[clang-tools-extra] [clang-tidy] Take type aliases into account (PR #150842)

[Danny Mösch via cfe-commits]

https://github.com/SimplyDanny updated https://github.com/llvm/llvm-project/pull/150842

>From d209f10977e816769065476ad1d9e517bd224431 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Danny=20M=C3=B6sch?= <danny.moesch at icloud.com>
Date: Sun, 27 Jul 2025 18:47:31 +0200
Subject: [PATCH] [clang-tidy] Add handling of type aliases in
 use-designated-initializers check

---
 .../UseDesignatedInitializersCheck.cpp        | 11 ++++---
 clang-tools-extra/docs/ReleaseNotes.rst       |  4 +++
 .../modernize/use-designated-initializers.cpp | 31 +++++++++++++++++++
 3 files changed, 41 insertions(+), 5 deletions(-)

diff --git a/clang-tools-extra/clang-tidy/modernize/UseDesignatedInitializersCheck.cpp b/clang-tools-extra/clang-tidy/modernize/UseDesignatedInitializersCheck.cpp
index 7ea9676b13ec0..bb8fb2404a9a5 100644
--- a/clang-tools-extra/clang-tidy/modernize/UseDesignatedInitializersCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/UseDesignatedInitializersCheck.cpp
@@ -121,10 +121,11 @@ void UseDesignatedInitializersCheck::registerMatchers(MatchFinder *Finder) {
       hasAnyBase(hasType(cxxRecordDecl(has(fieldDecl()))));
   Finder->addMatcher(
       initListExpr(
-          hasType(cxxRecordDecl(
-                      RestrictToPODTypes ? isPOD() : isAggregate(),
-                      unless(anyOf(HasBaseWithFields, hasName("::std::array"))))
-                      .bind("type")),
+          hasType(hasUnqualifiedDesugaredType(recordType(hasDeclaration(
+              cxxRecordDecl(
+                  RestrictToPODTypes ? isPOD() : isAggregate(),
+                  unless(anyOf(HasBaseWithFields, hasName("::std::array"))))
+                  .bind("type"))))),
           IgnoreSingleElementAggregates ? hasMoreThanOneElement() : anything(),
           unless(isFullyDesignated()))
           .bind("init"),
@@ -155,7 +156,7 @@ void UseDesignatedInitializersCheck::check(
       DiagnosticBuilder Diag =
           diag(InitList->getLBraceLoc(),
                "use designated initializer list to initialize %0");
-      Diag << Type << InitList->getSourceRange();
+      Diag << InitList->getType() << InitList->getSourceRange();
       for (const Stmt *InitExpr : *SyntacticInitList) {
         const auto Designator = Designators[InitExpr->getBeginLoc()];
         if (Designator && !Designator->empty())
diff --git a/clang-tools-extra/docs/ReleaseNotes.rst b/clang-tools-extra/docs/ReleaseNotes.rst
index 3ea1c5104316f..61debd89becaa 100644
--- a/clang-tools-extra/docs/ReleaseNotes.rst
+++ b/clang-tools-extra/docs/ReleaseNotes.rst
@@ -128,6 +128,10 @@ Changes in existing checks
 - Improved :doc:`misc-header-include-cycle
   <clang-tidy/checks/misc/header-include-cycle>` check performance.
 
+- Improved :doc:`modernize-use-designated-initializers
+  <clang-tidy/checks/modernize/use-designated-initializers>` check to
+  suggest using designated initializers for aliased aggregate types.
+
 - Improved :doc:`modernize-use-std-format
   <clang-tidy/checks/modernize/use-std-format>` check to correctly match
   when the format string is converted to a different type by an implicit
diff --git a/clang-tools-extra/test/clang-tidy/checkers/modernize/use-designated-initializers.cpp b/clang-tools-extra/test/clang-tidy/checkers/modernize/use-designated-initializers.cpp
index cdadeed5bd850..2117420bcc14c 100644
--- a/clang-tools-extra/test/clang-tidy/checkers/modernize/use-designated-initializers.cpp
+++ b/clang-tools-extra/test/clang-tidy/checkers/modernize/use-designated-initializers.cpp
@@ -224,3 +224,34 @@ std::array a{1,2,3};
 std::array<int,2> b{10, 11};
 using array = std::array<int, 2>;
 array c{10, 11};
+
+struct S16 {
+    int a;
+    int b;
+};
+
+using S17 = S16;
+
+S17 s171{1, 2};
+// CHECK-MESSAGES: :[[@LINE-1]]:9: warning: use designated initializer list to initialize 'S17' (aka 'S16') [modernize-use-designated-initializers]
+// CHECK-MESSAGES: :[[@LINE-9]]:1: note: aggregate type is defined here
+// CHECK-FIXES: S17 s171{.a=1, .b=2};
+// CHECK-MESSAGES-POD: :[[@LINE-4]]:9: warning: use designated initializer list to initialize 'S17' (aka 'S16') [modernize-use-designated-initializers]
+// CHECK-MESSAGES-POD: :[[@LINE-12]]:1: note: aggregate type is defined here
+// CHECK-FIXES-POD: S17 s171{.a=1, .b=2};
+
+S17 s172{.a=1, 2};
+// CHECK-MESSAGES: :[[@LINE-1]]:16: warning: use designated init expression to initialize field 'b' [modernize-use-designated-initializers]
+// CHECK-MESSAGES-POD: :[[@LINE-2]]:16: warning: use designated init expression to initialize field 'b' [modernize-use-designated-initializers]
+// CHECK-FIXES: S17 s172{.a=1, .b=2};
+
+typedef S16 S18;
+
+S18 s181{1, 2};
+// CHECK-MESSAGES: :[[@LINE-1]]:9: warning: use designated initializer list to initialize 'S18' (aka 'S16') [modernize-use-designated-initializers]
+// CHECK-MESSAGES-POD: :[[@LINE-2]]:9: warning: use designated initializer list to initialize 'S18' (aka 'S16') [modernize-use-designated-initializers]
+
+S18 s182{1, .b=2};
+// CHECK-MESSAGES: :[[@LINE-1]]:10: warning: use designated init expression to initialize field 'a' [modernize-use-designated-initializers]
+// CHECK-MESSAGES-POD: :[[@LINE-2]]:10: warning: use designated init expression to initialize field 'a' [modernize-use-designated-initializers]
+// CHECK-FIXES: S18 s182{.a=1, .b=2};