Introduce CollectionForEach Refaster rule (#390)

Fixes #387.

error-prone-contrib/src/main/java/tech/picnic/errorprone/refasterrules/CollectionRules.java

@@ -17,6 +17,7 @@
 import java.util.Queue;
 import java.util.Set;
 import java.util.SortedSet;
+import java.util.function.Consumer;
 import java.util.function.IntFunction;
 import java.util.stream.Stream;
 import tech.picnic.errorprone.refaster.annotation.OnlineDocumentation;
@@ -404,6 +405,19 @@ Optional<T> after(Queue<T> queue) {
     }
   }
 
+  /** Prefer {@link Collection#forEach(Consumer)} over more contrived alternatives. */
+  static final class CollectionForEach<T> {
+    @BeforeTemplate
+    void before(Collection<T> collection, Consumer<? super T> consumer) {
+      collection.stream().forEach(consumer);
+    }
+
+    @AfterTemplate
+    void after(Collection<T> collection, Consumer<? super T> consumer) {
+      collection.forEach(consumer);
+    }
+  }
+
   // XXX: collection.stream().noneMatch(e -> e.equals(other))
   // ^ This is !collection.contains(other). Do we already rewrite variations on this?
 }

error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/CollectionRulesTestInput.java

@@ -186,4 +186,8 @@ ImmutableSet<Optional<String>> testRemoveOptionalFirstQueueElement() {
             ? Optional.ofNullable(new LinkedList<String>().remove())
             : Optional.empty());
   }
+
+  void testCollectionForEach() {
+    ImmutableSet.of(1).stream().forEach(String::valueOf);
+  }
 }

error-prone-contrib/src/test/resources/tech/picnic/errorprone/refasterrules/CollectionRulesTestOutput.java

@@ -136,4 +136,8 @@ ImmutableSet<Optional<String>> testRemoveOptionalFirstQueueElement() {
         Optional.ofNullable(new LinkedList<String>().poll()),
         Optional.ofNullable(new LinkedList<String>().poll()));
   }
+
+  void testCollectionForEach() {
+    ImmutableSet.of(1).forEach(String::valueOf);
+  }
 }