core: fix synthetic constructor remove (#265)

jadx-core/src/main/java/jadx/core/dex/nodes/DexNode.java

@@ -210,7 +210,7 @@ public class DexNode implements IDexNode {
 
 	@Override
 	public String toString() {
-		return "DEX";
+		return "DEX: " + file;
 	}
 
 }

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

@@ -11,6 +11,7 @@ import jadx.core.dex.info.FieldInfo;
 import jadx.core.dex.info.MethodInfo;
 import jadx.core.dex.instructions.IndexInsnNode;
 import jadx.core.dex.instructions.InsnType;
+import jadx.core.dex.instructions.args.ArgType;
 import jadx.core.dex.instructions.args.InsnArg;
 import jadx.core.dex.instructions.args.RegisterArg;
 import jadx.core.dex.instructions.args.SSAVar;
@@ -133,29 +134,62 @@ public class ClassModifier extends AbstractVisitor {
 			if (af.isBridge() && af.isSynthetic() && !isMethodUniq(cls, mth)) {
 				// TODO add more checks before method deletion
 				mth.add(AFlag.DONT_GENERATE);
+			} else {
+				// remove synthetic constructor for inner classes
+				if (af.isSynthetic() && af.isConstructor() && mth.getBasicBlocks().size() == 2) {
+					List<RegisterArg> args = mth.getArguments(false);
+					if (isRemovedClassInArgs(cls, args)) {
+						modifySyntheticMethod(cls, mth, args);
+					}
+				}
+			}
+		}
+	}
+
+	private static boolean isRemovedClassInArgs(ClassNode cls, List<RegisterArg> mthArgs) {
+		for (RegisterArg arg : mthArgs) {
+			ArgType argType = arg.getType();
+			if (!argType.isObject()) {
 				continue;
 			}
-			// remove synthetic constructor for inner classes
-			if (af.isSynthetic() && af.isConstructor() && mth.getBasicBlocks().size() == 2) {
-				List<InsnNode> insns = mth.getBasicBlocks().get(0).getInstructions();
-				if (insns.size() == 1 && insns.get(0).getType() == InsnType.CONSTRUCTOR) {
-					ConstructorInsn constr = (ConstructorInsn) insns.get(0);
-					List<RegisterArg> args = mth.getArguments(false);
-					if (constr.isThis() && !args.isEmpty()) {
-						// remove first arg for non-static class (references to outer class)
-						if (args.get(0).getType().equals(cls.getParentClass().getClassInfo().getType())) {
-							args.get(0).add(AFlag.SKIP_ARG);
-						}
-						// remove unused args
-						for (RegisterArg arg : args) {
-							SSAVar sVar = arg.getSVar();
-							if (sVar != null && sVar.getUseCount() == 0) {
-								arg.add(AFlag.SKIP_ARG);
-							}
-						}
-						mth.add(AFlag.DONT_GENERATE);
+			ClassNode argCls = cls.dex().resolveClass(argType);
+			if (argCls == null) {
+				// check if missing class from current top class
+				ClassInfo argClsInfo = ClassInfo.fromType(cls.root(), argType);
+				if (argClsInfo.isInner()
+						&& cls.getFullName().startsWith(argClsInfo.getParentClass().getFullName())) {
+					return true;
+				}
+			} else {
+				if (argCls.contains(AFlag.DONT_GENERATE)) {
+					return true;
+				}
+			}
+		}
+		return false;
+	}
+
+	/**
+	 * Remove synthetic constructor and redirect calls to existing constructor
+	 */
+	private static void modifySyntheticMethod(ClassNode cls, MethodNode mth, List<RegisterArg> args) {
+		List<InsnNode> insns = mth.getBasicBlocks().get(0).getInstructions();
+		if (insns.size() == 1 && insns.get(0).getType() == InsnType.CONSTRUCTOR) {
+			ConstructorInsn constr = (ConstructorInsn) insns.get(0);
+			if (constr.isThis() && !args.isEmpty()) {
+				// remove first arg for non-static class (references to outer class)
+				RegisterArg firstArg = args.get(0);
+				if (firstArg.getType().equals(cls.getParentClass().getClassInfo().getType())) {
+					firstArg.add(AFlag.SKIP_ARG);
+				}
+				// remove unused args
+				for (RegisterArg arg : args) {
+					SSAVar sVar = arg.getSVar();
+					if (sVar != null && sVar.getUseCount() == 0) {
+						arg.add(AFlag.SKIP_ARG);
 					}
 				}
+				mth.add(AFlag.DONT_GENERATE);
 			}
 		}
 	}
@@ -191,5 +225,4 @@ public class ClassModifier extends AbstractVisitor {
 			}
 		}
 	}
-
 }

jadx-core/src/test/java/jadx/tests/api/SmaliTest.java

@@ -37,7 +37,7 @@ public abstract class SmaliTest extends IntegrationTest {
 		if (smaliFile.exists()) {
 			return smaliFile;
 		}
-		throw new AssertionError("Smali file not found: " + SMALI_TESTS_DIR + "/" + clsName + SMALI_TESTS_EXT);
+		throw new AssertionError("Smali file not found: " + smaliFile.getAbsolutePath());
 	}
 
 	private static boolean compileSmali(File input, File output) {

jadx-core/src/test/java/jadx/tests/integration/inner/TestInnerClassFakeSyntheticConstructor.java

+package jadx.tests.integration.inner;
+
+import org.junit.Test;
+
+import jadx.core.dex.nodes.ClassNode;
+import jadx.tests.api.IntegrationTest;
+import jadx.tests.api.SmaliTest;
+
+import static jadx.tests.api.utils.JadxMatchers.containsOne;
+import static org.junit.Assert.assertThat;
+
+public class TestInnerClassFakeSyntheticConstructor extends SmaliTest {
+
+//	public class TestCls {
+//		public /* synthetic */ TestCls(String a) {
+//			this(a, true);
+//		}
+//
+//		public TestCls(String a, boolean b) {
+//		}
+//
+//		public static TestCls build(String str) {
+//			return new TestCls(str);
+//		}
+//	}
+
+	@Test
+	public void test() {
+		ClassNode cls = getClassNodeFromSmali("inner/TestInnerClassFakeSyntheticConstructor", "jadx.tests.inner.TestCls");
+		String code = cls.getCode().toString();
+
+		assertThat(code, containsOne("TestCls(String a) {"));
+		// and must compile
+	}
+}

jadx-core/src/test/java/jadx/tests/integration/inner/TestInnerClassSyntheticConstructor.java

+package jadx.tests.integration.inner;
+
+import org.junit.Test;
+
+import jadx.tests.api.IntegrationTest;
+import jadx.tests.api.SmaliTest;
+
+import static org.hamcrest.Matchers.not;
+import static org.junit.Assert.assertThat;
+
+public class TestInnerClassSyntheticConstructor extends IntegrationTest {
+
+	private class TestCls {
+		private int mth() {
+			return 1;
+		}
+	}
+
+	public int call() {
+		return new TestCls().mth();
+	}
+
+	@Test
+	public void test() {
+		getClassNode(TestInnerClassSyntheticConstructor.class);
+		// must compile, no usage of removed synthetic empty class
+	}
+}

jadx-core/src/test/smali/inner/TestInnerClassFakeSyntheticConstructor.smali

+.class public Ljadx/tests/inner/TestCls;
+.super Ljava/lang/Object;
+
+# direct methods
+.method public synthetic constructor <init>(Ljava/lang/String;)V
+    .registers 3
+    .param p1, "a"    # Ljava/lang/String;
+
+    .prologue
+    const/4 v0, 0x1
+
+    invoke-direct {p0, p1, v0}, Ljadx/tests/inner/TestCls;-><init>(Ljava/lang/String;Z)V
+
+    return-void
+.end method
+
+.method public constructor <init>(Ljava/lang/String;Z)V
+    .registers 3
+    .param p1, "a"    # Ljava/lang/String;
+    .param p2, "b"    # Z
+
+    .prologue
+    invoke-direct {p0}, Ljava/lang/Object;-><init>()V
+
+    return-void
+.end method
+
+.method public static build(Ljava/lang/String;)Ljadx/tests/inner/TestCls;
+    .registers 2
+    .param p0, "str"    # Ljava/lang/String;
+
+    .prologue
+    new-instance v0, Ljadx/tests/inner/TestCls;
+
+    invoke-direct {v0, p0}, Ljadx/tests/inner/TestCls;-><init>(Ljava/lang/String;)V
+
+    return-object v0
+.end method