Incorrect alternative label displayed for grammar rule

[markkrijgsman]

It seems that the plugin does not visualize the matching alternative label for a rule correctly. Take the following grammar:

grammar EverythingAndGrammar;

query       : expression;

expression  : expression 'AND' expression   #AndExpr
            | TERM+                         #LeafExpr;

TERM        : [a-z]+;

WS          : (' ' | '\t' | '\n' | '\r')+ -> skip;

Input: term term

Expected behaviour:

Actual behaviour:

However, when I implement a Listener for this grammar, the LeafExpr methods are called and not the AndExpr methods (as expected).

[bjansen]

@parrt it looks like in this case, org.antlr.v4.tool.GrammarInterpreterRuleContext#outerAltNum is not updated and keeps its default value (1), which unfortunately corresponds to the AndExpr alternative. I'm not familiar enough with ANTLR's internals to understand what's going on, though :(

[parrt]

Hmm...I wonder if that's a bug or whether I never made the interpreter update those values. It seems like since it displays a different alternative I expected this to work. I guess I will have to look at it sometime. thanks for looking

[bjansen]

In some cases it works as expected. If we add a third 'OrExpr' alt to the grammar, the interpreter will correctly update the value when the input is an OR expr. It just never gets updated when the input text is just a TERM. Maybe because it doesn't have any named rule?