typescript-lexer: generated typescript lexer imports 'DecisionState' but the antlr4 node-module does not export

[foofighter2146]

Bug

Antlr 4.13.2 generates from a lexer grammar a typescript lexer which imports 'DecisionState':

import {
	ATN,
	ATNDeserializer,
	CharStream,
	DecisionState, DFA,
	Lexer,
	LexerATNSimulator,
	RuleContext,
	PredictionContextCache,
	Token
} from "antlr4";

But the antlr4 node-module (version 4.13.2) does not export 'DecisionState'. This can be verified by executing a small javascript:

import * as antlr4 from 'antlr4';
console.log(Object.keys(antlr4));

The output does not contain 'DecisionState'.

Workaround

Because DecisionState is only used as type decleration in

static DecisionsToDFA = CalcLexer._ATN.decisionToState.map( (ds: DecisionState, index: number) => new DFA(ds, index) );

it can be simply removed from the typescript lexer file by executing a post processor.

Suggestion for a Fix

This issue could be fixed either by exporting 'DecisionState' in the antlr4 node-module or removing the explicit usage in the generated lexer file.

[foofighter2146]

Same for parser. Here are the exports for 'TokenStream' and 'DecisionState' both missed.