typeintersect: followup cleanup for the nothrow path of type instantiation (JuliaLang#54514)

N5N3 · lazarusA · commit 8ef5504fdad8 · 2024-07-12T11:58:37.000+02:00
Adopt suggestions from JuliaLang#54465 (review) and fix various added regession & residual MWE.
diff --git a/src/jltypes.c b/src/jltypes.c
@@ -1499,11 +1499,11 @@ jl_unionall_t *jl_rename_unionall(jl_unionall_t *u)
     return (jl_unionall_t*)t;
 }
 
-jl_value_t *jl_substitute_var_nothrow(jl_value_t *t, jl_tvar_t *var, jl_value_t *val)
+jl_value_t *jl_substitute_var_nothrow(jl_value_t *t, jl_tvar_t *var, jl_value_t *val, int nothrow)
 {
     if (val == (jl_value_t*)var)
         return t;
-    int nothrow = jl_is_typevar(val) ? 0 : 1;
+    nothrow = jl_is_typevar(val) ? 0 : nothrow;
     jl_typeenv_t env = { var, val, NULL };
     return inst_type_w_(t, &env, NULL, 1, nothrow);
 }
@@ -1725,7 +1725,7 @@ void jl_precompute_memoized_dt(jl_datatype_t *dt, int cacheable)
     dt->hash = typekey_hash(dt->name, jl_svec_data(dt->parameters), l, cacheable);
 }
 
-static void check_datatype_parameters(jl_typename_t *tn, jl_value_t **params, size_t np)
+static int check_datatype_parameters(jl_typename_t *tn, jl_value_t **params, size_t np, int nothrow)
 {
     jl_value_t *wrapper = tn->wrapper;
     jl_value_t **bounds;
@@ -1743,6 +1743,10 @@ static void check_datatype_parameters(jl_typename_t *tn, jl_value_t **params, si
         assert(jl_is_unionall(wrapper));
         jl_tvar_t *tv = ((jl_unionall_t*)wrapper)->var;
         if (!within_typevar(params[i], bounds[2*i], bounds[2*i+1])) {
+            if (nothrow) {
+                JL_GC_POP();
+                return 1;
+            }
             if (tv->lb != bounds[2*i] || tv->ub != bounds[2*i+1])
                 // pass a new version of `tv` containing the instantiated bounds
                 tv = jl_new_typevar(tv->name, bounds[2*i], bounds[2*i+1]);
@@ -1752,12 +1756,26 @@ static void check_datatype_parameters(jl_typename_t *tn, jl_value_t **params, si
         int j;
         for (j = 2*i + 2; j < 2*np; j++) {
             jl_value_t *bj = bounds[j];
-            if (bj != (jl_value_t*)jl_any_type && bj != jl_bottom_type)
-                bounds[j] = jl_substitute_var(bj, tv, params[i]);
+            if (bj != (jl_value_t*)jl_any_type && bj != jl_bottom_type) {
+                int isub = j & 1;
+                // use different nothrow level for lb and ub substitution.
+                // TODO: This assuming the top instantiation could only start with
+                // `nothrow == 2` or `nothrow == 0`. If `nothrow` is initially set to 1
+                // then we might miss some inner error, perhaps the normal path should
+                // also follow this rule？
+                jl_value_t *nb = jl_substitute_var_nothrow(bj, tv, params[i], nothrow ? (isub ? 2 : 1) : 0 );
+                if (nb == NULL) {
+                    assert(nothrow);
+                    JL_GC_POP();
+                    return 1;
+                }
+                bounds[j] = nb;
+            }
         }
         wrapper = ((jl_unionall_t*)wrapper)->body;
     }
     JL_GC_POP();
+    return 0;
 }
 
 static jl_value_t *extract_wrapper(jl_value_t *t JL_PROPAGATES_ROOT) JL_NOTSAFEPOINT JL_GLOBALLY_ROOTED
@@ -2004,13 +2022,8 @@ static jl_value_t *inst_datatype_inner(jl_datatype_t *dt, jl_svec_t *p, jl_value
     // for whether this is even valid
     if (check && !istuple) {
         assert(ntp > 0);
-        JL_TRY {
-            check_datatype_parameters(tn, iparams, ntp);
-        }
-        JL_CATCH {
-            if (!nothrow) jl_rethrow();
+        if (check_datatype_parameters(tn, iparams, ntp, nothrow))
             return NULL;
-        }
     }
     else if (ntp == 0 && jl_emptytuple_type != NULL) {
         // empty tuple type case
@@ -2401,7 +2414,8 @@ static jl_value_t *inst_tuple_w_(jl_value_t *t, jl_typeenv_t *env, jl_typestack_
         jl_value_t *elt = jl_svecref(tp, i);
         jl_value_t *pi = inst_type_w_(elt, env, stack, check, nothrow);
         if (pi == NULL) {
-            if (i == ntp-1 && jl_is_vararg(elt)) {
+            assert(nothrow);
+            if (nothrow == 1 || (i == ntp-1 && jl_is_vararg(elt))) {
                 t = NULL;
                 break;
             }
@@ -2420,6 +2434,10 @@ static jl_value_t *inst_tuple_w_(jl_value_t *t, jl_typeenv_t *env, jl_typestack_
     return t;
 }
 
+// `nothrow` means that when type checking fails, the type instantiation should
+// return `NULL` instead of immediately throwing an error. If `nothrow` == 2 then
+// we further assume that the imprecise instantiation for non invariant parameters
+// is acceptable, and inner error (`NULL`) would be ignored.
 static jl_value_t *inst_type_w_(jl_value_t *t, jl_typeenv_t *env, jl_typestack_t *stack, int check, int nothrow)
 {
     size_t i;
@@ -2440,11 +2458,10 @@ static jl_value_t *inst_type_w_(jl_value_t *t, jl_typeenv_t *env, jl_typestack_t
         jl_value_t *var = NULL;
         jl_value_t *newbody = NULL;
         JL_GC_PUSH3(&lb, &var, &newbody);
-        JL_TRY {
-            lb = inst_type_w_(ua->var->lb, env, stack, check, 0);
-        }
-        JL_CATCH {
-            if (!nothrow) jl_rethrow();
+        // set nothrow <= 1 to ensure lb's accuracy.
+        lb = inst_type_w_(ua->var->lb, env, stack, check, nothrow ? 1 : 0);
+        if (lb == NULL) {
+            assert(nothrow);
             t = NULL;
         }
         if (t != NULL) {
@@ -2468,11 +2485,9 @@ static jl_value_t *inst_type_w_(jl_value_t *t, jl_typeenv_t *env, jl_typestack_t
             if (newbody == NULL) {
                 t = NULL;
             }
-            else if (newbody == (jl_value_t*)jl_emptytuple_type) {
-                // NTuple{0} => Tuple{} can make a typevar disappear
-                t = (jl_value_t*)jl_emptytuple_type;
-            }
-            else if (nothrow && !jl_has_typevar(newbody, (jl_tvar_t *)var)) {
+            else if (!jl_has_typevar(newbody, (jl_tvar_t *)var)) {
+                // inner instantiation might make a typevar disappear, e.g.
+                // NTuple{0,T} => Tuple{}
                 t = newbody;
             }
             else if (newbody != ua->body || var != (jl_value_t*)ua->var) {
@@ -2489,16 +2504,21 @@ static jl_value_t *inst_type_w_(jl_value_t *t, jl_typeenv_t *env, jl_typestack_t
         jl_value_t *b = NULL;
         JL_GC_PUSH2(&a, &b);
         b = inst_type_w_(u->b, env, stack, check, nothrow);
+        if (nothrow) {
+            // ensure jl_type_union nothrow.
+            if (a && !(jl_is_typevar(a) || jl_is_type(a)))
+                a = NULL;
+            if (b && !(jl_is_typevar(b) || jl_is_type(b)))
+                b = NULL;
+        }
         if (a != u->a || b != u->b) {
             if (!check) {
                 // fast path for `jl_rename_unionall`.
                 t = jl_new_struct(jl_uniontype_type, a, b);
             }
-            else if (nothrow && a == NULL) {
-                t = b;
-            }
-            else if (nothrow && b == NULL) {
-                t = a;
+            else if (a == NULL || b == NULL) {
+                assert(nothrow);
+                t = nothrow == 1 ? NULL : a == NULL ? b : a;
             }
             else {
                 assert(a != NULL && b != NULL);
@@ -2516,15 +2536,21 @@ static jl_value_t *inst_type_w_(jl_value_t *t, jl_typeenv_t *env, jl_typestack_t
         JL_GC_PUSH2(&T, &N);
         if (v->T) {
             T = inst_type_w_(v->T, env, stack, check, nothrow);
-            if (T == NULL)
-                T = jl_bottom_type;
-            if (v->N) // This branch should never throw.
-                N = inst_type_w_(v->N, env, stack, check, 0);
+            if (T == NULL) {
+                if (nothrow == 2)
+                    T = jl_bottom_type;
+                else
+                    t = NULL;
+            }
+            if (t && v->N) {
+                // set nothrow <= 1 to ensure invariant parameter's accuracy.
+                N = inst_type_w_(v->N, env, stack, check, nothrow ? 1 : 0);
+                if (N == NULL)
+                    t = NULL;
+            }
         }
-        if (T != v->T || N != v->N) {
-            // `Vararg` is special, we'd better handle inner error at Tuple level.
+        if (t && (T != v->T || N != v->N))
             t = (jl_value_t*)jl_wrap_vararg(T, N, check, nothrow);
-        }
         JL_GC_POP();
         return t;
     }
@@ -2543,16 +2569,15 @@ static jl_value_t *inst_type_w_(jl_value_t *t, jl_typeenv_t *env, jl_typestack_t
     int bound = 0;
     for (i = 0; i < ntp; i++) {
         jl_value_t *elt = jl_svecref(tp, i);
-        JL_TRY {
-            jl_value_t *pi = inst_type_w_(elt, env, stack, check, 0);
-            iparams[i] = pi;
-            bound |= (pi != elt);
-        }
-        JL_CATCH {
-            if (!nothrow) jl_rethrow();
+        // set nothrow <= 1 to ensure invariant parameter's accuracy.
+        jl_value_t *pi = inst_type_w_(elt, env, stack, check, nothrow ? 1 : 0);
+        if (pi == NULL) {
+            assert(nothrow);
             t = NULL;
+            break;
         }
-        if (t == NULL) break;
+        iparams[i] = pi;
+        bound |= (pi != elt);
     }
     // if t's parameters are not bound in the environment, return it uncopied (#9378)
     if (t != NULL && bound)
diff --git a/src/julia_internal.h b/src/julia_internal.h
@@ -757,7 +757,7 @@ JL_DLLEXPORT int jl_type_morespecific_no_subtype(jl_value_t *a, jl_value_t *b);
 jl_value_t *jl_instantiate_type_with(jl_value_t *t, jl_value_t **env, size_t n);
 JL_DLLEXPORT jl_value_t *jl_instantiate_type_in_env(jl_value_t *ty, jl_unionall_t *env, jl_value_t **vals);
 jl_value_t *jl_substitute_var(jl_value_t *t, jl_tvar_t *var, jl_value_t *val);
-jl_value_t *jl_substitute_var_nothrow(jl_value_t *t, jl_tvar_t *var, jl_value_t *val);
+jl_value_t *jl_substitute_var_nothrow(jl_value_t *t, jl_tvar_t *var, jl_value_t *val, int nothrow);
 jl_unionall_t *jl_rename_unionall(jl_unionall_t *u);
 JL_DLLEXPORT jl_value_t *jl_unwrap_unionall(jl_value_t *v JL_PROPAGATES_ROOT) JL_NOTSAFEPOINT;
 JL_DLLEXPORT jl_value_t *jl_rewrap_unionall(jl_value_t *t, jl_value_t *u);
diff --git a/src/subtype.c b/src/subtype.c
@@ -2784,7 +2784,7 @@ static jl_value_t *omit_bad_union(jl_value_t *u, jl_tvar_t *t)
                 res = jl_bottom_type;
             }
             else if (obviously_egal(var->lb, ub)) {
-                res = jl_substitute_var_nothrow(body, var, ub);
+                res = jl_substitute_var_nothrow(body, var, ub, 2);
                 if (res == NULL)
                     res = jl_bottom_type;
             }
@@ -2958,9 +2958,11 @@ static jl_value_t *finish_unionall(jl_value_t *res JL_MAYBE_UNROOTED, jl_varbind
                 }
             }
             if (varval) {
-                *btemp->ub = jl_substitute_var_nothrow(iub, vb->var, varval);
-                if (*btemp->ub == NULL)
+                iub = jl_substitute_var_nothrow(iub, vb->var, varval, 2);
+                if (iub == NULL)
                     res = jl_bottom_type;
+                else
+                    *btemp->ub = iub;
             }
             else if (iub == (jl_value_t*)vb->var) {
                 // TODO: this loses some constraints, such as in this test, where we replace T4<:S3 (e.g. T4==S3 since T4 only appears covariantly once) with T4<:Any
@@ -3091,12 +3093,12 @@ static jl_value_t *finish_unionall(jl_value_t *res JL_MAYBE_UNROOTED, jl_varbind
         if (varval) {
             // you can construct `T{x} where x` even if T's parameter is actually
             // limited. in that case we might get an invalid instantiation here.
-            res = jl_substitute_var_nothrow(res, vb->var, varval);
+            res = jl_substitute_var_nothrow(res, vb->var, varval, 2);
             // simplify chains of UnionAlls where bounds become equal
             while (res != NULL && jl_is_unionall(res) && obviously_egal(((jl_unionall_t*)res)->var->lb,
                                                          ((jl_unionall_t*)res)->var->ub)) {
                 jl_unionall_t * ures = (jl_unionall_t *)res;
-                res = jl_substitute_var_nothrow(ures->body, ures->var, ures->var->lb);
+                res = jl_substitute_var_nothrow(ures->body, ures->var, ures->var->lb, 2);
             }
             if (res == NULL)
                 res = jl_bottom_type;
diff --git a/test/subtype.jl b/test/subtype.jl
@@ -2617,13 +2617,30 @@ end
 #issue 54356
 abstract type A54356{T<:Real} end
 struct B54356{T} <: A54356{T} end
-let S = Tuple{Val, Val{T}} where {T}, R = Tuple{Val{Val{T}}, Val{T}} where {T}
-    # general parameters check
+struct C54356{S,T<:Union{S,Complex{S}}} end
+struct D54356{S<:Real,T} end
+let S = Tuple{Val, Val{T}} where {T}, R = Tuple{Val{Val{T}}, Val{T}} where {T},
+    SS = Tuple{Val, Val{T}, Val{T}} where {T}, RR = Tuple{Val{Val{T}}, Val{T}, Val{T}} where {T}
+    # parameters check for self
     @testintersect(Tuple{Val{A}, A} where {B, A<:Union{Val{B}, Complex{B}}}, S{1}, R{1})
+    # parameters check for supertype (B54356 -> A54356)
     @testintersect(Tuple{Val{A}, A} where {B, A<:Union{Val{B}, B54356{B}}}, S{1}, R{1})
+    # enure unused TypeVar skips the `UnionAll` wrapping
+    @testintersect(Tuple{Val{A}, A} where {B, A<:(Union{Val{B}, D54356{B,C}} where {C})}, S{1}, R{1})
+    # invariant parameter should not get narrowed
+    @testintersect(Tuple{Val{A}, A} where {B, A<:Union{Val{B}, Val{Union{Int,Complex{B}}}}}, S{1}, R{1})
+    # bit value could not be `Union` element
+    @testintersect(Tuple{Val{A}, A, Val{B}} where {B, A<:Union{B, Val{B}}}, SS{1}, RR{1})
+    @testintersect(Tuple{Val{A}, A, Val{B}} where {B, A<:Union{B, Complex{B}}}, SS{1}, Union{})
+    # `check_datatype_parameters` should ignore bad `Union` elements in constraint's ub
+    T = Tuple{Val{Union{Val{Nothing}, Val{C54356{V,V}}}}, Val{Nothing}} where {Nothing<:V<:Nothing}
+    @test T <: S{Nothing}
+    @test T <: Tuple{Val{A}, A} where {B, C, A<:Union{Val{B}, Val{C54356{B,C}}}}
+    @test T <: typeintersect(Tuple{Val{A}, A} where {B, C, A<:Union{Val{B}, Val{C54356{B,C}}}}, S{Nothing})
     # extra check for Vararg
     @testintersect(Tuple{Val{A}, A} where {B, A<:Union{Val{B}, NTuple{B,Any}}}, S{-1}, R{-1})
     @testintersect(Tuple{Val{A}, A} where {B, A<:Union{Val{B}, Tuple{Any,Vararg{Any,B}}}}, S{-1}, R{-1})
+    @testintersect(Tuple{Val{A}, A} where {B, A<:Union{Val{B}, Tuple{Vararg{Int,Union{Int,Complex{B}}}}}}, S{1}, R{1})
     # extra check for NamedTuple
     @testintersect(Tuple{Val{A}, A} where {B, A<:Union{Val{B}, NamedTuple{B,Tuple{Int}}}}, S{1}, R{1})
     @testintersect(Tuple{Val{A}, A} where {B, A<:Union{Val{B}, NamedTuple{B,Tuple{Int}}}}, S{(1,)}, R{(1,)})
