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build/node_modules/acorn/src/lval.js

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+import {types as tt} from "./tokentype"
+import {Parser} from "./state"
+import {has} from "./util"
+
+const pp = Parser.prototype
+
+// Convert existing expression atom to assignable pattern
+// if possible.
+
+pp.toAssignable = function(node, isBinding) {
+  if (this.options.ecmaVersion >= 6 && node) {
+    switch (node.type) {
+      case "Identifier":
+      if (this.inAsync && node.name === "await")
+        this.raise(node.start, "Can not use 'await' as identifier inside an async function")
+      break
+
+    case "ObjectPattern":
+    case "ArrayPattern":
+      break
+
+    case "ObjectExpression":
+      node.type = "ObjectPattern"
+      for (let i = 0; i < node.properties.length; i++) {
+        let prop = node.properties[i]
+        if (prop.kind !== "init") this.raise(prop.key.start, "Object pattern can't contain getter or setter")
+        this.toAssignable(prop.value, isBinding)
+      }
+      break
+
+    case "ArrayExpression":
+      node.type = "ArrayPattern"
+      this.toAssignableList(node.elements, isBinding)
+      break
+
+    case "AssignmentExpression":
+      if (node.operator === "=") {
+        node.type = "AssignmentPattern"
+        delete node.operator
+        this.toAssignable(node.left, isBinding)
+        // falls through to AssignmentPattern
+      } else {
+        this.raise(node.left.end, "Only '=' operator can be used for specifying default value.")
+        break
+      }
+
+    case "AssignmentPattern":
+      break
+
+    case "ParenthesizedExpression":
+      node.expression = this.toAssignable(node.expression, isBinding)
+      break
+
+    case "MemberExpression":
+      if (!isBinding) break
+
+    default:
+      this.raise(node.start, "Assigning to rvalue")
+    }
+  }
+  return node
+}
+
+// Convert list of expression atoms to binding list.
+
+pp.toAssignableList = function(exprList, isBinding) {
+  let end = exprList.length
+  if (end) {
+    let last = exprList[end - 1]
+    if (last && last.type == "RestElement") {
+      --end
+    } else if (last && last.type == "SpreadElement") {
+      last.type = "RestElement"
+      let arg = last.argument
+      this.toAssignable(arg, isBinding)
+      if (arg.type !== "Identifier" && arg.type !== "MemberExpression" && arg.type !== "ArrayPattern")
+        this.unexpected(arg.start)
+      --end
+    }
+
+    if (isBinding && last && last.type === "RestElement" && last.argument.type !== "Identifier")
+      this.unexpected(last.argument.start)
+  }
+  for (let i = 0; i < end; i++) {
+    let elt = exprList[i]
+    if (elt) this.toAssignable(elt, isBinding)
+  }
+  return exprList
+}
+
+// Parses spread element.
+
+pp.parseSpread = function(refDestructuringErrors) {
+  let node = this.startNode()
+  this.next()
+  node.argument = this.parseMaybeAssign(false, refDestructuringErrors)
+  return this.finishNode(node, "SpreadElement")
+}
+
+pp.parseRest = function(allowNonIdent) {
+  let node = this.startNode()
+  this.next()
+
+  // RestElement inside of a function parameter must be an identifier
+  if (allowNonIdent) node.argument = this.type === tt.name ? this.parseIdent() : this.unexpected()
+  else node.argument = this.type === tt.name || this.type === tt.bracketL ? this.parseBindingAtom() : this.unexpected()
+
+  return this.finishNode(node, "RestElement")
+}
+
+// Parses lvalue (assignable) atom.
+
+pp.parseBindingAtom = function() {
+  if (this.options.ecmaVersion < 6) return this.parseIdent()
+  switch (this.type) {
+  case tt.name:
+    return this.parseIdent()
+
+  case tt.bracketL:
+    let node = this.startNode()
+    this.next()
+    node.elements = this.parseBindingList(tt.bracketR, true, true)
+    return this.finishNode(node, "ArrayPattern")
+
+  case tt.braceL:
+    return this.parseObj(true)
+
+  default:
+    this.unexpected()
+  }
+}
+
+pp.parseBindingList = function(close, allowEmpty, allowTrailingComma, allowNonIdent) {
+  let elts = [], first = true
+  while (!this.eat(close)) {
+    if (first) first = false
+    else this.expect(tt.comma)
+    if (allowEmpty && this.type === tt.comma) {
+      elts.push(null)
+    } else if (allowTrailingComma && this.afterTrailingComma(close)) {
+      break
+    } else if (this.type === tt.ellipsis) {
+      let rest = this.parseRest(allowNonIdent)
+      this.parseBindingListItem(rest)
+      elts.push(rest)
+      if (this.type === tt.comma) this.raise(this.start, "Comma is not permitted after the rest element")
+      this.expect(close)
+      break
+    } else {
+      let elem = this.parseMaybeDefault(this.start, this.startLoc)
+      this.parseBindingListItem(elem)
+      elts.push(elem)
+    }
+  }
+  return elts
+}
+
+pp.parseBindingListItem = function(param) {
+  return param
+}
+
+// Parses assignment pattern around given atom if possible.
+
+pp.parseMaybeDefault = function(startPos, startLoc, left) {
+  left = left || this.parseBindingAtom()
+  if (this.options.ecmaVersion < 6 || !this.eat(tt.eq)) return left
+  let node = this.startNodeAt(startPos, startLoc)
+  node.left = left
+  node.right = this.parseMaybeAssign()
+  return this.finishNode(node, "AssignmentPattern")
+}
+
+// Verify that a node is an lval — something that can be assigned
+// to.
+
+pp.checkLVal = function(expr, isBinding, checkClashes) {
+  switch (expr.type) {
+  case "Identifier":
+    if (this.strict && this.reservedWordsStrictBind.test(expr.name))
+      this.raiseRecoverable(expr.start, (isBinding ? "Binding " : "Assigning to ") + expr.name + " in strict mode")
+    if (checkClashes) {
+      if (has(checkClashes, expr.name))
+        this.raiseRecoverable(expr.start, "Argument name clash")
+      checkClashes[expr.name] = true
+    }
+    break
+
+  case "MemberExpression":
+    if (isBinding) this.raiseRecoverable(expr.start, (isBinding ? "Binding" : "Assigning to") + " member expression")
+    break
+
+  case "ObjectPattern":
+    for (let i = 0; i < expr.properties.length; i++)
+      this.checkLVal(expr.properties[i].value, isBinding, checkClashes)
+    break
+
+  case "ArrayPattern":
+    for (let i = 0; i < expr.elements.length; i++) {
+      let elem = expr.elements[i]
+      if (elem) this.checkLVal(elem, isBinding, checkClashes)
+    }
+    break
+
+  case "AssignmentPattern":
+    this.checkLVal(expr.left, isBinding, checkClashes)
+    break
+
+  case "RestElement":
+    this.checkLVal(expr.argument, isBinding, checkClashes)
+    break
+
+  case "ParenthesizedExpression":
+    this.checkLVal(expr.expression, isBinding, checkClashes)
+    break
+
+  default:
+    this.raise(expr.start, (isBinding ? "Binding" : "Assigning to") + " rvalue")
+  }
+}