Cannot transmute between ZST and zero-sized generic array #98104
Open
Description
I tried this code: (Playground)
struct GenericZst<T> {
a: [T; 0],
}
fn foo<T>() -> GenericZst<T> {
unsafe { ::core::mem::transmute::<(), GenericZst<T>>(()) }
}I expected this to compile, because [T; 0] is always zero-sized.
Instead, it fails to compile with this error:
error[E0512]: cannot transmute between types of different sizes, or dependently-sized types
--> src/lib.rs:6:14
|
6 | unsafe { ::core::mem::transmute::<(), GenericZst<T>>(()) }
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= note: source type: `()` (0 bits)
= note: target type: `GenericZst<T>` (size can vary because of T)
For more information about this error, try `rustc --explain E0512`.
error: could not compile `playground` due to previous error
Meta
rustc --version --verbose:
rustc 1.63.0-nightly (ca122c7eb 2022-06-13)
binary: rustc
commit-hash: ca122c7ebb3ab50149c9d3d24ddb59c252b32272
commit-date: 2022-06-13
host: x86_64-unknown-linux-gnu
release: 1.63.0-nightly
LLVM version: 14.0.5
somewhat related: #98064