Pavel Yaskevich 46d945fdcf [ConstraintSystem] Avoid exploring too much search space when call arguments are holes ...

Detect that disjunction is going to be applied to arguments which
don't provide any additional contextual information and allow only
a single choice to be attempted in such case to avoid triggering
exponential behavior in the solver.

The problem is most visible with operators e.g.

```swift
.foo == .bar || 1 == .baz
```

If neither member could be contextually determined and solver was
allowed to attempt all of the overloads for `==` and `||` that
would lead to exponential behavior (because each has 30+ overloads)
and generation of hundreds of partial solutions.

Resolves: rdar://problem/56400265

2020-02-20 16:52:30 -08:00

366 KiB

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