Unwrap y::UnionALL eagerly when x<:y if x isa ∀-var. (#49023)

Close #45874
JuliaLang · Mar 16, 2023 · c1d1bde · c1d1bde
1 parent 3919a89
commit c1d1bde
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Showing 2 changed files with 15 additions and 7 deletions.
diff --git a/src/subtype.c b/src/subtype.c
@@ -1296,6 +1296,16 @@ static int subtype(jl_value_t *x, jl_value_t *y, jl_stenv_t *e, int param)
             // to other left-side variables, so using || here is safe.
             return subtype(xub, y, e, param) || subtype(x, ylb, e, param);
         }
+        if (jl_is_unionall(y)) {
+            jl_varbinding_t *xb = lookup(e, (jl_tvar_t*)x);
+            if (xb == NULL ? !e->ignore_free : !xb->right) {
+                // We'd better unwrap `y::UnionAll` eagerly if `x` isa ∀-var.
+                // This makes sure the following cases work correct:
+                // 1) `∀T <: Union{∃S, SomeType{P}} where {P}`: `S == Any` ==> `S >: T`
+                // 2) `∀T <: Union{∀T, SomeType{P}} where {P}`:
+                return subtype_unionall(x, (jl_unionall_t*)y, e, 1, param);
+            }
+        }
         return var_lt((jl_tvar_t*)x, y, e, param);
     }
     if (jl_is_typevar(y))

diff --git a/test/subtype.jl b/test/subtype.jl
@@ -2282,7 +2282,7 @@ struct Z38497{T>:Int} <: Y38497{T} end
 @test only(intersection_env(Union{S, Matrix{Int}} where S<:Matrix, Matrix)[2]) isa TypeVar
 T46784{B<:Val, M<:AbstractMatrix} = Tuple{<:Union{B, <:Val{<:B}}, M, Union{AbstractMatrix{B}, AbstractMatrix{<:Vector{<:B}}}}
 @testintersect(T46784{T,S} where {T,S}, T46784, !Union{})
-@test_broken T46784 <: T46784{T,S} where {T,S}
+@test T46784 <: T46784{T,S} where {T,S}
 
 #issue 36185
 let S = Tuple{Type{T},Array{Union{T,Missing},N}} where {T,N},
@@ -2376,12 +2376,10 @@ abstract type P47654{A} end
 
 @testset "known subtype/intersect issue" begin
     #issue 45874
-    # Causes a hang due to jl_critical_error calling back into malloc...
-    # let S = Pair{Val{P}, AbstractVector{<:Union{P,<:AbstractMatrix{P}}}} where P,
-    #     T = Pair{Val{R}, AbstractVector{<:Union{P,<:AbstractMatrix{P}}}} where {P,R}
-    #     @test_broken S <: T
-    #     @test_broken typeintersect(S,T) === S
-    # end
+    let S = Pair{Val{P}, AbstractVector{<:Union{P,<:AbstractMatrix{P}}}} where P,
+        T = Pair{Val{R}, AbstractVector{<:Union{P,<:AbstractMatrix{P}}}} where {P,R}
+        @test S <: T
+    end
 
     #issue 41561
     @test_broken typeintersect(Tuple{Vector{VT}, Vector{VT}} where {N1, VT<:AbstractVector{N1}},