[SE-0286] Revise proposal for improved source compatibility (#1166)
[SE-0286] Revise proposal for improved source compatibility (#1166)

* [SE-0286] Revise proposal for improved source compatibility

Taking the suggestions from Pavel Yaskevich and Xiaodi Wu, improve the
source compatibility guarantees by performing both a forward and
backward scan in Swift < 6, resolving ambiguities in favor of the
backward scan. When the backward scan is chosen, provide a warning +
Fix-It that rewrites the code to not use a trailing closure, thereby
eliminating the ambiguity.

* Update proposals/0286-forward-scan-trailing-closures.md

Co-authored-by: Ben Rimmington <b1c1d8736f20db3fb6c1c66bb1455ed43909f0d8@benrimmington.com>

* Update proposals/0286-forward-scan-trailing-closures.md

Co-authored-by: Ben Rimmington <b1c1d8736f20db3fb6c1c66bb1455ed43909f0d8@benrimmington.com>

Co-authored-by: Ben Rimmington <b1c1d8736f20db3fb6c1c66bb1455ed43909f0d8@benrimmington.com>
apple/swift-evolution,natecook1000/swift-evolution,apple/swift-evolution,natecook1000/swift-evolution,abertelrud/swift-evolution,abertelrud/swift-evolution