Parametric constructors cause `SIGNATURE` and `TYPEDSIGNATURE` to be empty / wrong

I have something similar to the following setup where I try to create a zero argument constructor for a parametric struct:

using DocStringExtensions

"""
# struct definition
My test struct with fields
$(TYPEDFIELDS)
"""
struct MyStruct{T<:Number}
    a::T
end

"""
# empty constructor. Call with
$(SIGNATURES) or:
$(TYPEDSIGNATURES)
"""
function MyStruct{T}() where {T<:Number}
    return MyStruct{T}(one(T))
end

The constructed documentation look like this:

help?> MyStruct
search: MyStruct

  struct definition
  ≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡

  My test struct with fields

    •  a::Number

  ────────────────────────────────────────

  empty constructor. Call with
  ≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡≡

  MyStruct(a)
  


  or:

  MyStruct(a::Number) -> MyStruct

Which does not reproduce the signature of the parametric constructor. Ideally, I would expect something like
MyStruct{T}() for $SIGNATURES andMyStruct{T<:Number}() -> MyStruct for $TYPEDSIGNATURES.

(In the documenter build, the result of SIGNATURES and TYPEDSIGNATURES seems to just be empty, hence the empty in the title.)

Start with the Julia example in the issue and inspect how SIGNATURES and TYPEDSIGNATURES process the parametric zero-argument constructor. Compare the generated documentation with the expected MyStruct{T}() and MyStruct{T<:Number}() -> MyStruct forms; the issue is done when both substitutions preserve the constructor's parametric signature.