alien.arrays/classes.struct: ensure specialized array types for struct array slots get instantiated at parse time

basis/alien/arrays/arrays.factor

@@ -35,10 +35,7 @@ M: array box-return drop void* box-return ;
 M: array stack-size drop void* stack-size ;
 
 M: array c-type-boxer-quot
-    unclip
-    [ array-length ]
-    [ [ require-c-array ] keep ] bi*
-    [ <c-direct-array> ] 2curry ;
+    unclip [ array-length ] dip [ <c-direct-array> ] 2curry ;
 
 M: array c-type-unboxer-quot drop [ >c-ptr ] ;
 

basis/classes/struct/struct.factor

@@ -147,6 +147,7 @@ M: struct-class initial-value* <struct> ; inline
 GENERIC: struct-slot-values ( struct -- sequence )
 
 M: struct-class reader-quot
+    dup array? [ dup first define-array-vocab drop ] when
     nip '[ _ read-struct-slot ] ;
 
 M: struct-class writer-quot