Fast-reject method probe candidates by self type head [in -0.51% batch]#52
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Fast-reject method probe candidates by self type head [in -0.51% batch]#52xmakro wants to merge 1 commit into
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Every method-call probe runs a by-value candidate pass before the autoref passes, and for the overwhelmingly common &self/&mut self methods that pass scans all name-matched candidates, paying for a snapshot, fresh args and normalization per candidate just to fail the self type unification. Compare the simplified head of the receiver against the simplified head of the method's declared self parameter first; two concrete, different heads cannot unify. Bare Self, aliases and non-method items fall through to the full check, and path-mode (UFCS) probes are exempt since they relate against the impl self type instead.
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Every method-call probe runs a by-value candidate pass before the autoref passes, and for the overwhelmingly common &self/&mut self methods that pass scans all name-matched candidates, paying for a snapshot, fresh args for the impl, and normalization per candidate just to fail the self type unification. Compare the simplified head of the receiver against the simplified head of the method's declared self parameter first; two concrete, different heads cannot unify, so the whole per-candidate machinery is skipped.
Bare Self, aliases and non-method items fall through to the full check. Path-mode (UFCS) probes are exempt: they relate against the impl self type, not the method's self parameter — the builtin Debug derive expands to exactly such qualified calls, so getting this wrong fails bootstrap immediately.
Measurement context: the four sibling batch-4 branches were measured together on top of the earlier branches (ThinLTO stage2, glibc allocator, instructions:u, full scenario): combined -0.51% geomean, syn check -1.18%, ripgrep check -1.12%, hyper check -0.87%, cargo check -0.77%, serde check -0.52%, 9 of 15 cells improved >= 0.25%, 0 regressed. Full tests/ui passes with the whole stack (only the 7 pre-existing triaged diffs). The compiler bootstraps itself with all of it. The whole 4-batch stack measures -3.42% geomean with every one of the 15 cells improved.