1 files changed, 113 insertions, 0 deletions
diff --git a/spec/ruby/language/numbered_parameters_spec.rb b/spec/ruby/language/numbered_parameters_spec.rb
new file mode 100644
index 0000000000..23e89a14be
--- /dev/null
+++ b/spec/ruby/language/numbered_parameters_spec.rb
@@ -0,0 +1,113 @@
+require_relative '../spec_helper'
+
+describe "Numbered parameters" do
+  it "provides default parameters _1, _2, ... in a block" do
+    -> { _1 }.call("a").should == "a"
+    proc { _1 }.call("a").should == "a"
+    lambda { _1 }.call("a").should == "a"
+    ["a"].map { _1 }.should == ["a"]
+  end
+
+  it "assigns nil to not passed parameters" do
+    proc { [_1, _2] }.call("a").should == ["a", nil]
+    proc { [_1, _2] }.call("a", "b").should == ["a", "b"]
+  end
+
+  it "supports variables _1-_9 only for the first 9 passed parameters" do
+    block = proc { [_1, _2, _3, _4, _5, _6, _7, _8, _9] }
+    result = block.call(1, 2, 3, 4, 5, 6, 7, 8, 9)
+    result.should == [1, 2, 3, 4, 5, 6, 7, 8, 9]
+  end
+
+  it "does not support more than 9 parameters" do
+    -> {
+      proc { [_10] }.call(1, 2, 3, 4, 5, 6, 7, 8, 9, 10)
+    }.should.raise(NameError, /undefined local variable or method [`']_10'/)
+  end
+
+  it "can not be used in both outer and nested blocks at the same time" do
+    -> {
+      eval("-> { _1; -> { _2 } }")
+    }.should.raise(SyntaxError, /numbered parameter is already used in/m)
+  end
+
+  it "cannot be overwritten with local variable" do
+    -> {
+      eval <<~CODE
+        _1 = 0
+        proc { _1 }.call("a").should == 0
+      CODE
+    }.should.raise(SyntaxError, /_1 is reserved for numbered parameter/)
+  end
+
+  it "errors when numbered parameter is overwritten with local variable" do
+    -> {
+      eval("_1 = 0")
+    }.should.raise(SyntaxError, /_1 is reserved for numbered parameter/)
+  end
+
+  it "raises SyntaxError when block parameters are specified explicitly" do
+    -> { eval("-> () { _1 }")         }.should.raise(SyntaxError, /ordinary parameter is defined/)
+    -> { eval("-> (x) { _1 }")        }.should.raise(SyntaxError, /ordinary parameter is defined/)
+
+    -> { eval("proc { || _1 }")       }.should.raise(SyntaxError, /ordinary parameter is defined/)
+    -> { eval("proc { |x| _1 }")      }.should.raise(SyntaxError, /ordinary parameter is defined/)
+
+    -> { eval("lambda { || _1 }")     }.should.raise(SyntaxError, /ordinary parameter is defined/)
+    -> { eval("lambda { |x| _1 }")    }.should.raise(SyntaxError, /ordinary parameter is defined/)
+
+    -> { eval("['a'].map { || _1 }")  }.should.raise(SyntaxError, /ordinary parameter is defined/)
+    -> { eval("['a'].map { |x| _1 }") }.should.raise(SyntaxError, /ordinary parameter is defined/)
+  end
+
+  describe "assigning to a numbered parameter" do
+    it "raises SyntaxError" do
+      -> { eval("proc { _1 = 0 }") }.should.raise(SyntaxError, /_1 is reserved for numbered parameter/)
+    end
+  end
+
+  it "affects block arity" do
+    -> { _1 }.arity.should == 1
+    -> { _2 }.arity.should == 2
+    -> { _3 }.arity.should == 3
+    -> { _4 }.arity.should == 4
+    -> { _5 }.arity.should == 5
+    -> { _6 }.arity.should == 6
+    -> { _7 }.arity.should == 7
+    -> { _8 }.arity.should == 8
+    -> { _9 }.arity.should == 9
+
+    ->     { _9 }.arity.should == 9
+    proc   { _9 }.arity.should == 9
+    lambda { _9 }.arity.should == 9
+  end
+
+  it "affects block parameters" do
+    -> { _1 }.parameters.should == [[:req, :_1]]
+    -> { _2 }.parameters.should == [[:req, :_1], [:req, :_2]]
+
+    proc { _1 }.parameters.should == [[:opt, :_1]]
+    proc { _2 }.parameters.should == [[:opt, :_1], [:opt, :_2]]
+  end
+
+  ruby_version_is ""..."4.0" do
+    it "affects binding local variables" do
+      -> { _1; binding.local_variables }.call("a").should == [:_1]
+      -> { _2; binding.local_variables }.call("a", "b").should == [:_1, :_2]
+    end
+  end
+
+  ruby_version_is "4.0" do
+    it "does not affect binding local variables" do
+      -> { _1; binding.local_variables }.call("a").should == []
+      -> { _2; binding.local_variables }.call("a", "b").should == []
+    end
+  end
+
+  it "does not work in methods" do
+    obj = Object.new
+    def obj.foo; _1 end
+
+    -> { obj.foo("a") }.should.raise(ArgumentError, /wrong number of arguments/)
+  end
+end