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

63 lines
1.5 KiB
JavaScript

"use strict";
let GrammarError = require("../../grammar-error");
let visitor = require("../visitor");
// Checks that each label is defined only once within each scope.
function reportDuplicateLabels(ast) {
function cloneEnv(env) {
let clone = {};
Object.keys(env).forEach(name => {
clone[name] = env[name];
});
return clone;
}
function checkExpressionWithClonedEnv(node, env) {
check(node.expression, cloneEnv(env));
}
let check = visitor.build({
rule(node) {
check(node.expression, { });
},
choice(node, env) {
node.alternatives.forEach(alternative => {
check(alternative, cloneEnv(env));
});
},
action: checkExpressionWithClonedEnv,
labeled(node, env) {
if (Object.prototype.hasOwnProperty.call(env, 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;