From a9ad6c2bb5771e54a3d4505e2d3146d280c3b093 Mon Sep 17 00:00:00 2001
From: Jeff Bezanson <jeff.bezanson@gmail.com>
Date: Sat, 6 Jul 2019 11:55:01 -0400
Subject: [PATCH] fix #32488, type intersection regression (#32509)

Issue was caused by 74305bf2c43546bf76843b72ff0d268a3fe16920, so this
reverts part of the new logic from there.
---
 src/subtype.c   | 23 ++++++++++++++++++++---
 test/subtype.jl | 17 +++++++++++++----
 2 files changed, 33 insertions(+), 7 deletions(-)

diff --git a/src/subtype.c b/src/subtype.c
index f6516c96a1b1c..0fbe5e809d05b 100644
--- a/src/subtype.c
+++ b/src/subtype.c
@@ -2129,19 +2129,35 @@ static jl_value_t *intersect_var(jl_tvar_t *b, jl_value_t *a, jl_stenv_t *e, int
     int d = bb->depth0;
     jl_value_t *root=NULL; jl_savedenv_t se;
     if (param == 2) {
-        if (!(subtype_in_env_existential(bb->lb, a, e, 0, d) && subtype_in_env_existential(a, bb->ub, e, 1, d)))
-            return jl_bottom_type;
-        jl_value_t *ub = a;
+        jl_value_t *ub = NULL;
+        JL_GC_PUSH2(&ub, &root);
+        if (!jl_has_free_typevars(a)) {
+            save_env(e, &root, &se);
+            int issub = subtype_in_env_existential(bb->lb, a, e, 0, d) && subtype_in_env_existential(a, bb->ub, e, 1, d);
+            restore_env(e, root, &se);
+            free(se.buf);
+            if (!issub) {
+                JL_GC_POP();
+                return jl_bottom_type;
+            }
+            ub = a;
+        }
+        else {
+            ub = R ? intersect_aside(a, bb->ub, e, 1, d) : intersect_aside(bb->ub, a, e, 0, d);
+            // TODO: we should probably check `bb->lb <: ub` here; find a test case for that
+        }
         if (ub != (jl_value_t*)b) {
             if (jl_has_free_typevars(ub)) {
                 // constraint X == Ref{X} is unsatisfiable. also check variables set equal to X.
                 if (var_occurs_inside(ub, b, 0, 0)) {
+                    JL_GC_POP();
                     return jl_bottom_type;
                 }
                 jl_varbinding_t *btemp = e->vars;
                 while (btemp != NULL) {
                     if (btemp->lb == (jl_value_t*)b && btemp->ub == (jl_value_t*)b &&
                         var_occurs_inside(ub, btemp->var, 0, 0)) {
+                        JL_GC_POP();
                         return jl_bottom_type;
                     }
                     btemp = btemp->prev;
@@ -2150,6 +2166,7 @@ static jl_value_t *intersect_var(jl_tvar_t *b, jl_value_t *a, jl_stenv_t *e, int
             bb->ub = ub;
             bb->lb = ub;
         }
+        JL_GC_POP();
         return ub;
     }
     else if (bb->constraintkind == 0) {
diff --git a/test/subtype.jl b/test/subtype.jl
index 2e03ec3d089f1..8e31d88df50da 100644
--- a/test/subtype.jl
+++ b/test/subtype.jl
@@ -1481,7 +1481,9 @@ CovType{T} = Union{AbstractArray{T,2},
 # issue #31703
 @testintersect(Pair{<:Any, Ref{Tuple{Ref{Ref{Tuple{Int}}},Ref{Float64}}}},
                Pair{T, S} where S<:(Ref{A} where A<:(Tuple{C,Ref{T}} where C<:(Ref{D} where D<:(Ref{E} where E<:Tuple{FF}) where FF<:B)) where B) where T,
-               Pair{Float64, Ref{Tuple{Ref{Ref{Tuple{Int}}},Ref{Float64}}}})
+               Pair{T, Ref{Tuple{Ref{Ref{Tuple{Int}}},Ref{Float64}}}} where T)
+# TODO: should be able to get this result
+#              Pair{Float64, Ref{Tuple{Ref{Ref{Tuple{Int}}},Ref{Float64}}}}
 
 module I31703
 using Test, LinearAlgebra
@@ -1608,6 +1610,13 @@ end
 #end
 
 # issue #32386
-# TODO: intersect currently returns a bad answer here (it has free typevars)
-@test typeintersect(Type{S} where S<:(Array{Pair{_A,N} where N, 1} where _A),
-                    Type{Vector{T}} where T) != Union{}
+@test typeintersect(Type{S} where S<:(Vector{Pair{_A,N} where N} where _A),
+                    Type{Vector{T}} where T) == Type{Vector{Pair{_A,N} where N}} where _A
+
+# issue #32488
+struct S32488{S <: Tuple, T, N, L}
+    data::NTuple{L,T}
+end
+@testintersect(Tuple{Type{T} where T<:(S32488{Tuple{_A}, Int64, 1, _A} where _A), Tuple{Vararg{Int64, D}} where D},
+               Tuple{Type{S32488{S, T, N, L}}, Tuple{Vararg{T, L}}} where L where N where T where S,
+               Tuple{Type{S32488{Tuple{L},Int64,1,L}},Tuple{Vararg{Int64,L}}} where L)