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`Scope#push(var)`, doesn't check for conflicting lexical bindings in outer scopes #6284

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nicolo-ribaudo opened this Issue Sep 20, 2017 · 0 comments

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nicolo-ribaudo commented Sep 20, 2017

AST Explorer

Choose one: is this a bug report or feature request?

Input Code

let a;
{ PLACEHOLDER }

Visitor

export default function ({ types: t }) {
  return {
    visitor: {
      Identifier(path) {
        if (path.node.name !== "PLACEHOLDER") return;
        path.scope.push({ kind: "var", id: t.identifier("a") });
      }
    }
  };
}

Expected Behavior

Duplicate declaration "a"

Current Behavior

let a;
{
  var a;
  PLACEHOLDER
}

Note that if I give that output to babel a second time, it correctly throws the error.

Your Environment

software version(s)
Babel 7.0.0-beta.1
node
npm
Operating System

@nicolo-ribaudo nicolo-ribaudo changed the title from When inserting a variable declared in an outer scope using `Scope#push`, references aren't updated to `Scope#push(var)`, doesn't check for conflicting lexical bindings in outer scopes Sep 20, 2017

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