E0027

Warning name: deprecated_syntax

The syntax is deprecated. Please refer to the warning message on the reason and potential fix.

For example, one deprecated usage is declaring a polymorphic function as fn f[T]. Instead, write the type parameters before the function name, as in fn[T] f.

Erroneous example

fn identity[T](value : T) -> T {
  //
  // Warning: The syntax fn f[..] for declaring polymorphic function is
  // deprecated. Use fn[..] f instead.
  value
}

fn main {
  println(identity("Hello, world!"))
}

Suggestion

Migrate the code according to the warning message. In this case, move the type parameter list before the function name.

///|
fn[T] identity(value : T) -> T {
  value
}

///|
fn main {
  println(identity("Hello, world!"))
}