[clang-tidy] Exclude delegate constructors in cppcoreguidelines-prefer-member-initializer

[PiotrZSL]

Summary

As proposed by check fix would result in compilation error,
lets exclude delegate constructors from being checked.

Fixes: #52818

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

: ClangTidyCheck(Name, Context),
                           .get("UseAssignment", false))) {}
 
 void PreferMemberInitializerCheck::storeOptions(
     ClangTidyOptions::OptionMap &Opts) {
   Options.store(Opts, "UseAssignment", UseAssignment);
 }
 
 void PreferMemberInitializerCheck::registerMatchers(MatchFinder *Finder) {
-  Finder->addMatcher(
-      cxxConstructorDecl(hasBody(compoundStmt()), unless(isInstantiated()))
+  Finder->addMatcher(cxxConstructorDecl(hasBody(compoundStmt()),
+                                        unless(isInstantiated()),
+                                        unless(isDelegatingConstructor()))
                          .bind("ctor"),
                      this);
 }
 
 void PreferMemberInitializerCheck::check(
     const MatchFinder::MatchResult &Result) {
   const auto *Ctor = Result.Nodes.getNodeAs<CXXConstructorDecl>("ctor");
   const auto *Body = cast<CompoundStmt>(Ctor->getBody());
 
   const CXXRecordDecl *Class = Ctor->getParent();

clang-tools-extra/docs/ReleaseNotes.rst

- Fixed bug in :doc:`bugprone-reserved-identifier
   <clang-tidy/checks/bugprone/reserved-identifier>`, so that it does not warn
   on macros starting with underscore and lowercase letter.
 
 - Improved :doc:`cppcoreguidelines-avoid-non-const-global-variables
   <clang-tidy/checks/cppcoreguidelines/avoid-non-const-global-variables>` check
   to ignore ``static`` variables declared within the scope of
   ``class``/``struct``.
 
+- Improved :doc:`cppcoreguidelines-prefer-member-initializer
+  <clang-tidy/checks/cppcoreguidelines/prefer-member-initializer>` check to
+  exclude delegate constructors from being checked.
+
 - Improved :doc:`llvm-namespace-comment
   <clang-tidy/checks/llvm/namespace-comment>` check to provide fixes for
   ``inline`` namespaces in the same format as :program:`clang-format`.
 
 - Improved :doc:`modernize-loop-convert
   <clang-tidy/checks/modernize/loop-convert>` to support for-loops with
   iterators initialized by free functions like ``begin``, ``end``, or ``size``.
 

clang-tools-extra/test/clang-tidy/checkers/cppcoreguidelines/prefer-member-initializer.cpp

struct MacroCantFix {
   int n; // NoFix
   // CHECK-FIXES: int n; // NoFix
   MacroCantFix() {
     ASSIGN_IN_MACRO(n, 0)
     // CHECK-MESSAGES: :[[@LINE-1]]:21: warning: 'n' should be initialized in a member initializer of the constructor
     // CHECK-FIXES: ASSIGN_IN_MACRO(n, 0)
   }
 };
+
+struct PR52818  {
+    PR52818() : bar(5) {}
+    PR52818(int) : PR52818() { bar = 3; }
+
+    int bar;
+};