[clang] Try to fix https://github.com/llvm/llvm-project/issues/41441 (PR #96464)

[via cfe-commits]

https://github.com/awson created https://github.com/llvm/llvm-project/pull/96464

The [last attempt](https://github.com/llvm/llvm-project/pull/89036) to fix https://github.com/llvm/llvm-project/issues/41441 has been reverted immediately.

Here I'm trying the simplest idea I've been able to come with:  skip handling dependent case in `BuildCXXNew`.

The original test (borrowed form https://github.com/llvm/llvm-project/pull/89036) passes.

Also I've created and added to the tests a minimal repro of the code https://github.com/llvm/llvm-project/pull/89036 fails on. This (obviously) also passes.

>From ad15dc4983e4d153b4eb19aa72b35c0a5ad919c0 Mon Sep 17 00:00:00 2001
From: awson <kyrab at mail.ru>
Date: Mon, 24 Jun 2024 10:34:51 +0300
Subject: [PATCH 1/2] Don't handle ArraySize/AllocType early.

---
 clang/lib/Sema/SemaExprCXX.cpp | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/clang/lib/Sema/SemaExprCXX.cpp b/clang/lib/Sema/SemaExprCXX.cpp
index f3af8dee6b090..2f79540faea00 100644
--- a/clang/lib/Sema/SemaExprCXX.cpp
+++ b/clang/lib/Sema/SemaExprCXX.cpp
@@ -2174,7 +2174,8 @@ ExprResult Sema::BuildCXXNew(SourceRange Range, bool UseGlobal,
 
   // Per C++0x [expr.new]p5, the type being constructed may be a
   // typedef of an array type.
-  if (!ArraySize) {
+  // Dependent case will be handled separately.
+  if (!ArraySize && !AllocType->isDependentType()) {
     if (const ConstantArrayType *Array
                               = Context.getAsConstantArrayType(AllocType)) {
       ArraySize = IntegerLiteral::Create(Context, Array->getSize(),

>From a6fd197eab12a579c68ab1190f1bf6d144114ba9 Mon Sep 17 00:00:00 2001
From: awson <kyrab at mail.ru>
Date: Mon, 24 Jun 2024 11:07:58 +0300
Subject: [PATCH 2/2] Tests for GH41441

I've borrowed size-calculation test from PR89036 and added another test, which PR89036 fails on.
---
 clang/test/SemaCXX/GH41441.cpp | 46 ++++++++++++++++++++++++++++++++++
 1 file changed, 46 insertions(+)
 create mode 100644 clang/test/SemaCXX/GH41441.cpp

diff --git a/clang/test/SemaCXX/GH41441.cpp b/clang/test/SemaCXX/GH41441.cpp
new file mode 100644
index 0000000000000..7a6260fef91b5
--- /dev/null
+++ b/clang/test/SemaCXX/GH41441.cpp
@@ -0,0 +1,46 @@
+// RUN: %clang --target=x86_64-pc-linux -S -fno-discard-value-names -emit-llvm -o - %s | FileCheck %s
+// RUN: %clang_cc1 %s -fsyntax-only -verify
+
+namespace std {
+  using size_t = decltype(sizeof(int));
+};
+void* operator new[](std::size_t, void*) noexcept;
+
+// CHECK: call void @llvm.memset.p0.i64(ptr align 1 %x, i8 0, i64 8, i1 false)
+// CHECK: call void @llvm.memset.p0.i64(ptr align 16 %x, i8 0, i64 32, i1 false)
+template <typename TYPE>
+void f()
+{
+    typedef TYPE TArray[8];
+
+    TArray x;
+    new(&x) TArray();
+}
+
+template <typename T>
+void f1() {
+  int (*x)[1] = new int[1][1];
+}
+template void f1<char>();
+void f2() {
+  int (*x)[1] = new int[1][1];
+}
+
+int main()
+{
+    f<char>();
+    f<int>();
+}
+
+// expected-no-diagnostics
+template <typename T> struct unique_ptr {unique_ptr(T* p){}};
+
+template <typename T>
+unique_ptr<T> make_unique(unsigned long long n) {
+  return unique_ptr<T>(new T[n]());
+}
+
+auto boro(int n){
+	typedef double HistoryBuffer[4];
+	return make_unique<HistoryBuffer>(n);
+}