Correctly return a FFI::function if the return type is FFI::FunctionType

Author: eregon

CHANGELOG.md

@@ -9,6 +9,7 @@ Bug fixes:
 * Implemented `rb_eval_string_protect`.
 * Fixed `rb_get_kwargs` to correctly handle optional and rest arguments.
 * Calling `Kernel#raise` with a raised exception will no longer set the cause of the exception to itself (#1682).
+* Return a `FFI::Function` correctly for functions returning a callback.
 
 Compatibility
 

lib/truffle/truffle/ffi_backend/function.rb

@@ -170,6 +170,9 @@ def free
       elsif FFI::Type::Builtin === type and type.unsigned?
         # TODO: NFI workaround
         type.signed2unsigned(value)
+      elsif FFI::FunctionType === type
+        ptr = FFI::Pointer.new(Truffle::Interop.as_pointer(value))
+        FFI::Function.new(type, nil, ptr)
       else
         value
       end