Antlr4: type mismatch between left and right labels in left-recursive rule

[parrt]

We thought we fixed this in https://github.com/antlr/antlr4/issues/195#issuecomment-268737026 but here's another case reported:

@ferhaterata says: provided a Grammar that ANTLR generates recognizer in 4.5.1 and 4.5.3 but fails in 4.6.1. The labels 'left' and 'right' represent two different types. Sorry for preparing a verbose grammar.

grammar Test;

module: formula* ;

formula:
      left=expression 'in'  right=expression    #in
    | left=formula    'and' right=formula       #and
    ;

expression:
      left=expression '+' right=expression      #union
    | variable                                  #var
    ;

variable: IDENTIFIER;

IDENTIFIER : [a-zA-Z];

It throws

error(75): Test.g4:2:13: label left=expression type mismatch with previous definition: left=formula
error(75): Test.g4:5:57: label right=formula type mismatch with previous definition: right=expression

In fact, this one works fine,

grammar test1;

example:
    left=integer '*' right=integer  #integerExample
  | left=string  '+' right=string   #stringExample
  ;

integer: IDENTIFIER;
string: INTEGER;

STRING: [a-zA-Z];
INTEGER: [a-zA-Z];

I assume the problem occurs once repetitions are allowed in labels.

[sharwell]

I'm working on this one today.

[sharwell]

@KvanTTT I fixed the regression by disabling this analysis for left-recursive rules altogether. I'm leaving this issue open, and you'll find a unit test with @Ignore which I added in #1570. After analysis is working for these rules the test can be enabled and this issue will be fully resolved.