522858 - Using "let" in different blocks can produce an error message referring to previous declared variable

Status: RESOLVED DUPLICATE of bug 469758

(Core :: JavaScript Engine, defect)

Description

[Ariel Fatecha]

User-Agent:       Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.0.14) Gecko/2009090217 Ubuntu/9.04 (jaunty) Firefox/3.0.14
Build Identifier: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.0.14)

"let" declare a variable in a block scope, but a null pointer exception show a message referring a variable in a previous block.

Reproducible: Always

Steps to Reproduce:
Test case :

<script type="text/javascript;version=1.8">
  if( true ) {
    let x = "Some value";
  }

  if( true ) {
    let y = null;
    alert(y.value);
  }
</script>

Actual Results:  
x is null

Expected Results:  
y is null

This occur in firefox 3.5 too.

This problem makes more difficult debugging.

Comment 1

[:Gavin Sharp [email: [e-mail]]]

Attachment: HTML testcase

I can reproduce in a current tip Tracemonkey shell, as well as in Firefox 3.5 and Minefield:

[gavin@gavin-mbp:~/mozilla/tracemonkey/obj-js]$ ./js
js> if (true) { let x = "Some value"; } if (true) { let y = null; y.value; } 
typein:1: TypeError: x is null

Comment 2

[:Gavin Sharp [email: [e-mail]]]

Bug occurs in Firefox 3.0.14 as well. I suppose it may have been there since the introduction of "let".