validation_functions_scope.ts

let validPattern = await fetch('something something');
type validString = string : (s) => s.includes(validPattern);
// error, the value of validPattern is not known at compile time

let validPattern = 'cool';
type validString = string : (s) => s.includes(validPattern);
// this should be perfectly valid, huh?

let isValidPattern = (s: string) => s.includes('cool');
type validString = string: (s) => isValidPattern(s);
// you don't want to write the code twice for runtime and compile time,
// so this should work, right?

let isValidPattern = (s: string) => {
  let pattern: validString = 'cool';
  return s.includes(pattern);
}
type validString = string: (s) => isValidPattern(s);
// so now you have to run isValidPattern in order to compile isValidPattern?
// this is a nightmare!