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# Diagnostics

## abstract_class

Objects can’t be created from abstract classes. Abstract classes are used as base classes for other classes, but they don’t have functionality on their own. You may want to use a non-abstract subclass instead.

## bad_syntax

The tokenizer encountered an unexpected sequence of characters that aren’t part of any known blueprint syntax.

## child_not_accepted

The parent class does not have child widgets (it does not implement Gtk.Buildable and is not a subclass of Gio.ListStore). Some classes use properties instead of children to add widgets. Check the parent class’s documentation.

## conversion_error

The value’s type cannot be converted to the target type.

Subclasses may be converted to their superclasses, but not vice versa. A type that implements an interface can be converted to that interface’s type. Many boxed types can be parsed from strings in a type-specific way.

## expected_bool

A boolean value was expected, but the value is not `true` or `false`.

## extension_not_repeatable

This extension can’t be used more than once in an object.

## extension_wrong_parent_type

No extension with the given name exists for this object’s class (or, for a child extension, the parent class).

## invalid_number_literal

The tokenizer encountered what it thought was a number, but it couldn’t parse it as a number.

## member_dne

The value is being interpreted as a member of an enum or flag type, but that type doesn’t have a member with the given name.

## missing_gtk_declaration

All blueprint files must start with a GTK declaration, e.g. `using Gtk 4.0;`.

## multiple_templates

Only one template is allowed per blueprint file, but there are multiple. The template keyword indicates which object is the one being instantiated.

## namespace_not_found

The `.typelib` files for the given namespace could not be found. There are several possibilities:

- There is a typo in the namespace name, e.g. `Adwaita` instead of `Adw`

- The version number is incorrect, e.g. `Adw 1.0` instead of `Adw 1`. The library’s documentation will tell you the correct version number to use.

- The packages for the library are not installed. On some distributions, the `.typelib` file is in a separate package from the main library, such as a `-devel` package.

- There is an issue with the path to the typelib file. The `GI_TYPELIB_PATH` environment variable can be used to add additional paths to search.

## namespace_not_imported

The given namespace was not imported at the top of the file. Importing the namespace is necessary because it tells blueprint-compiler which version of the library to use.

## object_dne

No object with the given ID exists in the current scope.

## property_dne

The class or interface doesn’t have a property with the given name.

## property_convert_error

The value given for the property can’t be converted to the property’s type.

## property_construct_only

The property can’t be bound because it is a construct-only property, meaning it can only be set once when the object is first constructed. Binding it to an expression could cause its value to change later.

## property_read_only

This property can’t be set because it is marked as read-only.

## signal_dne

The class or interface doesn’t have a signal with the given name.

## type_dne

The given type doesn’t exist in the namespace.

## type_not_a_class

The given type exists in the namespace, but it isn’t a class. An object’s type must be a concrete (not abstract) class, not an interface or boxed type.

## version_conflict

This error occurs when two versions of a namespace are imported (possibly transitively) in the same file. For example, this will cause a version conflict:

    using Gtk 4.0;
    using Gtk 3.0;

But so will this:

    using Gtk 4.0;
    using Handy 1;

because libhandy imports `Gtk 3.0`.

## wrong_compiler_version

This version of blueprint-compiler is for GTK 4 blueprints only. Future GTK versions will use different versions of blueprint-compiler.