Member predicate Raw::VarDecl::getPropertyWrapperBackingVar

Gets the property wrapper backing variable of this variable declaration, if it exists.

This is the compiler synthesized variable holding the property wrapper for this variable, if any.

For a property wrapper like

@propertyWrapper struct MyWrapper { ... }

struct S {
  @MyWrapper var x : Int = 42
}

the compiler synthesizes a variable in S along the lines of

  var _x = MyWrapper(wrappedValue: 42)

This predicate returns such variable declaration.