From 8f0047957aa211b8d3e5730596f084de3c07d73b Mon Sep 17 00:00:00 2001
From: Daniel Vandersluis <daniel.vandersluis@gmail.com>
Date: Mon, 3 May 2021 14:56:53 -0400
Subject: [PATCH] [Fix #9762] Update `VariableForce` to be able to handle
 `case-match` nodes.

---
 .../fix_update_variableforce_to_be_able_to.md     |  1 +
 lib/rubocop/cop/variable_force/branch.rb          | 15 +++++++++++++++
 spec/rubocop/cop/lint/useless_assignment_spec.rb  | 15 +++++++++++++++
 3 files changed, 31 insertions(+)
 create mode 100644 changelog/fix_update_variableforce_to_be_able_to.md

diff --git a/changelog/fix_update_variableforce_to_be_able_to.md b/changelog/fix_update_variableforce_to_be_able_to.md
new file mode 100644
index 00000000000..301c40a3d35
--- /dev/null
+++ b/changelog/fix_update_variableforce_to_be_able_to.md
@@ -0,0 +1 @@
+* [#9762](https://github.com/rubocop/rubocop/issues/9762): Update `VariableForce` to be able to handle `case-match` nodes. ([@dvandersluis][])
diff --git a/lib/rubocop/cop/variable_force/branch.rb b/lib/rubocop/cop/variable_force/branch.rb
index e66a38438d7..ffc3eb72bb3 100644
--- a/lib/rubocop/cop/variable_force/branch.rb
+++ b/lib/rubocop/cop/variable_force/branch.rb
@@ -226,6 +226,21 @@ def always_run?
           end
         end
 
+        # case target
+        # in pattern # in_pattern
+        # else
+        #   else_body
+        # end
+        class CaseMatch < Base
+          define_predicate :target?,     child_index: 0
+          define_predicate :in_pattern?, child_index: 1..-2
+          define_predicate :else_body?,  child_index: -1
+
+          def always_run?
+            target?
+          end
+        end
+
         # for element in collection
         #   loop_body
         # end
diff --git a/spec/rubocop/cop/lint/useless_assignment_spec.rb b/spec/rubocop/cop/lint/useless_assignment_spec.rb
index d3e6245742b..b0e0ee29e9b 100644
--- a/spec/rubocop/cop/lint/useless_assignment_spec.rb
+++ b/spec/rubocop/cop/lint/useless_assignment_spec.rb
@@ -1416,4 +1416,19 @@ def some_method(environment)
       end
     end
   end
+
+  context 'inside a `case-match` node', :ruby27 do
+    it 'does not register an offense when the variable is used' do
+      expect_no_offenses(<<~RUBY)
+        case '0'
+        in String
+          res = 1
+        else
+          res = 2
+        end
+
+        do_something(res)
+      RUBY
+    end
+  end
 end