fix #33768, inference of _apply with strange argument list lengths

base/compiler/abstractinterpretation.jl

@@ -639,11 +639,33 @@ function pure_eval_call(@nospecialize(f), argtypes::Vector{Any}, @nospecialize(a
     end
 end
 
+function argtype_by_index(argtypes::Vector{Any}, i::Int)
+    n = length(argtypes)
+    if isvarargtype(argtypes[n])
+        return i >= n ? unwrapva(argtypes[n]) : argtypes[i]
+    else
+        return i > n ? Bottom : argtypes[i]
+    end
+end
+
+function argtype_tail(argtypes::Vector{Any}, i::Int)
+    n = length(argtypes)
+    if isvarargtype(argtypes[n]) && i > n
+        i = n
+    end
+    return argtypes[i:n]
+end
+
 function abstract_call(@nospecialize(f), fargs::Union{Nothing,Vector{Any}}, argtypes::Vector{Any}, vtypes::VarTable, sv::InferenceState, max_methods = sv.params.MAX_METHODS)
     if f === _apply
-        return abstract_apply(nothing, argtypes[2], argtypes[3:end], vtypes, sv, max_methods)
+        ft = argtype_by_index(argtypes, 2)
+        ft === Bottom && return Bottom
+        return abstract_apply(nothing, ft, argtype_tail(argtypes, 3), vtypes, sv, max_methods)
     elseif f === _apply_iterate
-        return abstract_apply(argtypes[2], argtypes[3], argtypes[4:end], vtypes, sv, max_methods)
+        itft = argtype_by_index(argtypes, 2)
+        ft = argtype_by_index(argtypes, 3)
+        (itft === Bottom || ft === Bottom) && return Bottom
+        return abstract_apply(itft, ft, argtype_tail(argtypes, 4), vtypes, sv, max_methods)
     end
 
     la = length(argtypes)

base/compiler/ssair/inlining.jl

@@ -885,6 +885,9 @@ function inline_apply!(ir::IRCode, idx::Int, sig::Signature, params::Params)
     while sig.f === Core._apply || sig.f === Core._apply_iterate
         arg_start = sig.f === Core._apply ? 2 : 3
         atypes = sig.atypes
+        if arg_start > length(atypes)
+            return nothing
+        end
         # Try to figure out the signature of the function being called
         # and if rewrite_apply_exprargs can deal with this form
         for i = (arg_start + 1):length(atypes)

src/builtins.c

@@ -476,7 +476,6 @@ static jl_function_t *jl_iterate_func JL_GLOBALLY_ROOTED;
 
 static jl_value_t *do_apply(jl_value_t *F, jl_value_t **args, uint32_t nargs, jl_value_t *iterate)
 {
-    JL_NARGSV(apply, 1);
     jl_function_t *f = args[0];
     if (nargs == 2) {
         // some common simple cases
@@ -634,11 +633,13 @@ static jl_value_t *do_apply(jl_value_t *F, jl_value_t **args, uint32_t nargs, jl
 
 JL_CALLABLE(jl_f__apply_iterate)
 {
+    JL_NARGSV(_apply_iterate, 2);
     return do_apply(F, args+1, nargs-1, args[0]);
 }
 
 JL_CALLABLE(jl_f__apply)
 {
+    JL_NARGSV(_apply, 1);
     return do_apply(F, args, nargs, NULL);
 }
 

test/compiler/inference.jl

@@ -2464,3 +2464,21 @@ let N = TypeVar(:N)
         Core.Compiler.PartialTypeVar(N, true, true),
         Core.Compiler.Const(Any)], Type{Tuple{Vararg{Any,N}}})
 end
+
+# issue #33768
+function f33768()
+    Core._apply()
+end
+function g33768()
+    a = Any[iterate, tuple, (1,)]
+    Core._apply_iterate(a...)
+end
+function h33768()
+    Core._apply_iterate()
+end
+@test_throws ArgumentError f33768()
+@test Base.return_types(f33768, ()) == Any[Union{}]
+@test g33768() === (1,)
+@test Base.return_types(g33768, ()) == Any[Any]
+@test_throws ArgumentError h33768()
+@test Base.return_types(h33768, ()) == Any[Union{}]