/**
 * A hard ceiling on element nesting.
 *
 * The parser recurses once per nested element, so input depth IS stack depth:
 * a generated or malicious document with tens of thousands of nested tags
 * takes the whole process down before any validator sees it — and in the
 * implementations without a recoverable stack overflow the process aborts
 * outright. Real configs nest a handful of levels; the ceiling sits far above
 * any legitimate document and far below any dangerous one.
 *
 * The guard is a parse listener rather than a parser subclass so every
 * implementation can use the same shape: all four ANTLR runtimes fire
 * `enterEveryRule` before the rule body recurses, which is exactly the moment
 * the 65th level is about to open and the stack is still shallow.
 */
import type { ErrorNode, ParseTreeListener, ParserRuleContext, TerminalNode } from 'antlr4ng';
/** Far above any real config (they nest ~4 levels), far below a dangerous one. */
export declare const MAX_ELEMENT_DEPTH = 64;
/** Thrown when a document nests elements deeper than {@link MAX_ELEMENT_DEPTH}. */
export declare class ElementDepthError extends Error {
    readonly line: number;
    readonly column: number;
    constructor(line: number, column: number);
}
/** Counts `element` rule entries and refuses the level past the ceiling. */
export declare class DepthGuard implements ParseTreeListener {
    private depth;
    enterEveryRule(node: ParserRuleContext): void;
    exitEveryRule(node: ParserRuleContext): void;
    visitTerminal(_node: TerminalNode): void;
    visitErrorNode(_node: ErrorNode): void;
}
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