inference: Guard TypeVar special case against vararg (#52721)

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

@@ -2021,10 +2021,10 @@ 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], 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, EFFECTS_THROWS, NoCallInfo())
+        2 ≤ la ≤ 4 || return CallMeta(Bottom, EFFECTS_THROWS, NoCallInfo())
         n = argtypes[2]
         ub_var = Const(Any)
         lb_var = Const(Union{})

test/compiler/inference.jl

@@ -5130,7 +5130,5 @@ let TV = TypeVar(:T)
     @test abstract_call_unionall_vararg(some) isa UnionAll
 end
 
-# Issue #51927
-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