Better invalid callable check

basis/prettyprint/backend/backend.factor

@@ -217,14 +217,24 @@ M: vector pprint* pprint-object ;
 M: byte-vector pprint* pprint-object ;
 M: hashtable pprint* pprint-object ;
 
+GENERIC: valid-callable? ( obj -- ? )
+
+M: object valid-callable? drop f ;
+
+M: quotation valid-callable? drop t ;
+
+M: curry valid-callable? quot>> valid-callable? ;
+
+M: compose valid-callable?
+    [ first>> ] [ second>> ] bi [ valid-callable? ] both? ;
+
 M: curry pprint*
-    dup quot>> callable? [ pprint-object ] [
+    dup valid-callable? [ pprint-object ] [
         "( invalid curry )" swap present-text
     ] if ;
 
 M: compose pprint*
-    dup [ first>> callable? ] [ second>> callable? ] bi and
-    [ pprint-object ] [
+    dup valid-callable? [ pprint-object ] [
         "( invalid compose )" swap present-text
     ] if ;
 

basis/prettyprint/prettyprint-tests.factor

@@ -365,3 +365,8 @@ M: started-out-hustlin' ended-up-ballin' ; inline
 [ "USING: prettyprint.tests ;\nM: started-out-hustlin' ended-up-ballin' ; inline\n" ] [
     [ { started-out-hustlin' ended-up-ballin' } see ] with-string-writer
 ] unit-test
+
+[ "( invalid curry )" ] [ 1 2 curry unparse ] unit-test
+[ "( invalid curry )" ] [ 1 2 3 curry curry unparse ] unit-test
+[ "( invalid compose )" ] [ 1 2 compose unparse ] unit-test
+[ "( invalid compose )" ] [ [ 1 ] 2 3 curry compose unparse ] unit-test