compute env for typeintersect better (#47925)

Avoid discarding intermediate information sooner than we must (e.g. at return).

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.

src/julia.h

@@ -1412,7 +1412,7 @@ 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);

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;
 }
 
@@ -2605,7 +2617,7 @@ 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();
@@ -3532,17 +3544,11 @@ 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();
@@ -3583,17 +3589,11 @@ 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;