[llvm] [ADT] Initialize function_ref::callable (PR #216686)

[Mehdi Amini via llvm-commits]

joker-eph wrote:

> It is more to protect from future potential mistakes and to silent a lot of coverity warning

We can silent coverity false positives like this one with a `// coverity[event_tag]` though. 

> one of the example from coverity

Wrong PR :)
This example is for the MLIR issue it seems.

https://github.com/llvm/llvm-project/pull/216686