message: Remove Prompt.ast.
diff: import * as events from "events";
  import {scan, Token, expandAliases} from "./Scanner";
  -import {ASTNode, CompleteCommand} from "./Parser";
  +import {CompleteCommand} from "./Parser";
  import {Session} from "./Session";
  export class Prompt extends events.EventEmitter {
  private _value = "";
  - private _ast: CompleteCommand;
  private _expandedAst: CompleteCommand;
  constructor(private session: Session) {
  @@ -20,14 +19,9 @@ export class Prompt extends events.EventEmitter {
  this._value = value;
  const tokens = scan(this.value);
  - this._ast = new CompleteCommand(tokens);
  this._expandedAst = new CompleteCommand(expandAliases(tokens, this.session.aliases));
  }
  - get ast(): ASTNode {
  - return this._ast;
  - }
  -
  get expandedTokens(): Token[] {
  return this._expandedAst.tokens;
  }
  