assert

Add the following extensions methods for dictionaries:

var dictionary = new Dictionary<string, string>
{
    ["key1"] = "value1",
    ["key2"] = "value2",
};

dictionary.Throw().IfContainsKey("key1");
dictionary.Throw().IfNotContainsKey("key3");

And the corresponding dictionary properties extension methods:

var dictionary = new Dictionary<string, string

Platform (all, jvm, js): all
Extension (none, kotlin 1.3): none

Code related feature

Would be nicer to have the build file in Kotlin instead of groovy

Your first contribution?

• Write a comment I'll work on this if you would like to take this issue over.
  This way we get the chance to revise the description in case things have changed in the meantime, we might give you addi

Describe the solution you'd like
Add compile-time String concactenation support in messages. Currently, constraits's message with concactenated strings can only be evaluated at runtime (gives the <Unknown> message at compile-time instead).

Describe alternatives you've considered
A potential solution would be to create our own instance of FromExpr[String] based on the stdlib's one