[Fix rubocop#6550] Prevent Layout/RescueEnsureAlignment from breaking…

… on assigned begin-end

We were missing some test cases for this cop, and accidentally introduced a
regression in rubocop#6437.

This change adds a relevant test case and fixes the issue.

CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## master (unreleased)
 
+### Bug fixes
+
+* [#6550](https://github.com/rubocop-hq/rubocop/issues/6550): Prevent Layout/RescueEnsureAlignment cop from breaking on assigned begin-end. ([@drenmi][])
+
 ## 0.61.0 (2018-12-05)
 
 ### New features

lib/rubocop/cop/layout/rescue_ensure_alignment.rb

@@ -114,7 +114,9 @@ def alignment_source(node, starting_loc)
 
         def alignment_node(node)
           ancestor_node = ancestor_node(node)
-          return nil if ancestor_node.nil?
+
+          return ancestor_node if ancestor_node.nil? ||
+                                  ancestor_node.kwbegin_type?
 
           assignment_node = assignment_node(ancestor_node)
           return assignment_node unless assignment_node.nil?

spec/rubocop/cop/layout/rescue_ensure_alignment_spec.rb

@@ -354,6 +354,16 @@ def method2
     RUBY
   end
 
+  it 'accepts correctly aligned rescue in assigned begin-end block' do
+    expect_no_offenses(<<-RUBY)
+      foo = begin
+              bar
+            rescue BazError
+              qux
+            end
+    RUBY
+  end
+
   context '>= Ruby 2.5', :ruby25 do
     it 'accepts aligned rescue in do-end block' do
       expect_no_offenses(<<-RUBY.strip_indent)