From 6b7e286c62f83b5ed92908134c9f1d405a682bd5 Mon Sep 17 00:00:00 2001
From: Jameson Nash <vtjnash@gmail.com>
Date: Mon, 5 Dec 2022 14:11:14 -0500
Subject: [PATCH] compute env for typeintersect better

Avoid discarding intermediate information sooner than we must (e.g. at return).
---
 src/jltypes.c |  2 +-
 src/julia.h   |  2 +-
 src/subtype.c | 40 ++++++++++++++++++++--------------------
 3 files changed, 22 insertions(+), 22 deletions(-)

diff --git a/src/jltypes.c b/src/jltypes.c
index b73d5ecab82aa..eb9eadca7b2d2 100644
--- a/src/jltypes.c
+++ b/src/jltypes.c
@@ -1910,7 +1910,7 @@ jl_datatype_t *jl_wrap_Type(jl_value_t *t)
 jl_vararg_t *jl_wrap_vararg(jl_value_t *t, jl_value_t *n)
 {
     if (n) {
-        if (jl_is_typevar(n)) {
+        if (jl_is_typevar(n) || jl_is_uniontype(jl_unwrap_unionall(n))) {
             // TODO: this is disabled due to #39698; it is also inconsistent
             // with other similar checks, where we usually only check substituted
             // values and not the bounds of variables.
diff --git a/src/julia.h b/src/julia.h
index 2c9be8ae1aa2a..7d34a465c0886 100644
--- a/src/julia.h
+++ b/src/julia.h
@@ -1410,7 +1410,7 @@ JL_DLLEXPORT int jl_type_equality_is_identity(jl_value_t *t1, jl_value_t *t2) JL
 JL_DLLEXPORT int jl_has_free_typevars(jl_value_t *v) JL_NOTSAFEPOINT;
 JL_DLLEXPORT int jl_has_typevar(jl_value_t *t, jl_tvar_t *v) JL_NOTSAFEPOINT;
 JL_DLLEXPORT int jl_has_typevar_from_unionall(jl_value_t *t, jl_unionall_t *ua);
-JL_DLLEXPORT int jl_subtype_env_size(jl_value_t *t);
+JL_DLLEXPORT int jl_subtype_env_size(jl_value_t *t) JL_NOTSAFEPOINT;
 JL_DLLEXPORT int jl_subtype_env(jl_value_t *x, jl_value_t *y, jl_value_t **env, int envsz);
 JL_DLLEXPORT int jl_isa(jl_value_t *a, jl_value_t *t);
 JL_DLLEXPORT int jl_types_equal(jl_value_t *a, jl_value_t *b);
diff --git a/src/subtype.c b/src/subtype.c
index fbb1a74143cf9..809b0567a54b0 100644
--- a/src/subtype.c
+++ b/src/subtype.c
@@ -717,6 +717,8 @@ static jl_value_t *widen_Type(jl_value_t *t JL_PROPAGATES_ROOT) JL_NOTSAFEPOINT
 // when a static parameter value is not known exactly.
 static jl_value_t *fix_inferred_var_bound(jl_tvar_t *var, jl_value_t *ty JL_MAYBE_UNROOTED)
 {
+    if (ty == NULL) // may happen if the user is intersecting with an incomplete type
+        return (jl_value_t*)var;
     if (!jl_is_typevar(ty) && jl_has_free_typevars(ty)) {
         jl_value_t *ans = ty;
         jl_array_t *vs = NULL;
@@ -849,7 +851,7 @@ static int subtype_unionall(jl_value_t *t, jl_unionall_t *u, jl_stenv_t *e, int8
         if (oldval && !jl_egal(oldval, val))
             e->envout[e->envidx] = (jl_value_t*)u->var;
         else
-            e->envout[e->envidx] = fix_inferred_var_bound(u->var, val);
+            e->envout[e->envidx] = val;
         // TODO: substitute the value (if any) of this variable into previous envout entries
     }
 
@@ -1897,6 +1899,16 @@ JL_DLLEXPORT int jl_subtype_env(jl_value_t *x, jl_value_t *y, jl_value_t **env,
     if (obvious_subtype == 0 || (obvious_subtype == 1 && envsz == 0))
         subtype = obvious_subtype; // this ensures that running in a debugger doesn't change the result
 #endif
+    if (env) {
+        jl_unionall_t *ub = (jl_unionall_t*)y;
+        int i;
+        for (i = 0; i < envsz; i++) {
+            assert(jl_is_unionall(ub));
+            jl_tvar_t *var = ub->var;
+            env[i] = fix_inferred_var_bound(var, env[i]);
+            ub = (jl_unionall_t*)ub->body;
+        }
+    }
     return subtype;
 }
 
@@ -2634,7 +2646,7 @@ static jl_value_t *finish_unionall(jl_value_t *res JL_MAYBE_UNROOTED, jl_varbind
         if (!varval || (!is_leaf_bound(varval) && !vb->occurs_inv))
             e->envout[e->envidx] = (jl_value_t*)vb->var;
         else if (!(oldval && jl_is_typevar(oldval) && jl_is_long(varval)))
-            e->envout[e->envidx] = fix_inferred_var_bound(vb->var, varval);
+            e->envout[e->envidx] = varval;
     }
 
     JL_GC_POP();
@@ -3595,17 +3607,11 @@ jl_value_t *jl_type_intersection_env_s(jl_value_t *a, jl_value_t *b, jl_svec_t *
     }
     if (penv) {
         jl_svec_t *e = jl_alloc_svec(sz);
-        *penv = e;
-        for (i = 0; i < sz; i++)
-            jl_svecset(e, i, env[i]);
-        jl_unionall_t *ub = (jl_unionall_t*)b;
         for (i = 0; i < sz; i++) {
-            assert(jl_is_unionall(ub));
-            // TODO: assert(env[i] != NULL);
-            if (env[i] == NULL)
-                env[i] = (jl_value_t*)ub->var;
-            ub = (jl_unionall_t*)ub->body;
+            assert(env[i]);
+            jl_svecset(e, i, env[i]);
         }
+        *penv = e;
     }
  bot:
     JL_GC_POP();
@@ -3646,17 +3652,11 @@ int jl_subtype_matching(jl_value_t *a, jl_value_t *b, jl_svec_t **penv)
         // copy env to svec for return
         int i = 0;
         jl_svec_t *e = jl_alloc_svec(szb);
-        *penv = e;
-        for (i = 0; i < szb; i++)
-            jl_svecset(e, i, env[i]);
-        jl_unionall_t *ub = (jl_unionall_t*)b;
         for (i = 0; i < szb; i++) {
-            assert(jl_is_unionall(ub));
-            // TODO: assert(env[i] != NULL);
-            if (env[i] == NULL)
-                env[i] = (jl_value_t*)ub->var;
-            ub = (jl_unionall_t*)ub->body;
+            assert(env[i]);
+            jl_svecset(e, i, env[i]);
         }
+        *penv = e;
     }
     JL_GC_POP();
     return sub;