Add quasiquote-to-append rule (#328)

Closes #326.

default-recommendations/list-shortcuts-test.rkt

@@ -139,6 +139,24 @@ test: "unnecessary quasiquotation with constants refactorable to list"
 ------------------------------
 
 
+test: "unnecessary splicing quasiquotation refactorable to append"
+------------------------------
+(define (f xs ys zs)
+  `(,@xs ,@ys ,@zs))
+------------------------------
+------------------------------
+(define (f xs ys zs)
+  (append xs ys zs))
+------------------------------
+
+
+test: "splicing quasiquotation with other subterms not refactorable to append"
+------------------------------
+(define (f xs ys zs)
+  `(a ,@xs b ,@ys c ,@zs d))
+------------------------------
+
+
 test: "ignored map expression refactorable to for-each"
 ------------------------------
 (define (f func xs ys zs)

default-recommendations/list-shortcuts.rkt

@@ -113,11 +113,18 @@
 
 (define-refactoring-rule quasiquote-to-list
   #:description "This quasiquotation is equialent to a simple `list` call."
-  #:literals (quasiquote unquote)
+  #:literals (quasiquote)
   (quasiquote (arg:unquoted ...))
   (list arg.expr ...))
 
 
+(define-refactoring-rule quasiquote-to-append
+  #:description "This quasiquotation is equialent to calling `append`."
+  #:literals (quasiquote unquote-splicing)
+  (quasiquote ((unquote-splicing arg) ...))
+  (append arg ...))
+
+
 (define-definition-context-refactoring-rule ignored-map-to-for-each
   #:description "The result of this `map` expression is unused. Consider using `for-each` instead."
   #:literals (map)
@@ -134,5 +141,6 @@
            filter-to-remv*
            first-reverse-to-last
            ignored-map-to-for-each
+           quasiquote-to-append
            quasiquote-to-list
            sort-with-keyed-comparator-to-sort-by-key))