1097512 - Allow using compound operators where the LHS and RHS are both CheckedInt<T>

Status: RESOLVED FIXED

(Core :: MFBT, defect)

Description

[Matthew Gregan [:kinetik]]

I was surprised to run into this.  Is it not generally useful enough to have, is there something subtle I'm missing, or am I just the lucky person to discover a minor hole in the functionality?

This works as expected:

  CheckedInt<int> a;
  CheckedInt<int> b;

  a = a + b

...but:

  a += b;

...fails to compile due to the static_assert firing because detailed::IsSupported<CheckedInt<int>>::value is false.

Comment 1

[Matthew Gregan [:kinetik]]

Attachment: simple fix

It seems like a simple fix, but maybe there's a reason we don't want to support this.

Comment 2

[Jeff Walden [:Waldo]]

Comment on attachment 8521197 [details] [diff] [review]
simple fix

Review of attachment 8521197 [details] [diff] [review]:
-----------------------------------------------------------------

Probably just an oversight, I think.

Please also add some trivial checks of some sort to mfbt/tests/TestCheckedInt.cpp to test it does the right thing.  Make sure to have checks where the RHS is a valid CheckedInt, and where it's not a valid CheckedInt.

Comment 3

[Matthew Gregan [:kinetik]]

Pushed with tests added:
https://hg.mozilla.org/integration/mozilla-inbound/rev/5a2271cb4a67

Comment 4

[Carsten Book [:Tomcat]]

https://hg.mozilla.org/mozilla-central/rev/5a2271cb4a67