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

NEWS.md

@@ -686,6 +686,9 @@ Deprecated or removed
   * `cumsum`, `cumprod`, `accumulate`, and their mutating versions now require a `dim`
     argument instead of defaulting to using the first dimension ([#24684]).
 
+  * `copy!` is deprecated for `AbstractSet` and `Associative`, with the intention to re-enable
+    it with a cleaner meaning in a future version ([#24844]).
+
 Command-line option changes
 ---------------------------
 

base/array.jl

@@ -630,7 +630,12 @@ 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/associative.jl

@@ -213,15 +213,6 @@ function merge!(combine::Function, d::Associative, others::Associative...)
     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{Associative,AbstractSet}, src)
-    for x in src
-        push!(dest, x)
-    end
-    return dest
-end
-
 """
     keytype(type)
 

base/deprecated.jl

@@ -2150,6 +2150,9 @@ end
 
 @deprecate merge!(repo::LibGit2.GitRepo, args...; kwargs...) LibGit2.merge!(repo, args...; kwargs...)
 
+@deprecate copy!(dest::AbstractSet, src) union!(dest, src)
+@deprecate copy!(dest::Associative, src) foldl(push!, dest, src)
+
 # END 0.7 deprecations
 
 # BEGIN 1.0 deprecations

base/dict.jl

@@ -177,7 +177,7 @@ function grow_to!(dest::Associative{K,V}, itr, st) where V where K
             dest[k] = v
         else
             new = similar(dest, Pair{typejoin(K,typeof(k)), typejoin(V,typeof(v))})
-            copy!(new, dest)
+            merge!(new, dest)
             new[k] = v
             return grow_to!(new, itr, st)
         end