inference: Guard TypeVar special case against vararg

Fix #52613 by making the TypeVar special case in inference check
for vararg first. There's nothing the special case can really do
with vararg anyway, so fall back to the ordinary abstract call
handling.

Author: Keno

base/compiler/abstractinterpretation.jl

@@ -2098,7 +2098,7 @@ function abstract_call_known(interp::AbstractInterpreter, @nospecialize(f),
     elseif isa(f, Core.OpaqueClosure)
         # calling an OpaqueClosure about which we have no information returns no information
         return CallMeta(typeof(f).parameters[2], Any, Effects(), NoCallInfo())
-    elseif f === TypeVar
+    elseif f === TypeVar && !isvarargtype(argtypes[end])
         # Manually look through the definition of TypeVar to
         # make sure to be able to get `PartialTypeVar`s out.
         (la < 2 || la > 4) && return CallMeta(Bottom, Any, EFFECTS_THROWS, NoCallInfo())

test/compiler/inference.jl

@@ -5614,3 +5614,6 @@ end
 let 𝕃 = Core.Compiler.fallback_lattice
     @test apply_type_tfunc(𝕃, Const(Tuple{Vararg{Any,N}} where N), Int) == Type{NTuple{_A, Any}} where _A
 end
+
+# Issue #52613
+@test (code_typed((Any,)) do x; TypeVar(x...); end)[1][2] === TypeVar