David Tolnay 3c0aac44d7 assertions: Add compile-time assertion macro ... A static assertion is particularly appropriate when unsafe code relies on two types to have the same size, or on some type to have a particular size. This is a pattern I observed in USB code, for example: ff7068402e/devices/src/usb/xhci/xhci_abi_schema.rs (522) EXAMPLE: extern crate assertions; use assertions::const_assert; fn main() { const_assert!(std::mem::size_of::<String>() == 24); } EXAMPLE THAT FAILS TO COMPILE: extern crate assertions; use assertions::const_assert; fn main() { // fails to compile: const_assert!(std::mem::size_of::<String>() == 8); } FAILURE LOOKS LIKE: error[E0271]: type mismatch resolving `<[(); 0] as assertions::Expr>::Value == assertions::True` --> src/main.rs:5:5 | 5 | const_assert!(std::mem::size_of::<String>() == 8); | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected struct `assertions::True`, found struct `assertions::False` TEST=`cargo test` the new crate Change-Id: I6abe36d5a6a4bd4acb1a02e3aa7c1ece5357f007 Reviewed-on: https://chromium-review.googlesource.com/1366819 Commit-Ready: ChromeOS CL Exonerator Bot <chromiumos-cl-exonerator@appspot.gserviceaccount.com> Tested-by: David Tolnay <dtolnay@chromium.org> Reviewed-by: Dylan Reid <dgreid@chromium.org>		2018-12-09 00:48:17 -08:00
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src	assertions: Add compile-time assertion macro	2018-12-09 00:48:17 -08:00
Cargo.toml	assertions: Add compile-time assertion macro	2018-12-09 00:48:17 -08:00