Support Ruby 2.7's in pattern syntax for Lint/LiteralAsCondition

This PR supports Ruby 2.7's `in` pattern syntax for `Lint/LiteralAsCondition`.

changelog/new_support_pattern_matching_for_lint_literal_as_condition.md

@@ -0,0 +1 @@
+* [#9877](https://github.com/rubocop/rubocop/pull/9877): Support Ruby 2.7's `in` pattern syntax for `Lint/LiteralAsCondition`. ([@koic][])

lib/rubocop/cop/lint/literal_as_condition.rb

@@ -5,7 +5,7 @@ module Cop
     module Lint
       # This cop checks for literals used as the conditions or as
       # operands in and/or expressions serving as the conditions of
-      # if/while/until.
+      # if/while/until/case-when/case-in.
       #
       # @example
       #
@@ -67,6 +67,18 @@ def on_case(case_node)
           end
         end
 
+        def on_case_match(case_match_node)
+          if case_match_node.condition
+            check_case(case_match_node)
+          else
+            case_match_node.each_in_pattern do |in_pattern_node|
+              next unless in_pattern_node.condition.literal?
+
+              add_offense(in_pattern_node)
+            end
+          end
+        end
+
         def on_send(node)
           return unless node.negation_method?
 

spec/rubocop/cop/lint/literal_as_condition_spec.rb

@@ -74,6 +74,25 @@
       RUBY
     end
 
+    context '>= Ruby 2.7', :ruby27 do
+      it "registers an offense for literal #{lit} in case match" do
+        expect_offense(<<~RUBY, lit: lit)
+          case %{lit}
+               ^{lit} Literal `#{lit}` appeared as a condition.
+          in x then top
+          end
+        RUBY
+      end
+
+      it "accepts literal #{lit} in a when of a case match" do
+        expect_no_offenses(<<~RUBY)
+          case x
+          in #{lit} then top
+          end
+        RUBY
+      end
+    end
+
     it "registers an offense for literal #{lit} in &&" do
       expect_offense(<<~RUBY, lit: lit)
         if x && %{lit}
@@ -174,6 +193,41 @@
     RUBY
   end
 
+  context '>= Ruby 2.7', :ruby27 do
+    it 'accepts array literal in case match, if it has non-literal elements' do
+      expect_no_offenses(<<~RUBY)
+        case [1, 2, x]
+        in [1, 2, 5] then top
+        end
+      RUBY
+    end
+
+    it 'accepts array literal in case match, if it has nested non-literal element' do
+      expect_no_offenses(<<~RUBY)
+        case [1, 2, [x, 1]]
+        in [1, 2, 5] then top
+        end
+      RUBY
+    end
+
+    it 'registers an offense for case match with a primitive array condition' do
+      expect_offense(<<~RUBY)
+        case [1, 2, [3, 4]]
+             ^^^^^^^^^^^^^^ Literal `[1, 2, [3, 4]]` appeared as a condition.
+        in [1, 2, 5] then top
+        end
+      RUBY
+    end
+
+    it 'accepts dstr literal in case match' do
+      expect_no_offenses(<<~'RUBY')
+        case "#{x}"
+        in [1, 2, 5] then top
+        end
+      RUBY
+    end
+  end
+
   it 'accepts `true` literal in `while`' do
     expect_no_offenses(<<~RUBY)
       while true