> What are the downsides of gradual typing on a codebase?
Typing complex business domains and interactions is hard. Most developers don’t have a lot of experience with it or the time to do it properly as they produce features. It doesn’t help that many developers start their career with untyped languages and transition into typed languages without learning it properly.
Typescript is a great example because a lot of frontend developers may have only ever worked in JavaScript and have absolutely no foundation to build on but trial and error on your companies production codebase.
It's definitely not that the developers are inexperienced with types. You're sort of making a "white man's burden" argument. Very few web developers are just writing javascript at work.
It's simply that you can't paint over a weakly typed language with strong types without causing all kinds of crazy edge cases. They're fundamentally different paradigms.
Typing complex business domains and interactions is hard. Most developers don’t have a lot of experience with it or the time to do it properly as they produce features. It doesn’t help that many developers start their career with untyped languages and transition into typed languages without learning it properly.
Typescript is a great example because a lot of frontend developers may have only ever worked in JavaScript and have absolutely no foundation to build on but trial and error on your companies production codebase.