golang: Add to quick checks to PredictionContext Equals checks (they …

…are in use

in other runtimes):

1. If pointers are equal it's the same object
2. If we are comparing singletons both types must be singletons

Signed-off-by: Eytan Heidingsfeld <32422402+ehmm@users.noreply.github.com>

runtime/Go/antlr/v4/prediction_context.go

@@ -115,6 +115,9 @@ func (p *PredictionContext) Hash() int {
 }
 
 func (p *PredictionContext) Equals(other Collectable[*PredictionContext]) bool {
+	if p == other {
+		return true
+	}
 	switch p.pcType {
 	case PredictionContextEmpty:
 		otherP := other.(*PredictionContext)
@@ -152,7 +155,7 @@ func (p *PredictionContext) SingletonEquals(other Collectable[*PredictionContext
 		return false
 	}
 	otherP := other.(*PredictionContext)
-	if otherP == nil {
+	if otherP == nil || otherP.pcType != PredictionContextSingleton {
 		return false
 	}