@enter fails for simple kwarg function

[staticfloat]

julia> function foo(a, b; c="foo", d="bar")
       return sum(a .+ b), c * d
       end
foo (generic function with 1 method)

julia> a = randn(10); b = a; @enter foo(a, b; c="haha")
ERROR: MethodError: no method matching haskey(::Array{Any,1}, ::Symbol)
Closest candidates are:
  haskey(::Base.TTY, ::Symbol) at stream.jl:480
  haskey(::Base.Iterators.Pairs, ::Any) at iterators.jl:247
  haskey(::Dict, ::Any) at dict.jl:546
  ...
Stacktrace:
 [1] evaluate_call(::ASTInterpreter2.JuliaStackFrame, ::Expr) at /home/staticfloat/.julia/dev/ASTInterpreter2/src/interpret.jl:66
 [2] eval_rhs(::ASTInterpreter2.JuliaStackFrame, ::Expr) at /home/staticfloat/.julia/dev/ASTInterpreter2/src/interpret.jl:93
 [3] _step_expr(::ASTInterpreter2.JuliaStackFrame, ::ASTInterpreter2.JuliaProgramCounter) at /home/staticfloat/.julia/dev/ASTInterpreter2/src/interpret.jl:115
 [4] next_until!(::getfield(ASTInterpreter2, Symbol("##7#8")), ::ASTInterpreter2.JuliaStackFrame, ::ASTInterpreter2.JuliaProgramCounter) at /home/staticfloat/.julia/dev/ASTInterpreter2/src/interpret.jl:172
 [5] next_call!(::ASTInterpreter2.JuliaStackFrame, ::ASTInterpreter2.JuliaProgramCounter) at /home/staticfloat/.julia/dev/ASTInterpreter2/src/interpret.jl:177
 [6] maybe_step_through_wrapper!(::Array{ASTInterpreter2.JuliaStackFrame,1}) at /home/staticfloat/.julia/dev/ASTInterpreter2/src/ASTInterpreter2.jl:399
 [7] top-level scope at /home/staticfloat/.julia/dev/ASTInterpreter2/src/ASTInterpreter2.jl:465

[KristofferC]

Still fails with #37

julia>  ASTInterpreter2.@enter foo(a, b; c="haha")
ERROR: MethodError: no method matching haskey(::Array{Any,1}, ::Symbol)
Closest candidates are:
  haskey(::Base.TTY, ::Symbol) at stream.jl:480
  haskey(::Base.Iterators.Pairs, ::Any) at iterators.jl:247
  haskey(::Dict, ::Any) at dict.jl:546
  ...
Stacktrace:
 [1] evaluate_call! at C:\Users\Kristoffer\ASTInterpreter2.jl\src\interpret.jl:112 [inlined]
 [2] _step_expr!(::Compiled, ::JuliaStackFrame, ::ASTInterpreter2.JuliaProgramCounter) at C:\Users\Kristoffer\ASTInterpreter2.jl\src\interpret.jl:205
 [3] next_until!(::getfield(ASTInterpreter2, Symbol("##7#8")), ::Compiled, ::JuliaStackFrame, ::ASTInterpreter2.JuliaProgramCounter) at C:\Users\Kristoffer\ASTInterpreter2.jl\src\interpret.jl:311
 [4] next_call!(::Compiled, ::JuliaStackFrame, ::ASTInterpreter2.JuliaProgramCounter) at C:\Users\Kristoffer\ASTInterpreter2.jl\src\interpret.jl:316
 [5] maybe_step_through_wrapper!(::Array{JuliaStackFrame,1}) at C:\Users\Kristoffer\ASTInterpreter2.jl\src\ASTInterpreter2.jl:837
 [6] top-level scope at C:\Users\Kristoffer\ASTInterpreter2.jl\src\ASTInterpreter2.jl:904

[timholy]

Fixed by #40