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size_hint can be malformed from rustc_middle::mir::traversal::Postorder #137919

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scottmcm opened this issue Mar 3, 2025 · 2 comments · Fixed by #138329
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size_hint can be malformed from rustc_middle::mir::traversal::Postorder #137919

scottmcm opened this issue Mar 3, 2025 · 2 comments · Fixed by #138329
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A-MIR Area: Mid-level IR (MIR) - https://blog.rust-lang.org/2016/04/19/MIR.html T-compiler Relevant to the compiler team, which will review and decide on the PR/issue.

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@scottmcm
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scottmcm commented Mar 3, 2025

Spotted with extra checking from 804cf26

size_hint (4, Some(2)) is malformed from iterator rustc_middle::mir::traversal::Postorder collecting into alloc::vec::Vec<rustc_middle::mir::BasicBlock>

query stack during panic:
#0 [analysis] running analysis passes on this crate
end of query stack
note: Clippy version: clippy 0.1.87 (7a632ba 2025-03-03)
@scottmcm scottmcm added the A-MIR Area: Mid-level IR (MIR) - https://blog.rust-lang.org/2016/04/19/MIR.html label Mar 3, 2025
@rustbot rustbot added the needs-triage This issue may need triage. Remove it if it has been sufficiently triaged. label Mar 3, 2025
@tmiasko tmiasko removed the needs-triage This issue may need triage. Remove it if it has been sufficiently triaged. label Mar 3, 2025
@scottmcm scottmcm self-assigned this Mar 3, 2025
@tmiasko tmiasko added the T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. label Mar 3, 2025
@matthiaskrgr
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should this be a debug assertion? 🤔

@scottmcm
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scottmcm commented Mar 3, 2025

@matthiaskrgr I definitely want to check in some form of checking this!

Probably as debug_assert, like you said. Not sure where would be best in the library; I'm tempted to try putting it in Iterator::collect, for example.

@scottmcm scottmcm mentioned this issue Mar 3, 2025
Merged
bors added a commit to rust-lang-ci/rust that referenced this issue Mar 3, 2025
@bors
Auto merge of rust-lang#137923 - scottmcm:fix-postorder-size-hint, r=…
6b39be3 
…<try>

Simplify `<Postorder as Iterator>::size_hint`

The current version is sometimes malformed (cc rust-lang#137919); let's see if we can get away with a loose but trivially-correct one.
@scottmcm scottmcm mentioned this issue Mar 3, 2025
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bors added a commit to rust-lang-ci/rust that referenced this issue Mar 4, 2025
@bors
Auto merge of rust-lang#137923 - scottmcm:fix-postorder-size-hint, r=…
6ee42d5 
…<try>

Simplify `<Postorder as Iterator>::size_hint`

The current version is sometimes malformed (cc rust-lang#137919); let's see if we can get away with a loose but trivially-correct one.
workingjubilee added a commit to workingjubilee/rustc that referenced this issue Mar 4, 2025
@workingjubilee
Rollup merge of rust-lang#137923 - scottmcm:fix-postorder-size-hint, …
088e780 
…r=tmiasko

Simplify `<Postorder as Iterator>::size_hint`

The current version is sometimes malformed (cc rust-lang#137919); let's see if we can get away with a loose but trivially-correct one.
workingjubilee added a commit to workingjubilee/rustc that referenced this issue Mar 5, 2025
@workingjubilee
Rollup merge of rust-lang#137923 - scottmcm:fix-postorder-size-hint, …
81a4349 
…r=tmiasko

Simplify `<Postorder as Iterator>::size_hint`

The current version is sometimes malformed (cc rust-lang#137919); let's see if we can get away with a loose but trivially-correct one.
rust-timer added a commit to rust-lang-ci/rust that referenced this issue Mar 5, 2025
@rust-timer
Unrolled build for rust-lang#137923
d615aa5 
Rollup merge of rust-lang#137923 - scottmcm:fix-postorder-size-hint, r=tmiasko

Simplify `<Postorder as Iterator>::size_hint`

The current version is sometimes malformed (cc rust-lang#137919); let's see if we can get away with a loose but trivially-correct one.
@scottmcm scottmcm mentioned this issue Mar 11, 2025
Merged
@bors bors closed this as completed in 01bc954 Mar 16, 2025
rust-timer added a commit to rust-lang-ci/rust that referenced this issue Mar 16, 2025
@rust-timer
Unrolled build for rust-lang#138329
7047d14 
Rollup merge of rust-lang#138329 - scottmcm:assert-hint, r=Mark-Simulacrum

debug-assert that the size_hint is well-formed in `collect`

Closes rust-lang#137919

In the hopes of helping to catch any future accidentally-incorrect rustc or stdlib iterators (like the ones rust-lang#137908 accidentally found), this has `Iterator::collect` call `size_hint` and check its `low` doesn't exceed its `Some(high)`.

There's of course a bazillion more places this *could* be checked, but the hope is that this one is a good tradeoff of being likely to catch lots of things while having minimal maintenance cost (especially compared to putting it in *every* container's `from_iter`).
github-actions bot pushed a commit to model-checking/verify-rust-std that referenced this issue Mar 19, 2025
@jieyouxu
Rollup merge of rust-lang#138329 - scottmcm:assert-hint, r=Mark-Simul…
c5f575e 
…acrum

debug-assert that the size_hint is well-formed in `collect`

Closes rust-lang#137919

In the hopes of helping to catch any future accidentally-incorrect rustc or stdlib iterators (like the ones rust-lang#137908 accidentally found), this has `Iterator::collect` call `size_hint` and check its `low` doesn't exceed its `Some(high)`.

There's of course a bazillion more places this *could* be checked, but the hope is that this one is a good tradeoff of being likely to catch lots of things while having minimal maintenance cost (especially compared to putting it in *every* container's `from_iter`).
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debug-assert that the size_hint is well-formed in collect scottmcm/rust
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