diff options
Diffstat (limited to 'compiler/rustc_index/src/lib.rs')
| -rw-r--r-- | compiler/rustc_index/src/lib.rs | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/compiler/rustc_index/src/lib.rs b/compiler/rustc_index/src/lib.rs index 9942c70c4ae..0c5f6ff7a79 100644 --- a/compiler/rustc_index/src/lib.rs +++ b/compiler/rustc_index/src/lib.rs @@ -29,6 +29,13 @@ pub use {idx::Idx, slice::IndexSlice, vec::IndexVec}; pub use rustc_macros::newtype_index; /// Type size assertion. The first argument is a type and the second argument is its expected size. +/// Note to the reader: Emitting hard errors from size assertions like this is generally not +/// recommended, especially in libraries, because they can cause build failures if the layout +/// algorithm or dependencies change. Here in rustc we control the toolchain and layout algorithm, +/// so the former is not a problem. For the latter we have a lockfile as rustc is an application and +/// precompiled library. +/// +/// Short version: Don't copy this macro into your own code. Use a `#[test]` instead. #[macro_export] macro_rules! static_assert_size { ($ty:ty, $size:expr) => { |