Afaik there was Turing limited kind of language which had Turing decidable fragments https://www.microsoft.com/en-us/research/wp-content/uploads/2021/08/BosqueI

Afaik there was Turing limited kind of language which had Turing decidable fragments https://www.microsoft.com/en-us/research/wp-content/uploads/2021/08/BosqueIR.pdf https://www.microsoft.com/en-us/research/wp-content/uploads/... afaik it is still in relatively active development