Move boolean condition check outside of loop

Author: ccocchi

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

@@ -541,20 +541,23 @@ def transform_values!
 
   def transform_keys(mapping = nil)
     has_block = block_given?
-    return to_enum(:transform_keys) { size } unless mapping || has_block
-
-    mapping = Truffle::Type.coerce_to(mapping, Hash, :to_hash) if mapping
-
     h = {}
-    each_pair do |key, value|
-      if mapping
+
+    if mapping
+      mapping = Truffle::Type.coerce_to(mapping, Hash, :to_hash)
+      each_pair do |key, value|
         k = Primitive.hash_get_or_undefined(mapping, key)
         k = has_block ? yield(key) : key if Primitive.undefined?(k)
         h[k] = value
-      else
+      end
+    else
+      return to_enum(:transform_keys) { size } unless has_block
+
+      each_pair do |key, value|
         h[yield(key)] = value
       end
     end
+
     h
   end
 
@@ -563,16 +566,18 @@ def transform_keys!(mapping = nil)
     return to_enum(:transform_keys!) { size } unless mapping || has_block
 
     Primitive.check_frozen self
-    mapping = Truffle::Type.coerce_to(mapping, Hash, :to_hash) if mapping
-
     h = {}
+
     begin
-      each_pair do |key, value|
-        if mapping
+      if mapping
+        mapping = Truffle::Type.coerce_to(mapping, Hash, :to_hash)
+        each_pair do |key, value|
           k = Primitive.hash_get_or_undefined(mapping, key)
           k = has_block ? yield(key) : key if Primitive.undefined?(k)
           h[k] = value
-        else
+        end
+      else
+        each_pair do |key, value|
           h[yield(key)] = value
         end
       end