Simplify polonius location-sensitive analysis #143093

lqd · 2025-06-27T13:50:59Z

This PR reworks the location-sensitive analysis into what we think is a worthwhile subset of the datalog analysis. A sort of polonius alpha analysis that handles NLL problem case 3 and more, but is still using the faster "reachability as an approximation of liveness", as well as the same loans-in-scope computation as NLLs -- and thus doesn't handle full flow-sensitivity like the datalog implementation.

In the last few months, we've identified this subset as being actionable:

we believe we can make a stabilizable version of this analysis
it is an improvement over the status quo
it can also be modeled in a-mir-formality, or some other formalism, for assurances about soundness, and I believe @nikomatsakis is interested in looking into this during H2.
and we've identified the areas of work we wish to explore later to gradually expand the supported cases: the differences between reachability and liveness, support of kills, and considerations of time-traveling, for example.

The approach in this PR is to try less to have the graph only represent live paths, by checking whether we reach a live region during traversal and recording the loan as live there, instead of equating traversal with liveness like today because it has subtleties with the typeck edges in statements (that could forward loans to the successor point without ensuring their liveness). We can then also simplify these typeck stmt edges. And we also can simplify traversal by removing looking at kills, because that's enough to handle a bunch of NLL problem 3 cases -- and we can gradually support them more and more in traversal in the future, to reduce the approximation of liveness.

There's still some in-progress pieces of work w/r/t opaque types that I'm expecting lcnr's opaque types rework, and amanda's SCCs rework to handle. That didn't seem to show up in tests until I rebased today (and shows lack of test coverage once again) when #142255 introduced a couple of test failures with the new captures rules from edition 2024. It's not unexpected since we know more work is needed with member constraints (and we're not even using SCCs in this prototype yet)

I'll look into these anyways, both for future work, and checking how these other 2 PRs would change things.

I'm not sure the following means a lot until we have some formalism in-place, but:

I've changed the polonius compare-mode to use this analysis: the tests pass with it, except 2 cases with minor diagnostics differences, and the 2 edition 2024 opaque types one I mentioned above and need to investigate
things that are expected to work still do work: it bootstraps, can run our rustc-perf benchmarks (and the results are not even that bad), and a crater run didn't find any regressions (forgetting that crater currently fails to test around a quarter of all crates 👼)
I've added tests with improvements, like the NLL problem case 3 and others, as well as some that behave the same as NLLs today and are thus worse than the datalog implementation

r? @jackh726

(no rush I know you're deep in phd work and "implmentating" the new trait solver for r-a :p <3)

This also fixes #135646, a diagnostics ICE from the previous implementation.

rustbot · 2025-06-27T13:51:08Z

This PR changes a file inside tests/crashes. If a crash was fixed, please move into the corresponding ui subdir and add 'Fixes #' to the PR description to autoclose the issue upon merge.

Some changes occurred in src/tools/compiletest

cc @jieyouxu

jackh726 · 2025-06-27T15:26:48Z

Happy to review, but don't expect it for 2 weeks :)

jackh726

First thought: there are a bunch of really useful tests added here. I'd really like to see them added separately, covering nll, polonius-legacy, and polonius-next. You can use known-bug as appropriate.

tests/ui/nll/issue-46589.rs

tests/ui/nll/polonius/nll-problem-case-3.rs

Add a lot of NLL `known-bug` tests r? `@jackh726` As requested in rust-lang#143093 (review) this extracts most tests from that PR and expands upon them as described. The handful of linked-list cursor-like tests will also turn into polonius=next known-bugs in rust-lang#143093 where the behavior w/r/t kills changes of course.

Add a lot of NLL `known-bug` tests r? ``@jackh726`` As requested in rust-lang#143093 (review) this extracts most tests from that PR and expands upon them as described. The handful of linked-list cursor-like tests will also turn into polonius=next known-bugs in rust-lang#143093 where the behavior w/r/t kills changes of course.

Rollup merge of #145053 - lqd:known-bugs, r=jackh726 Add a lot of NLL `known-bug` tests r? ``@jackh726`` As requested in #143093 (review) this extracts most tests from that PR and expands upon them as described. The handful of linked-list cursor-like tests will also turn into polonius=next known-bugs in #143093 where the behavior w/r/t kills changes of course.

The suboptimal error only appears with NLLs due to liveness differences where polonius cannot have as many boring locals. Sometimes this causes NLLs to emit a duplicate error as well.

Remove incomplete handling of kills during traversal for loan liveness to get to a simpler and actionable prototype. This handles the cases, on sufficiently simple examples, that were deferred from NLLs (NLL problem case 3, lending iterators), and is still a good step to put in people's hands without needing to wait for another full implementation. This is a practical cut in scope, but it also shows where are the areas of improvement, that we will explore in the future.

These are just some sanity checks to ensure NLLs, the polonius alpha analysis, and the datalog implementation behave the same on these common examples.

This test showcases the same imprecision as NLLs, unlike the datalog implementation, when using reachability as a liveness approximation.

This is an example similar to the linked-list cursor examples where the alpha shows the same imprecision as NLLs, but that can work due to the loans not being live after the loop, or the constraint graph being simple enough that the cfg/subset relationships are the same for reachability and liveness.

- linked-list cursor-like patterns - issue-46589 These are known-bugs for the polonius alpha, where they show the same imprecision as NLLs, but are supported by the old datalog implementation.

lqd · 2025-08-08T15:23:21Z

Rebased to remove and update the tests now that #145053 has landed.

Add a lot of NLL `known-bug` tests r? ``@jackh726`` As requested in rust-lang/rust#143093 (review) this extracts most tests from that PR and expands upon them as described. The handful of linked-list cursor-like tests will also turn into polonius=next known-bugs in rust-lang/rust#143093 where the behavior w/r/t kills changes of course.

jackh726 · 2025-08-09T16:26:36Z

Seems good to me.

@bors r+

bors · 2025-08-09T16:26:38Z

📌 Commit b99fe2b has been approved by jackh726

It is now in the queue for this repository.

Simplify polonius location-sensitive analysis This PR reworks the location-sensitive analysis into what we think is a worthwhile subset of the datalog analysis. A sort of polonius alpha analysis that handles NLL problem case 3 and more, but is still using the faster "reachability as an approximation of liveness", as well as the same loans-in-scope computation as NLLs -- and thus doesn't handle full flow-sensitivity like the datalog implementation. In the last few months, we've identified this subset as being actionable: - we believe we can make a stabilizable version of this analysis - it is an improvement over the status quo - it can also be modeled in a-mir-formality, or some other formalism, for assurances about soundness, and I believe `@nikomatsakis` is interested in looking into this during H2. - and we've identified the areas of work we wish to explore later to gradually expand the supported cases: the differences between reachability and liveness, support of kills, and considerations of time-traveling, for example. The approach in this PR is to try less to have the graph only represent live paths, by checking whether we reach a live region during traversal and recording the loan as live there, instead of equating traversal with liveness like today because it has subtleties with the typeck edges in statements (that could forward loans to the successor point without ensuring their liveness). We can then also simplify these typeck stmt edges. And we also can simplify traversal by removing looking at kills, because that's enough to handle a bunch of NLL problem 3 cases -- and we can gradually support them more and more in traversal in the future, to reduce the approximation of liveness. There's still some in-progress pieces of work w/r/t opaque types that I'm expecting [lcnr's opaque types rework](rust-lang#139587), and [amanda's SCCs rework](rust-lang#130227) to handle. That didn't seem to show up in tests until I rebased today (and shows lack of test coverage once again) when rust-lang#142255 introduced a couple of test failures with the new captures rules from edition 2024. It's not unexpected since we know more work is needed with member constraints (and we're not even using SCCs in this prototype yet) I'll look into these anyways, both for future work, and checking how these other 2 PRs would change things. --- I'm not sure the following means a lot until we have some formalism in-place, but: - I've changed the polonius compare-mode to use this analysis: the tests pass with it, except 2 cases with minor diagnostics differences, and the 2 edition 2024 opaque types one I mentioned above and need to investigate - things that are expected to work still do work: it bootstraps, can run our rustc-perf benchmarks (and the results are not even that bad), and a crater run didn't find any regressions (forgetting that crater currently fails to test around a quarter of all crates 👼) - I've added tests with improvements, like the NLL problem case 3 and others, as well as some that behave the same as NLLs today and are thus worse than the datalog implementation r? `@jackh726` (no rush I know you're deep in phd work and "implmentating" the new trait solver for r-a :p <3) This also fixes rust-lang#135646, a diagnostics ICE from the previous implementation.

Simplify polonius location-sensitive analysis This PR reworks the location-sensitive analysis into what we think is a worthwhile subset of the datalog analysis. A sort of polonius alpha analysis that handles NLL problem case 3 and more, but is still using the faster "reachability as an approximation of liveness", as well as the same loans-in-scope computation as NLLs -- and thus doesn't handle full flow-sensitivity like the datalog implementation. In the last few months, we've identified this subset as being actionable: - we believe we can make a stabilizable version of this analysis - it is an improvement over the status quo - it can also be modeled in a-mir-formality, or some other formalism, for assurances about soundness, and I believe ``@nikomatsakis`` is interested in looking into this during H2. - and we've identified the areas of work we wish to explore later to gradually expand the supported cases: the differences between reachability and liveness, support of kills, and considerations of time-traveling, for example. The approach in this PR is to try less to have the graph only represent live paths, by checking whether we reach a live region during traversal and recording the loan as live there, instead of equating traversal with liveness like today because it has subtleties with the typeck edges in statements (that could forward loans to the successor point without ensuring their liveness). We can then also simplify these typeck stmt edges. And we also can simplify traversal by removing looking at kills, because that's enough to handle a bunch of NLL problem 3 cases -- and we can gradually support them more and more in traversal in the future, to reduce the approximation of liveness. There's still some in-progress pieces of work w/r/t opaque types that I'm expecting [lcnr's opaque types rework](rust-lang#139587), and [amanda's SCCs rework](rust-lang#130227) to handle. That didn't seem to show up in tests until I rebased today (and shows lack of test coverage once again) when rust-lang#142255 introduced a couple of test failures with the new captures rules from edition 2024. It's not unexpected since we know more work is needed with member constraints (and we're not even using SCCs in this prototype yet) I'll look into these anyways, both for future work, and checking how these other 2 PRs would change things. --- I'm not sure the following means a lot until we have some formalism in-place, but: - I've changed the polonius compare-mode to use this analysis: the tests pass with it, except 2 cases with minor diagnostics differences, and the 2 edition 2024 opaque types one I mentioned above and need to investigate - things that are expected to work still do work: it bootstraps, can run our rustc-perf benchmarks (and the results are not even that bad), and a crater run didn't find any regressions (forgetting that crater currently fails to test around a quarter of all crates 👼) - I've added tests with improvements, like the NLL problem case 3 and others, as well as some that behave the same as NLLs today and are thus worse than the datalog implementation r? ``@jackh726`` (no rush I know you're deep in phd work and "implmentating" the new trait solver for r-a :p <3) This also fixes rust-lang#135646, a diagnostics ICE from the previous implementation.

Simplify polonius location-sensitive analysis This PR reworks the location-sensitive analysis into what we think is a worthwhile subset of the datalog analysis. A sort of polonius alpha analysis that handles NLL problem case 3 and more, but is still using the faster "reachability as an approximation of liveness", as well as the same loans-in-scope computation as NLLs -- and thus doesn't handle full flow-sensitivity like the datalog implementation. In the last few months, we've identified this subset as being actionable: - we believe we can make a stabilizable version of this analysis - it is an improvement over the status quo - it can also be modeled in a-mir-formality, or some other formalism, for assurances about soundness, and I believe ```@nikomatsakis``` is interested in looking into this during H2. - and we've identified the areas of work we wish to explore later to gradually expand the supported cases: the differences between reachability and liveness, support of kills, and considerations of time-traveling, for example. The approach in this PR is to try less to have the graph only represent live paths, by checking whether we reach a live region during traversal and recording the loan as live there, instead of equating traversal with liveness like today because it has subtleties with the typeck edges in statements (that could forward loans to the successor point without ensuring their liveness). We can then also simplify these typeck stmt edges. And we also can simplify traversal by removing looking at kills, because that's enough to handle a bunch of NLL problem 3 cases -- and we can gradually support them more and more in traversal in the future, to reduce the approximation of liveness. There's still some in-progress pieces of work w/r/t opaque types that I'm expecting [lcnr's opaque types rework](rust-lang#139587), and [amanda's SCCs rework](rust-lang#130227) to handle. That didn't seem to show up in tests until I rebased today (and shows lack of test coverage once again) when rust-lang#142255 introduced a couple of test failures with the new captures rules from edition 2024. It's not unexpected since we know more work is needed with member constraints (and we're not even using SCCs in this prototype yet) I'll look into these anyways, both for future work, and checking how these other 2 PRs would change things. --- I'm not sure the following means a lot until we have some formalism in-place, but: - I've changed the polonius compare-mode to use this analysis: the tests pass with it, except 2 cases with minor diagnostics differences, and the 2 edition 2024 opaque types one I mentioned above and need to investigate - things that are expected to work still do work: it bootstraps, can run our rustc-perf benchmarks (and the results are not even that bad), and a crater run didn't find any regressions (forgetting that crater currently fails to test around a quarter of all crates 👼) - I've added tests with improvements, like the NLL problem case 3 and others, as well as some that behave the same as NLLs today and are thus worse than the datalog implementation r? ```@jackh726``` (no rush I know you're deep in phd work and "implmentating" the new trait solver for r-a :p <3) This also fixes rust-lang#135646, a diagnostics ICE from the previous implementation.

Simplify polonius location-sensitive analysis This PR reworks the location-sensitive analysis into what we think is a worthwhile subset of the datalog analysis. A sort of polonius alpha analysis that handles NLL problem case 3 and more, but is still using the faster "reachability as an approximation of liveness", as well as the same loans-in-scope computation as NLLs -- and thus doesn't handle full flow-sensitivity like the datalog implementation. In the last few months, we've identified this subset as being actionable: - we believe we can make a stabilizable version of this analysis - it is an improvement over the status quo - it can also be modeled in a-mir-formality, or some other formalism, for assurances about soundness, and I believe ````@nikomatsakis```` is interested in looking into this during H2. - and we've identified the areas of work we wish to explore later to gradually expand the supported cases: the differences between reachability and liveness, support of kills, and considerations of time-traveling, for example. The approach in this PR is to try less to have the graph only represent live paths, by checking whether we reach a live region during traversal and recording the loan as live there, instead of equating traversal with liveness like today because it has subtleties with the typeck edges in statements (that could forward loans to the successor point without ensuring their liveness). We can then also simplify these typeck stmt edges. And we also can simplify traversal by removing looking at kills, because that's enough to handle a bunch of NLL problem 3 cases -- and we can gradually support them more and more in traversal in the future, to reduce the approximation of liveness. There's still some in-progress pieces of work w/r/t opaque types that I'm expecting [lcnr's opaque types rework](rust-lang#139587), and [amanda's SCCs rework](rust-lang#130227) to handle. That didn't seem to show up in tests until I rebased today (and shows lack of test coverage once again) when rust-lang#142255 introduced a couple of test failures with the new captures rules from edition 2024. It's not unexpected since we know more work is needed with member constraints (and we're not even using SCCs in this prototype yet) I'll look into these anyways, both for future work, and checking how these other 2 PRs would change things. --- I'm not sure the following means a lot until we have some formalism in-place, but: - I've changed the polonius compare-mode to use this analysis: the tests pass with it, except 2 cases with minor diagnostics differences, and the 2 edition 2024 opaque types one I mentioned above and need to investigate - things that are expected to work still do work: it bootstraps, can run our rustc-perf benchmarks (and the results are not even that bad), and a crater run didn't find any regressions (forgetting that crater currently fails to test around a quarter of all crates 👼) - I've added tests with improvements, like the NLL problem case 3 and others, as well as some that behave the same as NLLs today and are thus worse than the datalog implementation r? ````@jackh726```` (no rush I know you're deep in phd work and "implmentating" the new trait solver for r-a :p <3) This also fixes rust-lang#135646, a diagnostics ICE from the previous implementation.

Rollup of 19 pull requests Successful merges: - #141624 (unstable-book: Add stubs for environment variables; document some of the important ones) - #143093 (Simplify polonius location-sensitive analysis) - #144402 (Stabilize loongarch32 inline asm) - #144403 (`tests/ui/issues/`: The Issues Strike Back [4/N]) - #144544 (Start reporting future breakage for `ILL_FORMED_ATTRIBUTE_INPUT` in dependencies) - #144739 (Use new public libtest `ERROR_EXIT_CODE` constant in rustdoc) - #145089 (Improve error output when a command fails in bootstrap) - #145112 ([win][arm64ec] Partial fix for raw-dylib-link-ordinal on Arm64EC) - #145129 ([win][arm64ec] Add `/machine:arm64ec` when linking LLVM as Arm64EC) - #145130 (improve "Documentation problem" issue template.) - #145135 (Stabilize `duration_constructors_lite` feature) - #145145 (some `derive_more` refactors) - #145147 (rename `TraitRef::from_method` to `from_assoc`) - #145156 (Override custom Cargo `build-dir` in bootstrap) - #145160 (Change days-threshold to 28 in [behind-upstream]) - #145162 (`{BTree,Hash}Map`: add "`Entry` API" section heading) - #145175 (Enable limit_rdylib_exports on Solaris) - #145187 (Fix an unstable feature comment that wasn't a doc comment) - #145191 (`suggest_borrow_generic_arg`: use the correct generic args) r? `@ghost` `@rustbot` modify labels: rollup

Simplify polonius location-sensitive analysis This PR reworks the location-sensitive analysis into what we think is a worthwhile subset of the datalog analysis. A sort of polonius alpha analysis that handles NLL problem case 3 and more, but is still using the faster "reachability as an approximation of liveness", as well as the same loans-in-scope computation as NLLs -- and thus doesn't handle full flow-sensitivity like the datalog implementation. In the last few months, we've identified this subset as being actionable: - we believe we can make a stabilizable version of this analysis - it is an improvement over the status quo - it can also be modeled in a-mir-formality, or some other formalism, for assurances about soundness, and I believe `````@nikomatsakis````` is interested in looking into this during H2. - and we've identified the areas of work we wish to explore later to gradually expand the supported cases: the differences between reachability and liveness, support of kills, and considerations of time-traveling, for example. The approach in this PR is to try less to have the graph only represent live paths, by checking whether we reach a live region during traversal and recording the loan as live there, instead of equating traversal with liveness like today because it has subtleties with the typeck edges in statements (that could forward loans to the successor point without ensuring their liveness). We can then also simplify these typeck stmt edges. And we also can simplify traversal by removing looking at kills, because that's enough to handle a bunch of NLL problem 3 cases -- and we can gradually support them more and more in traversal in the future, to reduce the approximation of liveness. There's still some in-progress pieces of work w/r/t opaque types that I'm expecting [lcnr's opaque types rework](rust-lang#139587), and [amanda's SCCs rework](rust-lang#130227) to handle. That didn't seem to show up in tests until I rebased today (and shows lack of test coverage once again) when rust-lang#142255 introduced a couple of test failures with the new captures rules from edition 2024. It's not unexpected since we know more work is needed with member constraints (and we're not even using SCCs in this prototype yet) I'll look into these anyways, both for future work, and checking how these other 2 PRs would change things. --- I'm not sure the following means a lot until we have some formalism in-place, but: - I've changed the polonius compare-mode to use this analysis: the tests pass with it, except 2 cases with minor diagnostics differences, and the 2 edition 2024 opaque types one I mentioned above and need to investigate - things that are expected to work still do work: it bootstraps, can run our rustc-perf benchmarks (and the results are not even that bad), and a crater run didn't find any regressions (forgetting that crater currently fails to test around a quarter of all crates 👼) - I've added tests with improvements, like the NLL problem case 3 and others, as well as some that behave the same as NLLs today and are thus worse than the datalog implementation r? `````@jackh726````` (no rush I know you're deep in phd work and "implmentating" the new trait solver for r-a :p <3) This also fixes rust-lang#135646, a diagnostics ICE from the previous implementation.

Rollup of 18 pull requests Successful merges: - #141624 (unstable-book: Add stubs for environment variables; document some of the important ones) - #143093 (Simplify polonius location-sensitive analysis) - #144402 (Stabilize loongarch32 inline asm) - #144403 (`tests/ui/issues/`: The Issues Strike Back [4/N]) - #144739 (Use new public libtest `ERROR_EXIT_CODE` constant in rustdoc) - #145089 (Improve error output when a command fails in bootstrap) - #145112 ([win][arm64ec] Partial fix for raw-dylib-link-ordinal on Arm64EC) - #145129 ([win][arm64ec] Add `/machine:arm64ec` when linking LLVM as Arm64EC) - #145130 (improve "Documentation problem" issue template.) - #145135 (Stabilize `duration_constructors_lite` feature) - #145145 (some `derive_more` refactors) - #145147 (rename `TraitRef::from_method` to `from_assoc`) - #145156 (Override custom Cargo `build-dir` in bootstrap) - #145160 (Change days-threshold to 28 in [behind-upstream]) - #145162 (`{BTree,Hash}Map`: add "`Entry` API" section heading) - #145175 (Enable limit_rdylib_exports on Solaris) - #145187 (Fix an unstable feature comment that wasn't a doc comment) - #145191 (`suggest_borrow_generic_arg`: use the correct generic args) r? `@ghost` `@rustbot` modify labels: rollup

Simplify polonius location-sensitive analysis This PR reworks the location-sensitive analysis into what we think is a worthwhile subset of the datalog analysis. A sort of polonius alpha analysis that handles NLL problem case 3 and more, but is still using the faster "reachability as an approximation of liveness", as well as the same loans-in-scope computation as NLLs -- and thus doesn't handle full flow-sensitivity like the datalog implementation. In the last few months, we've identified this subset as being actionable: - we believe we can make a stabilizable version of this analysis - it is an improvement over the status quo - it can also be modeled in a-mir-formality, or some other formalism, for assurances about soundness, and I believe ``````@nikomatsakis`````` is interested in looking into this during H2. - and we've identified the areas of work we wish to explore later to gradually expand the supported cases: the differences between reachability and liveness, support of kills, and considerations of time-traveling, for example. The approach in this PR is to try less to have the graph only represent live paths, by checking whether we reach a live region during traversal and recording the loan as live there, instead of equating traversal with liveness like today because it has subtleties with the typeck edges in statements (that could forward loans to the successor point without ensuring their liveness). We can then also simplify these typeck stmt edges. And we also can simplify traversal by removing looking at kills, because that's enough to handle a bunch of NLL problem 3 cases -- and we can gradually support them more and more in traversal in the future, to reduce the approximation of liveness. There's still some in-progress pieces of work w/r/t opaque types that I'm expecting [lcnr's opaque types rework](rust-lang#139587), and [amanda's SCCs rework](rust-lang#130227) to handle. That didn't seem to show up in tests until I rebased today (and shows lack of test coverage once again) when rust-lang#142255 introduced a couple of test failures with the new captures rules from edition 2024. It's not unexpected since we know more work is needed with member constraints (and we're not even using SCCs in this prototype yet) I'll look into these anyways, both for future work, and checking how these other 2 PRs would change things. --- I'm not sure the following means a lot until we have some formalism in-place, but: - I've changed the polonius compare-mode to use this analysis: the tests pass with it, except 2 cases with minor diagnostics differences, and the 2 edition 2024 opaque types one I mentioned above and need to investigate - things that are expected to work still do work: it bootstraps, can run our rustc-perf benchmarks (and the results are not even that bad), and a crater run didn't find any regressions (forgetting that crater currently fails to test around a quarter of all crates 👼) - I've added tests with improvements, like the NLL problem case 3 and others, as well as some that behave the same as NLLs today and are thus worse than the datalog implementation r? ``````@jackh726`````` (no rush I know you're deep in phd work and "implmentating" the new trait solver for r-a :p <3) This also fixes rust-lang#135646, a diagnostics ICE from the previous implementation.

Simplify polonius location-sensitive analysis This PR reworks the location-sensitive analysis into what we think is a worthwhile subset of the datalog analysis. A sort of polonius alpha analysis that handles NLL problem case 3 and more, but is still using the faster "reachability as an approximation of liveness", as well as the same loans-in-scope computation as NLLs -- and thus doesn't handle full flow-sensitivity like the datalog implementation. In the last few months, we've identified this subset as being actionable: - we believe we can make a stabilizable version of this analysis - it is an improvement over the status quo - it can also be modeled in a-mir-formality, or some other formalism, for assurances about soundness, and I believe ```````@nikomatsakis``````` is interested in looking into this during H2. - and we've identified the areas of work we wish to explore later to gradually expand the supported cases: the differences between reachability and liveness, support of kills, and considerations of time-traveling, for example. The approach in this PR is to try less to have the graph only represent live paths, by checking whether we reach a live region during traversal and recording the loan as live there, instead of equating traversal with liveness like today because it has subtleties with the typeck edges in statements (that could forward loans to the successor point without ensuring their liveness). We can then also simplify these typeck stmt edges. And we also can simplify traversal by removing looking at kills, because that's enough to handle a bunch of NLL problem 3 cases -- and we can gradually support them more and more in traversal in the future, to reduce the approximation of liveness. There's still some in-progress pieces of work w/r/t opaque types that I'm expecting [lcnr's opaque types rework](rust-lang#139587), and [amanda's SCCs rework](rust-lang#130227) to handle. That didn't seem to show up in tests until I rebased today (and shows lack of test coverage once again) when rust-lang#142255 introduced a couple of test failures with the new captures rules from edition 2024. It's not unexpected since we know more work is needed with member constraints (and we're not even using SCCs in this prototype yet) I'll look into these anyways, both for future work, and checking how these other 2 PRs would change things. --- I'm not sure the following means a lot until we have some formalism in-place, but: - I've changed the polonius compare-mode to use this analysis: the tests pass with it, except 2 cases with minor diagnostics differences, and the 2 edition 2024 opaque types one I mentioned above and need to investigate - things that are expected to work still do work: it bootstraps, can run our rustc-perf benchmarks (and the results are not even that bad), and a crater run didn't find any regressions (forgetting that crater currently fails to test around a quarter of all crates 👼) - I've added tests with improvements, like the NLL problem case 3 and others, as well as some that behave the same as NLLs today and are thus worse than the datalog implementation r? ```````@jackh726``````` (no rush I know you're deep in phd work and "implmentating" the new trait solver for r-a :p <3) This also fixes rust-lang#135646, a diagnostics ICE from the previous implementation.

Rollup of 17 pull requests Successful merges: - #141624 (unstable-book: Add stubs for environment variables; document some of the important ones) - #143093 (Simplify polonius location-sensitive analysis) - #144402 (Stabilize loongarch32 inline asm) - #144403 (`tests/ui/issues/`: The Issues Strike Back [4/N]) - #144739 (Use new public libtest `ERROR_EXIT_CODE` constant in rustdoc) - #145089 (Improve error output when a command fails in bootstrap) - #145112 ([win][arm64ec] Partial fix for raw-dylib-link-ordinal on Arm64EC) - #145129 ([win][arm64ec] Add `/machine:arm64ec` when linking LLVM as Arm64EC) - #145130 (improve "Documentation problem" issue template.) - #145135 (Stabilize `duration_constructors_lite` feature) - #145145 (some `derive_more` refactors) - #145147 (rename `TraitRef::from_method` to `from_assoc`) - #145156 (Override custom Cargo `build-dir` in bootstrap) - #145160 (Change days-threshold to 28 in [behind-upstream]) - #145162 (`{BTree,Hash}Map`: add "`Entry` API" section heading) - #145187 (Fix an unstable feature comment that wasn't a doc comment) - #145191 (`suggest_borrow_generic_arg`: use the correct generic args) r? `@ghost` `@rustbot` modify labels: rollup

Rollup merge of #143093 - lqd:polonius-pre-alpha, r=jackh726 Simplify polonius location-sensitive analysis This PR reworks the location-sensitive analysis into what we think is a worthwhile subset of the datalog analysis. A sort of polonius alpha analysis that handles NLL problem case 3 and more, but is still using the faster "reachability as an approximation of liveness", as well as the same loans-in-scope computation as NLLs -- and thus doesn't handle full flow-sensitivity like the datalog implementation. In the last few months, we've identified this subset as being actionable: - we believe we can make a stabilizable version of this analysis - it is an improvement over the status quo - it can also be modeled in a-mir-formality, or some other formalism, for assurances about soundness, and I believe ````````@nikomatsakis```````` is interested in looking into this during H2. - and we've identified the areas of work we wish to explore later to gradually expand the supported cases: the differences between reachability and liveness, support of kills, and considerations of time-traveling, for example. The approach in this PR is to try less to have the graph only represent live paths, by checking whether we reach a live region during traversal and recording the loan as live there, instead of equating traversal with liveness like today because it has subtleties with the typeck edges in statements (that could forward loans to the successor point without ensuring their liveness). We can then also simplify these typeck stmt edges. And we also can simplify traversal by removing looking at kills, because that's enough to handle a bunch of NLL problem 3 cases -- and we can gradually support them more and more in traversal in the future, to reduce the approximation of liveness. There's still some in-progress pieces of work w/r/t opaque types that I'm expecting [lcnr's opaque types rework](#139587), and [amanda's SCCs rework](#130227) to handle. That didn't seem to show up in tests until I rebased today (and shows lack of test coverage once again) when #142255 introduced a couple of test failures with the new captures rules from edition 2024. It's not unexpected since we know more work is needed with member constraints (and we're not even using SCCs in this prototype yet) I'll look into these anyways, both for future work, and checking how these other 2 PRs would change things. --- I'm not sure the following means a lot until we have some formalism in-place, but: - I've changed the polonius compare-mode to use this analysis: the tests pass with it, except 2 cases with minor diagnostics differences, and the 2 edition 2024 opaque types one I mentioned above and need to investigate - things that are expected to work still do work: it bootstraps, can run our rustc-perf benchmarks (and the results are not even that bad), and a crater run didn't find any regressions (forgetting that crater currently fails to test around a quarter of all crates 👼) - I've added tests with improvements, like the NLL problem case 3 and others, as well as some that behave the same as NLLs today and are thus worse than the datalog implementation r? ````````@jackh726```````` (no rush I know you're deep in phd work and "implmentating" the new trait solver for r-a :p <3) This also fixes #135646, a diagnostics ICE from the previous implementation.

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lqd force-pushed the polonius-pre-alpha branch from 09a0ec6 to 3d44596 Compare June 27, 2025 13:53

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Scalable Polonius support on nightly rust-lang/rust-project-goals#118

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lqd force-pushed the polonius-pre-alpha branch from 3d44596 to 24b9e97 Compare July 2, 2025 09:31

lqd mentioned this pull request Jul 17, 2025

Propose 2025h2 goal for polonius alpha rust-lang/rust-project-goals#341

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rustbot added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Jul 26, 2025

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Add a lot of NLL known-bug tests #145053

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lqd added 2 commits August 8, 2025 14:10

switch polonius compare-mode to polonius=next

43327b5

update test expectations for boring locals + dropckoutlives interactions

f4094ea

The suboptimal error only appears with NLLs due to liveness differences where polonius cannot have as many boring locals. Sometimes this causes NLLs to emit a duplicate error as well.

lqd force-pushed the polonius-pre-alpha branch 3 times, most recently from 9f959bd to 1e087f2 Compare August 8, 2025 14:59

lqd added 4 commits August 8, 2025 15:14

new impl fixes crash test

1330898

turn expensive assert into debug assertion

d4bbd68

add some test cases for overlapping yielded items

b172980

These are just some sanity checks to ensure NLLs, the polonius alpha analysis, and the datalog implementation behave the same on these common examples.

lqd added 3 commits August 8, 2025 15:14

add NLL-like imprecision example

48ebae9

This test showcases the same imprecision as NLLs, unlike the datalog implementation, when using reachability as a liveness approximation.

mark polonius=next's NLL imprecisions as known-bugs

b99fe2b

- linked-list cursor-like patterns - issue-46589 These are known-bugs for the polonius alpha, where they show the same imprecision as NLLs, but are supported by the old datalog implementation.

lqd force-pushed the polonius-pre-alpha branch from 1e087f2 to b99fe2b Compare August 8, 2025 15:18

bors 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-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Aug 9, 2025

Zalathar mentioned this pull request Aug 10, 2025

Rollup of 21 pull requests #145192

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Rollup of 19 pull requests #145195

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Rollup of 19 pull requests #145197

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Rollup of 18 pull requests #145204

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Rollup of 17 pull requests #145210

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bors merged commit e5b98a9 into rust-lang:master Aug 10, 2025
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lqd deleted the polonius-pre-alpha branch August 10, 2025 18:21

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