docs/_docs/reference/error-codes/E117.md
This error is emitted when a structural refinement includes a polymorphic (generic) method that does not override a method in the parent type.
Structural refinement in Scala does not allow for polymorphic methods that are not already defined in the parent type.
type Example = AnyRef { def foo[T](x: T): T }
-- [E117] Syntax Error: example.scala:1:28 -------------------------------------
1 |type Example = AnyRef { def foo[T](x: T): T }
| ^^^^^^^^^^^^^^^^^^^
|Polymorphic refinement method foo without matching type in parent type AnyRef is no longer allowed
|-----------------------------------------------------------------------------
| Explanation (enabled by `-explain`)
|- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
| Polymorphic method foo is not allowed in the structural refinement of type AnyRef because
| method foo does not override any method in type AnyRef. Structural refinement does not allow for
| polymorphic methods.
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// Define the polymorphic method in a trait
trait HasFoo:
def foo[T](x: T): T
type Example = HasFoo
// Or use a non-polymorphic method in the refinement
type Example = AnyRef { def foo(x: Int): Int }