DataType not contained in roots of Method

[petvana]

While working on PR #44332 I found that there is a problem that struct X is not in the roots of setindex! Method. So, I've prepared MWE to demonstrate the issue. Not sure, if this is a bug or not. (The failing CI test comes originally from #43793.)

using Test

mutable struct Dict2{K,V} <: AbstractDict{K,V}
    pairs::Vector{Pair{K,V}} # stored pairs (key::K => value::V)

    function Dict2{K,V}() where V where K
        n = 16
        new(Vector{Pair{K,V}}(undef, n))
    end
end

function setindex2!(h::Dict2{K,Any}, v, key::K) where K
    @nospecialize v
    h.pairs[1] = Pair{K,Any}(key, v)   
end

struct X end
@noinline function f(d)
    @noinline
    setindex2!(d, nothing, X())
end
function callboth()
    f(Dict2{X,Any}())
    nothing
end
precompile(callboth, ())

m = which(setindex2!, (Dict2{X,Any}, Any, X))
@test X in m.roots

Outputs:

Test Failed at REPL[9]:1
  Expression: X in m.roots
   Evaluated: X in Any[:(:pairs), :setindex2!, Symbol("REPL[3]"), Pair{X, Any}, :($(QuoteNode(X()))), :($(QuoteNode(Pair{X, Any}(X(), nothing))))]
ERROR: There was an error during testinwe.jl:29

[timholy]

FWIW, that test just exploits Dict as a convenient example of code where compilation creates new roots. It would be fine to change that test to something else that does the same thing.

Codegen root-creation is in

julia/src/codegen.cpp

Lines 2368 to 2389 in 9b8253c

	static void jl_add_method_root(jl_codectx_t &ctx, jl_value_t *val)
	{
	if (jl_is_concrete_type(val) || jl_is_bool(val) || jl_is_symbol(val) || val == jl_nothing ||
	val == (jl_value_t*)jl_any_type || val == (jl_value_t*)jl_bottom_type || val == (jl_value_t*)jl_core_module)
	return;
	JL_GC_PUSH1(&val);
	if (ctx.roots == NULL) {
	ctx.roots = jl_alloc_vec_any(1);
	jl_array_ptr_set(ctx.roots, 0, val);
	}
	else {
	size_t rlen = jl_array_dim0(ctx.roots);
	for (size_t i = 0; i < rlen; i++) {
	if (jl_array_ptr_ref(ctx.roots,i) == val) {
	JL_GC_POP();
	return;
	}
	}
	jl_array_ptr_1d_push(ctx.roots, val);
	}
	JL_GC_POP();
	}

and compression root-generation is in

julia/src/ircode.c

Line 58 in 9b8253c

jl_add_method_root(s->method, jl_precompile_toplevel_module, v);

which calls

julia/src/method.c

Lines 1049 to 1063 in 9b8253c

	JL_DLLEXPORT void jl_add_method_root(jl_method_t *m, jl_module_t *mod, jl_value_t* root)
	{
	JL_GC_PUSH2(&m, &root);
	uint64_t modid = 0;
	if (mod) {
	assert(jl_is_module(mod));
	modid = mod->build_id;
	}
	assert(jl_is_method(m));
	prepare_method_for_roots(m, modid);
	if (current_root_id(m->root_blocks) != modid)
	add_root_block(m->root_blocks, modid, jl_array_len(m->roots));
	jl_array_ptr_1d_push(m->roots, root);
	JL_GC_POP();
	}