name: unicodeable-subscript default: true advisory: true fix: true since: 0.2.0

unicodeable-subscript

Braced super/subscript that has a single-codepoint Unicode form.

What it does

Flags math-region subscripts whose contents are simple enough to express as Unicode subscript characters: single digits, single letters that have a Unicode subscript codepoint, and short sign/digit pairs, when the surrounding context is prose rather than display math.

Why

In running prose like the i-th element x_i, the TeX form x_i renders as a code-styled fragment in most renderers; the Unicode form xᵢ is cleaner, screen-reader-friendly, and copyable. The rule fires only when the substitution is unambiguous and the surrounding context does not already use TeX-style display math.

The autofix substitutes the Unicode form (safe: false); review the change before applying.

Example (bad)

Take the i-th component, x_i.

Example (good)

Take the i-th component, xᵢ.

Configuration

• Disable inline: <!-- mdwright: allow unicodeable-subscript -->.
• Disable in config: [lint] ignore = ["unicodeable-subscript"].
• Severity: advisory.

References

• Unicode subscript block: U+2080–U+209F.
• mdwright's substitution table (mdwright-math/src/unicode.rs).