using AMDGPU
using Random
function kernel()
    Random.seed!(123)
    return nothing
end
@roc kernel()

julia> @roc kernel()
ERROR: GPU compilation of kernel #kernel() failed
KernelError: kernel returns a value of type `Union{}`

Make sure your kernel function ends in `return`, `return nothing` or `nothing`.
If the returned value is of type `Union{}`, your Julia code probably throws an exception.
Inspect the code with `@device_code_warntype` for more details.

Stacktrace:
 [1] check_method(job::GPUCompiler.CompilerJob)
   @ GPUCompiler ~/.julia/packages/GPUCompiler/kb6yJ/src/validation.jl:41
 [2] macro expansion
   @ ~/.julia/packages/TimerOutputs/LHjFw/src/TimerOutput.jl:253 [inlined]
 [3] macro expansion
   @ ~/.julia/packages/GPUCompiler/kb6yJ/src/driver.jl:152 [inlined]
 [4] emit_julia(job::GPUCompiler.CompilerJob)
   @ GPUCompiler ~/.julia/packages/GPUCompiler/kb6yJ/src/utils.jl:83
 [5] rocfunction_compile(job::GPUCompiler.CompilerJob)
   @ AMDGPU.Compiler ~/.julia/dev/AMDGPU/src/compiler/codegen.jl:181
 [6] cached_compilation(cache::Dict{UInt64, Any}, job::GPUCompiler.CompilerJob, compiler::typeof(AMDGPU.Compiler.rocfunction_compile), linker::typeof(AMDGPU.Compiler.rocfunction_link))
   @ GPUCompiler ~/.julia/packages/GPUCompiler/kb6yJ/src/cache.jl:90
 [7] rocfunction(f::typeof(kernel), tt::Type; name::Nothing, device::ROCDevice, global_hooks::NamedTuple{(), Tuple{}})
   @ AMDGPU.Compiler ~/.julia/dev/AMDGPU/src/compiler/codegen.jl:165
 [8] rocfunction(f::typeof(kernel), tt::Type)
   @ AMDGPU.Compiler ~/.julia/dev/AMDGPU/src/compiler/codegen.jl:154
 [9] top-level scope
   @ ~/.julia/dev/AMDGPU/src/highlevel.jl:430