Always copy Hash's default block on #dup and #clone (#10744)

spec/std/hash_spec.cr

@@ -494,6 +494,16 @@ describe "Hash" do
       clone = h.clone
       clone.should be(clone.first[1])
     end
+
+    it "retains default block on clone" do
+      h1 = Hash(Int32, String).new("a")
+      h2 = h1.clone
+      h2[0].should eq("a")
+
+      h1[1] = "b"
+      h3 = h1.clone
+      h3[0].should eq("a")
+    end
   end
 
   describe "dup" do
@@ -536,6 +546,16 @@ describe "Hash" do
       h1.delete(0)
       h2[0].should eq([0])
     end
+
+    it "retains default block on dup" do
+      h1 = Hash(Int32, String).new("a")
+      h2 = h1.dup
+      h2[0].should eq("a")
+
+      h1[1] = "b"
+      h3 = h1.dup
+      h3[0].should eq("a")
+    end
   end
 
   it "initializes with block" do

src/hash.cr

@@ -640,6 +640,7 @@ class Hash(K, V)
   # Initializes a `dup` copy from the contents of `other`.
   protected def initialize_dup(other)
     initialize_compare_by_identity(other)
+    initialize_default_block(other)
 
     return if other.empty?
 
@@ -650,6 +651,7 @@ class Hash(K, V)
   # Initializes a `clone` copy from the contents of `other`.
   protected def initialize_clone(other)
     initialize_compare_by_identity(other)
+    initialize_default_block(other)
 
     return if other.empty?
 
@@ -661,6 +663,10 @@ class Hash(K, V)
     compare_by_identity if other.compare_by_identity?
   end
 
+  private def initialize_default_block(other)
+    @block = other.@block
+  end
+
   # Initializes `@entries` for a dup copy.
   # Here we only need to duplicate the buffer.
   private def initialize_dup_entries(other)
@@ -685,14 +691,13 @@ class Hash(K, V)
     end
   end
 
-  # Initializes all variables other than `@entries` for a copy.
+  # Initializes all variables other than `@entries` and `@block` for a copy.
   private def initialize_copy_non_entries_vars(other)
     @indices_bytesize = other.@indices_bytesize
     @first = other.@first
     @size = other.@size
     @deleted_count = other.@deleted_count
     @indices_size_pow2 = other.@indices_size_pow2
-    @block = other.@block
 
     unless other.@indices.null?
       @indices = malloc_indices(other.indices_size)