Add FactoryFromConstructor

src/main/java/io/github/opencubicchunks/cubicchunks/mixin/ASMConfigPlugin.java

@@ -38,6 +38,7 @@
 import io.github.notstirred.dasm.util.Pair;
 import io.github.opencubicchunks.cc_core.annotation.Public;
 import io.github.opencubicchunks.cubicchunks.CubicChunks;
+import io.github.opencubicchunks.cubicchunks.util.asm.FactoryFromConstructor;
 import net.minecraft.Util;
 import net.neoforged.fml.loading.FMLEnvironment;
 import org.apache.logging.log4j.LogManager;
@@ -185,6 +186,7 @@ public ASMConfigPlugin() {
 
     @Override public void postApply(String targetClassName, ClassNode targetClass, String mixinClassName, IMixinInfo mixinInfo) {
         doPublicAnnotation(targetClass);
+        doFactoryFromConstructorAnnotation(targetClass);
 
         // Apply POST_APPLY dasm transforms
         boolean wasTransformed;
@@ -261,6 +263,47 @@ private void doPublicAnnotation(ClassNode targetClass) {
         }
     }
 
+    private void doFactoryFromConstructorAnnotation(ClassNode targetClass) {
+        // Generate constructor calls matching the signature of methods annotated with @FactoryFromConstructor
+        for (MethodNode method : targetClass.methods) {
+            List<AnnotationNode> annotations = method.invisibleAnnotations;
+            if (annotations != null) {
+                if (annotations.stream().anyMatch(
+                        annotationNode -> annotationNode.desc.equals("L" + FactoryFromConstructor.class.getName().replace('.', '/') + ";"))) {
+                    if ((method.access & ACC_STATIC) == 0) {
+                        throw new IllegalStateException("Tried to generate a factory method on a non-static dst");
+                    }
+                    transformStubToFactory(method);
+                }
+            }
+        }
+    }
+
+    private static void transformStubToFactory(MethodNode method) {
+        method.access &= ~ACC_NATIVE;
+        Type methodType = Type.getMethodType(method.desc);
+        Type returnType = methodType.getReturnType();
+        Type[] argumentTypes = methodType.getArgumentTypes();
+
+        method.instructions.clear();
+        method.visitTypeInsn(NEW, returnType.getInternalName());
+        method.visitInsn(DUP);
+        for (int i = 0; i < argumentTypes.length; i++) {
+            Type argumentType = argumentTypes[i];
+            switch (argumentType.getSort()) {
+                case Type.OBJECT, Type.ARRAY -> method.visitVarInsn(ALOAD, i);
+                case Type.LONG -> method.visitVarInsn(LLOAD, i);
+                case Type.INT, Type.SHORT, Type.BYTE, Type.BOOLEAN, Type.CHAR -> method.visitVarInsn(ILOAD, i);
+                case Type.DOUBLE -> method.visitVarInsn(DLOAD, i);
+                case Type.FLOAT -> method.visitVarInsn(FLOAD, i);
+                default -> throw new IllegalStateException("Unexpected sort: " + argumentType.getSort());
+            }
+        }
+        method.visitMethodInsn(INVOKESPECIAL, returnType.getInternalName(), "<init>",
+                method.desc.substring(0, method.desc.lastIndexOf(')') + 1) + "V", false);
+        method.visitInsn(ARETURN);
+    }
+
     /**
      * @return Whether any transformation was done to the targetClass
      */

src/main/java/io/github/opencubicchunks/cubicchunks/util/asm/FactoryFromConstructor.java

@@ -0,0 +1,26 @@
+package io.github.opencubicchunks.cubicchunks.util.asm;
+
+import static java.lang.annotation.ElementType.METHOD;
+
+import java.lang.annotation.Target;
+
+/**
+ * Can be placed on a native stub factory method within a mixin class, the generated method will call the constructor of the return type with the
+ * given arguments
+ * <h2>Example:</h2>
+ * 
+ * <pre>{@code
+ * @FactoryFromConstructor
+ * private native static Vec3i createVec3i(int x, int y, int z);
+ * }</pre>
+ * 
+ * Will generate this method based on the stub signature.
+ * 
+ * <pre>{@code
+ * private static Vec3i createVec3i(int x, int y, int z) {
+ *     return new Vec3i(x, y, z);
+ * }
+ * }</pre>
+ */
+@Target({ METHOD })
+public @interface FactoryFromConstructor {}

src/main/java/io/github/opencubicchunks/cubicchunks/util/asm/package-info.java

@@ -0,0 +1,7 @@
+@ParametersAreNonnullByDefault
+@MethodsReturnNonnullByDefault
+package io.github.opencubicchunks.cubicchunks.util.asm;
+
+import javax.annotation.ParametersAreNonnullByDefault;
+
+import io.github.opencubicchunks.cc_core.annotation.MethodsReturnNonnullByDefault;