Fix `first_line_width` to be tab-aware
Author: jieyouxuCreated Sep 15, 2026Updated Sep 15, 2026
LabelsC-bugA-whitespaceSO-hard_tabs
Follow-up to https://github.com/rust-lang/rustfmt/pull/6883. The PR fixes `last_line_width`, but it looks like `first_line_width` helper has the same tab-unaware problem.
Source: rust-lang/rustfmt