A language that is Turing complete at compile means that an IDE cannot reliably tell whether code has a syntax error without running a program that can take arbitrarily wrong.
All other tooling faces the same issue. What variables have a given type? If determining the type takes arbitrarily long, how are you supposed to discover them? Now consider the plight of an automated refactoring tool.
The IDEs and tools can still be written, of course. But they take more work and can't be as reliable.
> A language that is Turing complete at compile means that an IDE cannot reliably tell whether code has a syntax error without running a program that can take arbitrarily wrong.
A language that is not Turing complete at compile-time does not necessarily mean that an IDE will be able to reliably tell whether a certain piece of code has a syntax error without running a program that can take an arbitrarily amount of time to finish.
No, that's not true actually. It's possible that the language is defined so that the syntax checker (lexing, parsing, name resolution) and even type checker is run first and compile time execution after that. The only thing what the undecidability then affects is whether we get the constant value or whether the program runs forever. But in the latter case, we have still performed successfully syntax checking.
All other tooling faces the same issue. What variables have a given type? If determining the type takes arbitrarily long, how are you supposed to discover them? Now consider the plight of an automated refactoring tool.
The IDEs and tools can still be written, of course. But they take more work and can't be as reliable.