[lworld] RFR: 8263900: [lworld] Make .default a separate node type in the parser. [v3]

[Jesper Steen Møller]

> To prepare for making .default a poly expression and to implement further logic, .default-expressions should be split off as a separate AST node.

Jesper Steen Møller has updated the pull request incrementally with one additional commit since the last revision:

  Spaces again = face+palm.

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Changes:
  - all: https://git.openjdk.java.net/valhalla/pull/370/files
  - new: https://git.openjdk.java.net/valhalla/pull/370/files/adc1372f..0341e68c

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=valhalla&pr=370&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=valhalla&pr=370&range=01-02

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/valhalla/pull/370.diff
  Fetch: git fetch https://git.openjdk.java.net/valhalla pull/370/head:pull/370

PR: https://git.openjdk.java.net/valhalla/pull/370