1282431 - Class redeclaration error message mentions "let" as cause

Status: RESOLVED FIXED

(Core :: JavaScript Engine, defect, P3)

Description

[Florian Scholz (Open Web Docs)]

In case you redeclare a class, the error message mentions `let` as the cause, which can be misleading when debugging. There is no `let` here at all:

> class Foo {}; class Foo {};

Firefox:
> SyntaxError: redeclaration of let Foo

Chrome:
> Uncaught SyntaxError: Identifier 'Foo' has already been declared

A more generic term like "identifier" works. If we can be specific, we could mention a "class redeclaration".

Comment 1

[Masaya Hayashi]

I'm working on this.

Comment 2

[Tooru Fujisawa [:arai]]

Thank you!

Comment 3

[Masaya Hayashi]

Attachment: Clarify error message for redeclaration of class

If you redeclare a class, you will get following error message.

> class Foo {}; class Foo {};

> SyntaxError: redeclaration of let Foo

In this patch, you will get following clearer error message instead of above one.

> SyntaxError: redeclaration of class Foo

I added `Class` to `DeclarationKind` and `BindingKind`, but class is handled as same as `let` after parsing, which is the same way as before.

Comment 4

[Tooru Fujisawa [:arai]]

Comment on attachment 8923681 [details] [diff] [review]
Clarify error message for redeclaration of class

Review of attachment 8923681 [details] [diff] [review]:
-----------------------------------------------------------------

Thank you for your patch :D
As talked in person, the change to BindingKind seems to be unnecessary for error reporting.
(BindingKind's string representation is used in EmitterScope::dump, but it's only for debug purpose, and not exposed to web developers, so keeping it "Let" should be fine)

Comment 5

[Masaya Hayashi]

Attachment: Clarify error message for redeclaration of class

Thank you for your review!
I discarded changes to BindingKind.

Comment 6

[Tooru Fujisawa [:arai]]

Comment on attachment 8923685 [details] [diff] [review]
Clarify error message for redeclaration of class

Review of attachment 8923685 [details] [diff] [review]:
-----------------------------------------------------------------

Thanks again!

Here's try run (automation for build and test),
when it runs without failure, feel free to add "checkin-needed" keyword to this bug, so this patch will be landed shortly.
https://treeherder.mozilla.org/#/jobs?repo=try&revision=7a89ff3c10296385c476f70d8a06881e48bb9cfe

Comment 7

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/mozilla-inbound/rev/dafc1282a533
Clarify error message for redeclaration of class. r=arai

Comment 8

[Natalia Csoregi [:nataliaCs]]

https://hg.mozilla.org/mozilla-central/rev/dafc1282a533