feat: support inplace parameter observed

Author: AayushSabharwal

src/systems/abstractsystem.jl

@@ -201,6 +201,17 @@ function generate_custom_function(sys::AbstractSystem, exprs, dvs = unknowns(sys
     end
 end
 
+function wrap_assignments(isscalar, assignments; let_block = false)
+    function wrapper(expr)
+        Func(expr.args, [], Let(assignments, expr.body, let_block))
+    end
+    if isscalar
+        wrapper
+    else
+        wrapper, wrapper
+    end
+end
+
 function wrap_array_vars(sys::AbstractSystem, exprs; dvs = unknowns(sys))
     isscalar = !(exprs isa AbstractArray)
     array_vars = Dict{Any, AbstractArray{Int}}()

src/systems/diffeqs/odesystem.jl

@@ -381,6 +381,7 @@ function build_explicit_observed_function(sys, ts;
         drop_expr = drop_expr,
         ps = full_parameters(sys),
         param_only = false,
+        return_inplace = false,
         op = Operator,
         throw = true)
     if (isscalar = symbolic_type(ts) !== NotSymbolic())
@@ -486,10 +487,22 @@ function build_explicit_observed_function(sys, ts;
     if inputs === nothing
         args = param_only ? [ps..., ivs...] : [dvs, ps..., ivs...]
     else
-        ipts = DestructuredArgs(inputs, inbounds = !checkbounds)
+        ipts = DestructuredArgs(unwrap.(inputs), inbounds = !checkbounds)
         args = param_only ? [ipts, ps..., ivs...] : [dvs, ipts, ps..., ivs...]
     end
     pre = get_postprocess_fbody(sys)
+    res = build_function(isscalar ? ts[1] : ts,
+        args...;
+        postprocess_fbody = pre,
+        wrap_code = wrap_array_vars(
+            sys, isscalar ? ts[1] : ts; dvs = param_only ? [] : unknowns(sys)) .∘
+                    wrap_assignments(isscalar, obsexprs),
+        expression = Val{expression})
+    if isscalar || return_inplace
+        return res
+    else
+        return res[1]
+    end
 
     ex = Func(args, [],
              pre(Let(obsexprs,