fix: fix build_explicit_observed_function for array parameter expressions

Author: AayushSabharwal

src/systems/diffeqs/odesystem.jl

@@ -420,7 +420,10 @@ function build_explicit_observed_function(sys, ts;
     subs = Dict()
     maxidx = 0
     for s in dep_vars
-        if s in param_set || s in param_set_ns
+        if s in param_set || s in param_set_ns ||
+           iscall(s) &&
+           operation(s) === getindex &&
+           (arguments(s)[1] in param_set || arguments(s)[1] in param_set_ns)
             continue
         end
         idx = get(observed_idx, s, nothing)

test/symbolic_indexing_interface.jl

@@ -85,3 +85,19 @@ analytic_function = (ps, t, x) -> -ps[1] * x * (x - 1) * sin(x) * exp(-2 * ps[1]
 @test isequal(pdesys.ps, [h])
 @test isequal(parameter_symbols(pdesys), [h])
 @test isequal(parameters(pdesys), [h])
+
+# Issue#2767
+using ModelingToolkit
+using ModelingToolkit: t_nounits as t, D_nounits as D
+using SymbolicIndexingInterface
+
+@parameters p1[1:2]=[1.0, 2.0] p2[1:2]=[0.0, 0.0]
+@variables x(t) = 0
+
+@named sys = ODESystem(
+    [D(x) ~ sum(p1) * t + sum(p2)],
+    t;
+)
+prob = ODEProblem(complete(sys))
+get_dep = @test_nowarn getu(prob, 2p1)
+@test get_dep(prob) == [2.0, 4.0]