fix: check enum constructor content before removing (#922)

jadx-core/src/main/java/jadx/core/codegen/ClassGen.java

@@ -9,6 +9,8 @@ import java.util.List;
 import java.util.Objects;
 import java.util.Set;
 
+import org.jetbrains.annotations.Nullable;
+
 import com.android.dx.rop.code.AccessFlags;
 import com.google.common.collect.Streams;
 
@@ -21,6 +23,7 @@ import jadx.core.dex.attributes.nodes.EnumClassAttr;
 import jadx.core.dex.attributes.nodes.EnumClassAttr.EnumField;
 import jadx.core.dex.attributes.nodes.JadxError;
 import jadx.core.dex.attributes.nodes.LineAttrNode;
+import jadx.core.dex.attributes.nodes.SkipMethodArgsAttr;
 import jadx.core.dex.info.AccessInfo;
 import jadx.core.dex.info.ClassInfo;
 import jadx.core.dex.instructions.args.ArgType;
@@ -420,12 +423,13 @@ public class ClassGen {
 			EnumField f = it.next();
 			code.startLine(f.getField().getAlias());
 			ConstructorInsn constrInsn = f.getConstrInsn();
-			if (constrInsn.getArgsCount() > f.getStartArg()) {
+			MethodNode callMth = cls.dex().resolveMethod(constrInsn.getCallMth());
+			int skipCount = getEnumCtrSkipArgsCount(callMth);
+			if (constrInsn.getArgsCount() > skipCount) {
 				if (igen == null) {
 					igen = makeInsnGen(enumFields.getStaticMethod());
 				}
-				MethodNode callMth = cls.dex().resolveMethod(constrInsn.getCallMth());
-				igen.generateMethodArguments(code, constrInsn, f.getStartArg(), callMth);
+				igen.generateMethodArguments(code, constrInsn, 0, callMth);
 			}
 			if (f.getCls() != null) {
 				code.add(' ');
@@ -446,6 +450,16 @@ public class ClassGen {
 		}
 	}
 
+	private int getEnumCtrSkipArgsCount(@Nullable MethodNode callMth) {
+		if (callMth != null) {
+			SkipMethodArgsAttr skipArgsAttr = callMth.get(AType.SKIP_MTH_ARGS);
+			if (skipArgsAttr != null) {
+				return skipArgsAttr.getSkipCount();
+			}
+		}
+		return 0;
+	}
+
 	private InsnGen makeInsnGen(MethodNode mth) {
 		MethodGen mthGen = new MethodGen(this, mth);
 		return new InsnGen(mthGen, false);

jadx-core/src/main/java/jadx/core/dex/attributes/nodes/EnumClassAttr.java

@@ -14,13 +14,11 @@ public class EnumClassAttr implements IAttribute {
 	public static class EnumField {
 		private final FieldNode field;
 		private final ConstructorInsn constrInsn;
-		private final int startArg;
 		private ClassNode cls;
 
-		public EnumField(FieldNode field, ConstructorInsn co, int startArg) {
+		public EnumField(FieldNode field, ConstructorInsn co) {
 			this.field = field;
 			this.constrInsn = co;
-			this.startArg = startArg;
 		}
 
 		public FieldNode getField() {
@@ -31,10 +29,6 @@ public class EnumClassAttr implements IAttribute {
 			return constrInsn;
 		}
 
-		public int getStartArg() {
-			return startArg;
-		}
-
 		public ClassNode getCls() {
 			return cls;
 		}

jadx-core/src/main/java/jadx/core/dex/attributes/nodes/SkipMethodArgsAttr.java

@@ -55,6 +55,10 @@ public class SkipMethodArgsAttr implements IAttribute {
 		return skipArgs.get(argNum);
 	}
 
+	public int getSkipCount() {
+		return skipArgs.cardinality();
+	}
+
 	@Override
 	public AType<SkipMethodArgsAttr> getType() {
 		return AType.SKIP_MTH_ARGS;

jadx-core/src/main/java/jadx/core/dex/visitors/EnumVisitor.java

@@ -19,6 +19,7 @@ import jadx.core.dex.attributes.AFlag;
 import jadx.core.dex.attributes.AType;
 import jadx.core.dex.attributes.nodes.EnumClassAttr;
 import jadx.core.dex.attributes.nodes.EnumClassAttr.EnumField;
+import jadx.core.dex.attributes.nodes.SkipMethodArgsAttr;
 import jadx.core.dex.info.AccessInfo;
 import jadx.core.dex.info.ClassInfo;
 import jadx.core.dex.info.FieldInfo;
@@ -287,8 +288,13 @@ public class EnumVisitor extends AbstractVisitor {
 		if (!clsInfo.equals(cls.getClassInfo()) && !constrCls.getAccessFlags().isEnum()) {
 			return null;
 		}
-		int startArg = co.getArgsCount() == 1 ? 1 : 2;
-		return new EnumField(enumFieldNode, co, startArg);
+		MethodInfo callMth = co.getCallMth();
+		MethodNode mth = cls.dex().resolveMethod(callMth);
+		if (mth == null) {
+			return null;
+		}
+		markArgsForSkip(mth);
+		return new EnumField(enumFieldNode, co);
 	}
 
 	@Nullable
@@ -306,10 +312,7 @@ public class EnumVisitor extends AbstractVisitor {
 	}
 
 	private void removeEnumMethods(ClassNode cls, ArgType clsType, FieldNode valuesField) {
-		String enumConstructor = "<init>(Ljava/lang/String;I)V";
-		String enumConstructorAlt = "<init>(Ljava/lang/String;)V";
 		String valuesMethod = "values()" + TypeGen.signature(ArgType.array(clsType));
-
 		FieldInfo valuesFieldInfo = valuesField.getFieldInfo();
 
 		// remove compiler generated methods
@@ -319,12 +322,11 @@ public class EnumVisitor extends AbstractVisitor {
 				continue;
 			}
 			String shortId = mi.getShortId();
-			boolean isSynthetic = mth.getAccessFlags().isSynthetic();
-			if (mi.isConstructor() && !isSynthetic) {
-				if (shortId.equals(enumConstructor)
-						|| shortId.equals(enumConstructorAlt)) {
+			if (mi.isConstructor()) {
+				if (isDefaultConstructor(mth, shortId)) {
 					mth.add(AFlag.DONT_GENERATE);
 				}
+				markArgsForSkip(mth);
 			} else if (shortId.equals(valuesMethod)
 					|| usesValuesField(mth, valuesFieldInfo)
 					|| simpleValueOfMth(mth, clsType)) {
@@ -333,6 +335,24 @@ public class EnumVisitor extends AbstractVisitor {
 		}
 	}
 
+	private void markArgsForSkip(MethodNode mth) {
+		// skip first and second args
+		SkipMethodArgsAttr.skipArg(mth, 0);
+		if (mth.getMethodInfo().getArgsCount() > 1) {
+			SkipMethodArgsAttr.skipArg(mth, 1);
+		}
+	}
+
+	private boolean isDefaultConstructor(MethodNode mth, String shortId) {
+		boolean defaultId = shortId.equals("<init>(Ljava/lang/String;I)V")
+				|| shortId.equals("<init>(Ljava/lang/String;)V");
+		if (defaultId) {
+			// check content
+			return mth.countInsns() == 0;
+		}
+		return false;
+	}
+
 	private boolean simpleValueOfMth(MethodNode mth, ArgType clsType) {
 		InsnNode returnInsn = InsnUtils.searchSingleReturnInsn(mth, insn -> insn.getArgsCount() == 1);
 		if (returnInsn == null) {