Store excluded arrangements in state

This optimization was removed a long time ago to simply the node data model. Now
that nodes can have mutable state again (43b0ab6), it can be restored.

Author: cdoublev

lib/parse/grammar.js

@@ -322,12 +322,17 @@ function* children(parent, alternative) {
  * @param {object} node
  * @yields {object}
  */
-function* alternatives({ children, definition: { type, value: set }, value }) {
+function* alternatives({ children, definition: { type, value: set }, state, value }) {
     if (type === '&&' || type === '||') {
-        const index = 0 < children.length
-            ? getPermutationIndex(set, children.map(node => node.definition))
-            : 0
-        yield* createPermutationIterator(set, type === '&&', index)
+        if (children.length === 0) {
+            const excluded = []
+            state.extended.set('excluded', excluded)
+            yield* createPermutationIterator(set, type === '&&', excluded)
+        } else {
+            const index = getPermutationIndex(set, children.map(node => node.definition))
+            const excluded = state.extended.get('excluded')
+            yield* createPermutationIterator(set, type === '&&', excluded, index)
+        }
     } else if (type === '|') {
         if (0 < children.length) {
             set = set.slice(set.indexOf(children[0].definition))

lib/parse/permutation.js

@@ -113,13 +113,13 @@ function findExcludedPermutationPattern(excluded, permutation) {
 /**
  * @param {object[]} sequence
  * @param {boolean} [full]
+ * @param {object[][]} [excluded]
  * @param {number} [index]
  * @yields {object}
  */
-function* createPermutationIterator(sequence, full, index = 0) {
+function* createPermutationIterator(sequence, full, excluded = [], index = 0) {
     const n = sequence.length
     const lastIndex = full ? factorial(n) : getAllPermutationsLength(n)
-    const excluded = []
     let permutation = 0 < index ? getNthPermutation(sequence, index) : sequence
     let valid = yield permutation
     while (true) {