55 lines
1.5 KiB
JavaScript
55 lines
1.5 KiB
JavaScript
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"use strict";
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var GrammarError = require("../../grammar-error"),
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arrays = require("../../utils/arrays"),
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objects = require("../../utils/objects"),
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visitor = require("../visitor");
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/* Checks that each label is defined only once within each scope. */
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function reportDuplicateLabels(ast) {
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function checkExpressionWithClonedEnv(node, env) {
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check(node.expression, objects.clone(env));
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}
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var check = visitor.build({
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rule: function(node) {
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check(node.expression, { });
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},
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choice: function(node, env) {
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arrays.each(node.alternatives, function(alternative) {
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check(alternative, objects.clone(env));
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});
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},
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action: checkExpressionWithClonedEnv,
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labeled: function(node, env) {
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if (env.hasOwnProperty(node.label)) {
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throw new GrammarError(
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"Label \"" + node.label + "\" is already defined "
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+ "at line " + env[node.label].start.line + ", "
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+ "column " + env[node.label].start.column + ".",
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node.location
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);
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}
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check(node.expression, env);
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env[node.label] = node.location;
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},
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text: checkExpressionWithClonedEnv,
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simple_and: checkExpressionWithClonedEnv,
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simple_not: checkExpressionWithClonedEnv,
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optional: checkExpressionWithClonedEnv,
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zero_or_more: checkExpressionWithClonedEnv,
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one_or_more: checkExpressionWithClonedEnv,
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group: checkExpressionWithClonedEnv
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});
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check(ast);
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}
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module.exports = reportDuplicateLabels;
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