Index: clang/docs/ReleaseNotes.rst
===================================================================
--- clang/docs/ReleaseNotes.rst
+++ clang/docs/ReleaseNotes.rst
@@ -175,6 +175,8 @@
   emitted as a dynamic initializer. Previously the variable would
   incorrectly be zero-initialized. In contexts where a dynamic
   initializer is not allowed this is now diagnosed as an error.
+- Fixed an assertion failure when evaluating a constexpr constructor
+  in an array initializer.
 
 Improvements to Clang's diagnostics
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Index: clang/lib/AST/ExprConstant.cpp
===================================================================
--- clang/lib/AST/ExprConstant.cpp
+++ clang/lib/AST/ExprConstant.cpp
@@ -10754,17 +10754,18 @@
   for (unsigned Index = 0; Index != NumEltsToInit; ++Index) {
     const Expr *Init =
         Index < E->getNumInits() ? E->getInit(Index) : FillerExpr;
-    if (!EvaluateInPlace(Result.getArrayInitializedElt(Index),
-                         Info, Subobject, Init) ||
-        !HandleLValueArrayAdjustment(Info, Init, Subobject,
-                                     CAT->getElementType(), 1)) {
+    if (Result.isArray() &&
+        (!EvaluateInPlace(Result.getArrayInitializedElt(Index), Info, Subobject,
+                          Init) ||
+         !HandleLValueArrayAdjustment(Info, Init, Subobject,
+                                      CAT->getElementType(), 1))) {
       if (!Info.noteFailure())
         return false;
       Success = false;
     }
   }
 
-  if (!Result.hasArrayFiller())
+  if (!Result.isArray() || !Result.hasArrayFiller())
     return Success;
 
   // If we get here, we have a trivial filler, which we can just evaluate
Index: clang/test/SemaCXX/constexpr-array-init.cpp
===================================================================
--- /dev/null
+++ clang/test/SemaCXX/constexpr-array-init.cpp
@@ -0,0 +1,19 @@
+// RUN: %clang_cc1 -std=c++20 -verify %s
+
+// FIXME: This code should compile without errors but as of right now doesn't.
+//   We're only testing that clang doesn't crash or run into an assertion.
+struct Foo {
+  int a; // expected-note {{subobject declared here}}
+  constexpr Foo()
+      : a(get_int()) {
+  }
+
+  constexpr int get_int() {
+    return 5;
+  }
+};
+
+static constexpr Foo bar[2][1] = { // expected-error {{constexpr variable 'bar' must be initialized by a constant expression}} \
+                                   // expected-note {{subobject of type 'int' is not initialized}}
+    {{}},
+};