Fix Performance/MapCompact autocorrect causing invalid syntax

CHANGELOG.md

@@ -362,3 +362,4 @@
 [@mvz]: https://github.com/mvz
 [@leoarnold]: https://github.com/leoarnold
 [@ydah]: https://github.com/ydah
+[@QQism]: https://github.com/QQism

changelog/fix_performance_mapcompact_autocorrect_causing_invalid_syntax.md

@@ -0,0 +1 @@
+* [#291](https://github.com/rubocop/rubocop-performance/pull/291): Fix `Performance/MapCompact` autocorrect causing invalid syntax when using multiline `map { ... }.compact` as an argument for an assignment method. ([@QQism][])

lib/rubocop/cop/performance/map_compact.rb

@@ -83,7 +83,7 @@ def map_method_and_compact_method_on_same_line?(map_node, compact_node)
         end
 
         def invoke_method_after_map_compact_on_same_line?(compact_node, chained_method)
-          compact_node.loc.selector.line == chained_method.loc.selector.line
+          compact_node.loc.selector.line == chained_method.loc.last_line
         end
 
         def compact_method_with_final_newline_range(compact_method_range)

spec/rubocop/cop/performance/map_compact_spec.rb

@@ -248,6 +248,19 @@
       RUBY
     end
 
+    it 'registers an offense when using multiline `map { ... }.compact` as an argument of an assignment method' do
+      expect_offense(<<~RUBY)
+        object.new_collection = collection.map do |item|
+                                           ^^^^^^^^^^^^^ Use `filter_map` instead.
+        end.compact
+      RUBY
+
+      expect_correction(<<~RUBY)
+        object.new_collection = collection.filter_map do |item|
+        end
+      RUBY
+    end
+
     it 'does not register an offense when using `collection.map(&:do_something).compact!`' do
       expect_no_offenses(<<~RUBY)
         collection.map(&:do_something).compact!