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view-types: propagate view types to rustc_middle - #159291

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view-types: propagate view types to rustc_middle#159291
scrabsha wants to merge 1 commit into
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scrabsha:view-types/in-mir

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@scrabsha scrabsha commented Jul 14, 2026 •
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⚠️ this PR is big and boring and need self-review. review from other people is welcome, but it is probably not worth your time (at least in its current state) ⚠️

TODO:

  • PR description
  • tracking issue
  • maybe some tests?

@rustbot rustbot added A-LLVM Area: Code generation parts specific to LLVM. Both correctness bugs and optimization-related issues. PG-exploit-mitigations Project group: Exploit mitigations S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. T-rustdoc Relevant to the rustdoc team, which will review and decide on the PR/issue. WG-trait-system-refactor The Rustc Trait System Refactor Initiative (-Znext-solver) labels Jul 14, 2026
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scrabsha force-pushed the view-types/in-mir branch from e9822b0 to 4600dd1 Compare July 14, 2026 14:42
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scrabsha force-pushed the view-types/in-mir branch from 4600dd1 to e2963ed Compare July 14, 2026 15:28
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scrabsha force-pushed the view-types/in-mir branch from e2963ed to 15cc52f Compare July 15, 2026 09:44
@rustbot rustbot added the T-clippy Relevant to the Clippy team. label Jul 15, 2026
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@scrabsha scrabsha mentioned this pull request Jul 26, 2026
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scrabsha force-pushed the view-types/in-mir branch from 15cc52f to 26818c0 Compare July 27, 2026 19:55
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scrabsha force-pushed the view-types/in-mir branch from 26818c0 to 8a1ca0e Compare July 27, 2026 20:01
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scrabsha force-pushed the view-types/in-mir branch from 8a1ca0e to 26b0846 Compare July 28, 2026 09:38
scrabsha
scrabsha commented Jul 30, 2026
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Comment thread compiler/rustc_middle/src/ty/sty.rs
/// Returns the type of the discriminant of this type.
pub fn discriminant_ty(self, tcx: TyCtxt<'tcx>) -> Ty<'tcx> {
match self.kind() {
// It is somewhat guaranteed that view types

@scrabsha scrabsha Jul 30, 2026 •
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??

View changes since the review

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rust-bors Bot commented Jul 31, 2026

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☔ The latest upstream changes (presumably #159836) made this pull request unmergeable. Please resolve the merge conflicts by rebasing.

@scrabsha

scrabsha commented Aug 2, 2026

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discussed privately with @oli-obk : we want to model the set of viewed fields as a type. something like:

enum TyKind {
    View(AdtDef, GenericArgs, Ty),
}

the Ty field would be either an inferred type, or a tuple: (FieldRepresentingType<Foo, FIRST_VARIANT, 0>, Foo<FIRST_VARIANT, 1>) would represent Foo.{ first_field, second_field }. this is handy because it makes viewed field set inference trivial: instaed of adding a new inference variable just for view types, we can leverage the already-existing and super cool type inference algorithms and just relate types in order to infer the set of viewed fields. cool stuff!!

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A-LLVM Area: Code generation parts specific to LLVM. Both correctness bugs and optimization-related issues. PG-exploit-mitigations Project group: Exploit mitigations S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. T-clippy Relevant to the Clippy team. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. T-rustdoc Relevant to the rustdoc team, which will review and decide on the PR/issue. WG-trait-system-refactor The Rustc Trait System Refactor Initiative (-Znext-solver)

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