/**
 * The case-fold CLASS of a code point under ECMAScript's NON-Unicode `/i`
 * matching — the exact relation `keywords({ caseInsensitive: true })` compiles to.
 *
 * A first-set drives O(1) `choice` dispatch, so it MUST be a superset of every
 * character the combinator can really start with. For a case-insensitive matcher
 * that means: for every input char X that the matcher would accept as the first
 * char, X is in the set. Under `/i` WITHOUT `u`, two chars match iff they share a
 * canonical form, and that relation is NOT simply `{c, toUpperCase(c),
 * toLowerCase(c)}` — 67 BMP code points sit in classes those three miss:
 *
 *   σ (U+03C3) ↔ Σ (U+03A3) ↔ ς (U+03C2)   final sigma is in the class but is
 *                                            neither the upper- nor lowercase of σ
 *   µ (U+00B5) ↔ μ (U+03BC) ↔ Μ (U+039C)   micro sign folds into Greek mu
 *   DŽ (U+01C4) ↔ Dž (U+01C5) ↔ dž (U+01C6)   titlecase digraphs (also LJLjljNJNjnjDZDzdz)
 *   ͅ (U+0345) ↔ ι (U+03B9) ↔ ι (U+1FBE)   combining iota subscript
 *
 * so widening a first-set by upper/lower alone is UNSOUND for them.
 *
 * The canonical form below is ECMAScript's `Canonicalize` for non-Unicode mode:
 * uppercase the char; if that is not exactly one char, or if it would cross the
 * ASCII boundary INTO Basic Latin, keep the original. That last clause is why
 * `/s/i` does not match `ſ` (U+017F) and `/k/i` does not match `K` (U+212A) —
 * cross-boundary folds are refused in BOTH directions, which is what keeps an
 * ASCII first-set tight and sound for the common all-ASCII keyword set.
 *
 * The classes are derived from the RUNNING engine's own `toUpperCase`, not a
 * frozen table, so they cannot drift from the regex engine that will do the
 * matching. Verified exhaustively against real `/i` behaviour across the BMP:
 * 1141 multi-member classes, 2307 members, zero disagreements in either
 * direction (see `test/unit/case-fold.test.ts`).
 */
/**
 * Every code point that a non-Unicode `/i` matcher treats as equal to `cp`,
 * INCLUDING `cp` itself. Union these into a first-set to keep case-insensitive
 * dispatch sound.
 */
export declare function caseFoldVariants(cp: number): readonly number[];
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