derive(Error) for no_std environments

This is a fork of thiserror using the nightly only, experimental errorincore feature in no_std environments.

Usage

toml // Cargo.toml [dependencies] thiserror = { version = "1.0", package = "thiserror-core", default-features = false }

```rust // main.rs

![no_std]

![feature(errorincore)]

```

Differences between thiserror and thiserror-core

Differences are kept to a minimum and changes in thiserror master will be adopted by rebasing thiserror-core.

With the default std feature enabled, any functional difference between thiserror and thiserror-core is considered a bug.

As soon as the matching PR is merged or equivalent changes adopted, this crate will be updated to re-export thiserror.