pub const FMT_MAX_PRECISION: usize = _; // 65_535usizeExpand description
Rust’s format!("{:.*}", n, x) panics when n exceeds the fmt runtime’s
internal precision limit. User-supplied precision can legally reach far
higher values (e.g. f"{1.5:.1000000}") — clamp here so we produce a
(truncated-but-valid) output instead of aborting the interpreter. Harmless
in practice: f64 carries only ~17 significant digits, so precision beyond
65K is padding zeros at best.
The two caps differ by 1: {:.*} (plain) accepts u16::MAX, but {:.*e}
(exponential) hits a tighter assertion (ndigits > 0 in
core::num::flt2dec) at exactly u16::MAX. Keeping plain at the higher
cap preserves byte-identical output with CPython up through
precision == u16::MAX for fixed / percent / general-non-scientific paths.