Enum InstanceHeadProblem 

pub enum InstanceHeadProblem {
    NotAClass,
    ClassApplied(usize),
    Variable(Name),
    Function,
    Record,
    ArgumentNotVariable,
    RepeatedVariable(Name),
}

What is wrong with an instance head — see Error::InvalidInstanceHead.

A head is a class name applied to one type, and that type is a declared type applied to distinct variables, a tuple of distinct variables, or ().

Variants

NotAClass

Something other than a class name applied to a type — instance a where.

ClassApplied(usize)

The class applied to some number of types other than one — instance Eq Int Char.

Variable(Name)

A bare type variable — instance Eq a.

Function

A function type — instance Eq (a -> b).

Record

A record type.

ArgumentNotVariable

An argument of the head’s type that is not a type variable — Int in instance Eq (Maybe Int).

RepeatedVariable(Name)

A variable the head already bound — the second a of instance Eq (Pair a a).

Trait Implementations

impl Clone for InstanceHeadProblem

fn clone(&self) -> InstanceHeadProblem

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for InstanceHeadProblem

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl PartialEq for InstanceHeadProblem

fn eq(&self, other: &InstanceHeadProblem) -> bool

Equality operator ==.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl StructuralPartialEq for InstanceHeadProblem