repr(transparent): do not consider repr(C) types to be 1-ZST#147185
Merged
bors merged 1 commit intorust-lang:masterfrom Oct 28, 2025
Merged
repr(transparent): do not consider repr(C) types to be 1-ZST#147185bors merged 1 commit intorust-lang:masterfrom
bors merged 1 commit intorust-lang:masterfrom
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Context: rust-lang/unsafe-code-guidelines#552
This experiments with a suggestion by @RustyYato to stop considering repr(C) types as 1-ZST for the purpose of repr(transparent). If we go with rust-lang/rfcs#3845 (or another approach for fixing repr(C)), they will anyway not be ZST on all targets any more, so this removes a portability hazard. Furthermore, zero-sized repr(C) structs may have to be treated as non-ZST for the win64 ABI (at least that's what gcc/clang do), so allowing them to be ignored in repr(transparent) types is not entirely coherent.
Turns out we already have an FCW for repr(transparent), namely #78586. This extends that lint to also check for repr(C).