Local indices in macros are not given gensym'd names

[odow]

A user contacted me with the following "feature." It's not clear what we should do, or how hard it would be to fix, but the error message is very unhelpful.

Potentially, the macros could look at the indices and compare against the model symbol?

model = Model()
@variable(model, x[model = 1:10] >= 1)

# results in

ERROR: MethodError: no method matching add_variable(::Int64, ::ScalarVariable{Int64,Float64,Float64,Float64}, ::String)
Closest candidates are:
  add_variable(::Model, ::ScalarVariable, ::String) at /Users/oscar/.julia/packages/JuMP/CZ8vV/src/variables.jl:792
  add_variable(::Model, ::ScalarVariable) at /Users/oscar/.julia/packages/JuMP/CZ8vV/src/variables.jl:792
  add_variable(::Model, ::VariableConstrainedOnCreation, ::String) at /Users/oscar/.julia/packages/JuMP/CZ8vV/src/variables.jl:857
  ...
Stacktrace:
 [1] (::getfield(Main, Symbol("##13#14")))(::Int64) at /Users/oscar/.julia/packages/JuMP/CZ8vV/src/Containers/macro.jl:183
 [2] (::getfield(JuMP.Containers, Symbol("##26#27")){getfield(Main, Symbol("##13#14"))})(::Tuple{Int64}) at /Users/oscar/.julia/packages/JuMP/CZ8vV/src/Containers/container.jl:70
 [3] iterate at ./generator.jl:47 [inlined]
 [4] collect(::Base.Generator{JuMP.Containers.VectorizedProductIterator{Tuple{Base.OneTo{Int64}}},getfield(JuMP.Containers, Symbol("##26#27")){getfield(Main, Symbol("##13#14"))}}) at ./array.jl:606
 [5] map(::Function, ::JuMP.Containers.VectorizedProductIterator{Tuple{Base.OneTo{Int64}}}) at ./abstractarray.jl:2044
 [6] container at /Users/oscar/.julia/packages/JuMP/CZ8vV/src/Containers/container.jl:70 [inlined]
 [7] container(::Function, ::JuMP.Containers.VectorizedProductIterator{Tuple{Base.OneTo{Int64}}}) at /Users/oscar/.julia/packages/JuMP/CZ8vV/src/Containers/container.jl:65
 [8] top-level scope at /Users/oscar/.julia/packages/JuMP/CZ8vV/src/macros.jl:79

This is also a problem in constraints as well

model = Model()
@variable(model, x[1:10])
@constraint(model, [model = 1:10], x[model] <= 1)

[mlubin]

This is a duplicate of #858.