Fix Hash#to_h called with a block and pass key and value to the block as separate arguments

Author: andrykonchin

CHANGELOG.md

@@ -33,6 +33,7 @@ Compatibility:
 * Fix `Enumerable#reduce` to handle non-Symbol method name parameter (#2931, @andrykonchin).
 * Fix `RangeError` message to match CRuby for `Integer#chr` called with invalid codepoint argument (#2795, @andrykonchin).
 * Joni has been updated from 2.1.44 to 2.2.1 (@andrykonchin).
+* Fix `Hash#to_h` called with a block and pass key and value to the block as separate arguments (#3607, @andrykonchin).
 
 Performance:
 

spec/ruby/core/hash/to_h_spec.rb

@@ -37,6 +37,16 @@
       { a: 1, b: 2 }.to_h { |k, v| [k.to_s, v*v]}.should == { "a" => 1, "b" => 4 }
     end
 
+    it "passes to a block each pair's key and value as separate arguments" do
+      ScratchPad.record []
+      { a: 1, b: 2 }.to_h { |k, v| ScratchPad << [k, v]; [k, v] }
+      ScratchPad.recorded.sort.should == [[:a, 1], [:b, 2]]
+
+      ScratchPad.record []
+      { a: 1, b: 2 }.to_h { |*args| ScratchPad << args; [args[0], args[1]] }
+      ScratchPad.recorded.sort.should == [[:a, 1], [:b, 2]]
+    end
+
     it "raises ArgumentError if block returns longer or shorter array" do
       -> do
         { a: 1, b: 2 }.to_h { |k, v| [k.to_s, v*v, 1] }

src/main/ruby/truffleruby/core/hash.rb

@@ -355,7 +355,21 @@ def slice(*keys)
 
   def to_h
     if block_given?
-      super
+      h = {}
+      each do |k, v|
+        elem = yield(k, v)
+        unless elem.respond_to?(:to_ary)
+          raise TypeError, "wrong element type #{Primitive.class(elem)} (expected array)"
+        end
+
+        ary = elem.to_ary
+        if ary.size != 2
+          raise ArgumentError, "element has wrong array length (expected 2, was #{ary.size})"
+        end
+
+        h[ary[0]] = ary[1]
+      end
+      h
     elsif instance_of? Hash
       self
     else