Can a programming language be written that makes it impossible to write invalid code and be expressive?

[JN]

On Sunday, 28 July 2019 at 04:58:40 UTC, Ike wrote:
> It seems that any programming language should have these 
> foundations covered as the root so that all programs written in 
> it are valid.

Depends on your definition of valid, but I believe solving this 
would require solving the "Halting problem" 
(https://en.wikipedia.org/wiki/Halting_problem) which is 
unsolvable on Turing machines.