list comprehensions with conditionals are not supported

``` julia> @resumable function f1() [i for i in 1:10 if i<5] end ERROR: LoadError: Illegal expression in generator: i = 1:10 if i < 5 Stacktrace: [1] error(s::String) @ Base ./error.jl:35 [2] scope_generator(expr::Expr, scope::ResumableFunctions.ScopeTracker) @ ResumableFunctions ~/Documents/ScratchSpace/quantumjulia/ResumableFunctions.jl/src/utils.jl:345 [3] scoping(expr::Expr, scope::ResumableFunctions.ScopeTracker) @ ResumableFunctions ~/Documents/ScratchSpace/quantumjulia/ResumableFunctions.jl/src/utils.jl:361 [4] scoping(expr::Expr, scope::ResumableFunctions.ScopeTracker) (repeats 2 times) @ ResumableFunctions ~/Documents/ScratchSpace/quantumjulia/ResumableFunctions.jl/src/utils.jl:565 [5] var"@resumable"(__source__::LineNumberNode, __module__::Module, ex::Vararg{Expr}) @ ResumableFunctions ~/Documents/ScratchSpace/quantumjulia/ResumableFunctions.jl/src/macro.jl:100 in expression starting at REPL[26]:1 julia> @resumable function f2() [i for i in 1:10] end f2 (generic function with 1 method) julia> function f3() [i for i in 1:10 if i<5] end f3 (generic function with 1 method) ```