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