test for number of arguments edgecase

Author: MilesCranmer

base/operators.jl

@@ -1211,7 +1211,7 @@ end
 
 function (f::Fix{F,N,T})(args::Vararg{Any,M}) where {F,N,T,M}
     @inline
-    M < N - 1 || throw(ArgumentError("expected at least $(N-1) arguments to a `Fix` function with `N=$(N)`"))
+    M < N - 1 || M == 0 || throw(ArgumentError("expected at least $(N-1) arguments to a `Fix` function with `N=$(N)`"))
     return f.f(args[begin:begin+(N-2)]..., f.x..., args[begin+(N-1):end]...)
 end
 

test/functional.jl

@@ -348,6 +348,17 @@ end
             h = Fix(*, Val(1), "1", "2", "3")
             @test h() == "123"
         end
+        @testset "with integer rather than Val" begin
+            function f(x, y)
+                g = Fix(1, x, y) do x, y
+                    x = x^2
+                    y = y * 3.5
+                    x + y
+                end
+                g()
+            end
+            @inferred f(1, 2)
+        end
 
         @testset "varargs inside Fix" begin
             lazy_sum = Fix(+, Val(1), 1, 2, 3, 4, 5)