nilpy: f-string format specs

• Type: feature (Nil-Python frontend) — Track N
• Status: done
• Opened: 2026-07-26 — probing songformatter under nilpy ([[feature-demo-songformatter-pxx-target]]).

Repro

print(f"{3.14159:.2f}")     # runtime: format spec ".2f" on a value of variant tag 3 is not supported
print(f"{'F':>5}")          # width/alignment

Compiles, then fails at runtime with a clear message (good — not silent, unlike [[bug-nilpy-percent-string-format-garbage]]).

Scope

Precision .Nf on floats, integer width, and </>/^ alignment with a fill. songformatter formats scores and pads labels; both are ordinary in real Python.

Gate

make test-nilpy green with a .npy case diffed against CPython, + --tier quick + self-host byte-identical.

Log

• 2026-07-31 — resolved, commit d87669fb2d6bbc902d982db95574fafa15ec4a0d.