RFR: [bworld] Inference failure with bang

[Chen Liang]

Fix a typo that causes a wrong ineligible type being null restricted. Affects the core reflection migration.

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Commit messages:
 - Alternative fix
 - Test framework tweak
 - Merge branch 'bworld' of https://github.com/openjdk/valhalla into fix/bang-infer-crash
 - [bworld] Inference failure with bang

Changes: https://git.openjdk.org/valhalla/pull/2075/files
  Webrev: https://webrevs.openjdk.org/?repo=valhalla&pr=2075&range=00
  Stats: 36 lines in 4 files changed: 26 ins; 5 del; 5 mod
  Patch: https://git.openjdk.org/valhalla/pull/2075.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/2075/head:pull/2075

PR: https://git.openjdk.org/valhalla/pull/2075