Class DispatcherWinner

java.lang.Object

org.ek9lang.compiler.support.DispatcherWinner

public final class DispatcherWinner
extends Object

THE single source of truth for "which handler WINS for this concrete type".

Third member of the dispatcher family, beside DispatcherHandlers (which handlers compete) and DispatcherReachableTypes (what types can arrive). Together the three answer the whole dispatch question, and they must be used together: a winner computed over a handler set or a type set that some other caller derived differently is a different dispatch model wearing the same name.

Selection rule. Lowest un-coerced assignment cost wins; a negative cost means "not assignable" and does not compete. Phase 5 (DispatcherAmbiguityOrError) has already rejected ties at equal cost, so for a program that compiles the winner is unique — the first-wins tie-break below is therefore unreachable in practice, and is kept only so this is total.

Why the cost comes back with the handler. Phase 7 needs only the winner, but a cost of exactly zero is what distinguishes a handler declared FOR this very type from one it merely inherits into — the DIRECT/INHERITED split the Oracle and IDE dispatcher views show. Recomputing that cost at the call site was how the previous copy drifted, so it is returned rather than left to be re-derived.

Deliberately ISymbol, not IAggregateSymbol. A dispatcher may route over a FUNCTION hierarchy, and FunctionSymbol is an IFunctionSymbol, NOT an IAggregateSymbol. Narrowing the parameter is precisely the defect that made a function handler silently unreachable in phase 5 and phase 7, and it had been re-made a third time in the Oracle extractor. Keep this signature wide.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static final record	DispatcherWinner.Selection	A winning handler and the assignment cost it won at.

Method Summary

Modifier and Type	Method	Description
static Optional<DispatcherWinner.Selection>	forParam(ISymbol concreteType, int paramIndex, List<MethodSymbol> handlers)	The winning handler for a concrete type at one parameter position.
static Optional<DispatcherWinner.Selection>	forParamPair(ISymbol type0, ISymbol type1, List<MethodSymbol> handlers)	The winning handler for a pair of concrete types across the first two parameters.

Methods inherited from class Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Details

forParam

public static Optional<DispatcherWinner.Selection> forParam(ISymbol concreteType,
 int paramIndex,
 List<MethodSymbol> handlers)

The winning handler for a concrete type at one parameter position.

Parameters:

concreteType - the type a value could actually have at this position

paramIndex - which parameter is being dispatched on

handlers - the handler set, from DispatcherHandlers.collectFor(IAggregateSymbol, MethodSymbol)

Returns:

the winner and the cost it won at, or empty when no handler accepts the type

forParamPair

public static Optional<DispatcherWinner.Selection> forParamPair(ISymbol type0,
 ISymbol type1,
 List<MethodSymbol> handlers)

The winning handler for a pair of concrete types across the first two parameters.

Parameters:

type0 - the type at parameter 0

type1 - the type at parameter 1

handlers - the handler set, from DispatcherHandlers.collectFor(IAggregateSymbol, MethodSymbol)

Returns:

the winner and the summed cost it won at, or empty when no handler accepts the pair