niti: chain implementation attempts

1. intern/extern
2. body
3. abort

Because of the lack of multiple return, `intern_call` returns an instance,
null, or a false object to indicate the error.

Signed-off-by: Jean Privat <jean@pryen.org>

diff --git a/src/interpreter/naive_interpreter.nit b/src/interpreter/naive_interpreter.nit
index cd264f1..d4c9173 100644 (file)
--- a/src/interpreter/naive_interpreter.nit
+++ b/src/interpreter/naive_interpreter.nit
@@ -501,6 +501,10 @@ private class NaiveInterpreter
        do
                return mtype.anchor_to(self.mainmodule, self.frame.arguments.first.mtype.as(MClassType))
        end
+
+       # Placebo instance used to mark internal error result when `null` already have a meaning.
+       # TODO: replace with multiple return or something better
+       var error_instance = new MutableInstance(modelbuilder.model.null_type) is lazy
 end
 
 # An instance represents a value of the executed program.
@@ -671,14 +675,28 @@ redef class AMethPropdef
                        v.call_without_varargs(superpd, arguments)
                end
 
+               if mpropdef.is_intern or mpropdef.is_extern then
+                       var res = intern_call(v, mpropdef, arguments)
+                       if res != v.error_instance then return res
+               end
+
                if n_block != null then
                        v.stmt(self.n_block)
                        return null
+               end
+
+               if mpropdef.is_intern then
+                       fatal(v, "NOT YET IMPLEMENTED intern {mpropdef}")
+               else if mpropdef.is_extern then
+                       fatal(v, "NOT YET IMPLEMENTED extern {mpropdef}")
                else
-                       return intern_call(v, mpropdef, arguments)
+                       fatal(v, "NOT YET IMPLEMENTED <wat?> {mpropdef}")
                end
+               abort
        end
 
+       # Interprets a intern or a shortcut extern method.
+       # Returns the result for a function, `null` for a procedure, or `error_instance` if the method is unknown.
        private fun intern_call(v: NaiveInterpreter, mpropdef: MMethodDef, args: Array[Instance]): nullable Instance
        do
                var pname = mpropdef.mproperty.name
@@ -986,14 +1004,7 @@ redef class AMethPropdef
                else if pname == "address_is_null" then
                        return v.false_instance
                end
-               if mpropdef.is_intern then
-                       fatal(v, "NOT YET IMPLEMENTED intern {mpropdef}")
-               else if mpropdef.is_extern then
-                       fatal(v, "NOT YET IMPLEMENTED extern {mpropdef}")
-               else
-                       fatal(v, "NOT YET IMPLEMENTED <wat?> {mpropdef}")
-               end
-               abort
+               return v.error_instance
        end
 end