407727 - Top-level |let Object| no longer works

Status: VERIFIED FIXED

(Core :: JavaScript Engine, defect)

Description

[Igor Bukanov]

As a result of changes from bug 376957 the following one-liner caused an error:

~/m/trunk/mozilla/js/src $ js -e 'let Object = 1; print(Object);'
-e:1: TypeError: redeclaration of const Object

Yet the same code inside  a block is fine:

~/m/trunk/mozilla/js/src $ js -e '{ let Object = 1; print(Object); }'
1

Comment 1

[Igor Bukanov]

One of the solution to this bug is to force the top-level let in scripts to create a new scope object and not pollute the global scope. This would have a consequence as a code like:

<script>
let a = 1;
</script> 

<script>
alert(typeof a);
</script> 

would show "undefined", but IMO this would allow to use the global let as a kind of static declarations in the script tags or loaded scripts without the fear of polluting the global scope.  

Comment 2

[Brendan Eich [:brendan]]

ES4 proposes exactly what comment 1 describes: an implicit block around top-level programs and function bodies. This bug is due to bug 346749 in combination with the patch for bug 376957 -- and the change to "type name binding" in the latter patch has been undone by the patch for bug 409252.

So this bug should be FIXED now, due to the patch for bug 409252 landing. Marking so, please re-open if I'm wrong.

/be

Comment 3

[Bob Clary [:bc] (inactive)]

Checking in regress-407727-01.js;
/cvsroot/mozilla/js/tests/js1_7/regress/regress-407727-01.js,v  <--  regress-407727-01.js
initial revision: 1.1
done
RCS file: /cvsroot/mozilla/js/tests/js1_7/regress/regress-407727-02.js,v
done
Checking in regress-407727-02.js;
/cvsroot/mozilla/js/tests/js1_7/regress/regress-407727-02.js,v  <--  regress-407727-02.js
initial revision: 1.1

Comment 4

[Bob Clary [:bc] (inactive)]

verified fixed 1.9.0