/**
 * @packageDocumentation
 * Shared helpers for parsing and flattening nullish comparison expressions.
 */
import { type TSESTree } from "@typescript-eslint/utils";
/**
 * Normalized representation of one binary comparison against null/undefined.
 */
export type NullishComparison = Readonly<{
    comparedExpression: TSESTree.Expression;
    kind: NullishComparisonKind;
    operator: NullishComparisonOperator;
}>;
/** Nullish literal kinds supported by comparison extraction. */
export type NullishComparisonKind = "null" | "undefined";
/** Operators supported by nullish comparison extraction. */
export type NullishComparisonOperator = "!=" | "!==" | "==" | "===";
/**
 * Flatten a logical-expression tree for one specific operator.
 *
 * @param options - Expression and logical operator to flatten.
 *
 * @returns Left-to-right list of terms participating in that operator chain.
 */
export declare const flattenLogicalTerms: ({ expression, operator, }: Readonly<{
    expression: Readonly<TSESTree.Expression>;
    operator: "&&" | "||";
}>) => readonly TSESTree.Expression[];
/**
 * Narrow a list of expressions to an exact two-term tuple.
 */
export declare const isExpressionPair: (terms: readonly Readonly<TSESTree.Expression>[]) => terms is readonly [TSESTree.Expression, TSESTree.Expression];
/**
 * Extract a normalized nullish comparison from an expression.
 */
export declare const getNullishComparison: ({ allowedOperators, allowTypeofComparedIdentifierForUndefined, comparedIdentifierName, expression, isGlobalUndefinedIdentifier, }: Readonly<{
    allowedOperators?: readonly NullishComparisonOperator[];
    allowTypeofComparedIdentifierForUndefined?: boolean;
    comparedIdentifierName?: string;
    expression: Readonly<TSESTree.Expression>;
    isGlobalUndefinedIdentifier: (expression: Readonly<TSESTree.Expression>) => boolean;
}>) => null | NullishComparison;
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