Index: clang/lib/AST/Interp/ByteCodeEmitter.cpp
===================================================================
--- clang/lib/AST/Interp/ByteCodeEmitter.cpp
+++ clang/lib/AST/Interp/ByteCodeEmitter.cpp
@@ -73,7 +73,9 @@
   }
 
   assert(Func);
-  if (!HasBody)
+  // For not-yet-defined functions, we only create a Function instance and
+  // compile their body later.
+  if (!FuncDecl->isDefined())
     return Func;
 
   // Compile the function body.
Index: clang/test/AST/Interp/records.cpp
===================================================================
--- clang/test/AST/Interp/records.cpp
+++ clang/test/AST/Interp/records.cpp
@@ -325,3 +325,9 @@
                                        // expected-error {{must be initialized by a constant expression}}
                                        // FIXME: Missing reason for rejection.
 };
+
+namespace EmptyCtor {
+  struct piecewise_construct_t { explicit piecewise_construct_t() = default; };
+  constexpr piecewise_construct_t piecewise_construct =
+    piecewise_construct_t();
+};