fix #39862, error in inference when trying to apply a non-type (#40047)

Author: JeffBezanson

base/compiler/tfuncs.jl

@@ -1144,7 +1144,7 @@ function apply_type_tfunc(@nospecialize(headtypetype), @nospecialize args...)
         end
         return allconst ? Const(ty) : Type{ty}
     end
-    istuple = (headtype == Tuple)
+    istuple = isa(headtype, Type) && (headtype == Tuple)
     if !istuple && !isa(headtype, UnionAll)
         return Union{}
     end

test/compiler/inference.jl

@@ -2985,3 +2985,8 @@ g38888() = S38888(Base.inferencebarrier(3), nothing)
 # issue #38971
 f28971() = (1, [2,3]...)::Tuple{Int,Int,Int}
 @test @inferred(Tuple{Int,Vararg{Int}}, f28971()) == (1, 2, 3)
+
+# issue #39862
+let f() = sin{Int}()
+    @test Base.return_types(f, ()) == Any[Union{}]
+end