ni_nitdoc: added fast copy past utility to signatures.
[nit.git] / src / naive_interpreter.nit
index 6c4ae9a..8aa6919 100644 (file)
@@ -21,6 +21,17 @@ import literal
 import typing
 import auto_super_init
 
+redef class ToolContext
+       # --discover-call-trace
+       var opt_discover_call_trace: OptionBool = new OptionBool("Trace calls of the first invocation of a method", "--discover-call-trace")
+
+       redef init
+       do
+               super
+               self.option_context.add_option(self.opt_discover_call_trace)
+       end
+end
+
 redef class ModelBuilder
        # Execute the program from the entry point (Sys::main) of the `mainmodule'
        # `arguments' are the command-line arguments in order
@@ -34,9 +45,16 @@ redef class ModelBuilder
                self.toolcontext.info("*** START INTERPRETING ***", 1)
 
                var interpreter = new NaiveInterpreter(self, mainmodule, arguments)
+               init_naive_interpreter(interpreter, mainmodule)
+
+               var time1 = get_time
+               self.toolcontext.info("*** END INTERPRETING: {time1-time0} ***", 2)
+       end
+
+       private fun init_naive_interpreter(interpreter: NaiveInterpreter, mainmodule: MModule) do
                var sys_type = mainmodule.sys_type
                if sys_type == null then return # no class Sys
-               var mainobj = new Instance(sys_type)
+               var mainobj = new MutableInstance(sys_type)
                interpreter.mainobj = mainobj
                interpreter.init_instance(mainobj)
                var initprop = mainmodule.try_get_primitive_method("init", sys_type)
@@ -48,9 +66,6 @@ redef class ModelBuilder
                if mainprop != null then
                        interpreter.send(mainprop, [mainobj])
                end
-
-               var time1 = get_time
-               self.toolcontext.info("*** END INTERPRETING: {time1-time0} ***", 2)
        end
 end
 
@@ -76,7 +91,7 @@ private class NaiveInterpreter
                self.arguments = arguments
                self.true_instance = new PrimitiveInstance[Bool](mainmodule.bool_type, true)
                self.false_instance = new PrimitiveInstance[Bool](mainmodule.bool_type, false)
-               self.null_instance = new Instance(mainmodule.model.null_type)
+               self.null_instance = new MutableInstance(mainmodule.model.null_type)
        end
 
        # Subtype test in the context of the mainmodule
@@ -85,9 +100,14 @@ private class NaiveInterpreter
                return sub.is_subtype(self.mainmodule, self.frame.arguments.first.mtype.as(MClassType), sup)
        end
 
+       fun force_get_primitive_method(name: String, recv: MType): MMethod
+       do
+               return self.modelbuilder.force_get_primitive_method(self.frame.current_node, name, recv, self.mainmodule)
+       end
+
        # Is a return executed?
-       # Set this mark to skip the evaluation until the end of the current method
-       var returnmark: Bool = false
+       # Set this mark to skip the evaluation until the end of the specified method frame
+       var returnmark: nullable Frame = null
 
        # Is a break executed?
        # Set this mark to skip the evaluation until a labeled statement catch it with `is_break'
@@ -99,7 +119,7 @@ private class NaiveInterpreter
 
        # Is a return or a break or a continue executed?
        # Use this function to know if you must skip the evaluation of statements
-       fun is_escaping: Bool do return returnmark or breakmark != null or continuemark != null
+       fun is_escaping: Bool do return returnmark != null or breakmark != null or continuemark != null
 
        # The value associated with the current return/break/continue, if any.
        # Set the value when you set a escapemark.
@@ -135,15 +155,25 @@ private class NaiveInterpreter
        # Evaluate `n' as an expression in the current context.
        # Return the value of the expression.
        # If `n' cannot be evaluated, then aborts.
-       fun expr(n: AExpr): Instance
+       fun expr(n: AExpr): nullable Instance
        do
-               var old = self.frame.current_node
-               self.frame.current_node = n
+               var frame = self.frame
+               var old = frame.current_node
+               frame.current_node = n
                #n.debug("IN Execute expr")
-               var i = n.expr(self).as(not null)
+               var i = n.expr(self)
+               if i == null and not self.is_escaping then
+                       n.debug("inconsitance: no value and not escaping.")
+               end
+               var implicit_cast_to = n.implicit_cast_to
+               if implicit_cast_to != null then
+                       var mtype = self.unanchor_type(implicit_cast_to)
+                       if not self.is_subtype(i.mtype, mtype) then n.fatal(self, "Cast failed")
+               end
+
                #n.debug("OUT Execute expr: value is {i}")
                #if not is_subtype(i.mtype, n.mtype.as(not null)) then n.debug("Expected {n.mtype.as(not null)} got {i}")
-               self.frame.current_node = old
+               frame.current_node = old
                return i
        end
 
@@ -153,11 +183,12 @@ private class NaiveInterpreter
        fun stmt(n: nullable AExpr)
        do
                if n != null then
-                       var old = self.frame.current_node
-                       self.frame.current_node = n
+                       var frame = self.frame
+                       var old = frame.current_node
+                       frame.current_node = n
                        #n.debug("Execute stmt")
                        n.stmt(self)
-                       self.frame.current_node = old
+                       frame.current_node = old
                end
        end
 
@@ -207,9 +238,9 @@ private class NaiveInterpreter
                assert not elttype.need_anchor
                var nat = new PrimitiveInstance[Array[Instance]](self.mainmodule.get_primitive_class("NativeArray").get_mtype([elttype]), values)
                var mtype = self.mainmodule.get_primitive_class("Array").get_mtype([elttype])
-               var res = new Instance(mtype)
+               var res = new MutableInstance(mtype)
                self.init_instance(res)
-               self.send(self.mainmodule.force_get_primitive_method("with_native", mtype), [res, nat, self.int_instance(values.length)])
+               self.send(self.force_get_primitive_method("with_native", mtype), [res, nat, self.int_instance(values.length)])
                self.check_init_instance(res)
                return res
        end
@@ -252,11 +283,28 @@ private class NaiveInterpreter
                exit(1)
        end
 
+       # Debug on the current node
+       fun debug(message: String)
+       do
+               if frames.is_empty then
+                       print message
+               else
+                       self.frame.current_node.debug(message)
+               end
+       end
+
+       # Store known method, used to trace methods as thez are reached
+       var discover_call_trace: Set[MMethodDef] = new HashSet[MMethodDef]
+
        # Execute `mpropdef' for a `args' (where args[0] is the receiver).
        # Return a falue if `mpropdef' is a function, or null if it is a procedure.
        # The call is direct/static. There is no message-seding/late-bindng.
        fun call(mpropdef: MMethodDef, args: Array[Instance]): nullable Instance
        do
+               if self.modelbuilder.toolcontext.opt_discover_call_trace.value and not self.discover_call_trace.has(mpropdef) then
+                       self.discover_call_trace.add mpropdef
+                       self.debug("Discovered {mpropdef}")
+               end
                var vararg_rank = mpropdef.msignature.vararg_rank
                if vararg_rank >= 0 then
                        assert args.length >= mpropdef.msignature.arity + 1 # because of self
@@ -282,15 +330,22 @@ private class NaiveInterpreter
                                args.add(rawargs[i+1])
                        end
                end
-               assert args.length == mpropdef.msignature.arity + 1 # because of self
+               if args.length < mpropdef.msignature.arity + 1 or args.length > mpropdef.msignature.arity + 1 + mpropdef.msignature.mclosures.length then
+                       fatal("NOT YET IMPLEMENTED: Invalid arity for {mpropdef}. {args.length} arguments given.")
+               end
+               if args.length < mpropdef.msignature.arity + 1 + mpropdef.msignature.mclosures.length then
+                       fatal("NOT YET IMPLEMENTED: default closures")
+               end
 
                # Look for the AST node that implements the property
                var mproperty = mpropdef.mproperty
                if self.modelbuilder.mpropdef2npropdef.has_key(mpropdef) then
                        var npropdef = self.modelbuilder.mpropdef2npropdef[mpropdef]
+                       self.parameter_check(npropdef, mpropdef, args)
                        return npropdef.call(self, mpropdef, args)
                else if mproperty.name == "init" then
                        var nclassdef = self.modelbuilder.mclassdef2nclassdef[mpropdef.mclassdef]
+                       self.parameter_check(nclassdef, mpropdef, args)
                        return nclassdef.call(self, mpropdef, args)
                else
                        fatal("Fatal Error: method {mpropdef} not found in the AST")
@@ -298,6 +353,51 @@ private class NaiveInterpreter
                end
        end
 
+       # Generate type checks in the C code to check covariant parameters
+       fun parameter_check(node: ANode, mpropdef: MMethodDef, args: Array[Instance])
+       do
+               var msignature = mpropdef.msignature
+               for i in [0..msignature.arity[ do
+                       # skip test for vararg since the array is instantiated with the correct polymorphic type
+                       if msignature.vararg_rank == i then continue
+
+                       # skip if the cast is not required
+                       var origmtype =  mpropdef.mproperty.intro.msignature.mparameters[i].mtype
+                       if not origmtype.need_anchor then continue
+
+                       # get the parameter type
+                       var mtype = msignature.mparameters[i].mtype
+                       var anchor = args.first.mtype.as(MClassType)
+                       mtype = mtype.anchor_to(self.mainmodule, anchor)
+                       if not args[i+1].mtype.is_subtype(self.mainmodule, anchor, mtype) then
+                               node.fatal(self, "Cast failed")
+                       end
+               end
+       end
+
+       fun call_closure(closure: ClosureInstance, args: Array[Instance]): nullable Instance
+       do
+               var nclosuredef = closure.nclosuredef
+               var f = closure.frame
+               for i in [0..closure.nclosuredef.mclosure.mtype.as(MSignature).arity[ do
+                       var variable = nclosuredef.variables[i]
+                       f.map[variable] = args[i]
+               end
+
+               self.frames.unshift(f)
+
+               self.stmt(nclosuredef.n_expr)
+
+               self.frames.shift
+
+               if self.is_continue(nclosuredef.escapemark) then
+                       var res = self.escapevalue
+                       self.escapevalue = null
+                       return res
+               end
+               return null
+       end
+
        # Execute `mproperty' for a `args' (where args[0] is the receiver).
        # Return a falue if `mproperty' is a function, or null if it is a procedure.
        # The call is polimotphic. There is a message-seding/late-bindng according to te receiver (args[0]).
@@ -315,16 +415,7 @@ private class NaiveInterpreter
                        fatal("Reciever is null")
                        abort
                end
-               var propdefs = mproperty.lookup_definitions(self.mainmodule, mtype)
-               if propdefs.length > 1 then
-                       fatal("NOT YET IMPLEMETED ERROR: Property conflict: {propdefs.join(", ")}")
-                       abort
-               end
-               assert propdefs.length == 1 else
-                       fatal("Fatal Error: No property '{mproperty}' for '{recv}'")
-                       abort
-               end
-               var propdef = propdefs.first
+               var propdef = mproperty.lookup_first_definition(self.mainmodule, mtype)
                return self.call(propdef, args)
        end
 
@@ -332,6 +423,7 @@ private class NaiveInterpreter
        # If the attribute in not yet initialized, then aborts with an error message.
        fun read_attribute(mproperty: MAttribute, recv: Instance): Instance
        do
+               assert recv isa MutableInstance
                if not recv.attributes.has_key(mproperty) then
                        fatal("Uninitialized attribute {mproperty.name}")
                        abort
@@ -339,34 +431,48 @@ private class NaiveInterpreter
                return recv.attributes[mproperty]
        end
 
-       # Fill the initial values of the newly created instance `recv'.
-       # `recv.mtype' is used to know what must be filled.
-       fun init_instance(recv: Instance)
+       # Collect attributes of a type in the order of their init
+       fun collect_attr_propdef(mtype: MType): Array[AAttrPropdef]
        do
-               for cd in recv.mtype.collect_mclassdefs(self.mainmodule)
-               do
+               var cache = self.collect_attr_propdef_cache
+               if cache.has_key(mtype) then return cache[mtype]
+
+               var res = new Array[AAttrPropdef]
+               var cds = mtype.collect_mclassdefs(self.mainmodule).to_a
+               self.mainmodule.linearize_mclassdefs(cds)
+               for cd in cds do
                        var n = self.modelbuilder.mclassdef2nclassdef[cd]
                        for npropdef in n.n_propdefs do
                                if npropdef isa AAttrPropdef then
-                                       npropdef.init_expr(self, recv)
+                                       res.add(npropdef)
                                end
                        end
                end
+
+               cache[mtype] = res
+               return res
+       end
+
+       var collect_attr_propdef_cache = new HashMap[MType, Array[AAttrPropdef]]
+
+       # Fill the initial values of the newly created instance `recv'.
+       # `recv.mtype' is used to know what must be filled.
+       fun init_instance(recv: Instance)
+       do
+               for npropdef in collect_attr_propdef(recv.mtype) do
+                       npropdef.init_expr(self, recv)
+               end
        end
 
        # Check that non nullable attributes of `recv' are correctly initialized.
        # This function is used as the last instruction of a new
-       # FIXME: this will work better once there is nullable types
        fun check_init_instance(recv: Instance)
        do
-               for cd in recv.mtype.collect_mclassdefs(self.mainmodule)
-               do
-                       var n = self.modelbuilder.mclassdef2nclassdef[cd]
-                       for npropdef in n.n_propdefs do
-                               if npropdef isa AAttrPropdef and npropdef.n_expr == null then
-                                       # Force read to check the initialization
-                                       self.read_attribute(npropdef.mpropdef.mproperty, recv)
-                               end
+               if not recv isa MutableInstance then return
+               for npropdef in collect_attr_propdef(recv.mtype) do
+                       if npropdef.n_expr == null then
+                               # Force read to check the initialization
+                               self.read_attribute(npropdef.mpropdef.mproperty, recv)
                        end
                end
        end
@@ -379,14 +485,11 @@ private class NaiveInterpreter
 end
 
 # An instance represents a value of the executed program.
-class Instance
+abstract class Instance
        # The dynamic type of the instance
        # ASSERT: not self.mtype.is_anchored
        var mtype: MType
 
-       # The values of the attributes
-       var attributes: Map[MAttribute, Instance] = new HashMap[MAttribute, Instance]
-
        # return true if the instance is the true value.
        # return false if the instance is the true value.
        # else aborts
@@ -396,17 +499,29 @@ class Instance
        fun eq_is(o: Instance): Bool do return self is o
 
        # Human readable object identity "Type#number"
-       redef fun to_s do return "{mtype}#{object_id}"
+       redef fun to_s do return "{mtype}"
 
-       # Return the integer valur is the instance is an integer.
+       # Return the integer value if the instance is an integer.
        # else aborts
        fun to_i: Int do abort
 
+       # Return the integer value if the instance is a float.
+       # else aborts
+       fun to_f: Float do abort
+
        # The real value encapsulated if the instance is primitive.
        # Else aborts.
        fun val: Object do abort
 end
 
+# A instance with attribute (standards objects)
+class MutableInstance
+       super Instance
+
+       # The values of the attributes
+       var attributes: Map[MAttribute, Instance] = new HashMap[MAttribute, Instance]
+end
+
 # Special instance to handle primitives values (int, bool, etc.)
 # The trick it just to encapsulate the <<real>> value
 class PrimitiveInstance[E: Object]
@@ -443,6 +558,23 @@ class PrimitiveInstance[E: Object]
        redef fun to_s do return "{mtype}#{val.object_id}({val})"
 
        redef fun to_i do return val.as(Int)
+
+       redef fun to_f do return val.as(Float)
+end
+
+private class ClosureInstance
+       super Instance
+
+       var frame: Frame
+
+       var nclosuredef: AClosureDef
+
+       init(mtype: MType, frame: Frame, nclosuredef: AClosureDef)
+       do
+               super(mtype)
+               self.frame = frame
+               self.nclosuredef = nclosuredef
+       end
 end
 
 # Information about local variables in a running method
@@ -465,10 +597,11 @@ redef class ANode
        private fun fatal(v: NaiveInterpreter, message: String)
        do
                if v.modelbuilder.toolcontext.opt_no_color.value == true then
-                       print("{message} ({location.file.filename}:{location.line_start})")
+                       stderr.write("Runtime error: {message} ({location.file.filename}:{location.line_start})\n")
                else
-                       print("{location}: {message}\n{location.colored_line("0;31")}")
-                       print(v.stack_trace)
+                       stderr.write("{location}: Runtime error: {message}\n{location.colored_line("0;31")}\n")
+                       stderr.write(v.stack_trace)
+                       stderr.write("\n")
                end
                exit(1)
        end
@@ -478,7 +611,7 @@ redef class APropdef
        # Execute a `mpropdef' associated with the current node.
        private fun call(v: NaiveInterpreter, mpropdef: MMethodDef, args: Array[Instance]): nullable Instance
        do
-               fatal(v, "Unimplemented {mpropdef}")
+               fatal(v, "NOT YET IMPLEMENTED method kind {class_name}. {mpropdef}")
                abort
        end
 end
@@ -492,6 +625,12 @@ redef class AConcreteMethPropdef
                        assert variable != null
                        f.map[variable] = args[i+1]
                end
+               for i in [0..mpropdef.msignature.mclosures.length[ do
+                       var c = mpropdef.msignature.mclosures[i]
+                       var variable = self.n_signature.n_closure_decls[i].variable
+                       assert variable != null
+                       f.map[variable] = args[i + 1 + mpropdef.msignature.arity]
+               end
 
                v.frames.unshift(f)
 
@@ -510,10 +649,13 @@ redef class AConcreteMethPropdef
 
                v.stmt(self.n_block)
                v.frames.shift
-               v.returnmark = false
-               var res = v.escapevalue
-               v.escapevalue = null
-               return res
+               if v.returnmark == f then
+                       v.returnmark = null
+                       var res = v.escapevalue
+                       v.escapevalue = null
+                       return res
+               end
+               return null
        end
 end
 
@@ -535,11 +677,11 @@ redef class AInternMethPropdef
                        end
                else if pname == "output_class_name" then
                        var recv = args.first
-                       print recv.mtype.as(MClassType).mclass
+                       print recv.mtype
                        return null
                else if pname == "native_class_name" then
                        var recv = args.first
-                       var txt = recv.mtype.as(MClassType).mclass.to_s
+                       var txt = recv.mtype.to_s
                        return v.native_string_instance(txt)
                else if pname == "==" then
                        # == is correclt redefined for instances
@@ -609,16 +751,27 @@ redef class AInternMethPropdef
                                return v.int_instance(recv <=> args[1].val.as(Char))
                        end
                else if cname == "Float" then
-                       if pname == "+" then
-                               return v.float_instance(args[0].val.as(Float) + args[1].val.as(Float))
+                       var recv = args[0].to_f
+                       if pname == "unary -" then
+                               return v.float_instance(-recv)
+                       else if pname == "+" then
+                               return v.float_instance(recv + args[1].to_f)
                        else if pname == "-" then
-                               return v.float_instance(args[0].val.as(Float) - args[1].val.as(Float))
+                               return v.float_instance(recv - args[1].to_f)
                        else if pname == "*" then
-                               return v.float_instance(args[0].val.as(Float) * args[1].val.as(Float))
+                               return v.float_instance(recv * args[1].to_f)
                        else if pname == "/" then
-                               return v.float_instance(args[0].val.as(Float) / args[1].val.as(Float))
+                               return v.float_instance(recv / args[1].to_f)
+                       else if pname == "<" then
+                               return v.bool_instance(recv < args[1].to_f)
+                       else if pname == ">" then
+                               return v.bool_instance(recv > args[1].to_f)
+                       else if pname == "<=" then
+                               return v.bool_instance(recv <= args[1].to_f)
+                       else if pname == ">=" then
+                               return v.bool_instance(recv >= args[1].to_f)
                        else if pname == "to_i" then
-                               return v.int_instance(args[0].val.as(Float).to_i)
+                               return v.int_instance(recv.to_i)
                        end
                else if cname == "NativeString" then
                        var recvval = args.first.val.as(Buffer)
@@ -676,12 +829,18 @@ redef class AInternMethPropdef
                        end
                else if pname == "calloc_array" then
                        var recvtype = args.first.mtype.as(MClassType)
-                       var mtype: MType = recvtype.supertype_to(v.mainmodule, recvtype, v.mainmodule.get_primitive_class("ArrayCapable"))
-                       mtype = mtype.as(MGenericType).arguments.first
+                       var mtype: MType
+                       mtype = recvtype.supertype_to(v.mainmodule, recvtype, v.mainmodule.get_primitive_class("ArrayCapable"))
+                       mtype = mtype.arguments.first
                        var val = new Array[Instance].filled_with(v.null_instance, args[1].to_i)
                        return new PrimitiveInstance[Array[Instance]](v.mainmodule.get_primitive_class("NativeArray").get_mtype([mtype]), val)
+               else if pname == "native_argc" then
+                       return v.int_instance(v.arguments.length)
+               else if pname == "native_argv" then
+                       var txt = v.arguments[args[1].to_i]
+                       return v.native_string_instance(txt)
                end
-               fatal(v, "Unimplemented intern {mpropdef}")
+               fatal(v, "NOT YET IMPLEMENTED intern {mpropdef}")
                abort
        end
 end
@@ -711,7 +870,7 @@ redef class AExternInitPropdef
                        var a1 = args[1].val.as(Buffer)
                        return new PrimitiveInstance[OStream](mpropdef.mclassdef.mclass.mclass_type, new OFStream.open(a1.to_s))
                end
-               fatal(v, "Unimplemented extern init {mpropdef}")
+               fatal(v, "NOT YET IMPLEMENTED extern init {mpropdef}")
                abort
        end
 end
@@ -751,8 +910,41 @@ redef class AExternMethPropdef
                                recvval.to_s.mkdir
                                return null
                        else if pname == "get_environ" then
-                               var txt = args.first.val.as(Buffer).to_s.environ
+                               var txt = recvval.to_s.environ
                                return v.native_string_instance(txt)
+                       else if pname == "system" then
+                               var res = sys.system(recvval.to_s)
+                               return v.int_instance(res)
+                       else if pname == "atof" then
+                               return v.float_instance(recvval.to_f)
+                       end
+               else if cname == "Int" then
+                       if pname == "rand" then
+                               return v.int_instance(args[0].to_i.rand)
+                       end
+               else if cname == "Float" then
+                       if pname == "cos" then
+                               return v.float_instance(args[0].to_f.cos)
+                       else if pname == "sin" then
+                               return v.float_instance(args[0].to_f.sin)
+                       else if pname == "tan" then
+                               return v.float_instance(args[0].to_f.tan)
+                       else if pname == "acos" then
+                               return v.float_instance(args[0].to_f.acos)
+                       else if pname == "asin" then
+                               return v.float_instance(args[0].to_f.asin)
+                       else if pname == "atan" then
+                               return v.float_instance(args[0].to_f.atan)
+                       else if pname == "sqrt" then
+                               return v.float_instance(args[0].to_f.sqrt)
+                       else if pname == "exp" then
+                               return v.float_instance(args[0].to_f.exp)
+                       else if pname == "log" then
+                               return v.float_instance(args[0].to_f.log)
+                       else if pname == "pow" then
+                               return v.float_instance(args[0].to_f.pow(args[1].to_f))
+                       else if pname == "rand" then
+                               return v.float_instance(args[0].to_f.rand)
                        end
                else if pname == "native_argc" then
                        return v.int_instance(v.arguments.length)
@@ -761,6 +953,13 @@ redef class AExternMethPropdef
                        return v.native_string_instance(txt)
                else if pname == "get_time" then
                        return v.int_instance(get_time)
+               else if pname == "srand_from" then
+                       srand_from(args[1].to_i)
+                       return null
+               else if pname == "atan2" then
+                       return v.float_instance(atan2(args[1].to_f, args[2].to_f))
+               else if pname == "pi" then
+                       return v.float_instance(pi)
                else if pname == "lexer_goto" then
                        return v.int_instance(lexer_goto(args[1].to_i, args[2].to_i))
                else if pname == "lexer_accept" then
@@ -770,7 +969,7 @@ redef class AExternMethPropdef
                else if pname == "parser_action" then
                        return v.int_instance(parser_action(args[1].to_i, args[2].to_i))
                end
-               fatal(v, "Unimplemented extern {mpropdef}")
+               fatal(v, "NOT YET IMPLEMENTED extern {mpropdef}")
                abort
        end
 end
@@ -778,12 +977,14 @@ end
 redef class AAttrPropdef
        redef fun call(v, mpropdef, args)
        do
+               var recv = args.first
+               assert recv isa MutableInstance
                var attr = self.mpropdef.mproperty
                if args.length == 1 then
-                       return v.read_attribute(attr, args.first)
+                       return v.read_attribute(attr, recv)
                else
                        assert args.length == 2
-                       args.first.attributes[attr] = args[1]
+                       recv.attributes[attr] = args[1]
                        return null
                end
        end
@@ -791,11 +992,13 @@ redef class AAttrPropdef
        # Evaluate and set the default value of the attribute in `recv'
        private fun init_expr(v: NaiveInterpreter, recv: Instance)
        do
+               assert recv isa MutableInstance
                var nexpr = self.n_expr
                if nexpr != null then
                        var f = new Frame(self, self.mpropdef.as(not null), [recv])
                        v.frames.unshift(f)
                        var val = v.expr(nexpr)
+                       assert val != null
                        v.frames.shift
                        assert not v.is_escaping
                        recv.attributes[self.mpropdef.mproperty] = val
@@ -810,6 +1013,14 @@ redef class AAttrPropdef
        end
 end
 
+redef class ADeferredMethPropdef
+       redef fun call(v, mpropdef, args)
+       do
+               fatal(v, "Deferred method called")
+               abort
+       end
+end
+
 redef class AClassdef
        # Execute an implicit `mpropdef' associated with the current node.
        private fun call(v: NaiveInterpreter, mpropdef: MMethodDef, args: Array[Instance]): nullable Instance
@@ -823,6 +1034,7 @@ redef class AClassdef
                        return null
                end
                var recv = args.first
+               assert recv isa MutableInstance
                var i = 1
                # Collect undefined attributes
                for npropdef in self.n_propdefs do
@@ -842,7 +1054,7 @@ redef class AExpr
        # This method is here to be implemented by subclasses.
        private fun expr(v: NaiveInterpreter): nullable Instance
        do
-               fatal(v, "Unimplemented expr {class_name}")
+               fatal(v, "NOT YET IMPLEMENTED expr {class_name}")
                abort
        end
 
@@ -872,6 +1084,7 @@ redef class AVardeclExpr
                var ne = self.n_expr
                if ne != null then
                        var i = v.expr(ne)
+                       if i == null then return
                        v.frame.map[self.variable.as(not null)] = i
                end
        end
@@ -888,6 +1101,7 @@ redef class AVarAssignExpr
        redef fun stmt(v)
        do
                var i = v.expr(self.n_value)
+               if i == null then return
                v.frame.map[self.variable.as(not null)] = i
        end
 end
@@ -897,6 +1111,7 @@ redef class AVarReassignExpr
        do
                var vari = v.frame.map[self.variable.as(not null)]
                var value = v.expr(self.n_value)
+               if value == null then return
                var res = v.send(reassign_property.mproperty, [vari, value])
                assert res != null
                v.frame.map[self.variable.as(not null)] = res
@@ -913,6 +1128,12 @@ end
 redef class AContinueExpr
        redef fun stmt(v)
        do
+               var ne = self.n_expr
+               if ne != null then
+                       var i = v.expr(ne)
+                       if i == null then return
+                       v.escapevalue = i
+               end
                v.continuemark = self.escapemark
        end
 end
@@ -920,6 +1141,12 @@ end
 redef class ABreakExpr
        redef fun stmt(v)
        do
+               var ne = self.n_expr
+               if ne != null then
+                       var i = v.expr(ne)
+                       if i == null then return
+                       v.escapevalue = i
+               end
                v.breakmark = self.escapemark
        end
 end
@@ -930,9 +1157,10 @@ redef class AReturnExpr
                var ne = self.n_expr
                if ne != null then
                        var i = v.expr(ne)
+                       if i == null then return
                        v.escapevalue = i
                end
-               v.returnmark = true
+               v.returnmark = v.frame
        end
 end
 
@@ -948,6 +1176,7 @@ redef class AIfExpr
        redef fun stmt(v)
        do
                var cond = v.expr(self.n_expr)
+               if cond == null then return
                if cond.is_true then
                        v.stmt(self.n_then)
                else
@@ -960,6 +1189,7 @@ redef class AIfexprExpr
        redef fun expr(v)
        do
                var cond = v.expr(self.n_expr)
+               if cond == null then return null
                if cond.is_true then
                        return v.expr(self.n_then)
                else
@@ -981,6 +1211,7 @@ redef class AWhileExpr
        do
                loop
                        var cond = v.expr(self.n_expr)
+                       if cond == null then return
                        if not cond.is_true then return
                        v.stmt(self.n_block)
                        if v.is_break(self.escapemark) then return
@@ -1006,20 +1237,30 @@ redef class AForExpr
        redef fun stmt(v)
        do
                var col = v.expr(self.n_expr)
+               if col == null then return
                #self.debug("col {col}")
-               var iter = v.send(v.mainmodule.force_get_primitive_method("iterator", col.mtype), [col]).as(not null)
+               var iter = v.send(v.force_get_primitive_method("iterator", col.mtype), [col]).as(not null)
                #self.debug("iter {iter}")
                loop
-                       var isok = v.send(v.mainmodule.force_get_primitive_method("is_ok", iter.mtype), [iter]).as(not null)
+                       var isok = v.send(v.force_get_primitive_method("is_ok", iter.mtype), [iter]).as(not null)
                        if not isok.is_true then return
-                       var item = v.send(v.mainmodule.force_get_primitive_method("item", iter.mtype), [iter]).as(not null)
-                       #self.debug("item {item}")
-                       v.frame.map[self.variables.first] = item
+                       if self.variables.length == 1 then
+                               var item = v.send(v.force_get_primitive_method("item", iter.mtype), [iter]).as(not null)
+                               #self.debug("item {item}")
+                               v.frame.map[self.variables.first] = item
+                       else if self.variables.length == 2 then
+                               var key = v.send(v.force_get_primitive_method("key", iter.mtype), [iter]).as(not null)
+                               v.frame.map[self.variables[0]] = key
+                               var item = v.send(v.force_get_primitive_method("item", iter.mtype), [iter]).as(not null)
+                               v.frame.map[self.variables[1]] = item
+                       else
+                               abort
+                       end
                        v.stmt(self.n_block)
                        if v.is_break(self.escapemark) then return
                        v.is_continue(self.escapemark) # Clear the break
                        if v.is_escaping then return
-                       v.send(v.mainmodule.force_get_primitive_method("next", iter.mtype), [iter])
+                       v.send(v.force_get_primitive_method("next", iter.mtype), [iter])
                end
        end
 end
@@ -1028,6 +1269,7 @@ redef class AAssertExpr
        redef fun stmt(v)
        do
                var cond = v.expr(self.n_expr)
+               if cond == null then return
                if not cond.is_true then
                        v.stmt(self.n_else)
                        if v.is_escaping then return
@@ -1046,6 +1288,7 @@ redef class AOrExpr
        redef fun expr(v)
        do
                var cond = v.expr(self.n_expr)
+               if cond == null then return null
                if cond.is_true then return cond
                return v.expr(self.n_expr2)
        end
@@ -1055,6 +1298,7 @@ redef class AAndExpr
        redef fun expr(v)
        do
                var cond = v.expr(self.n_expr)
+               if cond == null then return null
                if not cond.is_true then return cond
                return v.expr(self.n_expr2)
        end
@@ -1064,6 +1308,7 @@ redef class ANotExpr
        redef fun expr(v)
        do
                var cond = v.expr(self.n_expr)
+               if cond == null then return null
                return v.bool_instance(not cond.is_true)
        end
 end
@@ -1072,6 +1317,7 @@ redef class AOrElseExpr
        redef fun expr(v)
        do
                var i = v.expr(self.n_expr)
+               if i == null then return null
                if i != v.null_instance then return i
                return v.expr(self.n_expr2)
        end
@@ -1081,7 +1327,9 @@ redef class AEeExpr
        redef fun expr(v)
        do
                var i = v.expr(self.n_expr)
+               if i == null then return null
                var i2 = v.expr(self.n_expr2)
+               if i2 == null then return null
                return v.bool_instance(i.eq_is(i2))
        end
 end
@@ -1112,9 +1360,11 @@ redef class AArrayExpr
        do
                var val = new Array[Instance]
                for nexpr in self.n_exprs.n_exprs do
-                       val.add(v.expr(nexpr))
+                       var i = v.expr(nexpr)
+                       if i == null then return null
+                       val.add(i)
                end
-               var mtype = v.unanchor_type(self.mtype.as(not null)).as(MGenericType)
+               var mtype = v.unanchor_type(self.mtype.as(not null)).as(MClassType)
                var elttype = mtype.arguments.first
                return v.array_instance(val, elttype)
        end
@@ -1125,9 +1375,9 @@ redef class AStringFormExpr
        do
                var txt = self.value.as(not null)
                var nat = v.native_string_instance(txt)
-               var res = new Instance(v.mainmodule.get_primitive_class("String").mclass_type)
+               var res = new MutableInstance(v.mainmodule.get_primitive_class("String").mclass_type)
                v.init_instance(res)
-               v.send(v.mainmodule.force_get_primitive_method("from_cstring", res.mtype), [res, nat])
+               v.send(v.force_get_primitive_method("from_cstring", res.mtype), [res, nat])
                v.check_init_instance(res)
                return res
        end
@@ -1138,10 +1388,12 @@ redef class ASuperstringExpr
        do
                var array = new Array[Instance]
                for nexpr in n_exprs do
-                       array.add(v.expr(nexpr))
+                       var i = v.expr(nexpr)
+                       if i == null then return null
+                       array.add(i)
                end
                var i = v.array_instance(array, v.mainmodule.get_primitive_class("Object").mclass_type)
-               var res = v.send(v.mainmodule.force_get_primitive_method("to_s", i.mtype), [i])
+               var res = v.send(v.force_get_primitive_method("to_s", i.mtype), [i])
                assert res != null
                return res
        end
@@ -1151,11 +1403,13 @@ redef class ACrangeExpr
        redef fun expr(v)
        do
                var e1 = v.expr(self.n_expr)
+               if e1 == null then return null
                var e2 = v.expr(self.n_expr2)
+               if e2 == null then return null
                var mtype = v.unanchor_type(self.mtype.as(not null))
-               var res = new Instance(mtype)
+               var res = new MutableInstance(mtype)
                v.init_instance(res)
-               v.send(v.mainmodule.force_get_primitive_method("init", mtype), [res, e1, e2])
+               v.send(v.force_get_primitive_method("init", mtype), [res, e1, e2])
                v.check_init_instance(res)
                return res
        end
@@ -1165,11 +1419,13 @@ redef class AOrangeExpr
        redef fun expr(v)
        do
                var e1 = v.expr(self.n_expr)
+               if e1 == null then return null
                var e2 = v.expr(self.n_expr2)
+               if e2 == null then return null
                var mtype = v.unanchor_type(self.mtype.as(not null))
-               var res = new Instance(mtype)
+               var res = new MutableInstance(mtype)
                v.init_instance(res)
-               v.send(v.mainmodule.force_get_primitive_method("without_last", mtype), [res, e1, e2])
+               v.send(v.force_get_primitive_method("without_last", mtype), [res, e1, e2])
                v.check_init_instance(res)
                return res
        end
@@ -1200,6 +1456,7 @@ redef class AIsaExpr
        redef fun expr(v)
        do
                var i = v.expr(self.n_expr)
+               if i == null then return null
                var mtype = v.unanchor_type(self.cast_type.as(not null))
                return v.bool_instance(v.is_subtype(i.mtype, mtype))
        end
@@ -1209,6 +1466,7 @@ redef class AAsCastExpr
        redef fun expr(v)
        do
                var i = v.expr(self.n_expr)
+               if i == null then return null
                var mtype = v.unanchor_type(self.mtype.as(not null))
                if not v.is_subtype(i.mtype, mtype) then
                        #fatal(v, "Cast failed expected {mtype}, got {i}")
@@ -1222,6 +1480,7 @@ redef class AAsNotnullExpr
        redef fun expr(v)
        do
                var i = v.expr(self.n_expr)
+               if i == null then return null
                var mtype = v.unanchor_type(self.mtype.as(not null))
                if i.mtype isa MNullType then
                        fatal(v, "Cast failed")
@@ -1244,6 +1503,7 @@ redef class AOnceExpr
                        return v.onces[self]
                else
                        var res = v.expr(self.n_expr)
+                       if res == null then return null
                        v.onces[self] = res
                        return res
                end
@@ -1254,12 +1514,26 @@ redef class ASendExpr
        redef fun expr(v)
        do
                var recv = v.expr(self.n_expr)
+               if recv == null then return null
                var args = [recv]
-               for a in compute_raw_arguments do
-                       args.add(v.expr(a))
+               for a in self.raw_arguments.as(not null) do
+                       var i = v.expr(a)
+                       if i == null then return null
+                       args.add(i)
+               end
+               for c in self.n_closure_defs do
+                       var mtype = c.mclosure.mtype
+                       var instance = new ClosureInstance(mtype, v.frame, c)
+                       args.add(instance)
                end
                var mproperty = self.mproperty.as(not null)
-               return v.send(mproperty, args)
+
+               var res = v.send(mproperty, args)
+               if v.is_break(self.escapemark) then
+                       res = v.escapevalue
+                       v.escapevalue = null
+               end
+               return res
        end
 end
 
@@ -1267,11 +1541,15 @@ redef class ASendReassignFormExpr
        redef fun stmt(v)
        do
                var recv = v.expr(self.n_expr)
+               if recv == null then return
                var args = [recv]
-               for a in compute_raw_arguments do
-                       args.add(v.expr(a))
+               for a in self.raw_arguments.as(not null) do
+                       var i = v.expr(a)
+                       if i == null then return
+                       args.add(i)
                end
                var value = v.expr(self.n_value)
+               if value == null then return
 
                var mproperty = self.mproperty.as(not null)
                var read = v.send(mproperty, args)
@@ -1292,7 +1570,9 @@ redef class ASuperExpr
                var recv = v.frame.arguments.first
                var args = [recv]
                for a in self.n_args.n_exprs do
-                       args.add(v.expr(a))
+                       var i = v.expr(a)
+                       if i == null then return null
+                       args.add(i)
                end
                if args.length == 1 then
                        args = v.frame.arguments
@@ -1310,12 +1590,7 @@ redef class ASuperExpr
 
                # stantard call-next-method
                var mpropdef = v.frame.mpropdef
-               # FIXME: we do not want an ugly static call!
-               var mpropdefs = mpropdef.mproperty.lookup_super_definitions(mpropdef.mclassdef.mmodule, mpropdef.mclassdef.bound_mtype)
-               if mpropdefs.length != 1 then
-                       debug("MPRODFEFS for super {mpropdef} for {recv}: {mpropdefs.join(", ")}")
-               end
-               mpropdef = mpropdefs.first
+               mpropdef = mpropdef.lookup_next_definition(v.mainmodule, recv.mtype)
                assert mpropdef isa MMethodDef
                var res = v.call(mpropdef, args)
                return res
@@ -1326,11 +1601,13 @@ redef class ANewExpr
        redef fun expr(v)
        do
                var mtype = v.unanchor_type(self.mtype.as(not null))
-               var recv = new Instance(mtype)
+               var recv: Instance = new MutableInstance(mtype)
                v.init_instance(recv)
                var args = [recv]
                for a in self.n_args.n_exprs do
-                       args.add(v.expr(a))
+                       var i = v.expr(a)
+                       if i == null then return null
+                       args.add(i)
                end
                var mproperty = self.mproperty.as(not null)
                var res2 = v.send(mproperty, args)
@@ -1347,6 +1624,8 @@ redef class AAttrExpr
        redef fun expr(v)
        do
                var recv = v.expr(self.n_expr)
+               if recv == null then return null
+               if recv.mtype isa MNullType then fatal(v, "Reciever is null")
                var mproperty = self.mproperty.as(not null)
                return v.read_attribute(mproperty, recv)
        end
@@ -1356,8 +1635,12 @@ redef class AAttrAssignExpr
        redef fun stmt(v)
        do
                var recv = v.expr(self.n_expr)
+               if recv == null then return
+               if recv.mtype isa MNullType then fatal(v, "Reciever is null")
                var i = v.expr(self.n_value)
+               if i == null then return
                var mproperty = self.mproperty.as(not null)
+               assert recv isa MutableInstance
                recv.attributes[mproperty] = i
        end
 end
@@ -1366,11 +1649,15 @@ redef class AAttrReassignExpr
        redef fun stmt(v)
        do
                var recv = v.expr(self.n_expr)
+               if recv == null then return
+               if recv.mtype isa MNullType then fatal(v, "Reciever is null")
                var value = v.expr(self.n_value)
+               if value == null then return
                var mproperty = self.mproperty.as(not null)
                var attr = v.read_attribute(mproperty, recv)
                var res = v.send(reassign_property.mproperty, [attr, value])
                assert res != null
+               assert recv isa MutableInstance
                recv.attributes[mproperty] = res
        end
 end
@@ -1379,11 +1666,30 @@ redef class AIssetAttrExpr
        redef fun expr(v)
        do
                var recv = v.expr(self.n_expr)
+               if recv == null then return null
+               if recv.mtype isa MNullType then fatal(v, "Reciever is null")
                var mproperty = self.mproperty.as(not null)
+               assert recv isa MutableInstance
                return v.bool_instance(recv.attributes.has_key(mproperty))
        end
 end
 
+redef class AClosureCallExpr
+       redef fun expr(v)
+       do
+               var args = new Array[Instance]
+               for a in self.n_args.n_exprs do
+                       var i = v.expr(a)
+                       if i == null then return null
+                       args.add(i)
+               end
+               var i = v.frame.map[self.variable.as(not null)]
+               assert i isa ClosureInstance
+               var res = v.call_closure(i, args)
+               return res
+       end
+end
+
 redef class ADebugTypeExpr
        redef fun stmt(v)
        do