package dotty.tools
package dotc
package core
import Types._, Contexts._, Symbols._
import util.SimpleMap
import collection.mutable
import printing.{Printer, Showable}
import printing.Texts._
import config.Config
import config.Printers._
/** Constraint over undetermined type parameters. Constraints are built
* over values of the following types:
*
* - PolyType A constraint constrains the type parameters of a set of PolyTypes
* - PolyParam The parameters of the constrained polytypes
* - TypeVar Every constrained parameter might be associated with a TypeVar
* that has the PolyParam as origin.
*/
abstract class Constraint extends Showable {
type This <: Constraint
/** Does the constraint's domain contain the type parameters of `pt`? */
def contains(pt: GenericType): Boolean
/** Does the constraint's domain contain the type parameter `param`? */
def contains(param: PolyParam): Boolean
/** Does this constraint contain the type variable `tvar` and is it uninstantiated? */
def contains(tvar: TypeVar): Boolean
/** The constraint entry for given type parameter `param`, or NoType if `param` is not part of
* the constraint domain. Note: Low level, implementation dependent.
*/
def entry(param: PolyParam): Type
/** The type variable corresponding to parameter `param`, or
* NoType, if `param` is not in constrained or is not paired with a type variable.
*/
def typeVarOfParam(param: PolyParam): Type
/** Is it known that `param1 <:< param2`? */
def isLess(param1: PolyParam, param2: PolyParam): Boolean
/** The parameters that are known to be smaller wrt <: than `param` */
def lower(param: PolyParam): List[PolyParam]
/** The parameters that are known to be greater wrt <: than `param` */
def upper(param: PolyParam): List[PolyParam]
/** lower(param) \ lower(butNot) */
def exclusiveLower(param: PolyParam, butNot: PolyParam): List[PolyParam]
/** upper(param) \ upper(butNot) */
def exclusiveUpper(param: PolyParam, butNot: PolyParam): List[PolyParam]
/** The constraint bounds for given type parameter `param`.
* Poly params that are known to be smaller or greater than `param`
* are not contained in the return bounds.
* @pre `param` is not part of the constraint domain.
*/
def nonParamBounds(param: PolyParam): TypeBounds
/** The lower bound of `param` including all known-to-be-smaller parameters */
def fullLowerBound(param: PolyParam)(implicit ctx: Context): Type
/** The upper bound of `param` including all known-to-be-greater parameters */
def fullUpperBound(param: PolyParam)(implicit ctx: Context): Type
/** The bounds of `param` including all known-to-be-smaller and -greater parameters */
def fullBounds(param: PolyParam)(implicit ctx: Context): TypeBounds
/** A new constraint which is derived from this constraint by adding
* entries for all type parameters of `poly`.
* @param tvars A list of type variables associated with the params,
* or Nil if the constraint will just be checked for
* satisfiability but will solved to give instances of
* type variables.
*/
def add(poly: GenericType, tvars: List[TypeVar])(implicit ctx: Context): This
/** A new constraint which is derived from this constraint by updating
* the entry for parameter `param` to `tp`.
* `tp` can be one of the following:
*
* - A TypeBounds value, indicating new constraint bounds
* - Another type, indicating a solution for the parameter
*
* @pre `this contains param`.
*/
def updateEntry(param: PolyParam, tp: Type)(implicit ctx: Context): This
/** A constraint that includes the relationship `p1 <: p2`.
* `<:` relationships between parameters ("edges") are propagated, but
* non-parameter bounds are left alone.
*/
def addLess(p1: PolyParam, p2: PolyParam)(implicit ctx: Context): This
/** A constraint resulting from adding p2 = p1 to this constraint, and at the same
* time transferring all bounds of p2 to p1
*/
def unify(p1: PolyParam, p2: PolyParam)(implicit ctx: Context): This
/** A new constraint which is derived from this constraint by removing
* the type parameter `param` from the domain and replacing all top-level occurrences
* of the parameter elsewhere in the constraint by type `tp`, or a conservative
* approximation of it if that is needed to avoid cycles.
* Occurrences nested inside a refinement or prefix are not affected.
*/
def replace(param: PolyParam, tp: Type)(implicit ctx: Context): This
/** Narrow one of the bounds of type parameter `param`
* If `isUpper` is true, ensure that `param <: `bound`, otherwise ensure
* that `param >: bound`.
*/
def narrowBound(param: PolyParam, bound: Type, isUpper: Boolean)(implicit ctx: Context): This
/** Is entry associated with `pt` removable? This is the case if
* all type parameters of the entry are associated with type variables
* which have their `inst` fields set.
*/
def isRemovable(pt: GenericType): Boolean
/** A new constraint with all entries coming from `pt` removed. */
def remove(pt: GenericType)(implicit ctx: Context): This
/** The polytypes constrained by this constraint */
def domainPolys: List[GenericType]
/** The polytype parameters constrained by this constraint */
def domainParams: List[PolyParam]
/** Check whether predicate holds for all parameters in constraint */
def forallParams(p: PolyParam => Boolean): Boolean
/** Perform operation `op` on all typevars, or only on uninstantiated
* typevars, depending on whether `uninstOnly` is set or not.
*/
def foreachTypeVar(op: TypeVar => Unit): Unit
/** The uninstantiated typevars of this constraint */
def uninstVars: collection.Seq[TypeVar]
/** The weakest constraint that subsumes both this constraint and `other` */
def & (other: Constraint)(implicit ctx: Context): Constraint
/** Check that no constrained parameter contains itself as a bound */
def checkNonCyclic()(implicit ctx: Context): Unit
/** Check that constraint only refers to PolyParams bound by itself */
def checkClosed()(implicit ctx: Context): Unit
}
