Optimization for non-union invariant parameter.

JuliaLang · Feb 2, 2023 · a62e3e9 · a62e3e9
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diff --git a/src/subtype.c b/src/subtype.c
@@ -1423,11 +1423,42 @@ static int is_definite_length_tuple_type(jl_value_t *x)
 
 static int _forall_exists_subtype(jl_value_t *x, jl_value_t *y, jl_stenv_t *e, int param, int *count, int *noRmore);
 
+static int may_contain_union_decision(jl_value_t *x, jl_stenv_t *e, jl_typeenv_t *log) JL_NOTSAFEPOINT
+{
+    if (x == NULL || x == (jl_value_t*)jl_any_type || x == jl_bottom_type)
+        return 0;
+    if (jl_is_unionall(x))
+        return may_contain_union_decision(((jl_unionall_t *)x)->body, e, log);
+    if (jl_is_datatype(x)) {
+        jl_datatype_t *xd = (jl_datatype_t *)x;
+        for (int i = 0; i < jl_nparams(xd); i++) {
+            jl_value_t *param = jl_tparam(xd, i);
+            if (jl_is_vararg(param))
+                param = jl_unwrap_vararg(param);
+            if (may_contain_union_decision(param, e, log))
+                return 1;
+        }
+        return 0;
+    }
+    if (!jl_is_typevar(x))
+        return 1;
+    jl_typeenv_t *t = log;
+    while (t != NULL) {
+        if (x == (jl_value_t *)t->var)
+            return 1;
+        t = t->prev;
+    }
+    jl_typeenv_t newlog = { (jl_tvar_t*)x, NULL, log };
+    jl_varbinding_t *xb = lookup(e, (jl_tvar_t *)x);
+    return may_contain_union_decision(xb ? xb->lb : ((jl_tvar_t *)x)->lb, e, &newlog) ||
+           may_contain_union_decision(xb ? xb->ub : ((jl_tvar_t *)x)->ub, e, &newlog);
+}
+
 static int local_forall_exists_subtype(jl_value_t *x, jl_value_t *y, jl_stenv_t *e, int param, int limit_slow)
 {
     int16_t oldRmore = e->Runions.more;
     int sub;
-    if (pick_union_decision(e, 1) == 0) {
+    if (may_contain_union_decision(y, e, NULL) && pick_union_decision(e, 1) == 0) {
         jl_saved_unionstate_t oldRunions; push_unionstate(&oldRunions, &e->Runions);
         e->Lunions.used = e->Runions.used = 0;
         e->Lunions.depth = e->Runions.depth = 0;

diff --git a/test/subtype.jl b/test/subtype.jl
@@ -2436,3 +2436,7 @@ let A = Tuple{Type{T}, T} where T,
     C = Tuple{Type{MyType47877{W, V} where V<:Union{MyAbstract47877{W}, Base.BitInteger}}, MyType47877{W, V} where V<:Union{MyAbstract47877{W}, Base.BitInteger}} where W<:Base.BitInteger
     @test typeintersect(B, A) == C
 end
+
+let a = (isodd(i) ? Pair{Char, String} : Pair{String, String} for i in 1:2000)
+    @test Tuple{Type{Pair{Union{Char, String}, String}}, a...} <: Tuple{Type{Pair{K, V}}, Vararg{Pair{A, B} where B where A}} where V where K
+end