undo #17318 workaround, add more constant-folding tests

test/broadcast.jl

@@ -170,10 +170,10 @@ rt = Base.return_types(broadcast!, Tuple{Function, Array{Float64, 3}, Array{Floa
 @test length(rt) == 1 && rt[1] == Array{Float64, 3}
 
 # f.(args...) syntax (#15032)
-let x = [1,3.2,4.7], y = [3.5, pi, 1e-4], α = 0.2342, n = 3
+let x = [1,3.2,4.7], y = [3.5, pi, 1e-4], α = 0.2342
     @test sin.(x) == broadcast(sin, x)
     @test sin.(α) == broadcast(sin, α)
-    @test factorial.(n) == broadcast(factorial, n)
+    @test factorial.(3) == broadcast(factorial, 3)
     @test atan2.(x, y) == broadcast(atan2, x, y)
     @test atan2.(x, y') == broadcast(atan2, x, y')
     @test atan2.(x, α) == broadcast(atan2, x, α)
@@ -220,6 +220,7 @@ end
 let x = sin.(1:10)
     @test atan2.((x->x+1).(x), (x->x+2).(x)) == atan2(x+1, x+2) == atan2(x.+1, x.+2)
     @test sin.(atan2.([x+1,x+2]...)) == sin.(atan2.(x+1,x+2))
+    @test sin.(atan2.(x, 3.7)) == broadcast(x -> sin(atan2(x,3.7)), x)
     @test atan2.(x, 3.7) == broadcast(x -> atan2(x,3.7), x) == broadcast(atan2, x, 3.7)
 end
 # Use side effects to check for loop fusion.  Note that, due to #17314,
@@ -236,6 +237,7 @@ let x = sin.(1:10), a = [x]
     @test atan2.(x, cos.(x)) == atan2.(a..., cos.(x)) == atan2(x, cos.(a...)) == atan2(a..., cos.(a...))
     @test ((args...)->cos(args[1])).(x) == cos.(x) == ((y,args...)->cos(y)).(x)
 end
+@test atan2.(3,4) == atan2(3,4) == (() -> atan2(3,4)).()
 
 # PR 16988
 @test Base.promote_op(+, Bool) === Int