Fix constructor

Author: gdalle

DifferentiationInterface/src/misc/differentiate_with.jl

@@ -74,32 +74,34 @@ struct DifferentiateWith{C, F, B <: AbstractADType, N <: NTuple{C, Any}}
     f::F
     backend::B
     context_wrappers::N
-end
 
-function DifferentiateWith(
-        f::F,
-        backend::B,
-        context_wrappers::NTuple{C, Any},
-    ) where {F, B <: AbstractADType, C}
-    for (i, wrapper) in pairs(context_wrappers)
-        # Accept typical constructor-like values: functions or types.
-        if !(wrapper isa Function || wrapper isa Type)
-            throw(
-                ArgumentError(
-                    "Each context wrapper must be a callable object or type " *
-                        "(e.g., a wrapper constructor like `Constant` or `Cache`), " *
-                        "but element $i has type $(typeof(wrapper)).",
-                ),
-            )
+    function DifferentiateWith(
+            f::F,
+            backend::B,
+            context_wrappers::NTuple{C, Any},
+        ) where {F, B <: AbstractADType, C}
+        for (i, wrapper) in pairs(context_wrappers)
+            # Accept typical constructor-like values: functions or types.
+            if !(wrapper isa Function || wrapper isa Type)
+                throw(
+                    ArgumentError(
+                        "Each context wrapper must be a callable object or type " *
+                            "(e.g., a wrapper constructor like `Constant` or `Cache`), " *
+                            "but element $i has type $(typeof(wrapper)).",
+                    ),
+                )
+            end
         end
+        return new{C, F, B, typeof(context_wrappers)}(
+            f,
+            backend,
+            context_wrappers,
+        )
     end
-    return DifferentiateWith{C, F, B, typeof(context_wrappers)}(
-        f,
-        backend,
-        context_wrappers,
-    )
 end
 
+DifferentiateWith(f::F, backend::AbstractADType) where {F} = DifferentiateWith(f, backend, ())
+
 function (dw::DifferentiateWith{C})(x, args::Vararg{Any, C}) where {C}
     return dw.f(x, args...)
 end