Document type classes

[mlutze]

Tracking ticket to list the features and details that should be covered.

InstanceErrors:

• OverlappingInstances
• MismatchedSignatures
• MissingImplementation
• ExtraneousDefinition
• DuplicateTypeVariableOccurrence
• ComplexInstanceType
• OrphanInstance
• MissingSuperClassInstance
• LawlessSuperClass
• UnlawfulSignature
• IllegalOverride
• UnmarkedOverride

ResolutionErrors:

• SealedClass

WeederErrors:

• IllegalPrivateDeclaration
• IllegalTypeConstraintParameter

NameErrors:

• IllegalSignature