fix #30741, fix #31082, stack overflow in type intersection

JuliaLang · Feb 25, 2019 · 045e233 · 045e233
1 parent 31234a5
commit 045e233
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Showing 2 changed files with 37 additions and 11 deletions.
diff --git a/src/subtype.c b/src/subtype.c
@@ -1382,6 +1382,20 @@ static int try_subtype_in_env(jl_value_t *a, jl_value_t *b, jl_stenv_t *e)
     return ret;
 }
 
+static void set_bound(jl_value_t **bound, jl_value_t *val, jl_tvar_t *v, jl_stenv_t *e)
+{
+    if (in_union(val, (jl_value_t*)v))
+        return;
+    jl_varbinding_t *btemp = e->vars;
+    while (btemp != NULL) {
+        if (btemp->lb == (jl_value_t*)v && btemp->ub == (jl_value_t*)v &&
+            in_union(val, (jl_value_t*)btemp->var))
+            return;
+        btemp = btemp->prev;
+    }
+    *bound = val;
+}
+
 static jl_value_t *intersect_var(jl_tvar_t *b, jl_value_t *a, jl_stenv_t *e, int8_t R, int param)
 {
     jl_varbinding_t *bb = lookup(e, b);
@@ -1445,8 +1459,7 @@ static jl_value_t *intersect_var(jl_tvar_t *b, jl_value_t *a, jl_stenv_t *e, int
             JL_GC_POP();
             return jl_bottom_type;
         }
-        if (ub != (jl_value_t*)b)
-            bb->ub = ub;
+        set_bound(&bb->ub, ub, b, e);
         JL_GC_POP();
         return (jl_value_t*)b;
     }
@@ -1456,8 +1469,7 @@ static jl_value_t *intersect_var(jl_tvar_t *b, jl_value_t *a, jl_stenv_t *e, int
         if (!subtype_in_env(a, bb->ub, e))
             return jl_bottom_type;
         jl_value_t *lb = simple_join(bb->lb, a);
-        if (lb != (jl_value_t*)b)
-            bb->lb = lb;
+        set_bound(&bb->lb, lb, b, e);
         return a;
     }
     assert(bb->constraintkind == 3);
@@ -1471,7 +1483,7 @@ static jl_value_t *intersect_var(jl_tvar_t *b, jl_value_t *a, jl_stenv_t *e, int
             // if the var has an equality constraint then make sure bounds stay consistent.
             // TODO: try to use this check in more cases
             bb->ub != bb->lb || try_subtype_in_env(bb->lb, ub, e)) {
-            bb->ub = ub;
+            set_bound(&bb->ub, ub, b, e);
             return (jl_value_t*)b;
         }
         return ub;
@@ -1486,8 +1498,7 @@ static jl_value_t *intersect_var(jl_tvar_t *b, jl_value_t *a, jl_stenv_t *e, int
     if (ii == jl_bottom_type) {
         restore_env(e, root, &se);
         ii = (jl_value_t*)b;
-        if (ub != (jl_value_t*)b)
-            bb->ub = ub;
+        set_bound(&bb->ub, ub, b, e);
     }
     free(se.buf);
     JL_GC_POP();
@@ -1694,12 +1705,14 @@ static jl_value_t *intersect_unionall_(jl_value_t *t, jl_unionall_t *u, jl_stenv
     e->vars = vb->prev;
 
     if (res != jl_bottom_type) {
-        // fail on circular constraints
-        if (jl_has_typevar(vb->lb, u->var) || jl_has_typevar(vb->ub, u->var))
+        if (vb->ub == jl_bottom_type && vb->occurs_cov) {
+            // T=Bottom in covariant position
             res = jl_bottom_type;
-        // T=Bottom in covariant position
-        if (vb->ub == jl_bottom_type && vb->occurs_cov)
+        }
+        else if (jl_has_typevar(vb->lb, u->var) || jl_has_typevar(vb->ub, u->var)) {
+            // fail on circular constraints
             res = jl_bottom_type;
+        }
     }
     if (res != jl_bottom_type)
         // res is rooted by callee
@@ -2040,6 +2053,11 @@ static jl_value_t *intersect(jl_value_t *x, jl_value_t *y, jl_stenv_t *e, int pa
                 if (R) flip_vars(e);
                 if (!ccheck)
                     return jl_bottom_type;
+                if (var_occurs_inside(xub, (jl_tvar_t*)y, 0, 0) && var_occurs_inside(yub, (jl_tvar_t*)x, 0, 0)) {
+                    // circular constraint. the result will be Bottom, but in the meantime
+                    // we need to avoid computing intersect(xub, yub) since it won't terminate.
+                    return y;
+                }
                 jl_value_t *ub=NULL, *lb=NULL;
                 JL_GC_PUSH2(&lb, &ub);
                 ub = intersect_aside(xub, yub, e, xx ? xx->depth0 : 0);

diff --git a/test/subtype.jl b/test/subtype.jl
@@ -1420,3 +1420,11 @@ let U = Tuple{Union{LT, LT1},Union{R, R1},Int} where LT1<:R1 where R1<:Tuple{Int
     @test U2 == V
     @test_broken U2 == V2
 end
+
+# issue #31082 and #30741
+@testintersect(Tuple{T, Ref{T}, T} where T,
+               Tuple{Ref{S}, S, S} where S,
+               Union{})
+@testintersect(Tuple{Pair{B,C},Union{C,Pair{B,C}},Union{B,Real}} where {B,C},
+               Tuple{Pair{B,C},C,C} where {B,C},
+               Tuple{Pair{B,C},C,C} where C<:Union{Real, B} where B)