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pegjs/lib/compiler/passes/report-duplicate-rules.js

29 lines
691 B
JavaScript

"use strict";
let GrammarError = require("../../grammar-error");
let visitor = require("../visitor");
// Checks that each rule is defined only once.
function reportDuplicateRules(ast) {
let rules = {};
let check = visitor.build({
rule(node) {
if (Object.prototype.hasOwnProperty.call(rules, node.name)) {
throw new GrammarError(
"Rule \"" + node.name + "\" is already defined "
+ "at line " + rules[node.name].start.line + ", "
+ "column " + rules[node.name].start.column + ".",
node.location
);
}
rules[node.name] = node.location;
}
});
check(ast);
}
module.exports = reportDuplicateRules;