Lower a type remapped to a fixed-size buffer to a pointer#745
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tannergooding merged 1 commit intoJul 13, 2026
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A type remapped to a fixed-size-buffer shape such as `sbyte[8]` was emitted verbatim, which is not a legal C# type in an unmanaged signature and was not detected as unsafe. Lower it to the equivalent pointer, matching how C decays an array to a pointer at the ABI boundary; this also marks the containing member unsafe via the existing `*` check. Fixes dotnet#593 Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
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A type remapped to a fixed-size-buffer shape such as
sbyte[8]was emitted verbatim, which is not a legal C# type in an unmanaged signature and was not detected as unsafe (yieldingCS0214). Lower it to the equivalent pointer inGetRemappedTypeName, matching how C decays an array to a pointer at the ABI boundary. This makes the emission legal and marks the containing memberunsafevia the existing*check.The lowering is gated on a numeric subscript (
[<digit>), so a managed array such asint[](empty subscript) is left untouched.Notably, no legal C input reaches this path -- real array parameters/returns already decay to
*, pointer-to-array (int (*)[8]) decays toint**, and array fields lower to_e__FixedBuffer/InlineArray/fixed. The only trigger is an explicit--remap X=T[N], so this supersedes the substring]heuristic previously considered for #593; pointer lowering is both legal and correctlyunsafe.Fixes #593
Co-authored-by: Copilot App 223556219+Copilot@users.noreply.github.com