This is a tracking issue for the RFC "Allow loop in constant evaluation" (rust-lang/rfcs#2344).

Steps:

• Implement the RFC (cc @rust-lang/compiler -- can anyone write up mentoring instructions?)
• Adjust documentation (see instructions on forge)
• Stabilization PR (see instructions on forge)

Unresolved questions:

• Should we add a true recursion check that hashes the interpreter state and detects if it has reached the same state again?
  • This will slow down const evaluation enormously and for complex iterations is essentially useless because it'll take forever (e.g. counting from 0 to u64::max_value())