fix inference of SparseVector cat

This little gadget creates a closure over Type{T} instead of DataType.

Fix JuliaLang/julia#50623

Author: vtjnash

src/sparsevector.jl

@@ -1108,7 +1108,9 @@ function hcat(Xin::AbstractSparseVector...)
     X = map(_unsafe_unfix, Xin)
     Tv = promote_type(map(eltype, X)...)
     Ti = promote_type(map(indtype, X)...)
-    r = _absspvec_hcat(map(x -> convert(SparseVector{Tv,Ti}, x), X)...)
+    r = (function (::Type{SV}) where SV
+        _absspvec_hcat(map(x -> convert(SV, x), X)...)
+    end)(SparseVector{Tv,Ti})
     return @if_move_fixed Xin... r
 end
 function _absspvec_hcat(X::AbstractSparseVector{Tv,Ti}...) where {Tv,Ti}
@@ -1144,7 +1146,9 @@ function vcat(Xin::AbstractSparseVector...)
     X = map(_unsafe_unfix, Xin)
     Tv = promote_type(map(eltype, X)...)
     Ti = promote_type(map(indtype, X)...)
-    r = _absspvec_vcat(map(x -> convert(SparseVector{Tv,Ti}, x), X)...)
+    r = (function (::Type{SV}) where SV
+            _absspvec_vcat(map(x -> convert(SV, x), X)...)
+        end)(SparseVector{Tv,Ti})
     return @if_move_fixed Xin... r
 end
 function _absspvec_vcat(X::AbstractSparseVector{Tv,Ti}...) where {Tv,Ti}