1102522 - Make redeclaration errors for lexical bindings ES6-compliant

Status: RESOLVED FIXED

(Core :: JavaScript Engine, defect)

Description

[Shu-yu Guo [:shu]]

According to ES6 13.1.1 [1], if the same identifier appears both in VarDeclaredNames and LexicallyDeclaredNames, an early error is raised.

AFAICT, VarDeclaredNames does not take hoisting into account, so the following is an early error even though the 'let' actually shadows the 'var':

function() { { var x; let x; } }

Currently we don't do the right thing here. If a lexical declaration appears after a 'var' declaration in a scope that in fact hoists the 'var' declaration out of the scope (like above), a TDZ instead of an early error is raised.

In the case of consts, we will raise a assign-to-const error instead of the early redecl error.

[1] http://people.mozilla.org/~jorendorff/es6-draft.html#sec-block-static-semantics-early-errors

Comment 1

[Shu-yu Guo [:shu]]

Fixed by bug 1263355.