import { type PreservedSource } from './source.js';
/**
 * The two facts about each statement that are derived from the token stream, computed together.
 *
 * `ends` is where a statement's text ends FOR THE WRITER, which is not always its terminator. A
 * comment after the semicolon with nothing but horizontal whitespace between them is the last
 * field's comment. Leaving it in the gap is invisible while the statement is copied, because the
 * gap is copied too, and wrong the moment it is reformatted: the writer emits its own field comment
 * and the author's then arrives from the gap on the line below, so the output carries a line nobody
 * wrote. It is not even a duplicate, because the ordinary writer drops the unit the original
 * usually carries, so it reads as a stray fragment.
 *
 * That is not the writer guessing which comment belongs to which object. "On the same line as the
 * terminator" is a positional fact, and it is the one case where the owner is not in question.
 *
 * Three consequences, decided rather than discovered:
 *
 * - A file written unchanged is byte-identical still. The extent grows and the gap shrinks by
 *   exactly the same characters, so the concatenation does not move.
 * - Removing an object takes that comment with it, where it used to be left on a line of its own
 *   describing a field that no longer exists.
 * - Reformatting replaces it, which is the defect this closes.
 *
 * `firstToken` is where each statement's tokens begin. `annotations` used to start its cursor at
 * zero and seek forward, which is a full prefix scan of the token stream per statement: quadratic
 * in the file, and invisible to the benchmarks because they time an UNCHANGED write, where no
 * statement is reformatted and `annotations` is never reached. On a ten thousand statement model
 * that is the difference between milliseconds and seconds.
 *
 * Both come from one pass with monotone cursors, because the statements and the tokens are both in
 * source order. Memoised per retained source, which never changes after the read, so the walk and
 * the two document accessors share one answer rather than each deriving it.
 */
interface Derived {
    /** Where each statement's text ends for the writer. */
    readonly ends: readonly number[];
    /** The first token at or after each statement's type name, as a cursor for `annotations`. */
    readonly firstToken: readonly number[];
}
/**
 * The derived facts for one retained source, computed once.
 *
 * Exported so `IdfDocument.regionOf` answers with the SAME extent this walk replaces. Handing a
 * consumer `statement.region` instead would stop short of the terminator-line comment, and an edit
 * built on it would leave that comment behind, which is the defect the extent exists to close.
 */
export declare function derivedOf(source: PreservedSource): Derived;
export {};
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