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/**
* @fileoverview Disallow shadowing of NaN, undefined, and Infinity (ES5 section 15.1.1)
* @author Michael Ficarra
*/
"use strict";
/**
* Determines if a variable safely shadows undefined.
* This is the case when a variable named `undefined` is never assigned to a value (i.e. it always shares the same value
* as the global).
* @param {eslintScope.Variable} variable The variable to check
* @returns {boolean} true if this variable safely shadows `undefined`
*/
function safelyShadowsUndefined(variable) {
return variable.name === "undefined" &&
variable.references.every(ref => !ref.isWrite()) &&
variable.defs.every(def => def.node.type === "VariableDeclarator" && def.node.init === null);
}
//------------------------------------------------------------------------------
// Rule Definition
//------------------------------------------------------------------------------
module.exports = {
meta: {
type: "suggestion",
docs: {
description: "disallow identifiers from shadowing restricted names",
category: "Variables",
recommended: true,
url: "https://eslint.org/docs/rules/no-shadow-restricted-names"
},
schema: []
},
create(context) {
const RESTRICTED = new Set(["undefined", "NaN", "Infinity", "arguments", "eval"]);
return {
"VariableDeclaration, :function, CatchClause"(node) {
for (const variable of context.getDeclaredVariables(node)) {
if (variable.defs.length > 0 && RESTRICTED.has(variable.name) && !safelyShadowsUndefined(variable)) {
context.report({
node: variable.defs[0].name,
message: "Shadowing of global property '{{idName}}'.",
data: {
idName: variable.name
}
});
}
}
}
};
}
};
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