separated state machine generation into an abstract class

src/Main.java

@@ -1,6 +1,8 @@
 import generator.RT;
 import generator.gen.Gen;
 
+import java.util.function.Supplier;
+
 public class Main implements Runnable {
     public static void main(String[] args) {
         RT.runWithGeneratorSupport(Main.class);
@@ -10,6 +12,23 @@ public class Main implements Runnable {
     public void run() {
 //        await();
         lexer();
+//        lambda();
+    }
+
+    void lambda(){
+        var gen = ((Supplier<Gen<Integer, String>>)() -> {
+            Gen.yield(12);
+            return Gen.ret("hello");
+        }).get();
+
+        while(true) {
+            var next = gen.next();
+            if(next instanceof Gen.Yield(var e)) System.out.println(e);
+            else if(next instanceof Gen.Ret(var ret)){
+                System.out.println(ret);
+                break;
+            }
+        }
     }
 
     void await(){
@@ -22,8 +41,11 @@ public class Main implements Runnable {
                 break;
             }
         }
+
+        Runnable meow = () -> {};
     }
 
+
     void lexer(){
         var gen = Lexer.parse("f7(x,y,z,w, u,v, othersIg) = v-(x*y+y+ln(z)^2*sin(z*pi/2))/(w*u)+sqrt(othersIg*120e-1)");
 //        var gen = Examples.test(new double[]{1,2,3,4});

src/generator/future/Future.java

@@ -11,6 +11,10 @@ public interface Future<R> {
         throw new RuntimeException();
     }
 
+    static <R> Future<R> ret(R r){
+        throw new RuntimeException();
+    }
+
     final class Pending{
         private static final Pending INSTANCE = new Pending();
         private Pending(){}

src/generator/runtime/GeneratorBuilder.java

@@ -1,104 +0,0 @@
-package generator.runtime;
-
-import generator.gen.Gen;
-
-import java.lang.classfile.*;
-import java.lang.classfile.attribute.InnerClassInfo;
-import java.lang.classfile.attribute.InnerClassesAttribute;
-import java.lang.classfile.attribute.NestHostAttribute;
-import java.lang.constant.ClassDesc;
-import java.lang.constant.ConstantDescs;
-import java.lang.constant.MethodTypeDesc;
-import java.lang.reflect.AccessFlag;
-import java.util.*;
-
-public class GeneratorBuilder {
-    public final static String PARAM_PREFIX = "param_";
-    public final static String LOCAL_PREFIX = "local_";
-    public final static String STACK_PREFIX = "stack_";
-    public final static String STATE_NAME = "state";
-
-    public final static ClassDesc CD_Gen = ClassDesc.ofDescriptor(Gen.class.descriptorString());
-    public final static ClassDesc CD_Res = ClassDesc.ofDescriptor(Gen.Res.class.descriptorString());
-    public final static ClassDesc CD_Yield = ClassDesc.ofDescriptor(Gen.Yield.class.descriptorString());
-    public final static ClassDesc CD_Ret = ClassDesc.ofDescriptor(Gen.Ret.class.descriptorString());
-    public final static MethodTypeDesc MTD_Res = MethodTypeDesc.of(CD_Res);
-    public final static MethodTypeDesc MTD_Gen_Obj = MethodTypeDesc.of(CD_Gen, ConstantDescs.CD_Object);
-    public final static MethodTypeDesc MTD_Gen = MethodTypeDesc.of(CD_Gen);
-    public static MethodTypeDesc MTD_Obj = MethodTypeDesc.of(ConstantDescs.CD_Object);
-
-    public final ClassDesc CD_this;
-    public final ClassDesc[] params;
-    public final MethodTypeDesc MTD_init;
-    public final int paramSlotOff;
-    public final ClassModel clm;
-
-    public interface ParamConsumer{
-        void consume(String param, int slot, ClassDesc type);
-    }
-
-    public GeneratorBuilder(ClassModel clm, ClassDesc cd, ClassDesc[] params){
-        this.clm = clm;
-        CD_this = cd;
-        this.params = params;
-        MTD_init = MethodTypeDesc.of(ConstantDescs.CD_void, params);
-        paramSlotOff = Arrays.stream(params).mapToInt(p -> TypeKind.from(p).slotSize()).sum();
-    }
-
-    public void params(int slot_start, ParamConsumer consumer){
-        int offset = 0;
-        for (var param : params) {
-            consumer.consume(PARAM_PREFIX+offset, offset+slot_start, param);
-            offset += TypeKind.from(param).slotSize();
-        }
-    }
-
-    public void buildGeneratorMethodShim(CodeBuilder cob){
-        cob.new_(CD_this).dup();
-        params(0, (_, slot, type) -> {
-            cob.loadLocal(TypeKind.from(type), slot);
-        });
-        cob.invokespecial(CD_this, ConstantDescs.INIT_NAME, MTD_init).areturn();
-    }
-
-    public byte[] buildGenerator(CodeModel com){
-        return ClassFile.of(ClassFile.StackMapsOption.STACK_MAPS_WHEN_REQUIRED, ClassFile.AttributesProcessingOption.PASS_ALL_ATTRIBUTES).build(CD_this, clb -> {
-
-            clm.findAttributes(Attributes.sourceFile()).forEach(clb::with);
-            clb.with(InnerClassesAttribute.of(InnerClassInfo.of(CD_this, Optional.of(clm.thisClass().asSymbol()), Optional.of(CD_this.displayName().split("\\$")[1]), AccessFlag.PUBLIC, AccessFlag.FINAL, AccessFlag.STATIC)));
-            clb.with(NestHostAttribute.of(clm.thisClass()));
-
-            clb.withInterfaces(List.of(clb.constantPool().classEntry(CD_Gen)));
-            // parameter fields
-            params(0, (param, _, type) -> {
-                clb.withField(param, type, ClassFile.ACC_PRIVATE);
-            });
-            // fms state
-            clb.withField(STATE_NAME, ConstantDescs.CD_int, ClassFile.ACC_PRIVATE);
-
-            // constructor
-            clb.withMethod(ConstantDescs.INIT_NAME, MTD_init, ClassFile.ACC_PUBLIC, mb -> mb.withCode(cob -> {
-                cob.aload(0).invokespecial(ConstantDescs.CD_Object, ConstantDescs.INIT_NAME, ConstantDescs.MTD_void);
-                params(1, (param, slot, type) -> {
-                    cob.aload(0).loadLocal(TypeKind.from(type), slot).putfield(CD_this, param, type);
-                });
-                cob.return_();
-            }));
-
-            // fms method
-            clb.withMethod("next", MethodTypeDesc.of(CD_Res), ClassFile.ACC_PUBLIC, mb -> mb.withCode(cob -> {
-                buildGeneratorNext(clb, cob, com);
-            }));
-        });
-    }
-
-    private void buildGeneratorNext(ClassBuilder clb, CodeBuilder cob, CodeModel com){
-        cob.trying(
-                tcob -> new StateMachineBuilder(this, clb, tcob, com).generateStateMachine(),
-                // catch anything set our state to -1 and throw the exception
-                ctb -> ctb.catchingAll(
-                        blc -> blc.aload(0).loadConstant(-1).putfield(CD_this, STATE_NAME, ConstantDescs.CD_int).athrow()
-                )
-        ).aconst_null().areturn();
-    }
-}

src/generator/runtime/GeneratorClassLoader.java

@@ -1,21 +1,18 @@
 package generator.runtime;
 
 import generator.gen.Gen;
+import generator.runtime.gen.GenSMBuilder;
 
 import java.io.IOException;
 import java.lang.classfile.*;
 import java.lang.classfile.attribute.*;
 import java.lang.classfile.constantpool.ClassEntry;
 import java.lang.constant.ClassDesc;
-import java.lang.constant.ConstantDescs;
-import java.lang.reflect.AccessFlag;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.util.*;
-import java.util.concurrent.atomic.AtomicReference;
 
 public class GeneratorClassLoader extends ClassLoader {
-    private final HashMap<String, byte[]> customClazzDefMap = new HashMap<>();
     private final HashMap<String, Class<?>> customClazzMap = new HashMap<>();
 
     public GeneratorClassLoader(ClassLoader parent) {
@@ -29,7 +26,6 @@ public class GeneratorClassLoader extends ClassLoader {
         } catch (IOException e) {
             throw new RuntimeException(e);
         }
-        customClazzDefMap.put(name, def);
         customClazzMap.put(name, defineClass(name, def, 0, def.length));
     }
 
@@ -68,8 +64,8 @@ public class GeneratorClassLoader extends ClassLoader {
                         cb.with(mem);
                     } else{
                         var gcd = generatorMethod(cb, mem, clm);
-                        innerCl.add(InnerClassInfo.of(gcd, Optional.of(clm.thisClass().asSymbol()), Optional.of(gcd.displayName()), AccessFlag.PUBLIC, AccessFlag.FINAL, AccessFlag.STATIC));
-                        nestMem.add(ClassDesc.of(gcd.displayName()));
+//                        innerCl.add(InnerClassInfo.of(gcd, Optional.of(clm.thisClass().asSymbol()), Optional.of(gcd.displayName()), AccessFlag.PUBLIC, AccessFlag.FINAL, AccessFlag.STATIC));
+//                        nestMem.add(ClassDesc.of(gcd.displayName()));
                     }
                 }
                 else if (ce instanceof Attribute<?> e){
@@ -85,29 +81,13 @@ public class GeneratorClassLoader extends ClassLoader {
         });
     }
 
-    private ClassDesc generatorMethod(ClassBuilder cb, MethodModel mem, ClassModel clm) {
-
-        AtomicReference<ClassDesc> gcd = new AtomicReference<>();
-
-        cb.withMethod(mem.methodName(), mem.methodType(), mem.flags().flagsMask(), mb -> {
-            for (var me : mem) {
-                if (me instanceof CodeModel com) {
-                    var mts = mem.methodTypeSymbol();
-                    mts = mts.changeReturnType(ConstantDescs.CD_void);
-                    if (!mem.flags().has(AccessFlag.STATIC)) {
-                        mts = mts.insertParameterTypes(0, clm.thisClass().asSymbol());
-                    }
-                    var name = clm.thisClass().name().stringValue()+"$Gen_" + mem.methodName().stringValue() + "_" + customClazzDefMap.size();
-
-                    gcd.set(ClassDesc.of(clm.thisClass().asSymbol().packageName(), name));
-                    var gb = new GeneratorBuilder(clm, gcd.get(), mts.parameterArray());
-
-                    mb.withCode(gb::buildGeneratorMethodShim);
-                    add(gb.CD_this.displayName(), gb.buildGenerator(com));
-                } else mb.with(me);
-            }
+    private ClassDesc generatorMethod(ClassBuilder cb, MethodModel src_mem, ClassModel src_clm) {
+        var com = src_mem.code().get();
+        var gb = new GenSMBuilder(src_clm, src_mem, com);
+        add(gb.CD_this.displayName(), gb.buildStateMachine());
+        cb.withMethod(src_mem.methodName(), src_mem.methodType(), src_mem.flags().flagsMask(), mb -> {
+            mb.withCode(gb::buildSourceMethodShim);
         });
-
-        return gcd.get();
+        return gb.CD_this;
     }
 }

src/generator/runtime/LocalTracker.java

@@ -8,7 +8,7 @@ import java.util.HashMap;
 
 import static java.lang.classfile.attribute.StackMapFrameInfo.SimpleVerificationTypeInfo.TOP;
 
-class LocalTracker {
+public class LocalTracker {
 
     record LocalStore(String name, ClassDesc cd) {
     }
@@ -23,7 +23,7 @@ class LocalTracker {
 
     LocalTracker(StateMachineBuilder smb, CodeModel com) {
         int offset = 0;
-        for (var param : smb.gb.params) {
+        for (var param : smb.params) {
             parameter_map.put(offset, param);
             offset += TypeKind.from(param).slotSize();
         }
@@ -32,8 +32,8 @@ class LocalTracker {
             var entries = new ArrayList<StackMapFrameInfo>();
             for (var smfi : attr.entries()) {
                 var locals = new ArrayList<>(smfi.locals());
-                for (int i = 0; i < smb.gb.params.length; i++) locals.removeFirst();
-                locals.addFirst(StackMapFrameInfo.ObjectVerificationTypeInfo.of(smb.gb.CD_this));
+                for (int i = 0; i < smb.params.length; i++) locals.removeFirst();
+                locals.addFirst(StackMapFrameInfo.ObjectVerificationTypeInfo.of(smb.CD_this));
                 entries.add(StackMapFrameInfo.of(smfi.target(), locals, smfi.stack()));
                 stackMapFrames.put(smfi.target(), entries.getLast());
             }
@@ -57,7 +57,7 @@ class LocalTracker {
                     break;
                 }
             if (name == null) {
-                name = GeneratorBuilder.LOCAL_PREFIX + localStore.size();
+                name = StateMachineBuilder.LOCAL_PREFIX + localStore.size();
                 localStore.add(new LocalStore(name, desc));
             }
             saved.add(new Saved(slot, name, desc));

src/generator/runtime/ParamConsumer.java

@@ -0,0 +1,7 @@
+package generator.runtime;
+
+import java.lang.constant.ClassDesc;
+
+public interface ParamConsumer {
+    void consume(String param, int slot, ClassDesc type);
+}

src/generator/runtime/ReplacementKind.java

@@ -0,0 +1,7 @@
+package generator.runtime;
+
+public enum ReplacementKind {
+    ImmediateReplacingPop,
+    Immediate,
+    ReplacingNextReturn,
+}

src/generator/runtime/SpecialMethod.java

@@ -0,0 +1,7 @@
+package generator.runtime;
+
+import java.lang.constant.ClassDesc;
+import java.lang.constant.MethodTypeDesc;
+
+public record SpecialMethod(ClassDesc owner, String name, MethodTypeDesc desc) {
+}

src/generator/runtime/SpecialMethodHandler.java

@@ -0,0 +1,13 @@
+package generator.runtime;
+
+import java.lang.classfile.CodeBuilder;
+
+public interface SpecialMethodHandler {
+    void handle(StateMachineBuilder smb, CodeBuilder cob);
+
+    default boolean removeCall() {
+        return true;
+    }
+
+    ReplacementKind replacementKind();
+}

src/generator/runtime/StateMachineBuilder.java

@@ -1,162 +1,161 @@
 package generator.runtime;
 
+import generator.gen.Gen;
+
 import java.lang.classfile.*;
+import java.lang.classfile.attribute.InnerClassInfo;
+import java.lang.classfile.attribute.InnerClassesAttribute;
+import java.lang.classfile.attribute.NestHostAttribute;
 import java.lang.classfile.instruction.*;
 import java.lang.constant.ClassDesc;
 import java.lang.constant.ConstantDescs;
 import java.lang.constant.MethodTypeDesc;
-import java.util.ArrayList;
-import java.util.HashMap;
-import java.util.function.Function;
+import java.lang.reflect.AccessFlag;
+import java.util.*;
+import java.util.function.BiFunction;
 
-public class StateMachineBuilder {
-    final ClassBuilder clb;
-    final CodeBuilder cob;
-    final CodeModel com;
-    final GeneratorBuilder gb;
-    final LocalTracker lt;
+public abstract class StateMachineBuilder {
+    public final static String PARAM_PREFIX = "param_";
+    public final static String LOCAL_PREFIX = "local_";
+    public final static String STATE_NAME = "state";
 
-    private HashMap<SpecialMethod, Function<StateMachineBuilder, SpecialMethodHandler>> smmap = new HashMap<>();
-    private boolean ignore_next_pop = false;
-    final ArrayList<SwitchCase> stateSwitchCases = new ArrayList<>();
-    final Label invalidState;
+    private static int sequence;
 
+    public final ClassDesc CD_this;
+    public final ClassDesc[] params;
+    public final MethodTypeDesc MTD_init;
+    public final int paramSlotOff;
 
-    public enum HandlerRan{
-        ImmediateRemovePop,
-        Immediate,
-        ReplacingNextReturn,
-    }
-    public interface SpecialMethodHandler {
-        void handle(StateMachineBuilder smb);
-        default boolean removeCall(){return true;}
-        default HandlerRan handlerRan(){return HandlerRan.ImmediateRemovePop;}
+    public final ClassModel src_clm;
+    public final MethodModel src_mem;
+    public final CodeModel src_com;
+
+    public final LocalTracker lt;
+
+    protected HashMap<SpecialMethod, BiFunction<StateMachineBuilder, CodeBuilder, SpecialMethodHandler>> smmap = new HashMap<>();
+
+    private final ArrayList<SwitchCase> stateSwitchCases = new ArrayList<>();
+
+    protected final String uniqueName(){
+        return sequence+++"";
     }
 
-    public record SpecialMethod(ClassDesc owner, String name, MethodTypeDesc desc) {
-    }
-
-    static class YieldHandler implements SpecialMethodHandler {
-        final int resume_state;
-        final Label resume_label;
-        final boolean is_void;
-
-        public YieldHandler(StateMachineBuilder smb, boolean is_void) {
-            resume_state = smb.add_state(resume_label = smb.cob.newLabel());
-            this.is_void = is_void;
-        }
-
-        @Override
-        public void handle(StateMachineBuilder smb) {
-            if(is_void)smb.cob.aconst_null();
-
-            smb.lt.savingLocals(smb.gb.CD_this, smb.cob, () -> {
-                smb.cob.aload(0).loadConstant(resume_state).putfield(smb.gb.CD_this, GeneratorBuilder.STATE_NAME, TypeKind.INT.upperBound())
-                        .new_(GeneratorBuilder.CD_Yield)
-                        .dup_x1()
-                        .swap()
-                        .invokespecial(GeneratorBuilder.CD_Yield, ConstantDescs.INIT_NAME, MethodTypeDesc.of(ConstantDescs.CD_void, ConstantDescs.CD_Object))
-                        .areturn();
-                smb.cob.labelBinding(resume_label);
-            });
-            smb.ignore_next_pop = true;
+    public void params(int slot_start, ParamConsumer consumer){
+        int offset = 0;
+        for (var param : params) {
+            consumer.consume(PARAM_PREFIX+offset, offset+slot_start, param);
+            offset += TypeKind.from(param).slotSize();
         }
     }
 
-    static class RetHandler implements SpecialMethodHandler {
-        final boolean is_void;
+    public StateMachineBuilder(ClassModel src_clm, MethodModel src_mem, CodeModel src_com){
+        this.src_clm = src_clm;
+        this.src_mem = src_mem;
+        this.src_com = src_com;
 
-        public RetHandler(boolean is_void) {
-            this.is_void = is_void;
+        var mts = src_mem.methodTypeSymbol();
+        mts = mts.changeReturnType(ConstantDescs.CD_void);
+        if (!src_mem.flags().has(AccessFlag.STATIC)) {
+            mts = mts.insertParameterTypes(0, src_clm.thisClass().asSymbol());
+        }
+        var name = src_clm.thisClass().name().stringValue() + "$" + src_mem.methodName().stringValue() + "$" + uniqueName();
+
+        this.CD_this = ClassDesc.of(src_clm.thisClass().asSymbol().packageName(), name);
+        this.params = mts.parameterArray();
+        this.MTD_init = MethodTypeDesc.of(ConstantDescs.CD_void, params);
+        this.paramSlotOff = Arrays.stream(params).mapToInt(p -> TypeKind.from(p).slotSize()).sum();
+
+        this.lt = new LocalTracker(this, src_com);
     }
 
-        public HandlerRan handlerRan(){return HandlerRan.ReplacingNextReturn;}
-
-        @Override
-        public void handle(StateMachineBuilder smb) {
-            if(is_void)smb.cob.aconst_null();
-
-            smb.cob.aload(0).loadConstant(-1).putfield(smb.gb.CD_this, GeneratorBuilder.STATE_NAME, TypeKind.INT.upperBound())
-                    .new_(GeneratorBuilder.CD_Ret)
-                    .dup_x1()
-                    .swap()
-                    .invokespecial(GeneratorBuilder.CD_Ret, ConstantDescs.INIT_NAME, MethodTypeDesc.of(ConstantDescs.CD_void, ConstantDescs.CD_Object))
-                    .areturn();
-        }
-    }
-
-    static class AwaitHandler implements SpecialMethodHandler{
-        final int yield_state;
-        final Label yield_label;
-
-        public AwaitHandler(StateMachineBuilder smb) {
-            yield_state = smb.add_state(yield_label = smb.cob.newLabel());
-        }
-
-        public HandlerRan handlerRan(){return HandlerRan.Immediate;}
-
-        @Override
-        public void handle(StateMachineBuilder smb) {
-            smb.cob.aload(0).loadConstant(yield_state).putfield(smb.gb.CD_this, GeneratorBuilder.STATE_NAME, TypeKind.INT.upperBound());
-            var start = smb.cob.newBoundLabel();
-            smb.cob.dup().dup()
-                    .invokeinterface(GeneratorBuilder.CD_Gen, "next", MethodTypeDesc.of(GeneratorBuilder.CD_Res)).dup()
-                    .instanceOf(GeneratorBuilder.CD_Ret);
-            smb.cob.ifThenElse(bcb -> {
-                bcb.checkcast(GeneratorBuilder.CD_Ret).invokevirtual(GeneratorBuilder.CD_Ret, "v", MethodTypeDesc.of(ConstantDescs.CD_Object)).swap().pop();
-            }, bcb -> {
-                smb.lt.savingLocals(smb.gb.CD_this, bcb, () -> {
-                    bcb.swap().loadLocal(TypeKind.from(smb.gb.CD_this), 0).swap().putfield(smb.gb.CD_this, "meow", GeneratorBuilder.CD_Gen);
-                    bcb.areturn().labelBinding(yield_label);
-                    bcb.loadLocal(TypeKind.from(smb.gb.CD_this), 0).getfield(smb.gb.CD_this, "meow", GeneratorBuilder.CD_Gen);
-                });
-                bcb.goto_(start);
-            });
-
-        }
-    }
-
-    StateMachineBuilder(GeneratorBuilder gb, ClassBuilder clb, CodeBuilder cob, CodeModel com) {
-        this.gb = gb;
-        this.clb = clb;
-        this.cob = cob;
-        this.com = com;
-        this.lt = new LocalTracker(this, com);
-        invalidState = cob.newLabel();
-
-        smmap.put(new SpecialMethod(GeneratorBuilder.CD_Gen, "yield", GeneratorBuilder.MTD_Gen_Obj),smb -> new YieldHandler(smb, false));
-        smmap.put(new SpecialMethod(GeneratorBuilder.CD_Gen, "yield", GeneratorBuilder.MTD_Gen),smb -> new YieldHandler(smb, true));
-        smmap.put(new SpecialMethod(GeneratorBuilder.CD_Gen, "ret", GeneratorBuilder.MTD_Gen_Obj),_ -> new RetHandler(false));
-        smmap.put(new SpecialMethod(GeneratorBuilder.CD_Gen, "ret", GeneratorBuilder.MTD_Gen),_ -> new RetHandler(true));
-        smmap.put(new SpecialMethod(GeneratorBuilder.CD_Gen, "await", GeneratorBuilder.MTD_Obj), AwaitHandler::new);
-    }
-
-    int add_state(Label label) {
+    public int add_state(Label label) {
         stateSwitchCases.add(SwitchCase.of(stateSwitchCases.size(), label));
         return stateSwitchCases.size() - 1;
     }
 
-    public void generateStateMachine() {
+    public void buildSourceMethodShim(CodeBuilder cob){
+        cob.new_(CD_this).dup();
+        params(0, (_, slot, type) -> {
+            cob.loadLocal(TypeKind.from(type), slot);
+        });
+        cob.invokespecial(CD_this, ConstantDescs.INIT_NAME, MTD_init).areturn();
+    }
+
+    public boolean shouldBeInnerClass(){
+        return false;
+    }
+
+    public byte[] buildStateMachine(){
+        return ClassFile.of(ClassFile.StackMapsOption.STACK_MAPS_WHEN_REQUIRED, ClassFile.AttributesProcessingOption.PASS_ALL_ATTRIBUTES).build(CD_this, clb -> {
+
+            if(shouldBeInnerClass()){
+                src_clm.findAttributes(Attributes.sourceFile()).forEach(clb::with);
+                clb.with(InnerClassesAttribute.of(InnerClassInfo.of(CD_this, Optional.of(src_clm.thisClass().asSymbol()), Optional.of(CD_this.displayName().split("\\$")[1]), AccessFlag.PUBLIC, AccessFlag.FINAL, AccessFlag.STATIC)));
+                clb.with(NestHostAttribute.of(src_clm.thisClass()));
+            }
+
+            // parameter fields
+            params(0, (param, _, type) -> {
+                clb.withField(param, type, ClassFile.ACC_PRIVATE);
+            });
+
+            clb.withField(STATE_NAME, ConstantDescs.CD_int, ClassFile.ACC_PRIVATE);
+
+            // constructor
+            clb.withMethod(ConstantDescs.INIT_NAME, MTD_init, ClassFile.ACC_PUBLIC, mb -> mb.withCode(cob -> {
+                cob.aload(0).invokespecial(ConstantDescs.CD_Object, ConstantDescs.INIT_NAME, ConstantDescs.MTD_void);
+                params(1, (param, slot, type) -> {
+                    cob.aload(0).loadLocal(TypeKind.from(type), slot).putfield(CD_this, param, type);
+                });
+                cob.return_();
+            }));
+
+            buildStateMachineMethod(clb);
+        });
+    }
+
+    protected abstract void buildStateMachineMethod(ClassBuilder clb);
+
+    public void buildStateMachineMethodCode(ClassBuilder clb, CodeBuilder cob){
+        cob.trying(
+                tcob -> buildStateMachineCode(clb, tcob),
+                // catch anything set our state to -1 and throw the exception
+                ctb -> ctb.catchingAll(
+                        blc ->
+                                blc.aload(0).loadConstant(-1).putfield(CD_this, STATE_NAME, ConstantDescs.CD_int)
+                                        .new_(ClassDesc.ofDescriptor(RuntimeException.class.descriptorString()))
+                                        .dup_x1()
+                                        .swap()
+                                        .invokespecial(ClassDesc.ofDescriptor(RuntimeException.class.descriptorString()), ConstantDescs.INIT_NAME, MethodTypeDesc.of(ConstantDescs.CD_void, ConstantDescs.CD_Throwable))
+                                        .athrow()
+                )
+        ).aconst_null().areturn();
+    }
+
+    public void buildStateMachineCode(ClassBuilder clb, CodeBuilder cob) {
+        boolean ignore_next_pop = false;
+
+        var invalidState = cob.newLabel();
         var start_label = cob.newLabel();
         add_state(start_label);
 
         var handlers = new ArrayList<SpecialMethodHandler>();
-        for (CodeElement coe : com) {
+        for (CodeElement coe : src_com) {
             if (coe instanceof InvokeInstruction is){
                 var handler = smmap.get(new SpecialMethod(is.owner().asSymbol(), is.name().stringValue(), is.typeSymbol()));
                 if(handler != null)
-                    handlers.add(handler.apply(this));
+                    handlers.add(handler.apply(this, cob));
             }
         }
-        cob.aload(0).getfield(gb.CD_this, GeneratorBuilder.STATE_NAME, TypeKind.INT.upperBound()).lookupswitch(invalidState, stateSwitchCases);
+        cob.aload(0).getfield(CD_this, STATE_NAME, TypeKind.INT.upperBound()).lookupswitch(invalidState, stateSwitchCases);
         var start = cob.startLabel();
         var end = cob.newLabel();
-        cob.localVariable(0, "this", gb.CD_this, start, end);
+        cob.localVariable(0, "this", CD_this, start, end);
 
         SpecialMethodHandler currentHandler = null;
 
         cob.labelBinding(start_label);
-        for (CodeElement coe : com) {
+        for (CodeElement coe : src_com) {
             if (coe instanceof Instruction i) {
                 if (ignore_next_pop)
                     if (i.opcode() == Opcode.POP) {
@@ -164,8 +163,8 @@ public class StateMachineBuilder {
                         continue;
                     }else throw new RuntimeException("Expected Pop Instruction");
                 if (i.opcode() == Opcode.ARETURN){
-                    if (currentHandler !=null && currentHandler.handlerRan() == HandlerRan.ReplacingNextReturn){
-                        currentHandler.handle(this);
+                    if (currentHandler !=null && currentHandler.replacementKind() == ReplacementKind.ReplacingNextReturn){
+                        currentHandler.handle(this, cob);
                         currentHandler = null;
                         continue;
                     }
@@ -179,9 +178,9 @@ public class StateMachineBuilder {
                     if(currentHandler!=null)throw new RuntimeException("Multiple method handlers at once not supported");
                     var handler = handlers.removeFirst();
                     if(!handler.removeCall()) cob.with(coe);
-                    if(handler.handlerRan() == HandlerRan.Immediate) handler.handle(this);
-                    else if(handler.handlerRan() == HandlerRan.ImmediateRemovePop) {
-                        handler.handle(this);
+                    if(handler.replacementKind() == ReplacementKind.Immediate) handler.handle(this, cob);
+                    else if(handler.replacementKind() == ReplacementKind.ImmediateReplacingPop) {
+                        handler.handle(this, cob);
                         ignore_next_pop = true;
                     }else
                         currentHandler = handler;
@@ -189,35 +188,33 @@ public class StateMachineBuilder {
                 }
             }
 
-//            System.out.println(coe);
-
             switch (coe) {
                 // locals which were once function parameters can be ignored
-                case LocalVariable lv when lv.slot() < gb.paramSlotOff -> {
+                case LocalVariable lv when lv.slot() < paramSlotOff -> {
                 }
                 case LocalVariable lv ->
-                        cob.localVariable(lv.slot() - gb.paramSlotOff + 1, lv.name(), lv.type(), lv.startScope(), lv.endScope());
+                        cob.localVariable(lv.slot() - paramSlotOff + 1, lv.name(), lv.type(), lv.startScope(), lv.endScope());
 
                 // increment indexes into the stack
-                case IncrementInstruction ii when ii.slot() < gb.paramSlotOff ->
-                        cob.aload(0).dup().getfield(gb.CD_this, GeneratorBuilder.PARAM_PREFIX + ii.slot(), ConstantDescs.CD_int)
+                case IncrementInstruction ii when ii.slot() < paramSlotOff ->
+                        cob.aload(0).dup().getfield(CD_this, PARAM_PREFIX + ii.slot(), ConstantDescs.CD_int)
                                 .loadConstant(ii.constant()).iadd()
-                                .putfield(gb.CD_this, GeneratorBuilder.PARAM_PREFIX + ii.slot(), ConstantDescs.CD_int);
-                case IncrementInstruction ii -> cob.iinc(ii.slot() - gb.paramSlotOff + 1, ii.constant());
+                                .putfield(CD_this, PARAM_PREFIX + ii.slot(), ConstantDescs.CD_int);
+                case IncrementInstruction ii -> cob.iinc(ii.slot() - paramSlotOff + 1, ii.constant());
 
                 // convert local function parameters to class fields and offset regular locals
-                case LoadInstruction li when li.slot() < gb.paramSlotOff ->
-                        cob.aload(0).getfield(gb.CD_this, GeneratorBuilder.PARAM_PREFIX + li.slot(), lt.paramType(li.slot()));
-                case LoadInstruction li -> cob.loadLocal(li.typeKind(), li.slot() - gb.paramSlotOff + 1);
+                case LoadInstruction li when li.slot() < paramSlotOff ->
+                        cob.aload(0).getfield(CD_this, PARAM_PREFIX + li.slot(), lt.paramType(li.slot()));
+                case LoadInstruction li -> cob.loadLocal(li.typeKind(), li.slot() - paramSlotOff + 1);
 
                 // convert local function parameters to class fields and offset regular locals
-                case StoreInstruction ls when ls.slot() < gb.paramSlotOff && ls.typeKind().slotSize() == 2 ->
-                        cob.aload(0).dup_x2().pop().putfield(gb.CD_this, GeneratorBuilder.PARAM_PREFIX + ls.slot(), lt.paramType(ls.slot()));
-                case StoreInstruction ls when ls.slot() < gb.paramSlotOff ->
-                        cob.aload(0).swap().putfield(gb.CD_this, GeneratorBuilder.PARAM_PREFIX + ls.slot(), lt.paramType(ls.slot()));
+                case StoreInstruction ls when ls.slot() < paramSlotOff && ls.typeKind().slotSize() == 2 ->
+                        cob.aload(0).dup_x2().pop().putfield(CD_this, PARAM_PREFIX + ls.slot(), lt.paramType(ls.slot()));
+                case StoreInstruction ls when ls.slot() < paramSlotOff ->
+                        cob.aload(0).swap().putfield(CD_this, PARAM_PREFIX + ls.slot(), lt.paramType(ls.slot()));
                 case StoreInstruction ls -> {
-                    lt.trackLocal(ls.slot() - gb.paramSlotOff + 1, ls.typeKind());
-                    cob.storeLocal(ls.typeKind(), ls.slot() - gb.paramSlotOff + 1);
+                    lt.trackLocal(ls.slot() - paramSlotOff + 1, ls.typeKind());
+                    cob.storeLocal(ls.typeKind(), ls.slot() - paramSlotOff + 1);
                 }
 
                 default -> cob.with(coe);
@@ -230,6 +227,5 @@ public class StateMachineBuilder {
         cob.labelBinding(end);
 
         lt.createLocalStoreFields(clb);
-        clb.withField("meow", GeneratorBuilder.CD_Gen, ClassFile.ACC_PRIVATE);
     }
 }

src/generator/runtime/future/FutureSMBuilder.java

@@ -0,0 +1,70 @@
+package generator.runtime.future;
+
+import generator.gen.Gen;
+import generator.runtime.ReplacementKind;
+import generator.runtime.SpecialMethod;
+import generator.runtime.SpecialMethodHandler;
+import generator.runtime.StateMachineBuilder;
+
+import java.lang.classfile.*;
+import java.lang.constant.ClassDesc;
+import java.lang.constant.ConstantDescs;
+import java.lang.constant.MethodTypeDesc;
+import java.util.List;
+
+public class FutureSMBuilder extends StateMachineBuilder {
+
+    public final static ClassDesc CD_Gen = ClassDesc.ofDescriptor(Gen.class.descriptorString());
+    public final static ClassDesc CD_Res = ClassDesc.ofDescriptor(Gen.Res.class.descriptorString());
+    public final static ClassDesc CD_Yield = ClassDesc.ofDescriptor(Gen.Yield.class.descriptorString());
+    public final static ClassDesc CD_Ret = ClassDesc.ofDescriptor(Gen.Ret.class.descriptorString());
+    public final static MethodTypeDesc MTD_Res = MethodTypeDesc.of(CD_Res);
+    public final static MethodTypeDesc MTD_Gen_Obj = MethodTypeDesc.of(CD_Gen, ConstantDescs.CD_Object);
+    public final static MethodTypeDesc MTD_Gen = MethodTypeDesc.of(CD_Gen);
+    public final static MethodTypeDesc MTD_Obj = MethodTypeDesc.of(ConstantDescs.CD_Object);
+
+    static class AwaitHandler implements SpecialMethodHandler{
+        final int yield_state;
+        final Label yield_label;
+
+        public AwaitHandler(StateMachineBuilder smb, CodeBuilder cob) {
+            yield_state = smb.add_state(yield_label = cob.newLabel());
+        }
+
+        public ReplacementKind replacementKind(){return ReplacementKind.Immediate;}
+
+        @Override
+        public void handle(StateMachineBuilder smb, CodeBuilder cob) {
+            cob.aload(0).loadConstant(yield_state).putfield(smb.CD_this, STATE_NAME, TypeKind.INT.upperBound());
+            var start = cob.newBoundLabel();
+            cob.dup().dup()
+                    .invokeinterface(CD_Gen, "next", MethodTypeDesc.of(CD_Res)).dup()
+                    .instanceOf(CD_Ret);
+            cob.ifThenElse(bcb -> {
+                bcb.checkcast(CD_Ret).invokevirtual(CD_Ret, "v", MethodTypeDesc.of(ConstantDescs.CD_Object)).swap().pop();
+            }, bcb -> {
+                smb.lt.savingLocals(smb.CD_this, bcb, () -> {
+                    bcb.swap().loadLocal(TypeKind.from(smb.CD_this), 0).swap().putfield(smb.CD_this, "meow", CD_Gen);
+                    bcb.areturn().labelBinding(yield_label);
+                    bcb.loadLocal(TypeKind.from(smb.CD_this), 0).getfield(smb.CD_this, "meow", CD_Gen);
+                });
+                bcb.goto_(start);
+            });
+
+        }
+    }
+
+    @Override
+    protected void buildStateMachineMethod(ClassBuilder clb){
+        clb.withInterfaces(List.of(clb.constantPool().classEntry(CD_Gen)));
+        clb.withMethod("next", MethodTypeDesc.of(CD_Res), ClassFile.ACC_PUBLIC, mb -> mb.withCode(cob -> {
+            buildStateMachineMethodCode(clb, cob);
+        }));
+        clb.withField("meow", CD_Gen, ClassFile.ACC_PRIVATE);
+    }
+
+    public FutureSMBuilder(ClassModel src_clm, MethodModel src_mem, CodeModel src_com) {
+        super(src_clm, src_mem, src_com);
+        smmap.put(new SpecialMethod(CD_Gen, "await", MTD_Obj), AwaitHandler::new);
+    }
+}

src/generator/runtime/gen/GenSMBuilder.java

@@ -0,0 +1,91 @@
+package generator.runtime.gen;
+
+import generator.gen.Gen;
+import generator.runtime.ReplacementKind;
+import generator.runtime.SpecialMethod;
+import generator.runtime.SpecialMethodHandler;
+import generator.runtime.StateMachineBuilder;
+
+import java.lang.classfile.*;
+import java.lang.constant.ClassDesc;
+import java.lang.constant.ConstantDescs;
+import java.lang.constant.MethodTypeDesc;
+import java.util.List;
+
+public class GenSMBuilder extends StateMachineBuilder {
+
+    public final static ClassDesc CD_Gen = ClassDesc.ofDescriptor(Gen.class.descriptorString());
+    public final static ClassDesc CD_Res = ClassDesc.ofDescriptor(Gen.Res.class.descriptorString());
+    public final static ClassDesc CD_Yield = ClassDesc.ofDescriptor(Gen.Yield.class.descriptorString());
+    public final static ClassDesc CD_Ret = ClassDesc.ofDescriptor(Gen.Ret.class.descriptorString());
+    public final static MethodTypeDesc MTD_Res = MethodTypeDesc.of(CD_Res);
+    public final static MethodTypeDesc MTD_Gen_Obj = MethodTypeDesc.of(CD_Gen, ConstantDescs.CD_Object);
+    public final static MethodTypeDesc MTD_Gen = MethodTypeDesc.of(CD_Gen);
+    public final static MethodTypeDesc MTD_Obj = MethodTypeDesc.of(ConstantDescs.CD_Object);
+
+    static class YieldHandler implements SpecialMethodHandler {
+        final int resume_state;
+        final Label resume_label;
+        final boolean is_void;
+
+        public YieldHandler(StateMachineBuilder smb, CodeBuilder cob, boolean is_void) {
+            resume_state = smb.add_state(resume_label = cob.newLabel());
+            this.is_void = is_void;
+        }
+
+        public ReplacementKind replacementKind(){return ReplacementKind.ImmediateReplacingPop;}
+
+        @Override
+        public void handle(StateMachineBuilder smb, CodeBuilder cob) {
+            if(is_void)cob.aconst_null();
+
+            smb.lt.savingLocals(smb.CD_this, cob, () -> {
+                cob.aload(0).loadConstant(resume_state).putfield(smb.CD_this, STATE_NAME, TypeKind.INT.upperBound())
+                        .new_(CD_Yield)
+                        .dup_x1()
+                        .swap()
+                        .invokespecial(CD_Yield, ConstantDescs.INIT_NAME, MethodTypeDesc.of(ConstantDescs.CD_void, ConstantDescs.CD_Object))
+                        .areturn();
+                cob.labelBinding(resume_label);
+            });
+        }
+    }
+
+    static class RetHandler implements SpecialMethodHandler {
+        final boolean is_void;
+
+        public RetHandler(boolean is_void) {
+            this.is_void = is_void;
+        }
+
+        public ReplacementKind replacementKind(){return ReplacementKind.ReplacingNextReturn;}
+
+        @Override
+        public void handle(StateMachineBuilder smb, CodeBuilder cob) {
+            if(is_void)cob.aconst_null();
+
+            cob.aload(0).loadConstant(-1).putfield(smb.CD_this, STATE_NAME, TypeKind.INT.upperBound())
+                    .new_(CD_Ret)
+                    .dup_x1()
+                    .swap()
+                    .invokespecial(CD_Ret, ConstantDescs.INIT_NAME, MethodTypeDesc.of(ConstantDescs.CD_void, ConstantDescs.CD_Object))
+                    .areturn();
+        }
+    }
+
+    public GenSMBuilder(ClassModel src_clm, MethodModel src_mem, CodeModel src_com) {
+        super(src_clm, src_mem, src_com);
+        smmap.put(new SpecialMethod(CD_Gen, "yield", MTD_Gen_Obj),(smb, cob) -> new YieldHandler(smb, cob, false));
+        smmap.put(new SpecialMethod(CD_Gen, "yield", MTD_Gen),(smb, cob) -> new YieldHandler(smb, cob, true));
+        smmap.put(new SpecialMethod(CD_Gen, "ret", MTD_Gen_Obj),(_, _) -> new RetHandler(false));
+        smmap.put(new SpecialMethod(CD_Gen, "ret", MTD_Gen),(_, _) -> new RetHandler(true));
+    }
+
+    @Override
+    protected void buildStateMachineMethod(ClassBuilder clb){
+        clb.withInterfaces(List.of(clb.constantPool().classEntry(CD_Gen)));
+        clb.withMethod("next", MethodTypeDesc.of(CD_Res), ClassFile.ACC_PUBLIC, mb -> mb.withCode(cob -> {
+            buildStateMachineMethodCode(clb, cob);
+        }));
+    }
+}