Add specs for it based on language/it_parameter_spec.rb

Author: eregon

.rubocop.yml

@@ -197,6 +197,7 @@ Style/Lambda:
     - 'language/lambda_spec.rb'
     - 'language/proc_spec.rb'
     - 'language/numbered_parameters_spec.rb'
+    - 'language/it_parameter_spec.rb'
     - 'core/kernel/lambda_spec.rb'
 
 Style/EmptyLambdaParameter:

language/it_parameter_spec.rb

@@ -0,0 +1,66 @@
+require_relative '../spec_helper'
+
+ruby_version_is "3.4" do
+  describe "The `it` parameter" do
+    it "provides it in a block" do
+      -> { it }.call("a").should == "a"
+      proc { it }.call("a").should == "a"
+      lambda { it }.call("a").should == "a"
+      ["a"].map { it }.should == ["a"]
+    end
+
+    it "assigns nil to not passed parameters" do
+      proc { it }.call().should == nil
+    end
+
+    it "can be used in both outer and nested blocks at the same time" do
+      -> { it + -> { it * it }.call(2) }.call(3).should == 7
+    end
+
+    it "is a regular local variable if there is already a 'it' local variable" do
+        it = 0
+        proc { it }.call("a").should == 0
+    end
+
+    it "raises SyntaxError when block parameters are specified explicitly" do
+      -> { eval("-> () { it }")         }.should raise_error(SyntaxError, /ordinary parameter is defined/)
+      -> { eval("-> (x) { it }")        }.should raise_error(SyntaxError, /ordinary parameter is defined/)
+
+      -> { eval("proc { || it }")       }.should raise_error(SyntaxError, /ordinary parameter is defined/)
+      -> { eval("proc { |x| it }")      }.should raise_error(SyntaxError, /ordinary parameter is defined/)
+
+      -> { eval("lambda { || it }")     }.should raise_error(SyntaxError, /ordinary parameter is defined/)
+      -> { eval("lambda { |x| it }")    }.should raise_error(SyntaxError, /ordinary parameter is defined/)
+
+      -> { eval("['a'].map { || it }")  }.should raise_error(SyntaxError, /ordinary parameter is defined/)
+      -> { eval("['a'].map { |x| it }") }.should raise_error(SyntaxError, /ordinary parameter is defined/)
+    end
+
+    it "affects block arity" do
+      -> {}.arity.should == 0
+      -> { it }.arity.should == 1
+    end
+
+    it "affects block parameters" do
+      -> { it }.parameters.should == [[:req]]
+
+      ruby_version_is ""..."4.0" do
+        proc { it }.parameters.should == [[:opt, nil]]
+      end
+      ruby_version_is "4.0" do
+        proc { it }.parameters.should == [[:opt]]
+      end
+    end
+
+    it "does not affect binding local variables" do
+      -> { it; binding.local_variables }.call("a").should == []
+    end
+
+    it "does not work in methods" do
+      obj = Object.new
+      def obj.foo; it; end
+
+      -> { obj.foo("a") }.should raise_error(ArgumentError, /wrong number of arguments/)
+    end
+  end
+end