subtype: add tests for Vararg expansion.

Ref JuliaLang#36443
Ref JuliaLang#37257

test/subtype.jl

@@ -2020,3 +2020,63 @@ end
 #issue #43082
 struct X43082{A, I, B<:Union{Ref{I},I}}; end
 @testintersect(Tuple{X43082{T}, Int} where T, Tuple{X43082{Int}, Any}, Tuple{X43082{Int}, Int})
+
+#issue #36443
+let C = Tuple{Val{3},Int,Int,Int},
+    As = (Tuple{Val{N},Vararg{T,N}} where {T,N},
+          Tuple{Val{N},Vararg{T,N}} where {N,T}),
+    Bs = (Tuple{Val{3},Int,Vararg{T,N}} where {T,N},
+          Tuple{Val{3},Int,Vararg{T,N}} where {N,T},
+          Tuple{Val{3},Int,Vararg{T}} where {T},
+          Tuple{Val{3},Int,Vararg{T,2}} where {T})
+    for A in As, B in Bs
+        @testintersect(A, B, C)
+    end
+end
+
+let A = Tuple{Type{Val{N}},Tuple{Vararg{T,N}} where T} where N,
+    C = Tuple{Type{Val{2}},Tuple{T,T} where T}
+    @testintersect(A, Tuple{Type{Val{2}},Tuple{Vararg{T,N}} where T} where N, C)
+    @testintersect(A, Tuple{Type{Val{2}},Tuple{T,Vararg{T,N}} where T} where N, C)
+    @testintersect(A, Tuple{Type{Val{2}},Tuple{T,T,Vararg{T,N}} where T} where N, C)
+end
+
+let f36443(::NTuple{N}=[(f36443,),(1,2)][2],::Val{N}=Val(2)) where{N} = 0
+    @test f36443() == 0;
+end
+
+let C = Tuple{Val{3},Int,Int,Int,Int},
+    As = (Tuple{Val{N},Int,Vararg{T,N}} where {T,N},
+          Tuple{Val{N},Int,Vararg{T,N}} where {N,T}),
+    Bs = (Tuple{Val{3},Vararg{T,N}} where {T,N},
+          Tuple{Val{3},Vararg{T,N}} where {N,T},
+          Tuple{Val{3},Vararg{T}} where {T})
+    for A in As, B in Bs
+        @testintersect(A, B, C)
+    end
+end
+
+#issue #37257
+let T = Tuple{Val{N}, Any, Any, Vararg{Any,N}} where N,
+    C = Tuple{Val{1}, Any, Any, Any}
+    @testintersect(T, Tuple{Val{1}, Vararg{Any}}, C)
+    @testintersect(T, Tuple{Val{1}, Any, Vararg{Any}}, C)
+    @testintersect(T, Tuple{Val{1}, Any, Any, Vararg{Any}}, C)
+    @testintersect(T, Tuple{Val{1}, Any, Any, Any, Vararg{Any}}, C)
+    @testintersect(T, Tuple{Val{1}, Any, Any, Any, Any, Vararg{Any}}, Union{})
+end
+
+let A = Tuple{NTuple{N,Any},Val{N}} where {N},
+    C = Tuple{NTuple{4,Any},Val{4}}
+    @testintersect(A, Tuple{Tuple{Vararg{Any,N}},Val{4}} where {N}, C)
+    @testintersect(A, Tuple{Tuple{Vararg{Any}},Val{4}}, C)
+    @testintersect(A, Tuple{Tuple{Vararg{Any,N}} where {N},Val{4}}, C)
+
+    @testintersect(A, Tuple{Tuple{Any,Vararg{Any,N}},Val{4}} where {N}, C)
+    @testintersect(A, Tuple{Tuple{Any,Vararg{Any}},Val{4}}, C)
+    @testintersect(A, Tuple{Tuple{Any,Vararg{Any,N}} where {N},Val{4}}, C)
+
+    @testintersect(A, Tuple{Tuple{Any,Any,Any,Any,Any,Vararg{Any,N}},Val{4}} where {N}, Union{})
+    @testintersect(A, Tuple{Tuple{Any,Any,Any,Any,Any,Vararg{Any}},Val{4}}, Union{})
+    @testintersect(A, Tuple{Tuple{Any,Any,Any,Any,Any,Vararg{Any,N}} where {N},Val{4}}, Union{})
+end