[Fix rubocop#8422] Fix an error for Lint/SelfAssignment

Fixes rubocop#8422. Fix an error for `Lint/SelfAssignment` when using or-assignment for constant.
koic · Jul 31, 2020 · bacc9b4 · bacc9b4
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diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -29,6 +29,7 @@
 * [#8391](https://github.com/rubocop-hq/rubocop/issues/8391): Mark `Style/ArrayCoercion` as not safe. ([@marcandre][])
 * [#8406](https://github.com/rubocop-hq/rubocop/issues/8406): Improve `Style/AccessorGrouping`'s auto-correction to remove redundant blank lines. ([@koic][])
 * [#8330](https://github.com/rubocop-hq/rubocop/issues/8330): Fix a false positive for `Style/MissingRespondToMissing` when defined method with inline access modifier. ([@koic][])
+* [#8422](https://github.com/rubocop-hq/rubocop/issues/8422): Fix an error for `Lint/SelfAssignment` when using or-assignment for constant. ([@koic][])
 
 ### Changes
 

diff --git a/lib/rubocop/cop/lint/self_assignment.rb b/lib/rubocop/cop/lint/self_assignment.rb
@@ -40,7 +40,7 @@ def on_lvasgn(node)
 
         def on_casgn(node)
           lhs_scope, lhs_name, rhs = *node
-          return unless rhs.const_type?
+          return unless rhs&.const_type?
 
           rhs_scope, rhs_name = *rhs
           add_offense(node) if lhs_scope == rhs_scope && lhs_name == rhs_name

diff --git a/spec/rubocop/cop/lint/self_assignment_spec.rb b/spec/rubocop/cop/lint/self_assignment_spec.rb
@@ -68,6 +68,12 @@
     RUBY
   end
 
+  it 'does not register an offense when using constant var or-assignment for constant from another scope' do
+    expect_no_offenses(<<~RUBY)
+      Foo ||= ::Foo
+    RUBY
+  end
+
   it 'registers an offense when using multiple var self-assignment' do
     expect_offense(<<~RUBY)
       foo, bar = foo, bar