[new-parser] rule super_key failed predicate #5703
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@tkobayas I'm taking this one. |
yurloc
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This is how one of the `selector` subrules looks like in the old parser:
(DOT super_key)=>DOT { helper.emit($DOT, DroolsEditorType.SYMBOL); } super_key superSuffix
The whole rule is guarded by a syntactic predicate that is used to make
the decision whether this alternative is viable.
Syntactic predicates were removed in ANTLR 4 so this subrule became:
DOT { helper.emit($DOT, DroolsEditorType.SYMBOL); } super_key superSuffix
The failing predicate is "hidden" inside the `super_key` rule but it actually
cannot be used to make the decision because it is now "invisible". See
https://github.com/antlr/antlr4/blob/master/doc/predicates.md#finding-visible-predicates
that explains how predicates can become invisible. The thing that makes
the predicate invisible here is the action after `DOT`. And since the
alternative is now unguarded it seems viable and so it is taken and
the `super_key` rule is evaluated.
At this point, inside `super_key` there is only a single alternative. It
is guarded by a predicate that evaluates to `false`, which is an error
condition.
The fix is to restore the guard in front of this `selector` alternative
that prevents taking should the super key predicate later turn out to be
false.
Fixes apache#5703.
yurloc
added a commit
to yurloc/drools
that referenced
this issue
Feb 27, 2024
This is how one of the `selector` subrules looks like in the old parser:
(DOT super_key)=>DOT { helper.emit($DOT, DroolsEditorType.SYMBOL); } super_key superSuffix
The whole rule is guarded by a syntactic predicate that is used to make
the decision whether this alternative is viable.
Syntactic predicates were removed in ANTLR 4 so this subrule became:
DOT { helper.emit($DOT, DroolsEditorType.SYMBOL); } super_key superSuffix
The failing predicate is "hidden" inside the `super_key` rule but it actually
cannot be used to make the decision because it is now "invisible". See
https://github.com/antlr/antlr4/blob/master/doc/predicates.md#finding-visible-predicates
that explains how predicates can become invisible. The thing that makes
the predicate invisible here is the action after `DOT`. And since the
alternative is now unguarded it seems viable and so it is taken and
the `super_key` rule is evaluated.
At this point, inside `super_key` there is only a single alternative. It
is guarded by a predicate that evaluates to `false`, which is an error
condition.
The fix is to restore the guard in front of this `selector` alternative
that prevents taking should the super key predicate later turn out to be
false.
Fixes apache#5703.
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Parent issue
Failing tests
org.drools.model.codegen.execmodel.NodeSharingTest#testShareAccumulateNotes
STANDARD_FROM_DRLonly.Rule code snippet
Error output
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