does not support an objective function of type MathOptInterface.SingleVariable.

[chkwon]

using JuMP, Cbc
m = Model(with_optimizer(Cbc.Optimizer))
@variable(m, x1>=0)
@objective(m, Min, x1)
optimize!(m)

produces

ERROR: The solver does not support an objective function of type MathOptInterface.SingleVariable.
Stacktrace:
 [1] error(::String, ::Type, ::String) at ./error.jl:42
 [2] set_objective_function(::Model, ::MathOptInterface.SingleVariable) at /Users/chkwon/.julia/packages/JuMP/xQHBA/src/objective.jl:63
 [3] set_objective_function at /Users/chkwon/.julia/packages/JuMP/xQHBA/src/objective.jl:73 [inlined]
 [4] set_objective(::Model, ::MathOptInterface.OptimizationSense, ::VariableRef) at /Users/chkwon/.julia/packages/JuMP/xQHBA/src/objective.jl:79
 [5] top-level scope at /Users/chkwon/.julia/packages/JuMP/xQHBA/src/macros.jl:914