RFR: type of TypeVar.ref is incorrect and should be fixed [v4]

[Vicente Romero]

> The type of TypeVar.ref is incorrect and should be fixed, in particular due to a bug, the compiler is not able to differentiate between  `T` and `T.ref` which should have a different type

Vicente Romero has updated the pull request incrementally with one additional commit since the last revision:

  minor refactoring

-------------

Changes:
  - all: https://git.openjdk.java.net/valhalla/pull/658/files
  - new: https://git.openjdk.java.net/valhalla/pull/658/files/50f7ae2f..df161eb5

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=valhalla&pr=658&range=03
 - incr: https://webrevs.openjdk.java.net/?repo=valhalla&pr=658&range=02-03

  Stats: 8 lines in 1 file changed: 5 ins; 0 del; 3 mod
  Patch: https://git.openjdk.java.net/valhalla/pull/658.diff
  Fetch: git fetch https://git.openjdk.java.net/valhalla pull/658/head:pull/658

PR: https://git.openjdk.java.net/valhalla/pull/658