unused-type-parameter

Flag a where clause type parameter that is never used in the signature or body, covering bare (where T), braced (where {T, S}), bounded (where {T<:Number}), and chained (where T where S) clauses. An unread parameter is usually a refactoring leftover or a forgotten ::T annotation. Struct type parameters are exempt (phantom parameters like struct Unit{T} end are idiomatic), as are all-underscore names.

T is bound but never referenced:

function f(x) where {T}
    x + 1
end

warning: unused-type-parameter
 --> example.jl:1:22
  |
1 | function f(x) where {T}
  |                      ^ type parameter `T` is never used