Use Core.Compiler.return_type

Author: serenity4

src/rulesets/Base/broadcast.jl

@@ -48,7 +48,7 @@ end
 # Path 2: This is roughly what `derivatives_given_output` is designed for, should be fast.
 
 function may_bc_derivatives(::Type{T}, f::F, args::Vararg{Any,N}) where {T,F,N}
-    TΔ = Base._return_type(derivatives_given_output, Tuple{T, F, map(_eltype, args)...})
+    TΔ = Core.Compiler.return_type(derivatives_given_output, Tuple{T, F, map(_eltype, args)...})
     return isconcretetype(TΔ)
 end
 
@@ -98,7 +98,7 @@ function may_bc_forwards(cfg::C, f::F, arg) where {C,F}
     TA = _eltype(arg)
     TA <: Real || return false
     cfg isa RuleConfig{>:HasForwardsMode} && return true  # allows frule_via_ad
-    TF = Base._return_type(frule, Tuple{C, Tuple{NoTangent, TA}, F, TA})
+    TF = Core.Compiler.return_type(frule, Tuple{C, Tuple{NoTangent, TA}, F, TA})
     return isconcretetype(TF) && TF <: Tuple
 end
 

src/rulesets/Base/mapreduce.jl

@@ -139,7 +139,7 @@ Works by seeing if the result of `derivatives_given_output(nothing, f, x)` can b
 The method of `derivatives_given_output` usually comes from `@scalar_rule`.
 """
 function _uses_input_only(f::F, ::Type{xT}) where {F,xT}
-    gT = Base._return_type(derivatives_given_output, Tuple{Nothing, F, xT})
+    gT = Core.Compiler.return_type(derivatives_given_output, Tuple{Nothing, F, xT})
     # Here we must check `<: Number`, to avoid this, the one rule which can return the `nothing`:
     # ChainRules.derivatives_given_output("anything", exp, 1) == (("anything",),)
     return isconcretetype(gT) && gT <: Tuple{Tuple{Number}}