Add ignored-map-to-for-each

Closes #223.

default-recommendations/list-shortcuts-test.rkt

@@ -137,3 +137,20 @@ test: "unnecessary quasiquotation with constants refactorable to list"
 (define (f x y z)
   (list x 1 y 2 z 3))
 ------------------------------
+
+
+test: "ignored map expression refactorable to for-each"
+------------------------------
+(define (f func xs ys zs)
+  ; comment before
+  (map func xs ys zs)
+  ; comment after
+  (displayln "foo"))
+------------------------------
+------------------------------
+(define (f func xs ys zs)
+  ; comment before
+  (for-each func xs ys zs)
+  ; comment after
+  (displayln "foo"))
+------------------------------

default-recommendations/list-shortcuts.rkt

@@ -16,6 +16,7 @@
          resyntax/default-recommendations/private/lambda-by-any-name
          resyntax/default-recommendations/private/literal-constant
          resyntax/default-recommendations/private/syntax-identifier-sets
+         resyntax/private/syntax-neighbors
          resyntax/refactoring-rule
          resyntax/refactoring-suite
          syntax/parse)
@@ -120,6 +121,13 @@
    (list arg.expr ...)])
 
 
+(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)
+  [(~seq body-before ... (~and map-expr (map proc list ...)) body-after ...)
+   (body-before ... (~replacement (for-each proc list ...) #:original map-expr) body-after ...)])
+
+
 (define list-shortcuts
   (refactoring-suite
    #:name (name list-shortcuts)
@@ -131,5 +139,6 @@
          filter-to-remq*
          filter-to-remv*
          first-reverse-to-last
+         ignored-map-to-for-each
          quasiquote-to-list
          sort-with-keyed-comparator-to-sort-by-key)))