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33 lines
902 B
JavaScript
33 lines
902 B
JavaScript
var arrays = require("../../utils/arrays"),
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GrammarError = require("../../grammar-error"),
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asts = require("../asts"),
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visitor = require("../visitor");
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/* Checks that no left recursion is present. */
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function reportLeftRecursion(ast) {
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var check = visitor.build({
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rule: function(node, appliedRules) {
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check(node.expression, appliedRules.concat(node.name));
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},
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sequence: function(node, appliedRules) {
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if (node.elements.length > 0) {
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check(node.elements[0], appliedRules);
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}
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},
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rule_ref: function(node, appliedRules) {
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if (arrays.contains(appliedRules, node.name)) {
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throw new GrammarError(
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"Left recursion detected for rule \"" + node.name + "\"."
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);
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}
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check(asts.findRule(ast, node.name), appliedRules);
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}
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});
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check(ast, []);
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}
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module.exports = reportLeftRecursion;
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