[clang-tidy] Add alias cppcoreguidelines-use-default-member-init

[carlosgalvezp]

Summary

And remove identical functionality from
cppcoreguidelines-prefer-member-initializer, which had too many
responsibilities and a tight coupling to the
modernize-use-default-member-init check.

Fixes https://github.com/llvm/llvm-project/issues/62164.

[carlosgalvezp]

Revert code removal, document deprecation notice instead.

[carlosgalvezp]

Rebase and fix conflicts.

[carlosgalvezp]

Add check to list of aliases.

[carlosgalvezp]

Remove check from list of checks, since we do not add
aliases there.

[PiotrZSL]

LGTM

[Eugene.Zelenko]

Please create issue for deprecation after commit.

clang-tools-extra/clang-tidy/cppcoreguidelines/CppCoreGuidelinesTidyModule.cpp

 //===-- CppCoreGuidelinesTidyModule.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 "../ClangTidy.h"
 #include "../ClangTidyModule.h"
 #include "../ClangTidyModuleRegistry.h"
 #include "../misc/NonPrivateMemberVariablesInClassesCheck.h"
 #include "../misc/UnconventionalAssignOperatorCheck.h"
 #include "../modernize/AvoidCArraysCheck.h"
+#include "../modernize/UseDefaultMemberInitCheck.h"
 #include "../modernize/UseOverrideCheck.h"
 #include "../readability/MagicNumbersCheck.h"
 #include "AvoidCapturingLambdaCoroutinesCheck.h"
 #include "AvoidConstOrRefDataMembersCheck.h"
 #include "AvoidDoWhileCheck.h"
 #include "AvoidGotoCheck.h"
 #include "AvoidNonConstGlobalVariablesCheck.h"
 #include "AvoidReferenceCoroutineParametersCheck.h"
CheckFactories.registerCheck<ProTypeUnionAccessCheck>(
         "cppcoreguidelines-pro-type-union-access");
     CheckFactories.registerCheck<ProTypeVarargCheck>(
         "cppcoreguidelines-pro-type-vararg");
     CheckFactories.registerCheck<RvalueReferenceParamNotMovedCheck>(
         "cppcoreguidelines-rvalue-reference-param-not-moved");
     CheckFactories.registerCheck<SpecialMemberFunctionsCheck>(
         "cppcoreguidelines-special-member-functions");
     CheckFactories.registerCheck<SlicingCheck>("cppcoreguidelines-slicing");
+    CheckFactories.registerCheck<modernize::UseDefaultMemberInitCheck>(
+        "cppcoreguidelines-use-default-member-init");
     CheckFactories.registerCheck<misc::UnconventionalAssignOperatorCheck>(
         "cppcoreguidelines-c-copy-assignment-signature");
     CheckFactories.registerCheck<VirtualClassDestructorCheck>(
         "cppcoreguidelines-virtual-class-destructor");
   }
 
   ClangTidyOptions getModuleOptions() override {
     ClangTidyOptions Options;

clang-tools-extra/clang-tidy/cppcoreguidelines/PreferMemberInitializerCheck.cpp

if (const auto *CondOp = dyn_cast<ConditionalOperator>(S)) {
           isNoReturnCallStatement(CondOp->getRHS()))
         return;
     }
 
     const FieldDecl *Field;
     const Expr *InitValue;
     std::tie(Field, InitValue) = isAssignmentToMemberOf(Class, S, Ctor);
     if (Field) {
-      if (IsUseDefaultMemberInitEnabled && getLangOpts().CPlusPlus11 &&
-          Ctor->isDefaultConstructor() &&
-          (getLangOpts().CPlusPlus20 || !Field->isBitField()) &&
-          !Field->hasInClassInitializer() &&
-          (!isa<RecordDecl>(Class->getDeclContext()) ||
-           !cast<RecordDecl>(Class->getDeclContext())->isUnion()) &&
-          shouldBeDefaultMemberInitializer(InitValue)) {
-
-        bool InvalidFix = false;
-        SourceLocation FieldEnd =
-            Lexer::getLocForEndOfToken(Field->getSourceRange().getEnd(), 0,
-                                       *Result.SourceManager, getLangOpts());
-        InvalidFix |= FieldEnd.isInvalid() || FieldEnd.isMacroID();
-        SourceLocation SemiColonEnd;
-        if (auto NextToken = Lexer::findNextToken(
-                S->getEndLoc(), *Result.SourceManager, getLangOpts()))
-          SemiColonEnd = NextToken->getEndLoc();
-        else
-          InvalidFix = true;
-        auto Diag =
-            diag(S->getBeginLoc(), "%0 should be initialized in an in-class"
-                                   " default member initializer")
-            << Field;
-        if (InvalidFix)
-          continue;
-        CharSourceRange StmtRange =
-            CharSourceRange::getCharRange(S->getBeginLoc(), SemiColonEnd);
-
-        SmallString<128> Insertion(
-            {UseAssignment ? " = " : "{",
-             Lexer::getSourceText(
-                 CharSourceRange(InitValue->getSourceRange(), true),
-                 *Result.SourceManager, getLangOpts()),
-             UseAssignment ? "" : "}"});
-
-        Diag << FixItHint::CreateInsertion(FieldEnd, Insertion)
-             << FixItHint::CreateRemoval(StmtRange);
-
-      } else {
-        StringRef InsertPrefix = "";
-        bool HasInitAlready = false;
-        SourceLocation InsertPos;
-        SourceRange ReplaceRange;
-        bool AddComma = false;
-        bool InvalidFix = false;
-        unsigned Index = Field->getFieldIndex();
-        const CXXCtorInitializer *LastInListInit = nullptr;
-        for (const CXXCtorInitializer *Init : Ctor->inits()) {
-          if (!Init->isWritten() || Init->isInClassMemberInitializer())
-            continue;
-          if (Init->getMember() == Field) {
-            HasInitAlready = true;
-            if (isa<ImplicitValueInitExpr>(Init->getInit()))
-              InsertPos = Init->getRParenLoc();
-            else {
-              ReplaceRange = Init->getInit()->getSourceRange();
-            }
-            break;
-          }
-          if (Init->isMemberInitializer() &&
-              Index < Init->getMember()->getFieldIndex()) {
-            InsertPos = Init->getSourceLocation();
-            // There are initializers after the one we are inserting, so add a
-            // comma after this insertion in order to not break anything.
-            AddComma = true;
-            break;
-          }
-          LastInListInit = Init;
-        }
-        if (HasInitAlready) {
-          if (InsertPos.isValid())
-            InvalidFix |= InsertPos.isMacroID();
-          else
-            InvalidFix |= ReplaceRange.getBegin().isMacroID() ||
-                          ReplaceRange.getEnd().isMacroID();
-        } else {
-          if (InsertPos.isInvalid()) {
-            if (LastInListInit) {
-              InsertPos = Lexer::getLocForEndOfToken(
-                  LastInListInit->getRParenLoc(), 0, *Result.SourceManager,
-                  getLangOpts());
-              // Inserting after the last constructor initializer, so we need a
-              // comma.
-              InsertPrefix = ", ";
-            } else {
-              InsertPos = Lexer::getLocForEndOfToken(
-                  Ctor->getTypeSourceInfo()
-                      ->getTypeLoc()
-                      .getAs<clang::FunctionTypeLoc>()
-                      .getLocalRangeEnd(),
-                  0, *Result.SourceManager, getLangOpts());
 
-              // If this is first time in the loop, there are no initializers so
-              // `:` declares member initialization list. If this is a
-              // subsequent pass then we have already inserted a `:` so continue
-              // with a comma.
-              InsertPrefix = FirstToCtorInits ? " : " : ", ";
-            }
-          }
-          InvalidFix |= InsertPos.isMacroID();
-        }
 
-        SourceLocation SemiColonEnd;
-        if (auto NextToken = Lexer::findNextToken(
-                S->getEndLoc(), *Result.SourceManager, getLangOpts()))
-          SemiColonEnd = NextToken->getEndLoc();
-        else
-          InvalidFix = true;
 
-        auto Diag =
-            diag(S->getBeginLoc(), "%0 should be initialized in a member"
+      auto Diag = diag(S->getBeginLoc(), "%0 should be initialized in a member"
                                          " initializer of the constructor")
                   << Field;
-        if (InvalidFix)
-          continue;
-        StringRef NewInit = Lexer::getSourceText(
-            CharSourceRange(InitValue->getSourceRange(), true),
-            *Result.SourceManager, getLangOpts());
-        if (HasInitAlready) {
-          if (InsertPos.isValid())
-            Diag << FixItHint::CreateInsertion(InsertPos, NewInit);
-          else
-            Diag << FixItHint::CreateReplacement(ReplaceRange, NewInit);
-        } else {
-          SmallString<128> Insertion({InsertPrefix, Field->getName(), "(",
-                                      NewInit, AddComma ? "), " : ")"});
-          Diag << FixItHint::CreateInsertion(InsertPos, Insertion,
-                                             FirstToCtorInits);
-          FirstToCtorInits = areDiagsSelfContained();
-        }
-        Diag << FixItHint::CreateRemoval(
-            CharSourceRange::getCharRange(S->getBeginLoc(), SemiColonEnd));
-      }
-    }
-  }
-}
 
 } // namespace clang::tidy::cppcoreguidelines

clang-tools-extra/docs/ReleaseNotes.rst

 - New alias :doc:`cert-msc24-c
   <clang-tidy/checks/cert/msc24-c>` to :doc:`bugprone-unsafe-functions
   <clang-tidy/checks/bugprone/unsafe-functions>` was added.
 
 - New alias :doc:`cert-msc33-c
   <clang-tidy/checks/cert/msc33-c>` to :doc:`bugprone-unsafe-functions
   <clang-tidy/checks/bugprone/unsafe-functions>` was added.
 
+- New alias :doc:`cppcoreguidelines-use-default-member-init
+  <clang-tidy/checks/cppcoreguidelines/use-default-member-init>` to
+  :doc:`modernize-use-default-member-init
+  <clang-tidy/checks/modernize/use-default-member-init>` was added.
+
 Changes in existing checks
 ^^^^^^^^^^^^^^^^^^^^^^^^^^
 - Improved :doc:`readability-redundant-string-cstr
   <clang-tidy/checks/readability/redundant-string-cstr>` check to recognise
   unnecessary ``std::string::c_str()`` and ``std::string::data()`` calls in
   arguments to ``std::print``, ``std::format`` or other functions listed in
   the ``StringParameterFunction`` check option.
 

 
 - Improved :doc:`bugprone-use-after-move
   <clang-tidy/checks/bugprone/use-after-move>` check to also cover constructor
   initializers.
 
 - Deprecated :doc:`cert-dcl21-cpp
   <clang-tidy/checks/cert/dcl21-cpp>` check.
 
+- Move C.48 enforcement from :doc:`cppcoreguidelines-prefer-member-initializer
+  <clang-tidy/checks/cppcoreguidelines/prefer-member-initializer>` to
+  :doc:`cppcoreguidelines-use-default-member-init
+  <clang-tidy/checks/cppcoreguidelines/use-default-member-init>`.
+
 - Deprecated check-local options `HeaderFileExtensions`
   in :doc:`google-build-namespaces
   <clang-tidy/checks/google/build-namespaces>` check.
   Global options of the same name should be used instead.
 
 - Deprecated check-local options `HeaderFileExtensions`
   in :doc:`google-global-names-in-headers
   <clang-tidy/checks/google/global-names-in-headers>` check.

clang-tools-extra/docs/clang-tidy/checks/cppcoreguidelines/prefer-member-initializer.rst

 .. title:: clang-tidy - cppcoreguidelines-prefer-member-initializer
 
 cppcoreguidelines-prefer-member-initializer
 ===========================================
 
 Finds member initializations in the constructor body which can be  converted
 into member initializers of the constructor instead. This not only improves
 the readability of the code but also positively affects its performance.
 Class-member assignments inside a control statement or following the first
 control statement are ignored.
 
 This check implements `C.49 <https://github.com/isocpp/CppCoreGuidelines/blob/master/CppCoreGuidelines.md#c49-prefer-initialization-to-assignment-in-constructors>`_ from the CppCoreGuidelines.
 
-If the language version is `C++ 11` or above, the constructor is the default
-constructor of the class, the field is not a bitfield (only in case of earlier
-language version than `C++ 20`), furthermore the assigned value is a literal,
-negated literal or ``enum`` constant then the preferred place of the
-initialization is at the class member declaration.
-
-This latter rule is `C.48 <https://github.com/isocpp/CppCoreGuidelines/blob/master/CppCoreGuidelines.md#c48-prefer-in-class-initializers-to-member-initializers-in-constructors-for-constant-initializers>`_ from CppCoreGuidelines.
-
-Please note, that this check does not enforce this latter rule for
-initializations already implemented as member initializers. For that purpose
-see check `modernize-use-default-member-init <../modernize/use-default-member-init.html>`_.
-
 Example 1
 ---------
 
 .. code-block:: c++
 
   class C {
     int n;
     int m;
   public:
     C() {
       n = 1; // Literal in default constructor
       if (dice())
         return;
       m = 1;
     }
   };
 
-Here ``n`` can be initialized using a default member initializer, unlike
+Here ``n`` can be initialized in the member initializer list, unlike
 ``m``, as ``m``'s initialization follows a control statement (``if``):
 
 .. code-block:: c++
 
   class C {
-    int n{1};
+    int n;
     int m;
   public:
-    C() {
+    C(): n(1) {
       if (dice())
         return;
       m = 1;
     }
 
 Example 2
 ---------
 

 
 .. code-block:: c++
 
   C(int nn, int mm) : n(nn) {
     if (dice())
       return;
     m = mm;
   }
-
-.. option:: UseAssignment
-
-   If this option is set to `true` (default is `false`), the check will initialize
-   members with an assignment. In this case the fix of the first example looks
-   like this:
-
-.. code-block:: c++
-
-  class C {
-    int n = 1;
-    int m;
-  public:
-    C() {
-      if (dice())
-        return;
-      m = 1;
-    }
-  };

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

+.. title:: clang-tidy - cppcoreguidelines-use-default-member-init
+.. meta::
+   :http-equiv=refresh: 5;URL=../modernize/use-default-member-init.html
+
+cppcoreguidelines-use-default-member-init
+=========================================
+
+This check implements `C.48 <https://github.com/isocpp/CppCoreGuidelines/blob/master/CppCoreGuidelines.md#c48-prefer-in-class-initializers-to-member-initializers-in-constructors-for-constant-initializers>`_ from the CppCoreGuidelines.
+
+The cppcoreguidelines-use-default-member-init check is an alias, please see
+`modernize-use-default-member-init <../modernize/use-default-member-init.html>`_
+for more information.

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

.. csv-table::
    `cppcoreguidelines-pro-type-member-init <cppcoreguidelines/pro-type-member-init.html>`_, "Yes"
    `cppcoreguidelines-pro-type-reinterpret-cast <cppcoreguidelines/pro-type-reinterpret-cast.html>`_,
    `cppcoreguidelines-pro-type-static-cast-downcast <cppcoreguidelines/pro-type-static-cast-downcast.html>`_, "Yes"
    `cppcoreguidelines-pro-type-union-access <cppcoreguidelines/pro-type-union-access.html>`_,
    `cppcoreguidelines-pro-type-vararg <cppcoreguidelines/pro-type-vararg.html>`_,
    `cppcoreguidelines-rvalue-reference-param-not-moved <cppcoreguidelines/rvalue-reference-param-not-moved.html>`_,
    `cppcoreguidelines-slicing <cppcoreguidelines/slicing.html>`_,
    `cppcoreguidelines-special-member-functions <cppcoreguidelines/special-member-functions.html>`_,
+   `cppcoreguidelines-use-default-member-init <cppcoreguidelines/use-default-member-init.html>`_, "Yes"
    `cppcoreguidelines-virtual-class-destructor <cppcoreguidelines/virtual-class-destructor.html>`_, "Yes"
    `darwin-avoid-spinlock <darwin/avoid-spinlock.html>`_,
    `darwin-dispatch-once-nonstatic <darwin/dispatch-once-nonstatic.html>`_, "Yes"
    `fuchsia-default-arguments-calls <fuchsia/default-arguments-calls.html>`_,
    `fuchsia-default-arguments-declarations <fuchsia/default-arguments-declarations.html>`_, "Yes"
    `fuchsia-multiple-inheritance <fuchsia/multiple-inheritance.html>`_,
    `fuchsia-overloaded-operator <fuchsia/overloaded-operator.html>`_,
    `fuchsia-statically-constructed-objects <fuchsia/statically-constructed-objects.html>`_,

clang-tools-extra/test/clang-tidy/checkers/cppcoreguidelines/prefer-member-initializer-modernize-use-default-member-init-assignment.cpp

-// RUN: %check_clang_tidy %s cppcoreguidelines-prefer-member-initializer,modernize-use-default-member-init %t -- \
-// RUN: -config="{CheckOptions: [{key: modernize-use-default-member-init.UseAssignment, value: true}]}"
-
-class Simple1 {
-  int n;
-  // CHECK-FIXES: int n = 0;
-  double x;
-  // CHECK-FIXES: double x = 0.0;
-
-public:
-  Simple1() {
-    n = 0;
-    // CHECK-MESSAGES: :[[@LINE-1]]:5: warning: 'n' should be initialized in an in-class default member initializer [cppcoreguidelines-prefer-member-initializer]
-    // CHECK-FIXES: {{^\ *$}}
-    x = 0.0;
-    // CHECK-MESSAGES: :[[@LINE-1]]:5: warning: 'x' should be initialized in an in-class default member initializer [cppcoreguidelines-prefer-member-initializer]
-    // CHECK-FIXES: {{^\ *$}}
-  }
-
-  Simple1(int nn, double xx) {
-    // CHECK-FIXES: Simple1(int nn, double xx) : n(nn), x(xx) {
-    n = nn;
-    // CHECK-MESSAGES: :[[@LINE-1]]:5: warning: 'n' should be initialized in a member initializer of the constructor [cppcoreguidelines-prefer-member-initializer]
-    // CHECK-FIXES: {{^\ *$}}
-    x = xx;
-    // CHECK-MESSAGES: :[[@LINE-1]]:5: warning: 'x' should be initialized in a member initializer of the constructor [cppcoreguidelines-prefer-member-initializer]
-    // CHECK-FIXES: {{^\ *$}}
-  }
-
-  ~Simple1() = default;
-};

clang-tools-extra/test/clang-tidy/checkers/cppcoreguidelines/prefer-member-initializer-modernize-use-default-member-init.cpp

-// RUN: %check_clang_tidy %s cppcoreguidelines-prefer-member-initializer,modernize-use-default-member-init %t
-
-class Simple1 {
-  int n;
-  // CHECK-FIXES: int n{0};
-  double x;
-  // CHECK-FIXES: double x{0.0};
-
-public:
-  Simple1() {
-    n = 0;
-    // CHECK-MESSAGES: :[[@LINE-1]]:5: warning: 'n' should be initialized in an in-class default member initializer [cppcoreguidelines-prefer-member-initializer]
-    // CHECK-FIXES: {{^\ *$}}
-    x = 0.0;
-    // CHECK-MESSAGES: :[[@LINE-1]]:5: warning: 'x' should be initialized in an in-class default member initializer [cppcoreguidelines-prefer-member-initializer]
-    // CHECK-FIXES: {{^\ *$}}
-  }
-
-  Simple1(int nn, double xx) {
-    // CHECK-FIXES: Simple1(int nn, double xx) : n(nn), x(xx) {
-    n = nn;
-    // CHECK-MESSAGES: :[[@LINE-1]]:5: warning: 'n' should be initialized in a member initializer of the constructor [cppcoreguidelines-prefer-member-initializer]
-    // CHECK-FIXES: {{^\ *$}}
-    x = xx;
-    // CHECK-MESSAGES: :[[@LINE-1]]:5: warning: 'x' should be initialized in a member initializer of the constructor [cppcoreguidelines-prefer-member-initializer]
-    // CHECK-FIXES: {{^\ *$}}
-  }
-
-  ~Simple1() = default;
-};