Make partialsort!() and partialsortperm!() return a view rather than a copy

Returning a copy (partially) defeats the purpose of these functions, which is
to avoid allocations.

Author: nalimilan

base/deprecated.jl

@@ -1633,10 +1633,10 @@ function SymTridiagonal(dv::AbstractVector{T}, ev::AbstractVector{S}) where {T,S
 end
 
 # issue #22791
-@deprecate_binding select partialsort
-@deprecate_binding select! partialsort!
-@deprecate_binding selectperm partialsortperm
-@deprecate_binding selectperm! partialsortperm!
+@deprecate select partialsort
+@deprecate select! partialsort!
+@deprecate selectperm partialsortperm
+@deprecate selectperm! partialsortperm!
 
 # END 0.7 deprecations
 

base/sort.jl

@@ -85,7 +85,12 @@ issorted(itr;
 function partialsort!(v::AbstractVector, k::Union{Int,OrdinalRange}, o::Ordering)
     inds = indices(v, 1)
     sort!(v, first(inds), last(inds), PartialQuickSort(k), o)
-    v[k]
+
+    if k isa Integer
+        return v[k]
+    else
+        return view(v, k)
+    end
 end
 
 """
@@ -704,7 +709,12 @@ function partialsortperm!(ix::AbstractVector{<:Integer}, v::AbstractVector,
 
     # do partial quicksort
     sort!(ix, PartialQuickSort(k), Perm(ord(lt, by, rev, order), v))
-    return ix[k]
+
+    if k isa Integer
+        return ix[k]
+    else
+        return view(ix, k)
+    end
 end
 
 ## sortperm: the permutation to sort an array ##