fix #28641, passing typevars to <: in typejoin and tuplemerge (#28655)

(cherry picked from commit 290684d)

base/compiler/typelimits.jl

@@ -412,6 +412,9 @@ function tuplemerge(a::DataType, b::DataType)
         for loop_b = (false, true)
             for i = (lt + 1):(loop_b ? lbr : lar)
                 ti = unwrapva(loop_b ? bp[i] : ap[i])
+                while ti isa TypeVar
+                    ti = ti.ub
+                end
                 # compare (ti <-> tail), (wrapper ti <-> tail), (ti <-> wrapper tail), then (wrapper ti <-> wrapper tail)
                 # until we find the first element that contains the other in the pair
                 # TODO: this result would be more stable (and more associative and more commutative)

base/promotion.jl

@@ -14,18 +14,18 @@ typejoin(@nospecialize(t)) = (@_pure_meta; t)
 typejoin(@nospecialize(t), ts...) = (@_pure_meta; typejoin(t, typejoin(ts...)))
 function typejoin(@nospecialize(a), @nospecialize(b))
     @_pure_meta
-    if a <: b
+    if isa(a, TypeVar)
+        return typejoin(a.ub, b)
+    elseif isa(b, TypeVar)
+        return typejoin(a, b.ub)
+    elseif a <: b
         return b
     elseif b <: a
         return a
     elseif isa(a, UnionAll)
         return UnionAll(a.var, typejoin(a.body, b))
     elseif isa(b, UnionAll)
         return UnionAll(b.var, typejoin(a, b.body))
-    elseif isa(a, TypeVar)
-        return typejoin(a.ub, b)
-    elseif isa(b, TypeVar)
-        return typejoin(a, b.ub)
     elseif isa(a, Union)
         return typejoin(typejoin(a.a, a.b), b)
     elseif isa(b, Union)

test/compiler/compiler.jl

@@ -1977,3 +1977,16 @@ function bar28444()
     e[1]
 end
 @test bar28444() == 1
+
+# issue #28641
+struct VoxelIndices{T <: Integer}
+    voxCrnrPos::NTuple{8,NTuple{3,T}}
+    voxEdgeCrnrs::NTuple{19, NTuple{2,T}}
+    voxEdgeDir::NTuple{19,T}
+    voxEdgeIx::NTuple{8,NTuple{8,T}}
+    subTets::NTuple{6,NTuple{4,T}}
+    tetEdgeCrnrs::NTuple{6,NTuple{2,T}}
+    tetTri::NTuple{16,NTuple{6,T}}
+end
+f28641(x::VoxelIndices, f) = getfield(x, f)
+@test Base.return_types(f28641, (Any,Symbol)) == Any[Tuple]

test/core.jl

@@ -141,6 +141,8 @@ end
 @test typejoin(Tuple{Vararg{Int,2}}, Tuple{Int,Int,Int}) === Tuple{Int,Int,Vararg{Int}}
 @test typejoin(Tuple{Vararg{Int,2}}, Tuple{Vararg{Int}}) === Tuple{Vararg{Int}}
 
+@test typejoin(NTuple{3,Tuple}, NTuple{2,T} where T) == Tuple{Any,Any,Vararg{Tuple}}
+
 # issue #26321
 struct T26321{N,S<:NTuple{N}}
     t::S