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

55 lines
1.5 KiB
JavaScript

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