rustc_builtin_macros: rename bench parameter to avoid collisions with user-defined function names #148279
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… user-defined function names
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oli-obk
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Oct 30, 2025
hkBst
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Oct 31, 2025
hkBst
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Oct 31, 2025
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hkBst
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Nov 5, 2025
hkBst
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| // A simple ident for a lambda | ||
| let b = Ident::from_str_and_span("b", attr_sp); | ||
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| // A collision-resistant ident for a lambda, using the user's function name within it to avoid collisions. |
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this is now repeating "collision", and should probably also link to the bug this solves.
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| // A collision-resistant ident for a lambda, using the user's function name within it to avoid collisions. | |
| // try to avoid name collisions, see bug #148275 |
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Resolves #148275 by preventing name collisions in the
#[bench]macro.Previously, a user-defined function named "b" could not be benchmarked because
the macro-generated lambda identity collided with the same name. We now generate
the lambda ident as
__bench_<function_name>, ensuring it is always distinctfrom the user’s function.
Because the prefix is applied recursively (e.g. benchmarking
__bench_bproduces a lambda ident
__bench___bench_b), there is no possible functionname that can equal its corresponding lambda ident. This guarantees that
the user can safely bench a function of any valid name without risk of
identifier collision.