remove a source of nondeterminism from the constraint solver

hopefully helps the problem discussed in commit 8d07d6f

src/jltypes.c

@@ -326,21 +326,17 @@ STATIC_INLINE int is_btv(jl_value_t *v)
  return jl_is_typevar(v) && ((jl_tvar_t*)v)->bound;
 }
 
-static void extend_(jl_value_t *var, jl_value_t *val, cenv_t *soln, int allow,
- int ordered)
+static void extend_(jl_value_t *var, jl_value_t *val, cenv_t *soln, int allowself)
 {
- if (!allow && var == val)
+ if (!allowself && var == val)
  return;
- if (!ordered && val < var && jl_is_typevar(val)) {
- jl_value_t *temp = val;
- val = var;
- var = temp;
- }
  for(int i=0; i < soln->n; i+=2) {
  if (soln->data[i]==var &&
  (soln->data[i+1]==val || (!jl_is_typevar(val) &&
  type_eqv_(soln->data[i+1],val))))
  return;
+ if (soln->data[i]==val && soln->data[i+1]==var)
+ return;
  }
  if (soln->n >= MAX_CENV_SIZE)
  jl_error("type too large");
@@ -350,12 +346,7 @@ static void extend_(jl_value_t *var, jl_value_t *val, cenv_t *soln, int allow,
 
 static void extend(jl_value_t *var, jl_value_t *val, cenv_t *soln)
 {
- extend_(var, val, soln, 0, 0);
-}
-
-static void extend_ordered(jl_value_t *var, jl_value_t *val, cenv_t *soln)
-{
- extend_(var, val, soln, 0, 1);
+ extend_(var, val, soln, 0);
 }
 
 static jl_value_t *jl_type_intersect(jl_value_t *a, jl_value_t *b,
@@ -734,10 +725,13 @@ static jl_value_t *intersect_typevar(jl_tvar_t *a, jl_value_t *b,
  }
  if (!jl_is_typevar(both))
  both = (jl_value_t*)jl_new_typevar(underscore_sym, jl_bottom_type, both);
- extend_ordered((jl_value_t*)a, both, penv);
- extend_ordered((jl_value_t*)b, both, penv);
+ extend((jl_value_t*)a, both, penv);
+ extend((jl_value_t*)b, both, penv);
  }
- extend((jl_value_t*)a, b, eqc);
+ if (is_btv(b))
+ extend(b, (jl_value_t*)a, eqc);
+ else
+ extend((jl_value_t*)a, b, eqc);
  }
  else {
  int i;
@@ -755,15 +749,15 @@ static jl_value_t *intersect_typevar(jl_tvar_t *a, jl_value_t *b,
  break;
  }
  }
- extend_ordered((jl_value_t*)a, b, penv);
+ extend((jl_value_t*)a, b, penv);
  if (jl_is_typevar(b)) {
  JL_GC_POP();
  return (jl_value_t*)a;
  }
  else {
  new_b = jl_new_typevar(underscore_sym, jl_bottom_type, b);
- extend_ordered((jl_value_t*)new_b, b, penv);
- extend_ordered((jl_value_t*)new_b, (jl_value_t*)a, penv);
+ extend((jl_value_t*)new_b, b, penv);
+ extend((jl_value_t*)new_b, (jl_value_t*)a, penv);
  JL_GC_POP();
  return (jl_value_t*)new_b;
  }
@@ -896,7 +890,7 @@ static jl_value_t *jl_type_intersect(jl_value_t *a, jl_value_t *b,
  }
  if (i >= penv->n) {
  temp = jl_box_long(alen-1);
- extend_ordered(lenvar, temp, penv);
+ extend(lenvar, temp, penv);
  }
  }
  }
@@ -1496,7 +1490,7 @@ jl_value_t *jl_type_intersection_matching(jl_value_t *a, jl_value_t *b,
  */
  jl_tvar_t *ntv = jl_new_typevar(tv->name, tv->lb, tv->ub);
  ntv->bound = tv->bound;
- extend_((jl_value_t*)tv, (jl_value_t*)ntv, &eqc, 1, 1);
+ extend_((jl_value_t*)tv, (jl_value_t*)ntv, &eqc, 1);
  }
  }
 
@@ -2741,7 +2735,7 @@ static jl_value_t *type_match_(jl_value_t *child, jl_value_t *parent,
  return jl_false;
  }
  }
- extend_ordered(parent, child, env);
+ extend(parent, child, env);
  return jl_true;
  }