Fixed #225: Void is not an Object nor a Value, it doesn't have any me…

…thods.

spec/compiler/type_inference/primitives_spec.cr

@@ -57,4 +57,14 @@ describe "Type inference: primitives" do
   it "types instance_sizeof" do
     assert_type("instance_sizeof(Reference)") { int32 }
   end
+
+  it "errors when comparing void (#225)" do
+    assert_error %(
+      lib Foo
+        fun foo
+      end
+
+      Foo.foo == 1
+      ), "undefined method '==' for Void"
+  end
 end

src/compiler/crystal/program.cr

@@ -32,7 +32,7 @@ module Crystal
       @number.abstract = true
 
       @types["NoReturn"] = @no_return = NoReturnType.new self
-      @types["Void"] = @void = VoidType.new self, self, "Void", @value, 1
+      @types["Void"] = @void = VoidType.new self
       @types["Nil"] = @nil = NilType.new self, self, "Nil", @value, 1
       @types["Bool"] = @bool = BoolType.new self, self, "Bool", @value, 1
       @types["Char"] = @char = CharType.new self, self, "Char", @value, 4

src/compiler/crystal/types.cr

@@ -395,33 +395,6 @@ module Crystal
     end
   end
 
-  class NoReturnType < Type
-    getter :program
-
-    def initialize(@program)
-    end
-
-    def lookup_matches(signature, owner = self, type_lookup = self, matches_array = nil)
-      Matches.new(nil, nil, self, false)
-    end
-
-    def no_return?
-      true
-    end
-
-    def primitive_like?
-      true
-    end
-
-    def parents
-      nil
-    end
-
-    def to_s(io)
-      io << "NoReturn"
-    end
-  end
-
   abstract class ContainedType < Type
     getter :program
     getter :container
@@ -1459,10 +1432,59 @@ module Crystal
     end
   end
 
-  class VoidType < PrimitiveType
+  abstract class EmptyType < Type
+    getter :program
+
+    def initialize(@program)
+    end
+
+    def lookup_defs(name)
+      [] of Def
+    end
+
+    def lookup_matches(signature, owner = self, type_lookup = self, matches_array = nil)
+      Matches.new(nil, nil, self, false)
+    end
+
+    def parents
+      nil
+    end
+
+    def allocated
+      true
+    end
+
+    def abstract
+      false
+    end
+  end
+
+  class NoReturnType < EmptyType
+    def no_return?
+      true
+    end
+
+    def primitive_like?
+      true
+    end
+
+    def to_s(io)
+      io << "NoReturn"
+    end
+  end
+
+  class VoidType < EmptyType
     def void?
       true
     end
+
+    def primitive_like?
+      true
+    end
+
+    def to_s(io)
+      io << "Void"
+    end
   end
 
   class ValueType < NonGenericClassType