Add require macro

[ethanfrey]

Suggestion from Twitter: https://twitter.com/gakonst/status/1440428252267376659?s=21

macros to reduce verbosity for very common operations is one (eg if !condition { return Err("some error string")} should really be require!(condition, "some error string"))

A more concrete example where we could do codeine, taking:

require!(info.sender == cfg.admin, ContractErr::Unauthorized{});

that generates something like:

if ! (info.sender == cfg.admin) {
    return Err(ContractErr::Unauthorized{});
}

Maybe this macro exists in a standard Rust package already and using it in sample contracts we could highlight it.

[webmaster128]

Makes sense. It's a pitty we don't get panic messages when compiling to Wasm because Rust already provides those types of tings (assert!(condition, "message");).

[ethanfrey]

Maybe for 1.0?

[webmaster128]

This is a compatible addition and can be done at any time

[ethanfrey]

This is basically what ensure! does

[ethanfrey]

Sure, no need to get it in 1.0. I want to use it soonish... will add to cw-plus

[webmaster128]

Happy to pull it in for maintenance from CosmWasm/cw-plus#469 when we see it works well in the caller code and devs like it.

[ethanfrey]

Great idea.
Let's get some feedback and quick iteration in cw-plus, then pull it into cosmwasm_std when it is stabilised