A classic :) Wrap your closure arguments in parenthesis in the guard and if clauses:
// Won't compile
if let x = a.first { ... } { ... }
// OK
if let x = a.first(where: { ... }) { ... }
A classic :) Wrap your closure arguments in parenthesis in the guard and if clauses:
// Won't compile
if let x = a.first { ... } { ... }
// OK
if let x = a.first(where: { ... }) { ... }