Show the nested goal chain for the next solver overflow FCW - #161341
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adwinwhite wants to merge 5 commits into
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Show the nested goal chain for the next solver overflow FCW#161341adwinwhite wants to merge 5 commits into
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| @@ -344,6 +344,10 @@ pub struct InferCtxt<'tcx> { | |||
| /// checking so we disable the FCW there as well. | |||
| enable_next_solver_overflow_fcw: bool, | |||
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change this to a Cell instead? 🤔
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| { | ||
| self.in_next_solver_overflow_fcw.set(true); | ||
| let ret = f(); | ||
| self.in_next_solver_overflow_fcw.set(false); |
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feels safer to replace previous entry and then revert to that one in functions like this, otherwise nesting it twice breaks the outer call
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August 20, 2026 08:35
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Some changes occurred to the core trait solver cc @rust-lang/initiative-trait-system-refactor |
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Previously we only showed a single root goal for the FCW. It was difficult to find out how the goal overflowed.
We display a proving chain now which should help users identify relevant types or auto traits.
This will affect perf for crates emitting the FCW. E.g.
calimero-storegoes from 4.7s -> 5.7s in local testing since it emits thousands of FCWs internally. The FCW is a mitigation of future hard error and authors are expected to resolve it so it's probably acceptable. It doesn't affect crates without the FCW.r? lcnr