257648 - "redeclaration of var" is wrong

Status: RESOLVED INVALID

(Core :: JavaScript Engine, defect)

Description

[Henrik Gemal]

I'm getting:
--------------
Warning: redeclaration of var x
Source File: file:///c:/temp/test.html
Line: 4, Column: 5
Source Code:
	var x;
--------------

my code:

<script>
var x=1;
if (typeof(x)=="undefined") {
	var x;
}
x=2;
</script>

Mozilla Firefox 20040830

Comment 1

[Boris Zbarsky [:bzbarsky]]

Aren't the declarations handled at compile time, not runtime (due to the fact
that they have function scope and don't need to come before use)? For example,
"x" is declared in the following JS and there should be no "assignment to
undeclared variable" warning:

  function foo() {
    x = 1;
    if (0) {
      var x;
    }
  }

Your testcase is pretty much the same and does indeed declare the variable twice.

Comment 2

[Nicholas Allen]

Variable declarations are hoisted to the top of their execution scope (in JS1
that's most enclosing function, or global if none).

Comment 3

[Boris Zbarsky [:bzbarsky]]

Per comment 2, invalid.