Fix property? macro for boolean properties.

Fix #163

spec/inheritance_spec.cr

@@ -35,6 +35,9 @@ private class UserObjectWithGProperties < GObject::Object
   @[GObject::Property]
   property signal_test : Bool = true
 
+  @[GObject::Property]
+  property? bool : Bool = false
+
   # This declaration tests if the property is created as readonly if it only have getter?
   @[GObject::Property]
   getter? readonly_bool : Bool = true
@@ -153,6 +156,17 @@ describe "Classes inheriting GObject::Object" do
     out_object = uninitialized Pointer(Void)
     LibGObject.g_object_get(obj, "object", pointerof(out_object), Pointer(Void).null)
     out_object.should eq(user_obj.to_unsafe)
+
+    obj.bool = true
+    out_bool = uninitialized Int32
+    LibGObject.g_object_get(obj, "bool", pointerof(out_bool), Pointer(Void).null)
+    GICrystal.to_bool(out_bool).should eq(true)
+    obj.bool?.should eq(true)
+
+    obj.bool = false
+    LibGObject.g_object_get(obj, "bool", pointerof(out_bool), Pointer(Void).null)
+    GICrystal.to_bool(out_bool).should eq(false)
+    obj.bool?.should eq(false)
   end
 
   it "emits notify signal on GObject properties access" do

src/bindings/g_object/object.cr

@@ -360,6 +360,15 @@ module GObject
               {% if name.is_a?(TypeDeclaration) %}
                 @{{name.var.id}} : {{name.type}}?
 
+                def {{name.var.id}} : {{name.type}}
+                  if (value = @{{name.var.id}}).nil?
+                    @{{name.var.id}} = {{yield}}
+                    _emit_notify_signal({{name.var.id}})
+                  else
+                    value
+                  end
+                end
+
                 def {{name.var.id}}? : {{name.type}}
                   if (value = @{{name.var.id}}).nil?
                     @{{name.var.id}} = {{yield}}
@@ -369,10 +378,19 @@ module GObject
                   end
                 end
 
-                def {{name.var.id}}=(@{{name.var.id}} : \{{name.type}})
+                def {{name.var.id}}=(@{{name.var.id}} : {{name.type}})
                   _emit_notify_signal({{name.var.id}})
                 end
               {% else %}
+                def {{name.id}}
+                  if (value = @{{name.id}}).nil?
+                    @{{name.id}} = {{yield}}
+                    _emit_notify_signal({{name.id}})
+                  else
+                    value
+                  end
+                end
+
                 def {{name.id}}?
                   if (value = @{{name.id}}).nil?
                     @{{name.id}} = {{yield}}
@@ -391,6 +409,10 @@ module GObject
                 {% if name.is_a?(TypeDeclaration) %}
                   @{{name}}
 
+                  def {{name.var.id}} : {{name.type}}
+                    @{{name.var.id}}
+                  end
+
                   def {{name.var.id}}? : {{name.type}}
                     @{{name.var.id}}
                   end
@@ -401,6 +423,10 @@ module GObject
                 {% elsif name.is_a?(Assign) %}
                   @{{name}}
 
+                  def {{name.target.id}}
+                    @{{name.target.id}}
+                  end
+
                   def {{name.target.id}}?
                     @{{name.target.id}}
                   end
@@ -409,6 +435,10 @@ module GObject
                     _emit_notify_signal({{name.target.id}})
                   end
                 {% else %}
+                  def {{name.id}}
+                    @{{name.id}}
+                  end
+
                   def {{name.id}}?
                     @{{name.id}}
                   end