From a3bc2489abb344d602900954bb9cc52ca0257d67 Mon Sep 17 00:00:00 2001
From: Koichi ITO <koic.ito@gmail.com>
Date: Tue, 28 Jun 2022 02:16:22 +0900
Subject: [PATCH] [Fix #10755] Fix a false positive for
 `Lint/LiteralAsCondition`

Fixes #10755.

This PR fixes a false positive for `Lint/LiteralAsCondition`
when using a literal in `case-in` condition where the match variable is used in
`in` are accepted as a pattern matching.
---
 ..._positive_for_lint_literal_as_condition.md |  1 +
 lib/rubocop/cop/lint/literal_as_condition.rb  |  5 +++++
 .../cop/lint/literal_as_condition_spec.rb     | 20 +++++++++++++++++--
 3 files changed, 24 insertions(+), 2 deletions(-)
 create mode 100644 changelog/fix_a_false_positive_for_lint_literal_as_condition.md

diff --git a/changelog/fix_a_false_positive_for_lint_literal_as_condition.md b/changelog/fix_a_false_positive_for_lint_literal_as_condition.md
new file mode 100644
index 00000000000..3c2547c16cf
--- /dev/null
+++ b/changelog/fix_a_false_positive_for_lint_literal_as_condition.md
@@ -0,0 +1 @@
+* [#10755](https://github.com/rubocop/rubocop/issues/10755): Fix a false positive for `Lint/LiteralAsCondition` when using a literal in `case-in` condition where the match variable is used in `in` are accepted as a pattern matching. ([@koic][])
diff --git a/lib/rubocop/cop/lint/literal_as_condition.rb b/lib/rubocop/cop/lint/literal_as_condition.rb
index 4f03eff4c55..a4473136830 100644
--- a/lib/rubocop/cop/lint/literal_as_condition.rb
+++ b/lib/rubocop/cop/lint/literal_as_condition.rb
@@ -7,6 +7,9 @@ module Lint
       # operands in and/or expressions serving as the conditions of
       # if/while/until/case-when/case-in.
       #
+      # NOTE: Literals in `case-in` condition where the match variable is used in
+      # `in` are accepted as a pattern matching.
+      #
       # @example
       #
       #   # bad
@@ -69,6 +72,8 @@ def on_case(case_node)
 
         def on_case_match(case_match_node)
           if case_match_node.condition
+            return if case_match_node.descendants.any?(&:match_var_type?)
+
             check_case(case_match_node)
           else
             case_match_node.each_in_pattern do |in_pattern_node|
diff --git a/spec/rubocop/cop/lint/literal_as_condition_spec.rb b/spec/rubocop/cop/lint/literal_as_condition_spec.rb
index aa8ce87dc31..3b4044ff1a0 100644
--- a/spec/rubocop/cop/lint/literal_as_condition_spec.rb
+++ b/spec/rubocop/cop/lint/literal_as_condition_spec.rb
@@ -75,11 +75,19 @@
     end
 
     context '>= Ruby 2.7', :ruby27 do
-      it "registers an offense for literal #{lit} in case match" do
+      it "accepts an offense for literal #{lit} in case match with a match var" do
+        expect_no_offenses(<<~RUBY, lit: lit)
+          case %{lit}
+          in x then top
+          end
+        RUBY
+      end
+
+      it "registers an offense for literal #{lit} in case match without a match var" do
         expect_offense(<<~RUBY, lit: lit)
           case %{lit}
                ^{lit} Literal `#{lit}` appeared as a condition.
-          in x then top
+          in CONST then top
           end
         RUBY
       end
@@ -219,6 +227,14 @@
       RUBY
     end
 
+    it 'accepts an offense for case match with a match var' do
+      expect_no_offenses(<<~RUBY)
+        case { a: 1, b: 2, c: 3 }
+        in a: Integer => m
+        end
+      RUBY
+    end
+
     it 'accepts dstr literal in case match' do
       expect_no_offenses(<<~'RUBY')
         case "#{x}"