interpreter: add Interpreter::string_instance

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

diff --git a/src/interpreter/naive_interpreter.nit b/src/interpreter/naive_interpreter.nit
index 6cd0bd0..cbdb607 100644 (file)
--- a/src/interpreter/naive_interpreter.nit
+++ b/src/interpreter/naive_interpreter.nit
@@ -256,6 +256,15 @@ class NaiveInterpreter
                return new PrimitiveInstance[Buffer](ic.mclass_type, val)
        end
 
+       # Return a new String instance for `txt`
+       fun string_instance(txt: String): Instance
+       do
+               var nat = native_string_instance(txt)
+               var res = self.send(self.force_get_primitive_method("to_s_with_length", nat.mtype), [nat, self.int_instance(txt.length)])
+               assert res != null
+               return res
+       end
+
        # The current frame used to store local variables of the current method executed
        fun frame: Frame do return frames.first
 
@@ -1460,9 +1469,7 @@ redef class AStringFormExpr
        redef fun expr(v)
        do
                var txt = self.value.as(not null)
-               var nat = v.native_string_instance(txt)
-               var res = v.send(v.force_get_primitive_method("to_s", nat.mtype), [nat]).as(not null)
-               return res
+               return v.string_instance(txt)
        end
 end