nitj: avoid calls to abstract methods

[nit.git] / src / compiler / java_compiler.nit

# This file is part of NIT ( http://www.nitlanguage.org ).
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

# Compile Nit code to Java code
#
# 3 runtime structures are used to represent Nit instance in Java generated code:
# * `RTClass` to represent a class, it's super-type table and its VFT
# * `RTMethod` to reprensent a compiled method definition
# * `RTVal` to reprensent a Nit instance, the null value or a native value
#
# More details are given in the documentation of these 3 classes.
#
# TODO Factorize with `abstract_compiler`
module java_compiler

import rapid_type_analysis
import frontend

redef class ToolContext

        # Where to output the generated binary
        var opt_output = new OptionString("Output file", "-o", "--output")

        # Where to output tmp files
        var opt_compile_dir = new OptionString("Directory used to generate temporary files", "--compile-dir")

        redef init do
                super
                option_context.add_option(opt_output, opt_compile_dir)
        end
end

redef class ModelBuilder

        # Start the Java compiler
        fun run_java_compiler(mainmodule: MModule, runtime_type_analysis: RapidTypeAnalysis) do
                var time0 = get_time
                toolcontext.info("*** GENERATING JAVA ***", 1)

                var compiler = new JavaCompiler(mainmodule, self, runtime_type_analysis)
                compiler.do_compilation

                var time1 = get_time
                toolcontext.info("*** END GENERATING JAVA: {time1-time0} ***", 2)
                write_and_make(compiler)
        end

        # Write Java code and compile it into an executable jar
        fun write_and_make(compiler: JavaCompiler) do
                var time0 = get_time
                toolcontext.info("*** WRITING JAVA ***", 1)

                compiler.compile_dir.mkdir

                var jfiles = write_java_files(compiler)

                var time1 = get_time
                toolcontext.info("*** END WRITING JAVA: {time1-time0} ***", 2)

                time0 = time1
                toolcontext.info("*** COMPILING JAVA ***", 1)

                build_with_make(compiler, jfiles)
                write_shell_script(compiler)

                time1 = get_time
                toolcontext.info("*** END COMPILING JAVA: {time1-time0} ***", 2)
        end

        # Write files managed by `compiler` into concrete files
        fun write_java_files(compiler: JavaCompiler): Array[String] do
                var jfiles = new Array[String]
                for f in compiler.files do
                        var file = new FileWriter.open("{compiler.compile_dir}/{f.filename}")
                        for line in f.lines do file.write(line)
                        file.close
                        jfiles.add(f.filename)
                end
                return jfiles
        end

        # Compile Java generated files using `make`
        fun build_with_make(compiler: JavaCompiler, jfiles: Array[String]) do
                write_manifest(compiler)
                write_makefile(compiler, jfiles)
                var compile_dir = compiler.compile_dir
                var outname = compiler.outname.to_path.filename
                toolcontext.info("make -N -C {compile_dir} -f {outname}.mk", 2)
                var res
                if toolcontext.verbose_level >= 3 then
                        res = sys.system("make -B -C {compile_dir} -f {outname}.mk 2>&1")
                else
                        res = sys.system("make -B -C {compile_dir} -f {outname}.mk 2>&1 > /dev/null")
                end
                if res != 0 then toolcontext.error(null, "make failed! Error code: {res}.")
        end

        # Write the Makefile used to compile Java generated files into an executable jar
        fun write_makefile(compiler: JavaCompiler, jfiles: Array[String]) do
                # list class files from jfiles
                var ofiles = new List[String]
                for f in jfiles do ofiles.add(f.strip_extension(".java") + ".class")

                var compile_dir = compiler.compile_dir
                var outname = compiler.outname.to_path.filename
                var outpath = (sys.getcwd / compiler.outname).simplify_path
                var makename = "{compile_dir}/{outname}.mk"
                var makefile = new FileWriter.open(makename)

                makefile.write("JC = javac\n")
                makefile.write("JAR = jar\n\n")

                makefile.write("all: {outpath}.jar\n\n")

                makefile.write("{outpath}.jar: {compiler.mainmodule.jname}_Main.class\n")
                makefile.write("\t$(JAR) cfm {outpath}.jar {outname}.mf {ofiles.join(" ")}\n\n")

                makefile.write("{compiler.mainmodule.jname}_Main.class:\n")
                makefile.write("\t$(JC) {jfiles.join(" ")}\n\n")

                makefile.write("clean:\n")
                makefile.write("\trm {ofiles.join(" ")} 2>/dev/null\n\n")

                makefile.close
                toolcontext.info("Generated makefile: {makename}", 2)
        end

        # Write the Java manifest file
        private fun write_manifest(compiler: JavaCompiler) do
                var compile_dir = compiler.compile_dir
                var outname = compiler.outname.to_path.filename
                var maniffile = new FileWriter.open("{compile_dir}/{outname}.mf")
                maniffile.write("Manifest-Version: 1.0\n")
                maniffile.write("Main-Class: {compiler.mainmodule.jname}_Main\n")
                maniffile.close
        end

        # Write a simple bash script that runs the jar like it was a binary generated by nitc
        private fun write_shell_script(compiler: JavaCompiler) do
                var outname = compiler.outname
                var shfile = new FileWriter.open(outname)
                shfile.write("#!/bin/bash\n")
                shfile.write("java -jar {outname}.jar \"$@\"\n")
                shfile.close
                sys.system("chmod +x {outname}")
        end
end

# Compiler that translates Nit code to Java code
class JavaCompiler
        # The main module of the program currently compiled
        var mainmodule: MModule

        # Modelbuilder used to know the model and the AST
        var modelbuilder: ModelBuilder

        # The result of the RTA (used to know live types and methods)
        var runtime_type_analysis: RapidTypeAnalysis

        # Where to generate tmp files
        var compile_dir: String is lazy do
                var dir = modelbuilder.toolcontext.opt_compile_dir.value
                if dir == null then dir = "nitj_compile"
                return dir
        end

        # Name of the generated executable
        var outname: String is lazy do
                var name = modelbuilder.toolcontext.opt_output.value
                if name == null then name = mainmodule.jname
                return name
        end

        # The list of all associated files
        # Used to generate .java files
        var files: Array[JavaCodeFile] = new Array[JavaCodeFile]

        # Force the creation of a new file
        # The point is to avoid contamination between must-be-compiled-separately files
        fun new_file(name: String): JavaCodeFile do
                var file = new JavaCodeFile(name)
                files.add(file)
                return file
        end

        # Kind of visitor to use
        type VISITOR: JavaCompilerVisitor

        # Initialize a visitor specific for the compiler engine
        fun new_visitor(filename: String): VISITOR do
                return new JavaCompilerVisitor(self, new_file(filename))
        end

        # RuntimeModel representation
        private var rt_model: JavaRuntimeModel is lazy do return new JavaRuntimeModel

        # Compile Nit code to Java
        fun do_compilation do
                # compile java classes used to represents the runtime model of the program
                rt_model.compile_rtmodel(self)
                compile_box_kinds

                # compile class structures
                compile_mclasses_to_java

                # compile method structures
                compile_mmethods_to_java

                # TODO compile main
                modelbuilder.toolcontext.info("NOT YET IMPLEMENTED", 0)
        end

        # Prepare the boxes used to represent Java primitive types
        fun compile_box_kinds do
                # Collect all bas box class
                # FIXME: this is not completely fine with a separate compilation scheme
                for classname in ["Int", "Bool", "Byte", "Char", "Float"] do
                        var classes = mainmodule.model.get_mclasses_by_name(classname)
                        if classes == null then continue
                        assert classes.length == 1 else print classes.join(", ")
                        box_kinds.add(classes.first.mclass_type)
                end
        end

        # Types of boxes used to represent Java primitive types
        var box_kinds = new Array[MClassType]

        # Generate a `RTClass` for each `MClass` found in model
        #
        # This is a global phase because we need to know all the program to build
        # attributes, fill vft and type table.
        fun compile_mclasses_to_java do
                for mclass in mainmodule.model.mclasses do
                        mclass.compile_to_java(new_visitor("{mclass.rt_name}.java"))
                end
        end

        # Generate a `RTMethod` for each `MMethodDef` found in model
        #
        # This is a separate phase.
        fun compile_mmethods_to_java do
                for mmodule in mainmodule.in_importation.greaters do
                        for mclassdef in mmodule.mclassdefs do
                                for mdef in mclassdef.mpropdefs do
                                        if mdef isa MMethodDef then
                                                mdef.compile_to_java(new_visitor("{mdef.rt_name}.java"))
                                        end
                                end
                        end
                end
        end
end

# The class visiting the AST
#
# A visitor is attached to one JavaCodeFile it writes into.
class JavaCompilerVisitor
        super Visitor

        # JavaCompiler used with this visitor
        type COMPILER: JavaCompiler

        # The associated compiler
        var compiler: JavaCompiler

        # The file to write generated code into
        var file: JavaCodeFile

        # Names handling

        private var names = new HashSet[String]
        private var last: Int = 0

        # Return a new name based on `s` and unique in the visitor
        fun get_name(s: String): String do
                if not self.names.has(s) then
                        self.names.add(s)
                        return s
                end
                var i = self.last + 1
                loop
                        var s2 = s + i.to_s
                        if not self.names.has(s2) then
                                self.last = i
                                self.names.add(s2)
                                return s2
                        end
                        i = i + 1
                end
        end

        # Variables handling

        # Registered variables
        protected var variables = new HashMap[Variable, RuntimeVariable]

        # Return the local RuntimeVariable associated to a Nit local variable
        fun variable(variable: Variable): RuntimeVariable do
                if variables.has_key(variable) then
                        return variables[variable]
                else
                        var name = get_name("var_{variable.name}")
                        var mtype = variable.declared_type.as(not null)
                        mtype = anchor(mtype)
                        var res = decl_var(name, mtype)
                        variables[variable] = res
                        return res
                end
        end

        # Return a new uninitialized local RuntimeVariable with `name`
        fun decl_var(name: String, mtype: MType): RuntimeVariable do
                var res = new RuntimeVariable(name, mtype, mtype)
                res.is_boxed = not mtype.is_java_primitive
                add("{mtype.java_type} {name} /* : {mtype} */;")
                return res
        end

        # Return a new uninitialized local RuntimeVariable
        fun new_var(mtype: MType): RuntimeVariable do
                mtype = anchor(mtype)
                var name = self.get_name("var")
                return decl_var(name, mtype)
        end

        # Calls handling

        # The current `JavaStaticFrame`
        var frame: nullable JavaStaticFrame = null is writable

        # Return a new local RuntimeVariable initialized from `args[0]`
        fun new_recv(mtype: MType): RuntimeVariable do
                var res = new_var(mtype)
                add("{res} = args[0];")
                return res
        end

        # Calls handling

        # Compile a call within a callsite
        fun compile_callsite(callsite: CallSite, arguments: Array[RuntimeVariable]): nullable RuntimeVariable do
                var initializers = callsite.mpropdef.initializers
                if not initializers.is_empty then
                        var recv = arguments.first

                        var i = 1
                        for p in initializers do
                                if p isa MMethod then
                                        var args = [recv]
                                        var msignature = p.intro.msignature
                                        if msignature != null then
                                                for x in msignature.mparameters do
                                                        args.add arguments[i]
                                                        i += 1
                                                end
                                        end
                                        send(p, args)
                                else if p isa MAttribute then
                                        info("NOT YET IMPLEMENTED {class_name}::compile_callsite for MAttribute `{p}`")
                                        #self.write_attribute(p, recv, arguments[i])
                                        i += 1
                                else abort
                        end
                        assert i == arguments.length

                        return send(callsite.mproperty, [recv])
                end

                return send(callsite.mproperty, arguments)
        end

        # Evaluate `args` as expressions in the call of `mpropdef` on `recv`.
        #
        # This method is used to manage varargs in signatures and returns the real array
        # of runtime variables to use in the call.
        fun varargize(mpropdef: MMethodDef, map: nullable SignatureMap, recv: RuntimeVariable, args: SequenceRead[AExpr]): Array[RuntimeVariable] do
                var msignature = mpropdef.new_msignature or else mpropdef.msignature.as(not null)
                var res = new Array[RuntimeVariable]
                res.add(recv)

                if msignature.arity == 0 then return res

                if map == null then
                        assert args.length == msignature.arity
                        for ne in args do
                                res.add expr(ne, null)
                        end
                        return res
                end

                # Eval in order of arguments, not parameters
                var exprs = new Array[RuntimeVariable].with_capacity(args.length)
                for ne in args do
                        exprs.add expr(ne, null)
                end

                # Fill `res` with the result of the evaluation according to the mapping
                for i in [0..msignature.arity[ do
                        var param = msignature.mparameters[i]
                        var j = map.map.get_or_null(i)
                        if j == null then
                                # default value
                                res.add(null_instance)
                                continue
                        end
                        if param.is_vararg and map.vararg_decl > 0 then
                                var vararg = exprs.sub(j, map.vararg_decl)
                                var elttype = param.mtype
                                var arg = self.vararg_instance(mpropdef, recv, vararg, elttype)
                                res.add(arg)
                                continue
                        end
                        res.add exprs[j]
                end
                return res
        end

        #  Generate a static call on a method definition (no receiver needed).
        fun static_call(mmethoddef: MMethodDef, arguments: Array[RuntimeVariable]): nullable RuntimeVariable do
                var res: nullable RuntimeVariable
                var ret = mmethoddef.msignature.as(not null).return_mtype
                if ret == null then
                        res = null
                else
                        ret = ret.resolve_for(mmethoddef.mclassdef.bound_mtype, mmethoddef.mclassdef.bound_mtype, mmethoddef.mclassdef.mmodule, true)
                        res = self.new_var(ret)
                end

                # Autobox arguments
                adapt_signature(mmethoddef, arguments)

                var rt_name = mmethoddef.rt_name
                if res == null then
                        add("{rt_name}.get{rt_name}().exec(new RTVal[]\{{arguments.join(",")}\});")
                        return null
                end
                var ress = new_expr("{rt_name}.get{rt_name}().exec(new RTVal[]\{{arguments.join(",")}\});", compiler.mainmodule.object_type)
                assign(res, ress)
                return res
        end

        #  Generate a polymorphic send for `method` with `arguments`
        fun send(mmethod: MMethod, arguments: Array[RuntimeVariable]): nullable RuntimeVariable do
                # Shortcut calls on primitives
                if arguments.first.mcasttype.is_java_primitive then
                        return monomorphic_send(mmethod, arguments.first.mcasttype, arguments)
                end
                # Polymorphic send
                return table_send(mmethod, arguments)
        end


        # Handle common special cases before doing the effective method invocation
        # This methods handle the `==` and `!=` methods and the case of the null receiver.
        # Note: a { is open in the generated C, that enclose and protect the effective method invocation.
        # Client must not forget to close the } after them.
        #
        # The value returned is the result of the common special cases.
        # If not null, client must compile it with the result of their own effective method invocation.
        #
        # If `before_send` can shortcut the whole message sending, a dummy `if(0){`
        # is generated to cancel the effective method invocation that will follow
        # TODO: find a better approach
        private fun before_send(res: nullable RuntimeVariable, mmethod: MMethodDef, arguments: Array[RuntimeVariable]) do
                var bool_type = compiler.mainmodule.bool_type
                var recv = arguments.first
                var consider_null = mmethod.name == "==" or mmethod.name == "!=" or mmethod.name == "is_same_instance"
                if recv.mcasttype isa MNullableType or recv.mcasttype isa MNullType then
                        add("if ({recv} == null || {recv}.is_null()) \{")
                        if mmethod.name == "==" or mmethod.name == "is_same_instance" then
                                if res == null then res = new_var(bool_type)
                                var arg = arguments[1]
                                if arg.mcasttype isa MNullableType then
                                        add("{res} = ({arg} == null || {arg}.is_null());")
                                else if arg.mcasttype isa MNullType then
                                        add("{res} = true; /* is null */")
                                else
                                        add("{res} = false; /* {arg.inspect} cannot be null */")
                                end
                        else if mmethod.name == "!=" then
                                if res == null then res = new_var(bool_type)
                                # res = self.new_var(bool_type)
                                var arg = arguments[1]
                                if arg.mcasttype isa MNullableType then
                                        add("{res} = ({arg} != null && !{arg}.is_null());")
                                else if arg.mcasttype isa MNullType then
                                        add("{res} = false; /* is null */")
                                else
                                        add("{res} = true; /* {arg.inspect} cannot be null */")
                                end
                        else
                                add_abort("Receiver is null")
                                ret(null_instance)
                        end
                        add("\} else \{")
                else
                        add "\{"
                        add "/* recv ({recv}) cannot be null since it's a {recv.mcasttype}"
                end
                if consider_null then
                        var arg = arguments[1]
                        if arg.mcasttype isa MNullType then
                                if res == null then res = new_var(bool_type)
                                if mmethod.name == "!=" then
                                        add("{res} = true; /* arg is null and recv is not */")
                                else # `==` and `is_same_instance`
                                        add("{res} = false; /* arg is null but recv is not */")
                                end
                                add("\}") # closes the null case
                                add("if (false) \{") # what follow is useless, Javac will drop it
                        end
                end
        end

        # Perform a method call through vft
        private fun table_send(mmethod: TableCallable, arguments: Array[RuntimeVariable]): nullable RuntimeVariable do
                var mdef: MMethodDef
                var name: String
                if mmethod isa MMethod then
                        mdef = mmethod.intro
                        name = mmethod.full_name
                else if mmethod isa MMethodDef then
                        mdef = mmethod
                        name = mmethod.full_name
                else
                        abort
                end

                var recv = arguments.first
                var rect = mdef.mclassdef.bound_mtype
                var msignature = mdef.msignature.as(not null)
                msignature = msignature.resolve_for(rect, rect, compiler.mainmodule, true)
                adapt_signature(mdef, arguments)

                var res: nullable RuntimeVariable
                var ret = msignature.return_mtype
                if ret == null then
                        res = null
                else
                        res = self.new_var(ret)
                end

                before_send(res, mdef, arguments)

                add "/* concrete call to {mdef} */"
                if res != null then
                        var ress = new_expr("{recv}.rtclass.vft.get(\"{name}\").exec(new RTVal[]\{{arguments.join(",")}\});", compiler.mainmodule.object_type)
                        assign(res, ress)
                else
                        add("{recv}.rtclass.vft.get(\"{name}\").exec(new RTVal[]\{{arguments.join(",")}\});")
                end

                add("\}") # closes the null case

                return res
        end

        # Generate a monomorphic send for the method `m`, the type `t` and the arguments `args`
        fun monomorphic_send(m: MMethod, t: MType, args: Array[RuntimeVariable]): nullable RuntimeVariable do
                assert t isa MClassType
                var propdef = m.lookup_first_definition(self.compiler.mainmodule, t)
                return self.static_call(propdef, args)
        end

        # Code generation

        # Add a line (will be suffixed by `\n`)
        fun add(line: String) do file.lines.add("{line}\n")

        # Add a new partial line (no `\n` suffix)
        fun addn(line: String) do file.lines.add(line)

        # Compile a statement (if any)
        fun stmt(nexpr: nullable AExpr) do
                if nexpr == null then return
                var old = self.current_node
                current_node = nexpr
                nexpr.stmt(self)
                current_node = old
        end

        # Compile an expression an return its result
        # `mtype` is the expected return type, pass null if no specific type is expected.
        fun expr(nexpr: AExpr, mtype: nullable MType): RuntimeVariable do
                var old = current_node
                current_node = nexpr

                var res = null
                if nexpr.mtype != null then
                        res = nexpr.expr(self)
                end

                if mtype != null then
                        mtype = anchor(mtype)
                        res = autobox(res, mtype)
                end

                current_node = old
                return res
        end

        # Correctly assign a left and a right value
        # Boxing and unboxing is performed if required
        fun assign(left, right: RuntimeVariable) do
                add("{left} = {autobox(right, left.mtype)};")
        end

        # Generate a return with `value`
        fun ret(value: RuntimeVariable) do
                var frame = self.frame
                assert frame != null
                var returnvar = frame.returnvar
                if returnvar != null then
                        assign(returnvar, value)
                end
                self.add("break {frame.returnlabel.as(not null)};")
        end

        # Return a new local RuntimeVariable initialized with the Java expression `jexpr`.
        #
        # `mtype` is used for the Java return variable initialization.
        fun new_expr(jexpr: String, mtype: MType): RuntimeVariable do
                var res = new_var(mtype)
                add("{res} = {jexpr};")
                return res
        end

        # Generate generic abort
        #
        # Used by aborts, asserts, casts, etc.
        fun add_abort(message: String) do
                add("System.err.print(\"Runtime error: {message}\");")
                var node = current_node
                if node != null then
                        add("System.err.print(\" ({node.location.short_location})\");")
                end
                add("System.err.println(\"\");")
                add("System.exit(1);")
        end

        # Types handling

        # Anchor a type to the main module and the current receiver
        fun anchor(mtype: MType): MType do
                if not mtype.need_anchor then return mtype
                return mtype.anchor_to(compiler.mainmodule, frame.as(not null).receiver)
        end

        # Adapt the arguments of a method according to targetted `MMethodDef`
        fun adapt_signature(m: MMethodDef, args: Array[RuntimeVariable]) do
                var msignature = m.msignature.as(not null).resolve_for(
                        m.mclassdef.bound_mtype,
                        m.mclassdef.bound_mtype,
                        m.mclassdef.mmodule, true)
                args.first = autobox(args.first, compiler.mainmodule.object_type)
                for i in [0..msignature.arity[ do
                        args[i+1] = autobox(args[i + 1], compiler.mainmodule.object_type)
                end
        end

        # Box primitive `value` to `mtype`.
        private fun box(value: RuntimeVariable, mtype: MType): RuntimeVariable do
                if value.is_boxed then return value
                var obj_type = compiler.mainmodule.object_type
                if value.mtype isa MNullType then
                        return new_expr("new RTVal(null, null)", compiler.mainmodule.model.null_type)
                end
                var mbox = value.mtype.as(MClassType).mclass
                return new_expr("new RTVal({mbox.rt_name}.get{mbox.rt_name}(), {value})", obj_type)
        end

        # Unbox primitive `value` to `mtype`.
        private fun unbox(value: RuntimeVariable, mtype: MType): RuntimeVariable do
                if not value.is_boxed then return value
                if not mtype.is_java_primitive then return value
                if compiler.box_kinds.has(mtype) then
                        return new_expr("({mtype.java_type}){value}.value", mtype)
                else
                        info "NOT YET IMPLEMENTED unbox for {value} ({mtype})"
                        abort
                end
        end

        # Box or unbox primitive `value` to `mtype` if needed.
        private fun autobox(value: RuntimeVariable, mtype: MType): RuntimeVariable do
                if mtype.is_java_primitive then return unbox(value, mtype)
                return box(value, mtype)
        end

        # Can this `value` be a primitive Java value?
        private fun can_be_primitive(value: RuntimeVariable): Bool do
                var t = value.mcasttype.undecorate
                if not t isa MClassType then return false
                var k = t.mclass.kind
                return k == interface_kind or t.is_java_primitive
        end

        # Native instances

        # Generate an integer value
        fun int_instance(value: Int): RuntimeVariable do
                var t = compiler.mainmodule.int_type
                return new RuntimeVariable(value.to_s, t, t)
        end

        # Generate a byte value
        fun byte_instance(value: Byte): RuntimeVariable do
                var t = compiler.mainmodule.byte_type
                return new RuntimeVariable(value.to_s, t, t)
        end

        # Generate a char value
        fun char_instance(value: Char): RuntimeVariable do
                var t = compiler.mainmodule.char_type
                return new RuntimeVariable("'{value.to_s.escape_to_c}'", t, t)
        end

        # Generate a float value
        #
        # FIXME pass a Float, not a string
        fun float_instance(value: String): RuntimeVariable do
                var t = compiler.mainmodule.float_type
                return new RuntimeVariable(value.to_s, t, t)
        end

        # Generate an integer value
        fun bool_instance(value: Bool): RuntimeVariable do
                var t = compiler.mainmodule.bool_type
                return new RuntimeVariable(value.to_s, t, t)
        end

        # Generate the `null` value
        fun null_instance: RuntimeVariable do
                var t = compiler.mainmodule.model.null_type
                return new RuntimeVariable("null", t, t)
        end

        # Get an instance of a array for a vararg
        fun vararg_instance(mpropdef: MPropDef, recv: RuntimeVariable, varargs: Array[RuntimeVariable], elttype: MType): RuntimeVariable do
                # TODO handle dynamic types
                info("NOT YET IMPLEMENTED vararg_instance")
                return null_instance
                # TODO return array_instance(varargs, elttype)
        end

        # Utils

        # Display a info message
        fun info(str: String) do compiler.modelbuilder.toolcontext.info(str, 0)
end

# A file containing Java code.
class JavaCodeFile

        # File name
        var filename: String

        # Lines to write
        var lines: List[String] = new List[String]
end

redef class MEntity
        # A Java compatible name for `self`
        private fun jname: String do return name.to_cmangle
end

# Handler for runtime classes generation
#
# We need 3 kinds of runtime structures:
# * `RTClass` to represent a global class
# * `RTMethod` to represent a method definition
# * `RTVal` to represent runtime variables
class JavaRuntimeModel

        # Compile JavaRuntimeModel structures
        fun compile_rtmodel(compiler: JavaCompiler) do
                compile_rtclass(compiler)
                compile_rtmethod(compiler)
                compile_rtval(compiler)
        end

        # Compile the abstract runtime class structure
        #
        # Runtime classes have 3 attributes:
        # * `class_name`: the class name as a String
        # * `vft`: the virtual function table for the class (flattened)
        # * `supers`: the super type table (used for type tests)
        fun compile_rtclass(compiler: JavaCompiler) do
                var v = compiler.new_visitor("RTClass.java")
                v.add("import java.util.HashMap;")
                v.add("public abstract class RTClass \{")
                v.add("  public String class_name;")
                v.add("  public HashMap<String, RTMethod> vft = new HashMap<>();")
                v.add("  public HashMap<String, RTClass> supers = new HashMap<>();")
                v.add("  protected RTClass() \{\}")
                v.add("\}")
        end

        # Compile the abstract runtime method structure
        #
        # Method body is executed through the `exec` method:
        # * `exec` always take an array of RTVal as arg, the first one must be the receiver
        # * `exec` always returns a RTVal (or null if the Nit return type is void)
        fun compile_rtmethod(compiler: JavaCompiler) do
                var v = compiler.new_visitor("RTMethod.java")
                v.add("public abstract class RTMethod \{")
                v.add("  protected RTMethod() \{\}")
                v.add("  public abstract RTVal exec(RTVal[] args);")
                v.add("\}")
        end

        # Compile the runtime value structure
        #
        # RTVal both represents object instances and primitives values:
        # * object instances:
        #   * `rtclass` the class of the RTVal is instance of
        #   * `attrs` contains the attributes of the instance
        # * primitive values:
        #   * `rtclass` represents the class of the primitive value Nit type
        #   * `value` contains the primitive value of the instance
        # * null values:
        #   * they must have both `rtclass` and `value` as null
        fun compile_rtval(compiler: JavaCompiler) do
                var v = compiler.new_visitor("RTVal.java")
                v.add("import java.util.HashMap;")
                v.add("public class RTVal \{")
                v.add("  public RTClass rtclass;")
                v.add("  public HashMap<String, RTVal> attrs = new HashMap<>();")
                v.add("  Object value;")
                v.add("  public RTVal(RTClass rtclass) \{")
                v.add("    this.rtclass = rtclass;")
                v.add("  \}")
                v.add("  public RTVal(RTClass rtclass, Object value) \{")
                v.add("    this.rtclass = rtclass;")
                v.add("    this.value = value;")
                v.add("  \}")
                v.add("  public boolean is_null() \{ return rtclass == null && value == null; \}")
                v.add("\}")
        end
end

# A runtime variable hold a runtime value in Java.
# Runtime variables are associated to Nit local variables and intermediate results in Nit expressions.
class RuntimeVariable

        # The name of the variable in the Java code
        var name: String

        # The static type of the variable (as declard in Java)
        var mtype: MType

        # The current casted type of the variable (as known in Nit)
        var mcasttype: MType is writable

        # If the variable exaclty a mcasttype?
        # false (usual value) means that the variable is a mcasttype or a subtype.
        var is_exact: Bool = false is writable

        # Is this variable declared as a RTVal or a Java primitive one?
        var is_boxed = false

        redef fun to_s do return name

        redef fun inspect
        do
                var exact_str
                if self.is_exact then
                        exact_str = " exact"
                else
                        exact_str = ""
                end
                var type_str
                if self.mtype == self.mcasttype then
                        type_str = "{mtype}{exact_str}"
                else
                        type_str = "{mtype}({mcasttype}{exact_str})"
                end
                return "<{name}:{type_str}>"
        end
end

# The static context of a visited property in a `JavaCompilerVisitor`
class JavaStaticFrame
        # The associated visitor
        var visitor: JavaCompilerVisitor

        # The executed property.
        # A Method in case of a call, an attribute in case of a default initialization.
        var mpropdef: MPropDef

        # The static type of the receiver
        var receiver: MClassType

        # Arguments of the method (the first is the receiver)
        var arguments: Array[RuntimeVariable]

        # The runtime_variable associated to the return (in a function)
        var returnvar: nullable RuntimeVariable = null is writable

        # The label at the end of the property
        var returnlabel: nullable String = null is writable
end

redef class Location
        # Return a shortened version of the location with `"{file}:{line_start}"`
        fun short_location: String do
                var file = self.file
                if file == null then return "<no file>:{line_start}"
                return "{file.filename.escape_to_c}:{line_start}"
        end
end

redef class MType
        # Return the Java type associated to a given Nit static type
        fun java_type: String do return "RTVal"

        # Is the associated Java type a primitive one?
        #
        # ENSURE `result == (java_type != "Object")`
        var is_java_primitive: Bool is lazy do return java_type != "RTVal"
end

redef class MClassType

        redef var java_type is lazy do
                if mclass.name == "Int" then
                        return "int"
                else if mclass.name == "Bool" then
                        return "boolean"
                else if mclass.name == "Char" then
                        return "char"
                else if mclass.name == "Float" then
                        return "double"
                else if mclass.name == "Byte" then
                        return "byte"
                else if mclass.name == "NativeString" then
                        return "String"
                else if mclass.name == "NativeArray" then
                        return "Array"
                end
                return "RTVal"
        end
end

redef class MClass

        # Runtime name
        private fun rt_name: String do return "RTClass_{intro.mmodule.jname}_{jname}"

        # Generate a Java RTClass for a Nit MClass
        fun compile_to_java(v: JavaCompilerVisitor) do
                v.add("public class {rt_name} extends RTClass \{")
                v.add("  protected static RTClass instance;")
                v.add("  private {rt_name}() \{")
                v.add("    this.class_name = \"{name}\";")
                compile_vft(v)
                compile_type_table(v)
                v.add("  \}")
                v.add("  public static RTClass get{rt_name}() \{")
                v.add("    if(instance == null) \{")
                v.add("      instance = new {rt_name}();")
                v.add("    \}")
                v.add("    return instance;")
                v.add("  \}")
                v.add("\}")
        end

        # Compile the virtual function table for the mclass
        private fun compile_vft(v: JavaCompilerVisitor) do
                # TODO handle generics
                if mclass_type.need_anchor then return
                var mclassdefs = mclass_type.collect_mclassdefs(v.compiler.mainmodule).to_a
                v.compiler.mainmodule.linearize_mclassdefs(mclassdefs)

                var mainmodule = v.compiler.mainmodule
                for mclassdef in mclassdefs.reversed do
                        for mprop in mclassdef.intro_mproperties do
                                var mpropdef = mprop.lookup_first_definition(mainmodule, intro.bound_mtype)
                                if not mpropdef isa MMethodDef then continue
                                var rt_name = mpropdef.rt_name
                                v.add("this.vft.put(\"{mprop.full_name}\", {rt_name}.get{rt_name}());")

                                # fill super next definitions
                                while mpropdef.has_supercall do
                                        var prefix = mpropdef.full_name
                                        mpropdef = mpropdef.lookup_next_definition(mainmodule, intro.bound_mtype)
                                        rt_name = mpropdef.rt_name
                                        v.add("this.vft.put(\"{prefix}\", {rt_name}.get{rt_name}());")
                                end
                        end
                end
        end

        # Compile the type table for the MClass
        fun compile_type_table(v: JavaCompilerVisitor) do
                for pclass in in_hierarchy(v.compiler.mainmodule).greaters do
                        if pclass == self then
                                v.add("supers.put(\"{pclass.jname}\", this);")
                        else
                                v.add("supers.put(\"{pclass.jname}\", {pclass.rt_name}.get{pclass.rt_name}());")
                        end
                end
        end
end

# Used as a common type between MMethod and MMethodDef for `table_send`
private interface TableCallable
end

redef class MMethod
        super TableCallable
end

redef class MMethodDef
        super TableCallable

        # Runtime name
        private fun rt_name: String do
                return "RTMethod_{mclassdef.mmodule.jname}_{mclassdef.mclass.jname}_{mproperty.jname}"
        end

        # Generate a Java RTMethod for `self`
        fun compile_to_java(v: JavaCompilerVisitor) do
                v.add("public class {rt_name} extends RTMethod \{")
                v.add("  protected static RTMethod instance;")
                v.add("  public static RTMethod get{rt_name}() \{")
                v.add("    if(instance == null) \{")
                v.add("      instance = new {rt_name}();")
                v.add("    \}")
                v.add("    return instance;")
                v.add("  \}")
                v.add("  @Override")
                v.add("  public RTVal exec(RTVal[] args) \{")
                compile_inside_to_java(v)
                v.add("  \}")
                v.add("\}")
        end

        # Compile the body of this function
        fun compile_inside_to_java(v: JavaCompilerVisitor) do

                var modelbuilder = v.compiler.modelbuilder
                var node = modelbuilder.mpropdef2node(self)

                if is_abstract then
                        v.add_abort("Abstract method `{mproperty.name}` called on `\"  + {selfvar}.rtclass.class_name +\"`")
                        v.add("return null;")
                        return
                end

                if node isa APropdef then
                        node.compile_to_java(v, self)
                else if node isa AClassdef then
                        # TODO compile attributes
                        v.info("NOT YET IMPLEMENTED attribute handling")
                else
                        abort
                end

        end
end

redef class APropdef

        # Compile that property definition to java code
        fun compile_to_java(v: JavaCompilerVisitor, mpropdef: MMethodDef) do
                v.info("NOT YET IMPLEMENTED {class_name}::compile_to_java")
                v.add("return null;")
        end
end

redef class AMethPropdef
        redef fun compile_to_java(v, mpropdef) do
                # TODO Call the implicit super-init

                # Compile intern methods
                if mpropdef.is_intern then
                        v.info("NOT YET IMPLEMENTED {class_name}::compile_intern")
                        # TODO if compile_intern_to_java(v, mpropdef, arguments) then return
                        v.ret(v.null_instance)
                        return
                end

                # Compile block if any
                var n_block = n_block
                if n_block != null then
                        v.stmt(n_block)
                        return
                end
        end
end

redef class AExpr
        # Try to compile self as an expression
        # Do not call this method directly, use `v.expr` instead
        private fun expr(v: JavaCompilerVisitor): nullable RuntimeVariable do
                v.info("NOT YET IMPLEMENTED {class_name}::expr")
                return null
        end

        # Try to compile self as a statement
        # Do not call this method directly, use `v.stmt` instead
        private fun stmt(v: JavaCompilerVisitor) do expr(v)
end

redef class ABlockExpr
        redef fun stmt(v)
        do
                for e in self.n_expr do v.stmt(e)
        end
        redef fun expr(v)
        do
                var last = self.n_expr.last
                for e in self.n_expr do
                        if e == last then break
                        v.stmt(e)
                end
                return v.expr(last, null)
        end
end

redef class ASendExpr
        redef fun expr(v) do
                var recv = v.expr(n_expr, null)
                var callsite = callsite.as(not null)
                var args = v.varargize(callsite.mpropdef, callsite.signaturemap, recv, raw_arguments)
                return v.compile_callsite(callsite, args)
        end
end

redef class ASelfExpr
        redef fun expr(v) do return v.frame.as(not null).arguments.first
end

redef class AImplicitSelfExpr
        redef fun expr(v) do return v.frame.as(not null).arguments.first
end

redef class AReturnExpr
        redef fun stmt(v) do
                var nexpr = self.n_expr
                var frame = v.frame
                assert frame != null
                if nexpr != null then
                        v.ret(v.expr(nexpr, frame.returnvar.as(not null).mtype))
                else
                        v.ret(v.null_instance)
                end
        end
end

redef class AVardeclExpr
        redef fun stmt(v) do
                var variable = self.variable.as(not null)
                var ne = self.n_expr
                var decl = v.variable(variable)
                if ne != null then
                        var i = v.expr(ne, variable.declared_type)
                        v.assign(decl, i)
                end
        end
end

redef class AVarExpr
        redef fun expr(v) do
                return v.variable(self.variable.as(not null))
        end
end

redef class AVarAssignExpr
        redef fun expr(v) do
                var variable = self.variable.as(not null)
                var i = v.expr(self.n_value, variable.declared_type)
                v.assign(v.variable(variable), i)
                return i
        end
end

redef class AIntExpr
        redef fun expr(v) do return v.int_instance(self.value.as(not null))
end

redef class AByteExpr
        redef fun expr(v) do return v.byte_instance(self.value.as(not null))
end

redef class AFloatExpr
        redef fun expr(v) do return v.float_instance("{self.n_float.text}") # FIXME use value, not n_float
end

redef class ACharExpr
        redef fun expr(v) do return v.char_instance(self.value.as(not null))
end

redef class ATrueExpr
        redef fun expr(v) do return v.bool_instance(true)
end

redef class AFalseExpr
        redef fun expr(v) do return v.bool_instance(false)
end

redef class ANullExpr
        redef fun expr(v) do return v.null_instance
end

redef class AAbortExpr
        redef fun stmt(v) do v.add_abort("Aborted")
end

redef class ADebugTypeExpr
        redef fun stmt(v) do end # do nothing
end