1 files changed, 108 insertions, 0 deletions
diff --git a/spec/ruby/language/it_parameter_spec.rb b/spec/ruby/language/it_parameter_spec.rb
new file mode 100644
index 0000000000..6ba67cbb4f
--- /dev/null
+++ b/spec/ruby/language/it_parameter_spec.rb
@@ -0,0 +1,108 @@
+require_relative '../spec_helper'
+
+ruby_version_is "3.4" do
+  eval <<-RUBY # use eval to avoid warnings on Ruby 3.3
+  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 "can be reassigned to act as a local variable" do
+      proc { tmp = it; it = tmp * 2; it }.call(21).should == 42
+    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 "is a regular local variable if there is a method `it` defined" do
+      o = Object.new
+      def o.it
+        21
+      end
+
+      o.instance_eval("proc { it * 2 }").call(1).should == 2
+    end
+
+    it "is not shadowed by an reassignment in a block" do
+      a = nil
+      proc { a = it; it = 42 }.call(0)
+      a.should == 0 # if `it` were shadowed its value would be nil
+    end
+
+    it "raises SyntaxError when block parameters are specified explicitly" do
+      -> { eval("-> () { it }")         }.should.raise(SyntaxError, /ordinary parameter is defined/)
+      -> { eval("-> (x) { it }")        }.should.raise(SyntaxError, /ordinary parameter is defined/)
+
+      -> { eval("proc { || it }")       }.should.raise(SyntaxError, /ordinary parameter is defined/)
+      -> { eval("proc { |x| it }")      }.should.raise(SyntaxError, /ordinary parameter is defined/)
+
+      -> { eval("lambda { || it }")     }.should.raise(SyntaxError, /ordinary parameter is defined/)
+      -> { eval("lambda { |x| it }")    }.should.raise(SyntaxError, /ordinary parameter is defined/)
+
+      -> { eval("['a'].map { || it }")  }.should.raise(SyntaxError, /ordinary parameter is defined/)
+      -> { eval("['a'].map { |x| it }") }.should.raise(SyntaxError, /ordinary parameter is defined/)
+    end
+
+    it "cannot be mixed with numbered parameters" do
+      -> {
+        eval("proc { it + _1 }")
+      }.should.raise(SyntaxError, /numbered parameters are not allowed when 'it' is already used|'it' is already used in/)
+
+      -> {
+        eval("proc { _1 + it }")
+      }.should.raise(SyntaxError, /numbered parameter is already used in|'it' is not allowed when a numbered parameter is already used/)
+    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(ArgumentError, /wrong number of arguments/)
+    end
+
+    context "given multiple arguments" do
+      it "provides it in a block and assigns the first argument for a block" do
+        proc { it }.call("a", "b").should == "a"
+      end
+
+      it "raises ArgumentError for a proc" do
+        -> { -> { it }.call("a", "b") }.should.raise(ArgumentError, "wrong number of arguments (given 2, expected 1)")
+        -> { lambda { it }.call("a", "b") }.should.raise(ArgumentError, "wrong number of arguments (given 2, expected 1)")
+      end
+    end
+  end
+  RUBY
+end