Merge pull request #17257 from JuliaLang/teh/emptytt_subtype

Type{Tuple{}} should not be a subtype of Type{Tuple}. Fixes #17198

Author: timholy

src/jltypes.c

@@ -2609,7 +2609,7 @@ static int jl_tuple_subtype_(jl_value_t **child, size_t clenr,
         if (cseq && !pseq)
             break;
         if (ci >= clenf) {
-            result = pi >= plenf || pseq;
+            result = pi >= plenf || (pseq && !invariant);
             break;
         }
         if (pi >= plenf && !pseq)

test/core.jl

@@ -45,8 +45,8 @@ isnot(x,y) = !is(x,y)
 @test !(Type{Rational{Int}} <: Type{Rational})
 @test Tuple{} <: Tuple{Vararg}
 @test Tuple{} <: NTuple{TypeVar(:N,true)}
-@test Type{Tuple{}} <: Type{Tuple{Vararg}}
-@test Type{Tuple{}} <: Type{NTuple{TypeVar(:N,true)}}
+@test !(Type{Tuple{}} <: Type{Tuple{Vararg}})
+@test !(Type{Tuple{}} <: Type{NTuple{TypeVar(:N,true)}})
 let T = TypeVar(:T,true)
     @testintersect(Array{Bottom},AbstractArray{T}, Bottom, isnot)
     @testintersect(Tuple{Type{Ptr{UInt8}},Ptr{Bottom}},
@@ -307,6 +307,9 @@ nttest1{n}(x::NTuple{n,Int}) = n
 @test Tuple{Vararg{Int32}} <: NTuple{TypeVar(:T),Int32}
 @test Tuple{Int32,Vararg{Int32}} <: NTuple{TypeVar(:T),Int32}
 
+# #17198
+@test_throws MethodError convert(Tuple{Int}, (1.0, 2.0, 3.0))
+
 # type declarations
 
 abstract Sup_{A,B}