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- Left recursion elimination and expression grammar simplification [ANTLR4:DONE]
- Scannerless parsing
- Error alternatives
- Maybe ambiguous alt parsing, yielding parse forest
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- Generate code that uses ST v4 [ANTLR4:DONE]
- Make default output=template action for single rule ref to be that rule's return value then perhaps $text for more complicated alts w/o -> actions.
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- Improve error messages when backtracking or using arbitrary lookahead
- Add Jim Idle's sync rule concept
- Make a real interpreter using NFA; allow access as library from Java code
- Tokens and Trees should both know their start/stop line, start/stop char position to make IDEs easier.
- Tree parser error handling should skip subtrees not nodes; these are programming errors not input errors. The flat stream makes it hard to resync.
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