[Fix #11783] Fix a false positive for Style/RedundantLineContinuation

Fixes #11783.

This PR fixes a false positive for `Style/RedundantLineContinuation`
using line concatenation for assigning a return value and without argument parentheses.

changelog/fix_false_positive_for_style_redundant_line_continuation.md

@@ -0,0 +1 @@
+* [#11783](https://github.com/rubocop/rubocop/issues/11783): Fix a false positive for `Style/RedundantLineContinuation` using line concatenation for assigning a return value and without argument parentheses. ([@koic][])

lib/rubocop/cop/style/redundant_line_continuation.rb

@@ -90,7 +90,7 @@ def require_line_continuation?(range)
           !ends_with_backslash_without_comment?(range.source_line) ||
             string_concatenation?(range.source_line) ||
             start_with_arithmetic_operator?(processed_source[range.line]) ||
-            inside_string_literal?(range)
+            inside_string_literal_or_method_with_argument?(range)
         end
 
         def ends_with_backslash_without_comment?(source_line)
@@ -101,9 +101,9 @@ def string_concatenation?(source_line)
           /["']\s*\\\z/.match?(source_line)
         end
 
-        def inside_string_literal?(range)
-          processed_source.tokens.each.any? do |token|
-            ALLOWED_STRING_TOKENS.include?(token.type) && token.pos.overlaps?(range)
+        def inside_string_literal_or_method_with_argument?(range)
+          processed_source.tokens.each_cons(2).any? do |token, next_token|
+            inside_string_literal?(range, token) || method_with_argument?(token, next_token)
           end
         end
 
@@ -115,6 +115,18 @@ def redundant_line_continuation?(range)
           parse(source.gsub(/\\\n/, "\n")).valid_syntax?
         end
 
+        def inside_string_literal?(range, token)
+          ALLOWED_STRING_TOKENS.include?(token.type) && token.pos.overlaps?(range)
+        end
+
+        # A method call without parentheses such as the following cannot remove `\`:
+        #
+        #   do_something \
+        #     argument
+        def method_with_argument?(current_token, next_token)
+          current_token.type == :tIDENTIFIER && next_token.type == :tIDENTIFIER
+        end
+
         def argument_newline?(node)
           node = node.children.first if node.root? && node.begin_type?
 

spec/rubocop/cop/style/redundant_line_continuation_spec.rb

@@ -134,6 +134,19 @@ def self.foo(bar,#{trailing_whitespace}
     RUBY
   end
 
+  it 'registers an offense and corrects when using redundant line concatenation for assigning a return value and with argument parentheses' do
+    expect_offense(<<~'RUBY')
+      foo = do_something( \
+                          ^ Redundant line continuation.
+        argument)
+    RUBY
+
+    expect_correction(<<~RUBY)
+      foo = do_something(#{trailing_whitespace}
+        argument)
+    RUBY
+  end
+
   it 'does not register an offense when line continuations for double quoted string' do
     expect_no_offenses(<<~'RUBY')
       foo = "foo \
@@ -178,6 +191,13 @@ def self.foo(bar,#{trailing_whitespace}
     RUBY
   end
 
+  it 'does not register an offense when using line concatenation for assigning a return value and without argument parentheses' do
+    expect_no_offenses(<<~'RUBY')
+      foo = do_something \
+        argument
+    RUBY
+  end
+
   it 'does not register an offense when line continuations with arithmetic operator' do
     expect_no_offenses(<<~'RUBY')
       1 \