relax withenv signature from Function to Any (JuliaLang#43584)

base/env.jl

@@ -155,15 +155,15 @@ function show(io::IO, ::EnvDict)
 end
 
 """
-    withenv(f::Function, kv::Pair...)
+    withenv(f, kv::Pair...)
 
 Execute `f` in an environment that is temporarily modified (not replaced as in `setenv`)
 by zero or more `"var"=>val` arguments `kv`. `withenv` is generally used via the
 `withenv(kv...) do ... end` syntax. A value of `nothing` can be used to temporarily unset an
 environment variable (if it is set). When `withenv` returns, the original environment has
 been restored.
 """
-function withenv(f::Function, keyvals::Pair{T}...) where T<:AbstractString
+function withenv(f, keyvals::Pair{T}...) where T<:AbstractString
     old = Dict{T,Any}()
     for (key,val) in keyvals
         old[key] = get(ENV,key,nothing)
@@ -176,4 +176,4 @@ function withenv(f::Function, keyvals::Pair{T}...) where T<:AbstractString
         end
     end
 end
-withenv(f::Function) = f() # handle empty keyvals case; see #10853
+withenv(f) = f() # handle empty keyvals case; see #10853

test/env.jl

@@ -27,6 +27,16 @@ end
         @test isempty(ENV) || first(ENV) in c
     end
 end
+
+# issue #43486
+struct Obj43486 end
+(::Obj43486)() = ENV["KEY"] == "VALUE"
+let
+    f = Obj43486()
+    @test !(f isa Function)
+    @test withenv(f, "KEY" => "VALUE")
+end
+
 @testset "non-existent keys" begin
     key = randstring(25)
     @test !haskey(ENV,key)