Check world age bounds on candidate ambiguities. Fixes #28899 (#28916)

(cherry picked from commit 513db98)

base/compiler/utilities.jl

@@ -122,7 +122,7 @@ function retrieve_code_info(linfo::MethodInstance)
 end
 
 function code_for_method(method::Method, @nospecialize(atypes), sparams::SimpleVector, world::UInt, preexisting::Bool=false)
-    if world < min_world(method)
+    if world < min_world(method) || world > max_world(method)
         return nothing
     end
     if isdefined(method, :generator) && !isdispatchtuple(atypes)

base/errorshow.jl

@@ -432,6 +432,8 @@ function show_method_candidates(io::IO, ex::MethodError, @nospecialize kwargs=()
                 end
                 if ex.world < min_world(method)
                     print(iob, " (method too new to be called from this world context.)")
+                elseif ex.world > max_world(method)
+                    print(iob, " (method deleted before this world age.)")
                 end
                 # TODO: indicate if it's in the wrong world
                 push!(lines, (buf, right_matches))

base/methodshow.jl

@@ -76,7 +76,7 @@ end
 
 function kwarg_decl(m::Method, kwtype::DataType)
     sig = rewrap_unionall(Tuple{kwtype, Any, unwrap_unionall(m.sig).parameters...}, m.sig)
-    kwli = ccall(:jl_methtable_lookup, Any, (Any, Any, UInt), kwtype.name.mt, sig, typemax(UInt))
+    kwli = ccall(:jl_methtable_lookup, Any, (Any, Any, UInt), kwtype.name.mt, sig, max_world(m))
     if kwli !== nothing
         kwli = kwli::Method
         src = uncompressed_ast(kwli)

base/reflection.jl

@@ -1103,7 +1103,7 @@ has_bottom_parameter(t::TypeVar) = t.ub == Bottom || has_bottom_parameter(t.ub)
 has_bottom_parameter(::Any) = false
 
 min_world(m::Method) = reinterpret(UInt, m.min_world)
-max_world(m::Method) = typemax(UInt)
+max_world(m::Method) = reinterpret(UInt, m.max_world)
 min_world(m::Core.MethodInstance) = reinterpret(UInt, m.min_world)
 max_world(m::Core.MethodInstance) = reinterpret(UInt, m.max_world)
 

src/dump.c

@@ -1647,6 +1647,7 @@ static jl_value_t *jl_deserialize_value_method(jl_serializer_state *s, jl_value_
     m->file = (jl_sym_t*)jl_deserialize_value(s, NULL);
     m->line = read_int32(s->s);
     m->min_world = jl_world_counter;
+    m->max_world = ~(size_t)0;
     m->ambig = jl_deserialize_value(s, (jl_value_t**)&m->ambig);
     jl_gc_wb(m, m->ambig);
     m->called = read_int32(s->s);
@@ -2992,7 +2993,7 @@ static jl_method_instance_t *jl_recache_method_instance(jl_method_instance_t *li
     //assert(ti != jl_bottom_type); (void)ti;
     if (ti == jl_bottom_type)
         env = jl_emptysvec; // the intersection may fail now if the type system had made an incorrect subtype env in the past
-    jl_method_instance_t *_new = jl_specializations_get_linfo(m, (jl_value_t*)argtypes, env, jl_world_counter);
+    jl_method_instance_t *_new = jl_specializations_get_linfo(m, (jl_value_t*)argtypes, env, jl_world_counter < max_world ? jl_world_counter : max_world);
     _new->max_world = max_world;
     jl_update_backref_list((jl_value_t*)li, (jl_value_t*)_new, start);
     return _new;

src/gf.c

@@ -148,7 +148,7 @@ static int8_t jl_cachearg_offset(jl_methtable_t *mt)
 // get or create the MethodInstance for a specialization
 JL_DLLEXPORT jl_method_instance_t *jl_specializations_get_linfo(jl_method_t *m, jl_value_t *type, jl_svec_t *sparams, size_t world)
 {
-    assert(world >= m->min_world && "typemap lookup is corrupted");
+    assert(world >= m->min_world && world <= m->max_world && "typemap lookup is corrupted");
     JL_LOCK(&m->writelock);
     jl_typemap_entry_t *sf =
         jl_typemap_assoc_by_type(m->specializations, type, NULL, /*subtype*/0, /*offs*/0, world, /*max_world_mask*/0);
@@ -169,7 +169,7 @@ JL_DLLEXPORT jl_method_instance_t *jl_specializations_get_linfo(jl_method_t *m,
         li->min_world = world;
     }
     if (world == jl_world_counter) {
-        li->max_world = ~(size_t)0;
+        li->max_world = m->max_world;
     }
     else {
         li->max_world = world;
@@ -358,6 +358,7 @@ JL_DLLEXPORT jl_method_instance_t* jl_set_method_inferred(
         else {
             JL_LOCK(&li->def.method->writelock);
             assert(min_world >= li->def.method->min_world);
+            assert(max_world <= li->def.method->max_world);
             int isinferred =  jl_is_rettype_inferred(li);
             if (!isinferred && li->min_world >= min_world && li->max_world <= max_world) {
                 // expand the current (uninferred) entry to cover the full inferred range
@@ -955,7 +956,7 @@ static jl_method_instance_t *cache_method(
     jl_tupletype_t *cachett = tt;
     jl_svec_t* guardsigs = jl_emptysvec;
     size_t min_valid = definition->min_world;
-    size_t max_valid = ~(size_t)0;
+    size_t max_valid = definition->max_world;
     if (!cache_with_orig) {
         // now examine what will happen if we chose to use this sig in the cache
         temp = ml_matches(mt->defs, 0, compilationsig, -1, 0, world, &min_valid, &max_valid); // TODO: use MAX_UNSPECIALIZED_CONFLICTS?
@@ -1501,6 +1502,7 @@ JL_DLLEXPORT void jl_method_table_disable(jl_methtable_t *mt, jl_method_t *metho
         jl_error("method not in method table");
     JL_LOCK(&mt->writelock);
     // Narrow the world age on the method to make it uncallable
+    method->max_world = jl_world_counter;
     methodentry->max_world = jl_world_counter++;
     // Recompute ambiguities (deleting a more specific method might reveal ambiguities that it previously resolved)
     check_ambiguous_matches(mt->defs, methodentry, check_disabled_ambiguous_visitor); // TODO: decrease repeated work?
@@ -1525,7 +1527,7 @@ JL_DLLEXPORT void jl_method_table_insert(jl_methtable_t *mt, jl_method_t *method
     JL_LOCK(&mt->writelock);
     jl_typemap_entry_t *newentry = jl_typemap_insert(&mt->defs, (jl_value_t*)mt,
             (jl_tupletype_t*)type, simpletype, jl_emptysvec, (jl_value_t*)method, 0, &method_defs,
-            method->min_world, ~(size_t)0, &oldvalue);
+            method->min_world, method->max_world, &oldvalue);
     if (oldvalue) {
         if (oldvalue == (jl_value_t*)method) {
             // redundant add of same method; no need to do anything
@@ -1982,7 +1984,7 @@ JL_DLLEXPORT int jl_is_call_ambiguous(jl_value_t *types, jl_method_t *m)
         return 0;
     for (size_t i = 0; i < jl_array_len(m->ambig); i++) {
         jl_method_t *mambig = (jl_method_t*)jl_array_ptr_ref(m->ambig, i);
-        if (jl_subtype((jl_value_t*)types, (jl_value_t*)mambig->sig))
+        if (mambig->min_world <= jl_world_counter && jl_world_counter <= mambig->max_world && jl_subtype((jl_value_t*)types, (jl_value_t*)mambig->sig))
             return 1;
     }
     return 0;
@@ -1996,7 +1998,7 @@ JL_DLLEXPORT int jl_has_call_ambiguities(jl_value_t *types, jl_method_t *m)
         return 0;
     for (size_t i = 0; i < jl_array_len(m->ambig); i++) {
         jl_method_t *mambig = (jl_method_t*)jl_array_ptr_ref(m->ambig, i);
-        if (!jl_has_empty_intersection(mambig->sig, types))
+        if (mambig->min_world <= jl_world_counter && jl_world_counter <= mambig->max_world && !jl_has_empty_intersection(mambig->sig, types))
             return 1;
     }
     return 0;

src/jltypes.c

@@ -2059,13 +2059,14 @@ void jl_init_types(void)
     jl_method_type =
         jl_new_datatype(jl_symbol("Method"), core,
                         jl_any_type, jl_emptysvec,
-                        jl_perm_symsvec(19,
+                        jl_perm_symsvec(20,
                             "name",
                             "module",
                             "file",
                             "line",
                             "sig",
                             "min_world",
+                            "max_world",
                             "ambig",
                             "specializations",
                             "sparam_syms",
@@ -2079,13 +2080,14 @@ void jl_init_types(void)
                             "nospecialize",
                             "isva",
                             "pure"),
-                        jl_svec(19,
+                        jl_svec(20,
                             jl_sym_type,
                             jl_module_type,
                             jl_sym_type,
                             jl_int32_type,
                             jl_type_type,
                             jl_long_type,
+                            jl_long_type,
                             jl_any_type, // Union{Array, Nothing}
                             jl_any_type, // TypeMap
                             jl_simplevector_type,
@@ -2099,7 +2101,7 @@ void jl_init_types(void)
                             jl_int32_type,
                             jl_bool_type,
                             jl_bool_type),
-                        0, 1, 9);
+                        0, 1, 10);
 
     jl_method_instance_type =
         jl_new_datatype(jl_symbol("MethodInstance"), core,
@@ -2211,7 +2213,7 @@ void jl_init_types(void)
     jl_svecset(jl_methtable_type->types, 7, jl_int32_type); // DWORD
 #endif
     jl_svecset(jl_methtable_type->types, 8, jl_int32_type); // uint32_t
-    jl_svecset(jl_method_type->types, 10, jl_method_instance_type);
+    jl_svecset(jl_method_type->types, 11, jl_method_instance_type);
     jl_svecset(jl_method_instance_type->types, 11, jl_voidpointer_type);
     jl_svecset(jl_method_instance_type->types, 12, jl_voidpointer_type);
     jl_svecset(jl_method_instance_type->types, 13, jl_voidpointer_type);

src/julia.h

@@ -264,6 +264,7 @@ typedef struct _jl_method_t {
     // method's type signature. redundant with TypeMapEntry->specTypes
     jl_value_t *sig;
     size_t min_world;
+    size_t max_world;
 
     // list of potentially-ambiguous methods (nothing = none, Vector{Any} of Methods otherwise)
     jl_value_t *ambig;

src/method.c

@@ -460,7 +460,7 @@ jl_method_instance_t *jl_get_specialized(jl_method_t *m, jl_value_t *types, jl_s
     new_linfo->specTypes = types;
     new_linfo->sparam_vals = sp;
     new_linfo->min_world = m->min_world;
-    new_linfo->max_world = ~(size_t)0;
+    new_linfo->max_world = m->max_world;
     return new_linfo;
 }
 
@@ -595,6 +595,7 @@ JL_DLLEXPORT jl_method_t *jl_new_method_uninit(jl_module_t *module)
     m->nargs = 0;
     m->traced = 0;
     m->min_world = 1;
+    m->max_world = ~(size_t)0;
     JL_MUTEX_INIT(&m->writelock);
     return m;
 }
@@ -639,6 +640,7 @@ static jl_method_t *jl_new_method(
 
     JL_GC_POP();
     m->min_world = ++jl_world_counter;
+    m->max_world = ~(size_t)0;
     return m;
 }
 

src/typemap.c

@@ -743,7 +743,7 @@ jl_typemap_entry_t *jl_typemap_entry_assoc_exact(jl_typemap_entry_t *ml, jl_valu
 {
     // some manually-unrolled common special cases
     while (ml->simplesig == (void*)jl_nothing && ml->guardsigs == jl_emptysvec && ml->isleafsig) {
-        // use a tight loop for a long as possible
+        // use a tight loop for as long as possible
         if (world >= ml->min_world && world <= ml->max_world) {
             if (n == jl_field_count(ml->sig) && jl_typeof(args[0]) == jl_tparam(ml->sig, 0)) {
                 if (n == 1)

test/reflection.jl

@@ -775,6 +775,18 @@ typeparam(::Type{T}, a::AbstractArray{T}) where T = 2
 @test typeparam(Float64, rand(2))  == 1
 @test typeparam(Int, rand(Int, 2)) == 2
 
+# prior ambiguities (issue #28899)
+uambig(::Union{Int,Nothing}) = 1
+uambig(::Union{Float64,Nothing}) = 2
+@test uambig(1) == 1
+@test uambig(1.0) == 2
+@test_throws MethodError uambig(nothing)
+m = which(uambig, Tuple{Int})
+Base.delete_method(m)
+@test_throws MethodError uambig(1)
+@test uambig(1.0) == 2
+@test uambig(nothing) == 2
+
 end
 
 # issue #26267