unsupported_calling_conventions: print which ABI this is about #142466
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We modify rustc_ast_lowering to prevent all unsupported ABIs
from leaking through the HIR without being checked for target support.
Previously ad-hoc checking on various HIR items required making sure
we check every HIR item which could contain an `extern "{abi}"` string.
This is a losing proposition compared to gating the lowering itself.
As a consequence, unsupported ABI strings will now hard-error instead of
triggering the FCW `unsupported_fn_ptr_calling_conventions`.
This FCW was upgraded to warn in dependencies in Rust 1.87 which was
released on 2025 May 17, and it is now 2025 June, so it has become
active within a stable Rust version.
As we already had errored on these ABIs in most other positions, and
have warned for fn ptrs, this breakage has had reasonable foreshadowing.
However, this does cause errors for usages of `extern "{abi}"` that were
theoretically writeable within source but could not actually be applied
in any useful way by Rust programmers without either warning or error.
For instance, trait declarations without impls were never checked.
These are the exact kinds of leakages that this new approach prevents.
A deprecation cycle is not useful for these marginal cases as upon impl,
even default impls within traits, different HIR objects would be used.
Details of our HIR analysis meant that those objects did get checked.
…ABIs Co-authored-by: Ralf Jung <[email protected]>
Co-authored-by: Ralf Jung <[email protected]>
rustbot
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A-test-infra-minicore
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Cherried, thanks! |
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Improve the lint message to say what the problematic ABI is. When macros are involved, that can otherwise be non-trivial to figure out.
Based on #142134 to reduce conflicts.
r? @workingjubilee
(alternatively, feel free to just cherry-pick this into your PR and close this one)