Are template litteral runtime checked??
If my parameter only accept "foo" or "bar" and that at runtime I send an invalid input, will I get a type runtime exception? Or will it silently allow the invalid input? If it's the former, that would be great news but then I wouldn't see the point in Io-ts, and where is the limit? Could they stop type erasure and allow generics reification?
nothing in TS is runtime checked.
That's what I thought, so you're telling me those validation types silently fail at runtime (so in most cases)? This is insane
If you are strict, don’t intentionally try to outsmart the type system, and use manual runtime type checking when necessary [0], TypeScript does a good practical job of ensuring that you won’t run into runtime type errors.
The reason TypeScript doesn’t automatically include runtime type information is (probably) because the overhead of runtime type checking would outweigh the benefit when static type checking does a good enough job.
Also, JavaScript being a dynamic language has allowed some pretty complex patterns of types to emerge from real-world use cases that would be exhausting to enforce all the time at runtime. Typically in TypeScript, runtime type checking is (manually) done when the type system cannot otherwise confidently guarantee the type of a value. For example, it’s common to have a runtime check for the shape of a JSON api response because you’re not necessarily in control of what that will actually return. There are community supported packages to help make this easier [1].
0: https://www.typescriptlang.org/docs/handbook/advanced-types....