yeet alias new_from_def_id by khyperia · Pull Request #162760 · rust-lang/rust

khyperia · 2026-09-14T10:56:44Z

this PR fixes the // FIXME: remove in favor of explicit construction on alias_term_kind_from_def_id

vaguely related to rust-lang/project-const-generics#98 / #152245

fyi @lcnr who didn't like AliasConstInherentArgsKind #161929 (comment) (it gets yeeted in this PR)

r? @BoxyUwU

rustbot · 2026-09-14T10:56:49Z

BoxyUwU is currently at their maximum review capacity.
They may take a while to respond.

rustbot · 2026-09-14T10:56:52Z

Some changes occurred in compiler/rustc_sanitizers

cc @rcvalle

Some changes occurred in match checking

cc @Nadrieril

Some changes occurred in rustc_ty_utils::consts.rs

cc @BoxyUwU

HIR ty lowering was modified

cc @fmease

khyperia · 2026-09-14T11:09:54Z

+                        ct: ty::AliasConst::new(
+                            self.tcx,
+                            ty::AliasConstKind::Anon { def_id: did },
+                            self.tcx.mk_args(&[]),


debating if I should pull this change out into another PR:

this changes the args from the ADT's args to []. This is because discriminant anon consts have no generics, but we were passing the ADT's generics to it here. This is wrong, and with this change, the debug assert in AliasConst::new for correct generic args triggers. Before, we were simply harmlessly ignoring the extra generic args.

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bit-aloo

LGTM 🚀 . Few questions though..

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bit-aloo · 2026-09-14T16:41:05Z

            let user_ty = user_ty.as_ref().and_then(push_cuta);
            // Under generic_const_args, `def_id` might be a regular const declared in a trait, but
            // is `impl`d as a directly represented const. We do not know whether it is here, so we
            // must use type system normalization for all consts under generic_const_args.


Can we reword this?

rustbot · 2026-09-16T04:43:44Z

This PR was rebased onto a different main commit. Here's a range-diff highlighting what actually changed.

Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers.

BoxyUwU

thx bit-aloo for reviews :3

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BoxyUwU · 2026-09-16T09:51:43Z

-        def_id: DefId,
-        args: GenericArgsRef<'tcx>,


unsure about this change, we want to maintain a fairly clear distinction between type system consts and non-type-system contains and this blurs that a bit 🤔

would quite like to not do this and then hand write the old logic into our handling of the THIR jank with a FIXME about how we don't want to be doing that 🤔

khyperia · 2026-09-17T04:59:29Z

with the latest update, this bit in the PR description no longer applies, this PR is no longer perf-questionable:

this PR might be slightly perf-positive due to calling def_kind less. the change to THIR ExprKind is maybe very tiny bit different perf characteristics too but highly unlikely.

well, there's still one or tw.o less calls to def_kind, but less significant than it was, and the change to THIR ExprKind has been reverted

noting it here rather than just doing a strikethrough in the PR description since the PR description gets committed ✨

BoxyUwU

did you handle bit-aloo's review about rewording a comment already?

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khyperia · 2026-09-17T08:42:45Z

did you handle bit-aloo's review about rewording a comment already?

the review is no longer applicable - the rewording was because I redid the def_id field to ct, so the comment should have said ct instead of def_id. but then I reverted the thing, so the comment should stay as-is.

BoxyUwU · 2026-09-17T08:44:03Z

@bors r+

rust-bors · 2026-09-17T08:44:06Z

📌 Commit caedbd8 has been approved by BoxyUwU

It is now in the queue for this repository.

@lcnr

…oxyUwU yeet alias new_from_def_id this PR fixes the `// FIXME: remove in favor of explicit construction` on `alias_term_kind_from_def_id` vaguely related to rust-lang/project-const-generics#98 / rust-lang#152245 fyi @lcnr who didn't like `AliasConstInherentArgsKind` rust-lang#161929 (comment) (it gets yeeted in this PR) r? @BoxyUwU

…uwer Rollup of 24 pull requests Successful merges: - #161596 (coretests: Add more pattern tests.) - #162177 (Properly implement the gpu-kernel ABI for amdgpu) - #162411 (Make Receiver `#[rustc_dyn_incompatible_trait]`) - #162760 (yeet alias new_from_def_id) - #162796 (libtest: do not early exit from test runners) - #162844 (Add loan reachability traces to polonius MIR dumps) - #162876 (Move operations out of `rustc_middle::query::job`) - #160108 (Stabilize `windows_process_extensions_main_thread_handle`) - #160212 (traits: Fix rigid alias liveness matching) - #160544 (Stabilize `feature(trim_prefix_suffix)` (`{str, [T], Path}::trim_prefix` and `{str, [T]}::trim_suffix`)) - #161305 (Use the entire type of a dropped local to compute variance (edge direction) for Polonius alpha) - #161838 (tests: accept LLVM 24 optimization in this test) - #162312 (core: Rewrite docs for try_as_dyn) - #162785 (Avoid creating overlapping assignments in MatchBranchSimplification) - #162805 (Add `must_use` lint to `ExitCode`) - #162825 (core: Add examples for `debug_closure_helpers`) - #162841 (enable asm tests for xtensa targets) - #162842 (reintroduce check RibKind::ConstParamTy did in direct consts) - #162845 (mgca: fix issue with mismatched array valtree/valtree tys) - #162856 (Stabilize CommandExt::show_window) - #162865 (Complex conjugate, negation and default) - #162874 (Add support for `annotate_snippets::snippet::AnnotationKind::Visible`) - #162881 (Simplify the macro for forwarding Decoder methods ) - #162888 (Fix a typo on the Armv7-R platform docs page)

…uwer Rollup of 23 pull requests Successful merges: - #161596 (coretests: Add more pattern tests.) - #162411 (Make Receiver `#[rustc_dyn_incompatible_trait]`) - #162760 (yeet alias new_from_def_id) - #162796 (libtest: do not early exit from test runners) - #162844 (Add loan reachability traces to polonius MIR dumps) - #162876 (Move operations out of `rustc_middle::query::job`) - #160108 (Stabilize `windows_process_extensions_main_thread_handle`) - #160212 (traits: Fix rigid alias liveness matching) - #160544 (Stabilize `feature(trim_prefix_suffix)` (`{str, [T], Path}::trim_prefix` and `{str, [T]}::trim_suffix`)) - #161305 (Use the entire type of a dropped local to compute variance (edge direction) for Polonius alpha) - #161838 (tests: accept LLVM 24 optimization in this test) - #162312 (core: Rewrite docs for try_as_dyn) - #162785 (Avoid creating overlapping assignments in MatchBranchSimplification) - #162805 (Add `must_use` lint to `ExitCode`) - #162825 (core: Add examples for `debug_closure_helpers`) - #162841 (enable asm tests for xtensa targets) - #162842 (reintroduce check RibKind::ConstParamTy did in direct consts) - #162845 (mgca: fix issue with mismatched array valtree/valtree tys) - #162856 (Stabilize CommandExt::show_window) - #162865 (Complex conjugate, negation and default) - #162874 (Add support for `annotate_snippets::snippet::AnnotationKind::Visible`) - #162881 (Simplify the macro for forwarding Decoder methods ) - #162888 (Fix a typo on the Armv7-R platform docs page)

@lcnr

Rollup merge of #162760 - khyperia:yeet-new_from_def_id, r=BoxyUwU yeet alias new_from_def_id this PR fixes the `// FIXME: remove in favor of explicit construction` on `alias_term_kind_from_def_id` vaguely related to rust-lang/project-const-generics#98 / #152245 fyi @lcnr who didn't like `AliasConstInherentArgsKind` #161929 (comment) (it gets yeeted in this PR) r? @BoxyUwU

matthiaskrgr · 2026-09-17T19:39:01Z

+                        }
+                    }
+                    DefKind::Const => ty::AliasConstKind::Free { def_id },
+                    _ => unreachable!(),


reachable via #162923

Its always better here to print the actual Defkind or whatever we are not expecting to be reachable as this makes categorizing the ICE a bit easier imho :)

aaaah sorry!! #162937

rustbot added 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. labels Sep 14, 2026

rustbot assigned BoxyUwU Sep 14, 2026

khyperia marked this pull request as ready for review September 14, 2026 10:56

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Sep 14, 2026

khyperia commented Sep 14, 2026

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khyperia force-pushed the yeet-new_from_def_id branch from 7e8f2a3 to 7fc2f33 Compare September 14, 2026 19:22

khyperia mentioned this pull request Sep 15, 2026

yeet AliasConstKind::opt_def_id #162797

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khyperia force-pushed the yeet-new_from_def_id branch from 7fc2f33 to 0ace795 Compare September 16, 2026 04:43

BoxyUwU reviewed Sep 16, 2026

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yeet alias new_from_def_id

caedbd8

khyperia force-pushed the yeet-new_from_def_id branch from 0ace795 to caedbd8 Compare September 17, 2026 04:55

BoxyUwU approved these changes Sep 17, 2026

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rust-bors Bot added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Sep 17, 2026

JonathanBrouwer mentioned this pull request Sep 17, 2026

Rollup of 24 pull requests #162893

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JonathanBrouwer mentioned this pull request Sep 17, 2026

Rollup of 23 pull requests #162907

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rust-bors Bot merged commit 7ddb377 into rust-lang:main Sep 17, 2026
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matthiaskrgr reviewed Sep 17, 2026

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khyperia deleted the yeet-new_from_def_id branch September 18, 2026 06:13

khyperia mentioned this pull request Sep 18, 2026

generic_const_args: fix unreachable #162937

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