add ambiguity fixes

Author: ChrisRackauckas

Diff for: Project.toml

@@ -1,7 +1,7 @@
 name = "ModelingToolkit"
 uuid = "961ee093-0014-501f-94e3-6117800e7a78"
 authors = ["Chris Rackauckas <[email protected]>"]
-version = "1.2.1"
+version = "1.2.2"
 
 [deps]
 DiffEqBase = "2b5f629d-d688-5b77-993f-72d75c75574e"

Diff for: src/differentials.jl

@@ -110,6 +110,8 @@ for (modu, fun, arity) ∈ DiffRules.diffrules()
 end
 
 derivative(::typeof(+), args::NTuple{T,Operation}, ::Val{i}) where {T,i} = args[i]
+derivative(::typeof(+), args::Tuple{Operation,Operation}, ::Val{1}) = args[1]
+derivative(::typeof(+), args::Tuple{Operation,Operation}, ::Val{2}) = args[2]
 
 function count_order(x)
     @assert !(x isa Symbol) "The variable $x must have an order of differentiation that is greater or equal to 1!"