Usage of where in if let assignment in Swift

Question

The Swift documentation at page 61 of the Swift manual hints to the possibility of using where to join an optional binding with a regular condition. Yet when I do i

Answer 1

Example with two conditions

if let x = y, let a = b, a == x && !x.isEmpty {

Answer 2

In xcode 9

if let str = textField.text as String!, !str.isEmpty
{
   params[key] = str
   TextFieldHelper.setup(textField: textField)
}
else
{ 
   TextFieldHelper.error(textField: textField)
}

Answer 3

In Swift 3 this syntax has changed.

What was

if let x = y, a = b where a == x {

Is now

if let x = y, let a = b, a == x {

The justification is that each sub-clause of the if ... { is now an independent boolean test.

See the Xcode Release notes & the Swift Evolution proposal for more info about this change.