Describe the PR

• Reorganize the antlr implementation to avoid extending both antlr base classes and PMD interfaces. This avoids API clashes like [core] Conflicting contracts of getChild between PMD & Antlr #2235
  • This is explained on BaseAntlrNode and AntlrGeneratedParserBase
• Make the ant script more generic, like the javacc wrapper. I don't want to end up in a situation like before [core] Merge JavaCC build scripts #2211 for antlr modules
• Fully flesh out the implementation of Node for Antlr, including
  • implement getIndexInParent, which is strongly relied upon by node streams
  • implement getXPathNodeName, including for terminals. See AntlrNameDictionary
  • add a SwiftNode interface, which implements GenericNode<SwiftNode>, take measures to enforce this is safe (eg add SwiftErrorNode, SwiftTerminalNode, add some runtime checks to make sure that antlr only adds children from our implementation).
• Add some parser tests for swift to ensure this is working properly
  • I just used the test files that were here for CPD. The parser actually fails on them, as evidenced by the 3000 error nodes on the BTree example....
• Rewrite some of the swift rules to not be so reliant on getText (which is the worst way to implement a rule), that method is renamed to joinTokenText and deprecated, which we can do since we don't inherit it from ParserRuleContext anymore

It's still unclear how we can add new attributes to antlr nodes, since they're all generated into the same file.... For the same reason, we might run into trouble if we try to add functionality to the RootNode interface. I guess we can deal with that later

Of note, that the generated tree is not an abstract syntax tree in any way, it's a parse tree. There's a node for every token, or every error, which makes gigantic trees. Antlr recommends building a separate AST if we want one, but then we would have to define all the nodes and visitor interface ourselves... This is a fundamental problem with using antlr, possibly it should be mentioned somewhere in the doc.

Related issues

• [core] Conflicting contracts of getChild between PMD & Antlr #2235
• [doc] Add ANTLR documentation #1881, which must be updated

Ready?

• Added unit tests for fixed bug/feature
• Passing all unit tests
• Complete build ./mvnw clean verify passes (checked automatically by travis)
  • I only did a partial build so will let travis take over
• Added (in-code) documentation (if needed)