tfuncs: remove unnecessary varargtype check from _builtin_nothrow

base/compiler/tfuncs.jl

@@ -2175,10 +2175,12 @@ end
  return boundscheck ⊑ Bool && memtype ⊑ GenericMemoryRef && order ⊑ Symbol
 end
 
-# Query whether the given builtin is guaranteed not to throw given the argtypes
+# Query whether the given builtin is guaranteed not to throw given the `argtypes`.
+# `argtypes` can be assumed not to contain varargs.
 function _builtin_nothrow(𝕃::AbstractLattice, @nospecialize(f::Builtin), argtypes::Vector{Any},
  @nospecialize(rt))
  ⊑ = partialorder(𝕃)
+ na = length(argtypes)
  if f === memoryref
  return memoryref_builtin_common_nothrow(argtypes)
  elseif f === memoryrefoffset
@@ -2194,13 +2196,7 @@ function _builtin_nothrow(𝕃::AbstractLattice, @nospecialize(f::Builtin), argt
  elseif f === Core._expr
  length(argtypes) >= 1 || return false
  return argtypes[1] ⊑ Symbol
- end
-
- # These builtins are not-vararg, so if we have varars, here, we can't guarantee
- # the correct number of arguments.
- na = length(argtypes)
- hasvarargtype(argtypes) && return false
- if f === Core._typevar
+ elseif f === Core._typevar
  na == 3 || return false
  return typevar_nothrow(𝕃, argtypes[1], argtypes[2], argtypes[3])
  elseif f === invoke