Trait Constraint

pub trait Constraint<Var, Value>: DynClone {
    // Required methods
    fn update(
        &mut self,
        assignment: &mut Assignment<Var, Value>,
        key: fn(&Value) -> &str,
    ) -> Result<bool, ConstraintError<Var, Value>>;
    fn pretty(&self) -> String;
}

A constraint that can be applied to variable assignments. Constraints are used in type inference to represent relationships between variables and values.

Required Methods

fn update( &mut self, assignment: &mut Assignment<Var, Value>, key: fn(&Value) -> &str, ) -> Result<bool, ConstraintError<Var, Value>>

Updates the assignment based on this constraint. Returns Ok(true) if the assignment was modified, Ok(false) if no changes were made, or Err if the constraint cannot be satisfied.

update is allowed to modify the constraint itself, e.g. to convert a delayed constraint into an immediate one. The key function gets a string representation of the value for display.

fn pretty(&self) -> String

Returns a human-readable string representation of this constraint.

Implementors