[ruby/fiddle] Move "type" constants to `Fiddle::Types` (https://github.com/ruby/fiddle/pull/112)

This helps to reduce repetition in code. Instead of doing "TYPE_*"
everywhere, you can do `include Fiddle::Types`, and write the type name
directly.

This PR is to help reduce repetition when writing Fiddle code. Right now
we have to type `TYPE_` everywhere, and you also have to include all of
`Fiddle` to access `TYPE_*` constants. With this change, you can just
include `Fiddle::Types` and it will shorten your code and also you only
have to include those constants.

Here is an example before:

```ruby
require "fiddle"

module MMAP
  # All Fiddle constants included
  include Fiddle

  def self.make_function name, args, ret
    ptr = Handle::DEFAULT[name]
    func = Function.new ptr, args, ret, name: name
    define_singleton_method name, &func.to_proc
  end

  make_function "munmap", [TYPE_VOIDP, # addr
                           TYPE_SIZE_T], # len
                           TYPE_INT

  make_function "mmap", [TYPE_VOIDP,
                         TYPE_SIZE_T,
                         TYPE_INT,
                         TYPE_INT,
                         TYPE_INT,
                         TYPE_INT], TYPE_VOIDP

  make_function "mprotect", [TYPE_VOIDP, TYPE_SIZE_T, TYPE_INT], TYPE_INT
end
```

After:

```ruby
require "fiddle"

module MMAP
  # Only type names included
  include Fiddle::Types

  def self.make_function name, args, ret
    ptr = Fiddle::Handle::DEFAULT[name]
    func = Fiddle::Function.new ptr, args, ret, name: name
    define_singleton_method name, &func.to_proc
  end

  make_function "munmap", [VOIDP, # addr
                           SIZE_T], # len
                           INT

  make_function "mmap", [VOIDP, SIZE_T, INT, INT, INT, INT], VOIDP

  make_function "mprotect", [VOIDP, SIZE_T, INT], INT
end
```

We only need to import the type names, and you don't have to type
`TYPE_` over and over. I think this makes Fiddle code easier to read.

https://github.com/ruby/fiddle/commit/49fa7233e5

Co-authored-by: Sutou Kouhei <kou@clear-code.com>

1 files changed, 6 insertions, 0 deletions

diff --git a/test/fiddle/test_import.rb b/test/fiddle/test_import.rb
index ca51781e8a..b4dab3de27 100644
--- a/test/fiddle/test_import.rb
+++ b/test/fiddle/test_import.rb
@@ -139,6 +139,12 @@ module Fiddle
       end
     end
 
+    def test_type_constants
+      Fiddle::Types.constants.each do |const|
+        assert_equal Fiddle::Types.const_get(const), Fiddle.const_get("TYPE_#{const}")
+      end
+    end
+
     def test_unsigned_result()
       d = (2 ** 31) + 1