f246c0b116
This is needed to handle cases like `[a, b.await, c]`. `ExprUseVisitor` considers `a` to be consumed when it is passed to the array, but the array is not quite live yet at that point. This means we were missing the `a` value across the await point. Attributing drops to the parent expression means we do not consider the value consumed until the consuming expression has finished. Issue #57478
For high-level intro to how type checking works in rustc, see the type checking chapter of the rustc dev guide.