Technically speaking, could we code in natural language once we pass the Turing test? Would passing the Turing test at least simplify programming languages' syntax?
No. Humans pass the Turing Test but cannot express themselves with enough precision and little enough ambiguity to code well in English (natural language). No machine will improve on that until it can greatly improve on human-level clarity in expressing their purpose when programming.
Is it possible to program in natural language? Yes, I think so. But it would require superhuman intelligence to anticipate all the possible confusions that might arise when a word is not sufficiently precise or accurate to represent an software activity or mechanism. This probably would require adopting a rigorous convention in choosing a subset of unambiguous words to form a "natural" programming language (a kind of creole). Coding consistently using only those words would require discipline that exceeds the ability of most humans, methinks.
I think this is a very interesting question. It's highly hypothetical, so my simple answer will also, necessarily, be hypothetical.
- If the AI can pass the Turing Test, it can be assumed it has a command of the human language(s) used in that process
Self-awareness in this context would seem to be irrelevant, as would the question of whether the AI actually "understands" the content, or is merely imitating natural language.
- If the AI has a command of the human language(s), it would be a reasonable assumption that it could translate natural language instructions into machine code
It might be best to think of the problem in the simplest terms. If you asked this hypothetical AI to "draw a red square on the screen", it's hard to see that task as impossible, or even difficult.
Obviously, as the instructions became more complicated, there would be a greater margin for error, and it would be useful to integrate precise, formal terms related to functions, as Randy points out.