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commit42b384ec0dfcd528d99a4db0a337d9188a9eecaa[log] [tgz]
authorbors <bors@rust-lang.org>Thu Oct 02 01:54:48 2025 +0000
committerbors <bors@rust-lang.org>Thu Oct 02 01:54:48 2025 +0000
tree3514e6cac9bc43fb0b255776653d322956ff4b75
parent3369e82c6bc03c5cdb66f730dba6f738b74c8e1d [diff]
parent413f095a85adb21331f6e64cf030ead124a6ba07 [diff]
Auto merge of #147055 - beepster4096:subtype_is_not_a_projection, r=lcnr

Turn ProjectionElem::Subtype into CastKind::Subtype

I noticed that drop elaboration can't, in general, handle `ProjectionElem::SubType`. It creates a disjoint move path that overlaps with other move paths. (`Subslice` does too, and I'm working on a different PR to make that special case less fragile.) If its skipped and treated as the same move path as its parent then `MovePath.place` has multiple possible projections. (It would probably make sense to remove all `Subtype` projections for the canonical place but it doesn't make sense to have this special case for a problem that doesn't actually occur in real MIR.)

The only reason this doesn't break is that `Subtype` is always the sole projection of the local its applied to. For the same reason, it works fine as a `CastKind` so I figured that makes more sense than documenting and validating this hidden invariant.

cc rust-lang/rust#112651, rust-lang/rust#133258

r? Icnr (bc you've been the main person dealing with `Subtype` it looks like)
tree: 3514e6cac9bc43fb0b255776653d322956ff4b75
  1. .github/
  2. compiler/
  3. library/
  4. LICENSES/
  5. src/
  6. tests/
  7. .clang-format
  8. .editorconfig
  9. .git-blame-ignore-revs
  10. .gitattributes
  11. .gitignore
  12. .gitmodules
  13. .ignore
  14. .mailmap
  15. bootstrap.example.toml
  16. Cargo.lock
  17. Cargo.toml
  18. CODE_OF_CONDUCT.md
  19. configure
  20. CONTRIBUTING.md
  21. COPYRIGHT
  22. INSTALL.md
  23. LICENSE-APACHE
  24. license-metadata.json
  25. LICENSE-MIT
  26. package-lock.json
  27. package.json
  28. README.md
  29. RELEASES.md
  30. REUSE.toml
  31. rust-bors.toml
  32. rustfmt.toml
  33. triagebot.toml
  34. typos.toml
  35. x
  36. x.ps1
  37. x.py
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