# @code\_warntype fails when function has a keyword argument
**URL:** https://discourse.julialang.org/t/code-warntype-fails-when-function-has-a-keyword-argument/21907
**Category:** New to Julia
**Created:** [March 15, 2019, 10:00am UTC](https://discourse.julialang.org/t/code-warntype-fails-when-function-has-a-keyword-argument/21907 "2019-03-15T10:00:57Z")
**Posts on this page:** 7
**Page:** 1
### Author:  [@tomtom](https://discourse.julialang.org/u/tomtom)
#### Post date: [March 15, 2019, 10:00am UTC](https://discourse.julialang.org/t/code-warntype-fails-when-function-has-a-keyword-argument/21907/1 "2019-03-15T10:00:58Z")
In the following two functions are identical except that `fun2()` has a keyword argument. However, `@code_warntype` fails to “go into” the `invoke Main...` part that should give a warntype!
```julia
function fun1(v)
kw = 1
println(v[1])
end
function fun2(v; kw=1)
println(v[1])
end
v = Vector{Real}(undef, 2)
v[1] = 1
v[2] = 2.2
julia> @code_warntype fun1(v)
Body::Nothing
1 ─ %1 = (Base.arrayref)(true, v, 1)::Real
│ %2 = (Main.println)(%1)::Core.Compiler.Const(nothing, false)
└── return %2
julia> @code_warntype fun2(v)
Body::Nothing
1 ─ %1 = invoke Main.:(#fun2#3)(1::Int64, _1::Function, _2::Array{Real,1})::Core.Compiler.Const(nothing, false)
└── return %1
```
it’s worrisome…
---
### Author:  [@Tamas\_Papp](https://discourse.julialang.org/u/Tamas_Papp)
#### Post date: [March 15, 2019, 10:51am UTC](https://discourse.julialang.org/t/code-warntype-fails-when-function-has-a-keyword-argument/21907/2 "2019-03-15T10:51:52Z")
> [@tomtom](#):
>
> `@code_warntype` fails to “go into” the `invoke Main...` part that should give a warntype!
This is not a failure — `@code_warntype` does not expand the callees recursively (unless they were inlined).
Just use `@code_warntype fun2(v; kw = 1)`.
Also, note that if you are debugging type stablity, you should use arguments with concrete types. Abstract type parameters like in `Vector{Real}` preclude the optimizations that are allowed by knowing types at compile time (“type stability”), so are not really relevant.
---
### Author:  [@mateuszbaran](https://discourse.julialang.org/u/mateuszbaran)
#### Post date: [March 15, 2019, 11:29am UTC](https://discourse.julialang.org/t/code-warntype-fails-when-function-has-a-keyword-argument/21907/3 "2019-03-15T11:29:18Z")
You can use [Cthulhu](https://github.com/JuliaDebug/Cthulhu.jl) to descend into ~~madness~~ functions with keyword arguments (among other things):
```julia
julia> @descend_code_typed fun2(v)
│ ─ %-1 = invoke fun2(::Array{Real,1})::Core.Compiler.Const(nothing, false)
CodeInfo(
@ REPL[2]:2 within `fun2'
1 ─ %1 = invoke Main.:(#fun2#3)(1::Int64, _1::Function, _2::Array{Real,1})::Core.Compiler.Const(nothing, false)
└── return %1
)
Select a call to descend into or ↩ to ascend. [q]uit.
Toggles: [o]ptimize, [w]arn, [d]ebuginfo.
Show: [L]LVM IR, [N]ative code
Advanced: dump [P]arams cache.
• %1 = invoke #fun2#3(::Int64,::Function,::Array{Real,1})
↩
│ ─ %-1 = invoke #fun2#3(::Int64,::Function,::Array{Real,1})::Core.Compiler.Const(nothing, false)
CodeInfo(
@ REPL[2]:2 within `#fun2#3'
┌ @ array.jl:729 within `getindex'
1 ─│ %1 = (Base.arrayref)(true, v, 1)::Real
│ └
│ %2 = (Main.println)(%1)::Core.Compiler.Const(nothing, false)
└── return %2
)
Select a call to descend into or ↩ to ascend. [q]uit.
Toggles: [o]ptimize, [w]arn, [d]ebuginfo.
Show: [L]LVM IR, [N]ative code
Advanced: dump [P]arams cache.
• ↩
```
---
### Author:  [@tomtom](https://discourse.julialang.org/u/tomtom)
#### Post date: [March 15, 2019, 11:42am UTC](https://discourse.julialang.org/t/code-warntype-fails-when-function-has-a-keyword-argument/21907/4 "2019-03-15T11:42:45Z")
> [@mateuszbaran](#):
>
> You can use [Cthulhu](https://github.com/JuliaDebug/Cthulhu.jl)
thanks. could you show how to install this package?
---
### Author:  [@mateuszbaran](https://discourse.julialang.org/u/mateuszbaran)
#### Post date: [March 15, 2019, 11:45am UTC](https://discourse.julialang.org/t/code-warntype-fails-when-function-has-a-keyword-argument/21907/5 "2019-03-15T11:45:57Z")
It’s not registered, so you have to do `add https://github.com/JuliaDebug/Cthulhu.jl` in [Pkg mode](https://docs.julialang.org/en/v1/stdlib/Pkg/index.html).
---
### Author:  [@tomtom](https://discourse.julialang.org/u/tomtom)
#### Post date: [March 15, 2019, 11:54am UTC](https://discourse.julialang.org/t/code-warntype-fails-when-function-has-a-keyword-argument/21907/6 "2019-03-15T11:54:51Z")
that `Vector{Real}` is intentional (or else no warntype to show at all).
with `@code_warntype` not recursively gives warning, we would need to **carefully watch out** any `invoke`. Or, use [Cthulhu](https://github.com/JuliaDebug/Cthulhu.jl) as @mateuszbaran suggested.
---
### Author:  [@Tamas\_Papp](https://discourse.julialang.org/u/Tamas_Papp)
#### Post date: [March 15, 2019, 12:15pm UTC](https://discourse.julialang.org/t/code-warntype-fails-when-function-has-a-keyword-argument/21907/7 "2019-03-15T12:15:46Z")
Perhaps you misunderstand the role of `@code_warntype`: the idea is that it helps you detect type instabilities when you call with concrete types. This will be marked even if we don’t descend into the callees. Eg
```julia
julia> @noinline f(x) = x > 0 ? 1 : 1.0
f (generic function with 1 method)
julia> g(x) = f(x^2)
g (generic function with 1 method)
julia> @code_warntype g(1)
Variables
#self#::Core.Compiler.Const(g, false)
x::Int64
Body::Union{Float64, Int64}
1 ─ %1 = Core.apply_type(Base.Val, 2)::Core.Compiler.Const(Val{2}, false)
│ %2 = (%1)()::Core.Compiler.Const(Val{2}(), false)
│ %3 = Base.literal_pow(Main.:^, x, %2)::Int64
│ %4 = Main.f(%3)::Union{Float64, Int64}
└── return %4
```
where the `::Union{Float64, Int64}` is highlighted if the terminal supports it. So you are not going to miss anything.