Add specs for reserved keywords (#1187)

Author: amomchilov

language/reserved_keywords.rb

@@ -0,0 +1,149 @@
+require_relative '../spec_helper'
+
+describe "Ruby's reserved keywords" do
+  # Copied from https://github.com/ruby/ruby/blob/master/defs/keywords
+  keywords = %w[
+    alias
+    and
+    begin
+    BEGIN
+    break
+    case
+    class
+    def
+    defined?
+    do
+    else
+    elsif
+    end
+    END
+    ensure
+    false
+    for
+    if
+    in
+    module
+    next
+    nil
+    not
+    or
+    redo
+    rescue
+    retry
+    return
+    self
+    super
+    then
+    true
+    undef
+    unless
+    until
+    when
+    while
+    yield
+    __ENCODING__
+    __FILE__
+    __LINE__
+  ]
+
+  keywords.each do |name|
+    describe "keyword '#{name}'" do
+      it "can't be used as local variable name" do
+        -> { eval(<<~RUBY) }.should raise_error(SyntaxError)
+            #{name} = :local_variable
+        RUBY
+      end
+
+      if name == "defined?"
+        it "can't be used as an instance variable name" do
+          -> { eval(<<~RUBY) }.should raise_error(SyntaxError)
+            @#{name} = :instance_variable
+          RUBY
+        end
+
+        it "can't be used as a class variable name" do
+          -> { eval(<<~RUBY) }.should raise_error(SyntaxError)
+            class C
+              @@#{name} = :class_variable
+            end
+          RUBY
+        end
+
+        it "can't be used as a global variable name" do
+          -> { eval(<<~RUBY) }.should raise_error(SyntaxError)
+            $#{name} = :global_variable
+          RUBY
+        end
+      else
+        it "can be used as an instance variable name" do
+          result = eval <<~RUBY
+            @#{name} = :instance_variable
+            @#{name}
+          RUBY
+
+          result.should == :instance_variable
+        end
+
+        it "can be used as a class variable name" do
+          result = eval <<~RUBY
+            class C
+              @@#{name} = :class_variable
+              @@#{name}
+            end
+          RUBY
+
+          result.should == :class_variable
+        end
+
+        it "can be used as a global variable name" do
+          result = eval <<~RUBY
+            $#{name} = :global_variable
+            $#{name}
+          RUBY
+
+          result.should == :global_variable
+        end
+      end
+
+      it "can't be used as a positional parameter name" do
+        -> { eval(<<~RUBY) }.should raise_error(SyntaxError)
+          def x(#{name}); end
+        RUBY
+      end
+
+      invalid_kw_param_names = ["BEGIN","END","defined?"]
+
+      if invalid_kw_param_names.include?(name)
+        it "can't be used a keyword parameter name" do
+          -> { eval(<<~RUBY) }.should raise_error(SyntaxError)
+            def m(#{name}:); end
+          RUBY
+        end
+      else
+        it "can be used a keyword parameter name" do
+          result = instance_eval <<~RUBY
+            def m(#{name}:)
+              binding.local_variable_get(:#{name})
+            end
+
+            m(#{name}: :argument)
+          RUBY
+
+          result.should == :argument
+        end
+      end
+
+      it "can be used as a method name" do
+        result = instance_eval <<~RUBY
+          def #{name}
+            :method_return_value
+          end
+
+          send(:#{name})
+        RUBY
+
+        result.should == :method_return_value
+      end
+    end
+  end
+end