Function getKeyPropertyName

test/fixtures/snapshot/typescript.js:69484–69504

(unionType)

        // Return the name of a discriminant property for which it was possible and feasible to construct a map of
        // constituent types keyed by the literal types of the property by that name in each constituent type.
        function getKeyPropertyName(unionType) {
            var types = unionType.types;
            // We only construct maps for unions with many non-primitive constituents.
            if (types.length < 10 || ts.getObjectFlags(unionType) & 32768 /* ObjectFlags.PrimitiveUnion */ ||
                ts.countWhere(types, function (t) { return !!(t.flags & (524288 /* TypeFlags.Object */ | 58982400 /* TypeFlags.InstantiableNonPrimitive */)); }) < 10) {
                return undefined;
            }
            if (unionType.keyPropertyName === undefined) {
                // The candidate key property name is the name of the first property with a unit type in one of the
                // constituent types.
                var keyPropertyName = ts.forEach(types, function (t) {
                    return t.flags & (524288 /* TypeFlags.Object */ | 58982400 /* TypeFlags.InstantiableNonPrimitive */) ?
                        ts.forEach(getPropertiesOfType(t), function (p) { return isUnitType(getTypeOfSymbol(p)) ? p.escapedName : undefined; }) :
                        undefined;
                });
                var mapByKeyProperty = keyPropertyName && mapTypesByKeyProperty(types, keyPropertyName);
                unionType.keyPropertyName = mapByKeyProperty ? keyPropertyName : "";
                unionType.constituentMap = mapByKeyProperty;
            }
            return unionType.keyPropertyName.length ? unionType.keyPropertyName : undefined;
        }
        // Given a union type for which getKeyPropertyName returned a non-undefined result, return the constituent
        // that corresponds to the given key type for that property name.
        function getConstituentTypeForKeyType(unionType, keyType) {