Compute distinguishing argument index

Compute distinguishing argument index

The "distinguishing argument index" is the next part of the overload
resolution algorithm.

In overload resolution, you first distinguish by number of arguments,
then distinguish by checking the type of a single argument at some index;
this CL adds the index computation.

In practice it's just the first index where types differ,
but there are additional conditions to check.
http://heycam.github.io/webidl/#dfn-distinguishing-argument-index

Next CL will add the very lengthy "distinguishability classes".

After that we'll finally be ready to start changing the code generation,
based first on number of arguments, secondly on type!

Also:
* Some refactoring
* Fixes some tests that were invalid overloads, and were caught
by the new checks!
(No invalid overloads in actual IDLs, but test cases were too simple.)

R=haraken
BUG=293561
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=173741

[Nils Barth (inactive), 2014-05-09 05:43:00]

Next step!
(Most of code is lots of grouping and slicing of lists.)

[Jens Widell, 2014-05-09 06:08:04]

https://codereview.chromium.org/275763002/diff/60001/Source/bindings/scripts/...
File Source/bindings/scripts/v8_interface.py (right):

https://codereview.chromium.org/275763002/diff/60001/Source/bindings/scripts/...
Source/bindings/scripts/v8_interface.py:501: except:
Maybe "except StopIteration:" instead, to avoid catching unrelated exceptions
here, and to make it more clear what we expect from the code above?

Catching everything and treating it as a single (expected) type of error,
without checking, is a good way to confuse oneself and hide typos and errors.
:-)

[Nils Barth (inactive), 2014-05-09 06:17:09]

https://codereview.chromium.org/275763002/diff/60001/Source/bindings/scripts/...
File Source/bindings/scripts/v8_interface.py (right):

https://codereview.chromium.org/275763002/diff/60001/Source/bindings/scripts/...
Source/bindings/scripts/v8_interface.py:501: except:
On 2014/05/09 06:08:05, Jens Lindström wrote:
> Maybe "except StopIteration:" instead, to avoid catching unrelated exceptions
> here, and to make it more clear what we expect from the code above?
> 
> Catching everything and treating it as a single (expected) type of error,
> without checking, is a good way to confuse oneself and hide typos and errors.
> :-)

(>.<)
Thanks, lint should have caught this, but guess that's not part of Blink pylint.

[haraken, 2014-05-09 07:52:50]

+jsbell

LGTM

https://codereview.chromium.org/275763002/diff/80001/Source/bindings/scripts/...
File Source/bindings/scripts/v8_interface.py (right):

https://codereview.chromium.org/275763002/diff/80001/Source/bindings/scripts/...
Source/bindings/scripts/v8_interface.py:500: if len(set(types)) > 1)

This looks very tricky. Can we make this a bit more readable?

[Nils Barth (inactive), 2014-05-09 08:04:47]

https://codereview.chromium.org/275763002/diff/80001/Source/bindings/scripts/...
File Source/bindings/scripts/v8_interface.py (right):

https://codereview.chromium.org/275763002/diff/80001/Source/bindings/scripts/...
Source/bindings/scripts/v8_interface.py:500: if len(set(types)) > 1)
On 2014/05/09 07:52:51, haraken wrote:
> This looks very tricky. Can we make this a bit more readable?

Revised (added an auxiliary variable).

This is idiomatic Python (use of next, enumerate, and zip),
but it's admittedly a bit dense.
I've split it out with an auxiliary variable so it's easier to understand.

The next() is how one does list.find() in Python,
and the enumerate() is for the index.

However, the zip with list unpacking on top of this makes it a bit much.

Hope it's more readable now!

[Nils Barth (inactive), 2014-05-09 08:04:53]

The CQ bit was checked by nbarth@chromium.org

[commit-bot: I haz the power, 2014-05-09 08:06:44]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/nbarth@chromium.org/275763002/100001

[commit-bot: I haz the power, 2014-05-09 09:22:39]

Change committed as 173741