deprecate copy! for sets and dicts (part of #24808)

NEWS.md

@@ -758,10 +758,14 @@ Deprecated or removed
     in the new `Unicode` standard library module ([#25021]).
 
   * The aliases `Complex32`, `Complex64` and `Complex128` have been deprecated in favor of `ComplexF16`,
-     `ComplexF32` and `ComplexF64` respectively (#24647).
+     `ComplexF32` and `ComplexF64` respectively ([#24647]).
 
   * `Associative` has been deprecated in favor of `AbstractDict` ([#25012]).
 
+  * `copy!` is deprecated for `AbstractSet` and `AbstractDict`, with the intention to re-enable
+    it with a cleaner meaning in a future version ([#24844]).
+
+>>>>>>> deprecate copy! for sets and dicts (part of #24808)
 Command-line option changes
 ---------------------------
 

base/abstractdict.jl

@@ -230,15 +230,6 @@ function merge!(combine::Function, d::AbstractDict, others::AbstractDict...)
     return d
 end
 
-# very similar to `merge!`, but accepts any iterable and extends code
-# that would otherwise only use `copy!` with arrays.
-function copy!(dest::Union{AbstractDict,AbstractSet}, src)
-    for x in src
-        push!(dest, x)
-    end
-    return dest
-end
-
 """
     keytype(type)
 

base/array.jl

@@ -585,7 +585,12 @@ function grow_to!(dest, itr, st)
             push!(dest, el::T)
         else
             new = similar(dest, typejoin(T, S))
-            copy!(new, dest)
+            if new isa AbstractSet
+                # TODO: merge back these two branches when copy! is re-enabled for sets
+                union!(new, dest)
+            else
+                copy!(new, dest)
+            end
             push!(new, el)
             return grow_to!(new, itr, st)
         end

base/deprecated.jl

@@ -2984,6 +2984,10 @@ end
 
 @deprecate merge!(repo::LibGit2.GitRepo, args...; kwargs...) LibGit2.merge!(repo, args...; kwargs...)
 
+# #24844
+@deprecate copy!(dest::AbstractSet, src) union!(dest, src)
+@deprecate copy!(dest::AbstractDict, src) foldl(push!, dest, src)
+
 # issue #24019
 @deprecate similar(a::AbstractDict) empty(a)
 @deprecate similar(a::AbstractDict, ::Type{Pair{K,V}}) where {K, V} empty(a, K, V)

base/dict.jl

@@ -180,7 +180,7 @@ function grow_to!(dest::AbstractDict{K,V}, itr, st) where V where K
             dest[k] = v
         else
             new = empty(dest, typejoin(K,typeof(k)), typejoin(V,typeof(v)))
-            copy!(new, dest)
+            merge!(new, dest)
             new[k] = v
             return grow_to!(new, itr, st)
         end