[clang] Fix false positive of [[clang::require_explicit_initialization]] on copy/move constructors (PR #126553)

[via cfe-commits]

https://github.com/higher-performance created https://github.com/llvm/llvm-project/pull/126553

Fixes #126490

>From 9200ea6649f449b3ecc71d3ee3cd942313d3b86b Mon Sep 17 00:00:00 2001
From: higher-performance <higher.performance.github at gmail.com>
Date: Mon, 10 Feb 2025 12:31:26 -0500
Subject: [PATCH] Fix false positive of
 [[clang::require_explicit_initialization]] on copy/move constructors

Fixes #126490
---
 clang/lib/Sema/SemaInit.cpp          |  4 +++-
 clang/test/SemaCXX/uninitialized.cpp | 16 +++++++++++++++-
 2 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/clang/lib/Sema/SemaInit.cpp b/clang/lib/Sema/SemaInit.cpp
index 308222a79d920c7..18090eb1c9e9ac9 100644
--- a/clang/lib/Sema/SemaInit.cpp
+++ b/clang/lib/Sema/SemaInit.cpp
@@ -4576,7 +4576,9 @@ static void TryConstructorInitialization(Sema &S,
     if (!IsListInit &&
         (Kind.getKind() == InitializationKind::IK_Default ||
          Kind.getKind() == InitializationKind::IK_Direct) &&
-        DestRecordDecl != nullptr && DestRecordDecl->isAggregate() &&
+        DestRecordDecl != nullptr &&
+        !(CtorDecl->isCopyOrMoveConstructor() && CtorDecl->isImplicit()) &&
+        DestRecordDecl->isAggregate() &&
         DestRecordDecl->hasUninitializedExplicitInitFields()) {
       S.Diag(Kind.getLocation(), diag::warn_field_requires_explicit_init)
           << /* Var-in-Record */ 1 << DestRecordDecl;
diff --git a/clang/test/SemaCXX/uninitialized.cpp b/clang/test/SemaCXX/uninitialized.cpp
index 7578b288d7b3fe7..6565bf31e05d72b 100644
--- a/clang/test/SemaCXX/uninitialized.cpp
+++ b/clang/test/SemaCXX/uninitialized.cpp
@@ -1582,7 +1582,21 @@ void aggregate() {
       F("___"),
       F("____")
   };
-  (void)ctors;
+
+  struct Copy {
+    Embed e;
+    EmbedDerived ed;
+    F f;
+    Copy(const Copy &c) : e(c.e), ed(c.ed), f(c.f) {} // no-error
+  };
+  F copy1(ctors[0]); // no-error
+  (void)copy1;
+  F copy2{ctors[0]}; // no-error
+  (void)copy2;
+  F copy3 = ctors[0]; // no-error
+  (void)copy3;
+  F copy4 = {ctors[0]}; // no-error
+  (void)copy4;
 
   S::foo(S{1, 2, 3, 4});
   S::foo(S{.s1 = 100, .s4 = 100});