+//===--- RedundantMemberInitCheck.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_READABILITY_REDUNDANT_MEMBER_INIT_H
+#define LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_READABILITY_REDUNDANT_MEMBER_INIT_H
+
+#include "../ClangTidy.h"
+
+namespace clang {
+namespace tidy {
+namespace readability {
+
+/// Finds member initializations that are unnecessary because the same default
+/// constructor would be called if they were not present.
+///
+/// For the user-facing documentation see:
+/// http://clang.llvm.org/extra/clang-tidy/checks/readability-redundant-member-init.html
+class RedundantMemberInitCheck : public ClangTidyCheck {
+public:
+  RedundantMemberInitCheck(StringRef Name, ClangTidyContext *Context)
+      : ClangTidyCheck(Name, Context) {}
+  void registerMatchers(ast_matchers::MatchFinder *Finder) override;
+  void check(const ast_matchers::MatchFinder::MatchResult &Result) override;
+};
+
+} // namespace readability
+} // namespace tidy
+} // namespace clang
+
+#endif // LLVM_CLANG_TOOLS_EXTRA_CLANG_TIDY_READABILITY_REDUNDANT_MEMBER_INIT_H

clang-tools-extra/docs/ReleaseNotes.rst

@@ -111,6 +111,12 @@ Improvements to clang-tidy
   Flags function parameters of a pointer type that could be changed to point to
   a constant type instead.
 
+- New `readability-redundant-member-init
+  <http://clang.llvm.org/extra/clang-tidy/checks/readability-redundant-member-init.html>`_ check
+
+  Flags member initializations that are unnecessary because the same default
+  constructor would be called if they were not present.
+
 Fixed bugs:
 
 - `modernize-make-unique

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

@@ -134,6 +134,7 @@ Clang-Tidy Checks
    readability-named-parameter
    readability-non-const-parameter
    readability-redundant-control-flow
+   readability-redundant-member-init
    readability-redundant-smartptr-get
    readability-redundant-string-cstr
    readability-redundant-string-init

clang-tools-extra/docs/clang-tidy/checks/readability-redundant-member-init.rst

@@ -0,0 +1,20 @@
+.. title:: clang-tidy - readability-redundant-member-init
+
+readability-redundant-member-init
+=================================
+
+Finds member initializations that are unnecessary because the same default
+constructor would be called if they were not present.
+
+Example:
+
+.. code-block:: c++
+
+  // Explicitly initializing the member s is unnecessary.
+  class Foo {
+  public:
+    Foo() : s() {}
+
+  private:
+    std::string s;
+  };

clang-tools-extra/test/clang-tidy/readability-redundant-member-init.cpp

@@ -0,0 +1,181 @@
+// RUN: %check_clang_tidy %s readability-redundant-member-init %t
+
+struct S {
+  S() = default;
+  S(int i) : i(i) {}
+  int i = 1;
+};
+
+struct T {
+  T(int i = 1) : i(i) {}
+  int i;
+};
+
+struct U {
+  int i;
+};
+
+union V {
+  int i;
+  double f;
+};
+
+// Initializer calls default constructor
+struct F1 {
+  F1() : f() {}
+  // CHECK-MESSAGES: :[[@LINE-1]]:10: warning: initializer for member 'f' is redundant
+  // CHECK-FIXES: F1()  {}
+  S f;
+};
+
+// Initializer calls default constructor with default argument
+struct F2 {
+  F2() : f() {}
+  // CHECK-MESSAGES: :[[@LINE-1]]:10: warning: initializer for member 'f' is redundant
+  // CHECK-FIXES: F2()  {}
+  T f;
+};
+
+// Multiple redundant initializers for same constructor
+struct F3 {
+  F3() : f(), g(1), h() {}
+  // CHECK-MESSAGES: :[[@LINE-1]]:10: warning: initializer for member 'f' is redundant
+  // CHECK-MESSAGES: :[[@LINE-2]]:21: warning: initializer for member 'h' is redundant
+  // CHECK-FIXES: F3() :  g(1) {}
+  S f, g, h;
+};
+
+// Templated class independent type
+template <class V>
+struct F4 {
+  F4() : f() {}
+  // CHECK-MESSAGES: :[[@LINE-1]]:10: warning: initializer for member 'f' is redundant
+  // CHECK-FIXES: F4()  {}
+  S f;
+};
+F4<int> f4i;
+F4<S> f4s;
+
+// Base class
+struct F5 : S {
+  F5() : S() {}
+  // CHECK-MESSAGES: :[[@LINE-1]]:10: warning: initializer for base class 'S' is redundant
+  // CHECK-FIXES: F5()  {}
+};
+
+// Constructor call requires cleanup
+struct Cleanup {
+  ~Cleanup() {}
+};
+
+struct UsesCleanup {
+  UsesCleanup(const Cleanup &c = Cleanup()) {}
+};
+
+struct F6 {
+  F6() : uc() {}
+  // CHECK-MESSAGES: :[[@LINE-1]]:10: warning: initializer for member 'uc' is redundant
+  // CHECK-FIXES: F6()  {}
+  UsesCleanup uc;
+};
+
+// Multiple inheritance
+struct F7 : S, T {
+  F7() : S(), T() {}
+  // CHECK-MESSAGES: :[[@LINE-1]]:10: warning: initializer for base class 'S' is redundant
+  // CHECK-MESSAGES: :[[@LINE-2]]:15: warning: initializer for base class 'T' is redundant
+  // CHECK-FIXES: F7()  {}
+};
+
+// Initializer not written
+struct NF1 {
+  NF1() {}
+  S f;
+};
+
+// Initializer doesn't call default constructor
+struct NF2 {
+  NF2() : f(1) {}
+  S f;
+};
+
+// Initializer calls default constructor without using default argument
+struct NF3 {
+  NF3() : f(1) {}
+  T f;
+};
+
+// Initializer calls default constructor without using default argument
+struct NF4 {
+  NF4() : f(2) {}
+  T f;
+};
+
+// Initializer is zero-initialization
+struct NF5 {
+  NF5() : i() {}
+  int i;
+};
+
+// Initializer is direct-initialization
+struct NF6 {
+  NF6() : i(1) {}
+  int i;
+};
+
+// Initializer is aggregate initialization of struct
+struct NF7 {
+  NF7() : f{} {}
+  U f;
+};
+
+// Initializer is zero-initialization of struct
+struct NF7b {
+  NF7b() : f() {}
+  U f;
+};
+
+// Initializer is aggregate initialization of array
+struct NF8 {
+  NF8() : f{} {}
+  int f[2];
+};
+
+struct NF9 {
+  NF9() : f{} {}
+  S f[2];
+};
+
+// Initializing member of union
+union NF10 {
+  NF10() : s() {}
+  int i;
+  S s;
+};
+
+// Templated class dependent type
+template <class V>
+struct NF11 {
+  NF11() : f() {}
+  V f;
+};
+NF11<int> nf11i;
+NF11<S> nf11s;
+
+// Delegating constructor
+class NF12 {
+  NF12() = default;
+  NF12(int) : NF12() {}
+};
+
+// Const member
+struct NF13 {
+  NF13() : f() {}
+  const S f;
+};
+
+// Union member
+struct NF14 {
+  NF14() : f() {}
+  V f;
+};