Array initializers can also be compound literals

We previously failed this test, stating that { 1, 2, 3 } was an invalid
array initializer.

Author: tautschnig

regression/cbmc/compound_literal1/main.c

@@ -6,6 +6,8 @@ union U { float f; int i; };
 // global scope, static lifetime
 int *global_scope_literal=&(int){ 43 };
 
+int array[3] = (int[3]){1, 2, 3};
+
 int main()
 {
   assert(*global_scope_literal==43);

src/ansi-c/c_typecheck_initializer.cpp

@@ -38,7 +38,9 @@ void c_typecheck_baset::do_initializer(
                    "any array must have a size");
 
     // we don't allow initialisation with symbols of array type
-    if(result.id() != ID_array && result.id() != ID_array_of)
+    if(
+      result.id() != ID_array && result.id() != ID_array_of &&
+      result.id() != ID_compound_literal)
     {
       error().source_location = result.source_location();
       error() << "invalid array initializer " << to_string(result)