error with BitVector

[CarloLucibello]

julia> function f1(x)   
         mask = x .< 0.5
         sum(x .* (1 .- mask))
       end
f1 (generic function with 1 method)

julia> gradient(f1, rand(3))
ERROR: MethodError: no method matching -(::Nothing)
Closest candidates are:
  -(::Any, ::ChainRulesCore.ZeroTangent) at /home/carlo/.julia/packages/ChainRulesCore/8vlYQ/src/tangent_arithmetic.jl:118
  -(::Any, ::ChainRulesCore.NoTangent) at /home/carlo/.julia/packages/ChainRulesCore/8vlYQ/src/tangent_arithmetic.jl:78
  -(::Any, ::ChainRulesCore.NotImplemented) at /home/carlo/.julia/packages/ChainRulesCore/8vlYQ/src/tangent_arithmetic.jl:63
  ...
Stacktrace:
 [1] (::Zygote.var"#1022#1023"{Int64, BitVector})(Δ::Vector{Float64})
   @ Zygote ~/.julia/packages/Zygote/EPhp6/src/lib/broadcast.jl:75
 [2] (::Zygote.var"#3755#back#1024"{Zygote.var"#1022#1023"{Int64, BitVector}})(Δ::Vector{Float64})
   @ Zygote ~/.julia/packages/ZygoteRules/OjfTt/src/adjoint.jl:59
 [3] Pullback
   @ ./REPL[31]:3 [inlined]
 [4] (::typeof(∂(f1)))(Δ::Float64)
   @ Zygote ~/.julia/packages/Zygote/EPhp6/src/compiler/interface2.jl:0
 [5] (::Zygote.var"#50#51"{typeof(∂(f1))})(Δ::Float64)
   @ Zygote ~/.julia/packages/Zygote/EPhp6/src/compiler/interface.jl:41
 [6] gradient(f::Function, args::Vector{Float64})
   @ Zygote ~/.julia/packages/Zygote/EPhp6/src/compiler/interface.jl:76
 [7] top-level scope
   @ REPL[32]:1

Without the - it works:

julia> function f2(x)   
         mask = x .< 0.5
         sum(x .* mask)
       end
f2 (generic function with 1 method)

julia> gradient(f2, rand(3))
([0.0, 0.0, 1.0],)

[DhairyaLGandhi]

Try with an older version of zygote.