Stack overflow using a grammar that has an extraneous | in a token definition #2860
Description
Minimal grammar:
grammar test;
TILDE: '~';
fragment
QSTRING: (TILDE|)+;
QUOTED_VALUE: '\'' QSTRING? '\'' ;
single_value: QUOTED_VALUE ;
Building and running results in a stack overflow.
I saw this first on the Python runtime and then the same issue on the Java runtime (using grun).
This is using antlr-4.8-complete.jar.
antlr4 *.g4 && javac *.java && echo -n "'~'" | grun test single_value -tokens
Exception in thread "main" java.lang.StackOverflowError
at org.antlr.v4.runtime.misc.Array2DHashSet.getOrAdd(Array2DHashSet.java:59)
at org.antlr.v4.runtime.atn.ATNConfigSet.add(ATNConfigSet.java:146)
at org.antlr.v4.runtime.atn.ATNConfigSet.add(ATNConfigSet.java:122)
at org.antlr.v4.runtime.atn.LexerATNSimulator.closure(LexerATNSimulator.java:446)
at org.antlr.v4.runtime.atn.LexerATNSimulator.closure(LexerATNSimulator.java:455)
at org.antlr.v4.runtime.atn.LexerATNSimulator.closure(LexerATNSimulator.java:455)