I tend to agree with the philosophy that a language should not require an IDE to be productive in. With function signatures, I think it's particularly relevant

I tend to agree with the philosophy that a language should not require an IDE to be productive in. With function signatures, I think it's particularly relevant for documentation as well. I should be able to look at a function signature in generated docs and know everything about what goes into and comes out of that function. For me the signature should be a complete contract, and changing code within a function body should not be able to change the signature.