built_in_identifier_in_declaration

The built-in identifier '{0}' can't be used as a prefix name.

The built-in identifier '{0}' can't be used as a type name.

The built-in identifier '{0}' can't be used as a type parameter name.

The built-in identifier '{0}' can't be used as a typedef name.

The built-in identifier '{0}' can't be used as an extension name.

The built-in identifier '{0}' can't be used as an extension type name.

The analyzer produces this diagnostic when the name used in the declaration of a class, extension, mixin, typedef, type parameter, or import prefix is a built-in identifier. Built-in identifiers can't be used to name any of these kinds of declarations.

The following code produces this diagnostic because mixin is a built-in identifier:

extension mixin on int {}

Choose a different name for the declaration.