Remove fallback code handling a missing type

* The type is always set by tool/generate-native-config.rb.

Author: eregon

lib/truffle/socket/truffle.rb

@@ -49,10 +49,8 @@ def self.config(struct_class, base, *fields)
         type   = Truffle::Config.lookup("#{base}.#{field}.type")
         type   = if type == 'char_array'
                    [:char, size]
-                 elsif type
-                   type.to_sym
                  else
-                   ffi_type_for_size(size)
+                   type.to_sym
                  end
 
         if !(Array === type) && ::FFI.find_type(type).size != size
@@ -65,17 +63,6 @@ def self.config(struct_class, base, *fields)
       struct_class.layout(*layout_args)
     end
 
-    def self.ffi_type_for_size(size)
-      case size
-      when 1 then :char
-      when 2 then :short
-      when 4 then :int
-      when 8 then :long
-      else
-        raise ArgumentError, "Unknown type for size #{size}"
-      end
-    end
-
     def self.aliases_for_hostname(hostname)
       pointer = Foreign.gethostbyname(hostname)
       return [] if pointer.null? # Truffle: added null check