From 86e83bcf91beb2b4db759d7f8e0a76f515f06e10 Mon Sep 17 00:00:00 2001
From: Jeff Bezanson <jeff.bezanson@gmail.com>
Date: Tue, 7 May 2019 15:48:28 -0400
Subject: [PATCH] fix #31899, type intersection involving Int in upper bound

---
 src/subtype.c   |  7 ++++++-
 test/subtype.jl | 20 ++++++++++++++++++++
 2 files changed, 26 insertions(+), 1 deletion(-)

diff --git a/src/subtype.c b/src/subtype.c
index c257bcae89393..84868a302022a 100644
--- a/src/subtype.c
+++ b/src/subtype.c
@@ -980,6 +980,8 @@ static int subtype(jl_value_t *x, jl_value_t *y, jl_stenv_t *e, int param)
         return var_gt((jl_tvar_t*)y, x, e, param);
     if (y == (jl_value_t*)jl_any_type && !jl_has_free_typevars(x))
         return 1;
+    if (x == jl_bottom_type && !jl_has_free_typevars(y))
+        return 1;
     jl_value_t *ux = jl_unwrap_unionall(x);
     jl_value_t *uy = jl_unwrap_unionall(y);
     if ((x != ux || y != uy) && y != (jl_value_t*)jl_any_type && jl_is_datatype(ux) && jl_is_datatype(uy) &&
@@ -1779,7 +1781,10 @@ static jl_value_t *finish_unionall(jl_value_t *res JL_MAYBE_UNROOTED, jl_varbind
     jl_tvar_t *newvar = vb->var;
     JL_GC_PUSH2(&res, &newvar);
     // try to reduce var to a single value
-    if (obviously_egal(vb->lb, vb->ub)) {
+    if (jl_is_long(vb->ub) && jl_is_typevar(vb->lb)) {
+        varval = vb->ub;
+    }
+    else if (obviously_egal(vb->lb, vb->ub)) {
         // given x<:T<:x, substitute x for T
         varval = vb->ub;
     }
diff --git a/test/subtype.jl b/test/subtype.jl
index d766c49079e1e..acd253fa035f0 100644
--- a/test/subtype.jl
+++ b/test/subtype.jl
@@ -1509,3 +1509,23 @@ end
 
 # issue #26083
 @testintersect(Base.RefValue{<:Tuple}, Ref{Tuple{M}} where M, Base.RefValue{Tuple{M}} where M)
+
+# issue #31899
+struct SA{N,L}
+end
+@testintersect(Tuple{Type{SA{Int, L} where L}, Type{SA{Int, Int8}}},
+               Tuple{Type{<:SA{N, L}}, Type{<:SA{N, L}}} where {N,L},
+               Union{})
+@testintersect(Tuple{Type{SA{2, L} where L}, Type{SA{2, 16}}},
+               Tuple{Type{<:SA{N, L}}, Type{<:SA{N, L}}} where {L,N},
+               Union{})
+@testintersect(Tuple{Type{SA{2, L} where L}, Type{SA{2, 16}}},
+               Tuple{Type{<:SA{N, L}}, Type{<:SA{N, L}}} where {N,L},
+               Union{})
+@testintersect(Tuple{Type{SA{2, L}}, Type{SA{2, L}}} where L,
+               Tuple{Type{<:SA{N, L}}, Type{<:SA{N, L}}} where {N,L},
+               Tuple{Type{SA{2, L}}, Type{SA{2, L}}} where L)
+@testintersect(Tuple{Type{SA{2, L}}, Type{SA{2, 16}}} where L,
+               Tuple{Type{<:SA{N, L}}, Type{<:SA{N, L}}} where {N,L},
+               # TODO: this could be narrower
+               Tuple{Type{SA{2, L}}, Type{SA{2, 16}}} where L)