49 lines
1.3 KiB
JavaScript
49 lines
1.3 KiB
JavaScript
var traverse = require("../../../traverse");
|
|
var t = require("../../../types");
|
|
|
|
var visitor = {
|
|
enter: function (node, parent, scope, context, state) {
|
|
if (!t.isReferencedIdentifier(node, parent)) return;
|
|
|
|
var declared = state.letRefs[node.name];
|
|
if (!declared) return;
|
|
|
|
// declared node is different in this scope
|
|
if (scope.get(node.name, true) !== declared) return;
|
|
|
|
var declaredLoc = declared.loc;
|
|
var referenceLoc = node.loc;
|
|
|
|
if (!declaredLoc || !referenceLoc) return;
|
|
|
|
// does this reference appear on a line before the declaration?
|
|
var before = referenceLoc.start.line < declaredLoc.start.line;
|
|
|
|
if (referenceLoc.start.line === declaredLoc.start.line) {
|
|
// this reference appears on the same line
|
|
// check it appears before the declaration
|
|
before = referenceLoc.start.col < declaredLoc.start.col;
|
|
}
|
|
|
|
if (before) {
|
|
throw state.file.errorWithNode(node, "Temporal dead zone - accessing a variable before it's initialized");
|
|
}
|
|
}
|
|
};
|
|
|
|
exports.optional = true;
|
|
|
|
exports.Loop =
|
|
exports.Program =
|
|
exports.BlockStatement = function (node, parent, scope, context, file) {
|
|
var letRefs = node._letReferences;
|
|
if (!letRefs) return;
|
|
|
|
var state = {
|
|
letRefs: letRefs,
|
|
file: file
|
|
};
|
|
|
|
traverse(node, visitor, scope, state);
|
|
};
|