Index: clang/include/clang/AST/ExprCXX.h
===================================================================
--- clang/include/clang/AST/ExprCXX.h
+++ clang/include/clang/AST/ExprCXX.h
@@ -2261,15 +2261,32 @@
 
   bool isArray() const { return CXXNewExprBits.IsArray; }
 
+  /// This might return None even if isArray() returns true,
+  /// since there might not be an array size expression.
+  /// If the result is not-None, it will never wrap a nullptr.
   Optional<Expr *> getArraySize() {
     if (!isArray())
       return None;
-    return cast_or_null<Expr>(getTrailingObjects<Stmt *>()[arraySizeOffset()]);
+
+    if (auto *Result =
+            cast_or_null<Expr>(getTrailingObjects<Stmt *>()[arraySizeOffset()]))
+      return Result;
+
+    return None;
   }
+
+  /// This might return None even if isArray() returns true,
+  /// since there might not be an array size expression.
+  /// If the result is not-None, it will never wrap a nullptr.
   Optional<const Expr *> getArraySize() const {
     if (!isArray())
       return None;
-    return cast_or_null<Expr>(getTrailingObjects<Stmt *>()[arraySizeOffset()]);
+
+    if (auto *Result =
+            cast_or_null<Expr>(getTrailingObjects<Stmt *>()[arraySizeOffset()]))
+      return Result;
+
+    return None;
   }
 
   unsigned getNumPlacementArgs() const {
Index: clang/lib/AST/ExprConstant.cpp
===================================================================
--- clang/lib/AST/ExprConstant.cpp
+++ clang/lib/AST/ExprConstant.cpp
@@ -9427,7 +9427,7 @@
   bool ValueInit = false;
 
   QualType AllocType = E->getAllocatedType();
-  if (Optional<const Expr*> ArraySize = E->getArraySize()) {
+  if (Optional<const Expr *> ArraySize = E->getArraySize()) {
     const Expr *Stripped = *ArraySize;
     for (; auto *ICE = dyn_cast<ImplicitCastExpr>(Stripped);
          Stripped = ICE->getSubExpr())
Index: clang/lib/AST/StmtPrinter.cpp
===================================================================
--- clang/lib/AST/StmtPrinter.cpp
+++ clang/lib/AST/StmtPrinter.cpp
@@ -2132,10 +2132,10 @@
   if (E->isParenTypeId())
     OS << "(";
   std::string TypeS;
-  if (Optional<Expr *> Size = E->getArraySize()) {
+  if (E->isArray()) {
     llvm::raw_string_ostream s(TypeS);
     s << '[';
-    if (*Size)
+    if (Optional<Expr *> Size = E->getArraySize())
       (*Size)->printPretty(s, Helper, Policy);
     s << ']';
   }
Index: clang/lib/Sema/TreeTransform.h
===================================================================
--- clang/lib/Sema/TreeTransform.h
+++ clang/lib/Sema/TreeTransform.h
@@ -11918,9 +11918,9 @@
 
   // Transform the size of the array we're allocating (if any).
   Optional<Expr *> ArraySize;
-  if (Optional<Expr *> OldArraySize = E->getArraySize()) {
+  if (E->isArray()) {
     ExprResult NewArraySize;
-    if (*OldArraySize) {
+    if (Optional<Expr *> OldArraySize = E->getArraySize()) {
       NewArraySize = getDerived().TransformExpr(*OldArraySize);
       if (NewArraySize.isInvalid())
         return ExprError();
Index: clang/test/AST/issue53742.cpp
===================================================================
--- /dev/null
+++ clang/test/AST/issue53742.cpp
@@ -0,0 +1,14 @@
+// RUN: %clang_cc1 -fsyntax-only %s -verify
+
+struct Data {
+  char *a;
+  char *b;
+  bool *c;
+};
+
+int main() {
+  Data in;
+  in.a = new char[](); // expected-error {{cannot determine allocated array size from initializer}}
+  in.c = new bool[100]();
+  in.b = new char[100]();
+}