Misconstructed AST on RNGLR with pathological ambiguities and tree actions

[woutersl]

Original report by Laurent Wouters (Bitbucket: 557058:675792b6-d731-4823-9f7d-c6dfcb2df2b5, ).

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The RNGLR algorithm use a Shared-Packed Parse Forest (SPPF) construction for the AST. When promote actions are applied on a rule that cause ambiguities, the SPPF builder sometimes reuse nodes on which promote actions have already been applied, thus mis-constructing the AST.

To reproduce: Grammar:

grammar Test { options {Axiom="s";} terminals { X->'x'; A->'a'; B->'b'; } rules { s->A^ s (B! s)?; s->X^; } }

Compile with RNGLR

Sample input: "axbx"

Expected AST: A ( X X )

Mis-constructed AST: A ( X X X ) The first two Xs are in fact the same AST node.

[woutersl]

Original comment by Laurent Wouters (Bitbucket: 557058:675792b6-d731-4823-9f7d-c6dfcb2df2b5, ).

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Verified

[woutersl]

Original comment by Laurent Wouters (Bitbucket: 557058:675792b6-d731-4823-9f7d-c6dfcb2df2b5, ).

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[fix] Fixing issue #34 in .Net runtime

[woutersl]

Original comment by Laurent Wouters (Bitbucket: 557058:675792b6-d731-4823-9f7d-c6dfcb2df2b5, ).

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[fix] Fixed issue #34 in the Java runtime