Add push! implementation for AbstractArray depending only on resize!

base/abstractarray.jl

@@ -3525,13 +3525,45 @@ julia> map(+, [1 2; 3 4], [1,10,100,1000], zeros(3,1))  # iterates until 3rd is
 """
 map(f, it, iters...) = collect(Generator(f, it, iters...))
 
+# Generic versions of push! for AbstractVector
+# These are specialized further for Vector for faster resizing and setindexing
+function push!(a::AbstractVector{T}, item) where T
+    # convert first so we don't grow the array if the assignment won't work
+    itemT = item isa T ? item : convert(T, item)::T
+    new_length = length(a) + 1
+    resize!(a, new_length)
+    a[new_length] = itemT
+    return a
+end
+
+# specialize and optimize the single argument case
+function push!(a::AbstractVector{Any}, @nospecialize x)
+    new_length = length(a) + 1
+    resize!(a, new_length)
+    a[new_length] = x
+    return a
+end
+function push!(a::AbstractVector{Any}, @nospecialize x...)
+    @_terminates_locally_meta
+    na = length(a)
+    nx = length(x)
+    resize!(a, na + nx)
+    for i = 1:nx
+        a[na+i] = x[i]
+    end
+    return a
+end
+
 # multi-item push!, pushfirst! (built on top of type-specific 1-item version)
 # (note: must not cause a dispatch loop when 1-item case is not defined)
 push!(A, a, b) = push!(push!(A, a), b)
 push!(A, a, b, c...) = push!(push!(A, a, b), c...)
 pushfirst!(A, a, b) = pushfirst!(pushfirst!(A, b), a)
 pushfirst!(A, a, b, c...) = pushfirst!(pushfirst!(A, c...), a, b)
 
+# sizehint! does not nothing by default
+sizehint!(a::AbstractVector, _) = a
+
 ## hashing AbstractArray ##
 
 const hash_abstractarray_seed = UInt === UInt64 ? 0x7e2d6fb6448beb77 : 0xd4514ce5

test/abstractarray.jl

@@ -1436,6 +1436,15 @@ using .Main.OffsetArrays
     end
 end
 
+@testset "Check push!($a, $args...)" for
+    a in (["foo", "Bar"], SimpleArray(["foo", "Bar"]), OffsetVector(["foo", "Bar"], 0:1)),
+    args in (("eenie",), ("eenie", "minie"), ("eenie", "minie", "mo"))
+        orig = copy(a)
+        push!(a, args...)
+        @test length(a) == length(orig) + length(args)
+        @test all(a[end-length(args)+1:end] .== args)
+end
+
 @testset "splatting into hvcat" begin
     t = (1, 2)
     @test [t...; 3 4] == [1 2; 3 4]