Compile-time assertions to ensure that invariants are met.

All assertions within this crate are performed at compile-time. This allows for finding errors quickly and early when it comes to ensuring certain features or aspects of a codebase. These macros are especially important when exposing a public API that requires types to be the same size or implement certain traits.

This crate is available on crates.io and can be used by adding the following to your project's Cargo.toml :

[dependencies] static_assertions = "0.3.4"

and this to your crate root ( main.rs or lib.rs ):

#[ macro_use ] extern crate static_assertions ;

Very thorough examples are provided in the docs for each individual macro. Failure case examples are also documented.

Due to implementation details, some macros can only be used normally from within the context of a function. To use these macros in other contexts, a unique label must be provided.

ⓘ This example deliberately fails to compile

const_assert ! ( true == true );

This can be fixed via:

const_assert ! ( label ; true == true );

This can be followed at issue #1.

The labeling workaround is not necessary (and is removed) when compiling on nightly Rust with the nightly feature flag enabled. This can be done by having the following in your project's Cargo.toml :

[dependencies.static_assertions] version = "0.3.4" features = ["nightly"]

To compile with nightly Rust, run the following in your shell or command prompt of choice:

rustup install nightly cargo +nightly build

Notice that this also requires enabling the underscore_const_names nightly Rust feature:

ⓘ This example is not tested

#![ feature ( underscore_const_names )] const_assert ! ( true != false ); fn main () { const_assert ! ( false != true ); }

See CHANGELOG.md for a complete list of what has changed from one version to another.

This project is made freely available (as in free beer), but unfortunately not all beer is free! So, if you would like to buy me a beer (or coffee or more), then consider supporting my work that's benefited your project and thousands of others.