AstGen: detect duplicate field names

This logic was previously in Sema, which was unnecessary complexity, and meant the issue was not detected unless the declaration was semantically analyzed. This commit finishes the work which 941090d started.

Resolves: #17916
1b8f7e46faDavid Rubin committed on 1/20/2024, 5:23:47 PM· committed by GitHubparent5c4cb60
13 files changedLine totals unavailable