core: improve error reporting

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

@@ -252,8 +252,8 @@ public class ClassGen {
 	}
 
 	private void addMethod(CodeWriter code, MethodNode mth) throws CodegenException {
-		MethodGen mthGen = new MethodGen(this, mth);
 		if (mth.getAccessFlags().isAbstract() || mth.getAccessFlags().isNative()) {
+			MethodGen mthGen = new MethodGen(this, mth);
 			mthGen.addDefinition(code);
 			if (cls.getAccessFlags().isAnnotation()) {
 				Object def = annotationGen.getAnnotationDefaultValue(mth.getName());
@@ -270,6 +270,12 @@ public class ClassGen {
 				code.startLine("/* Code decompiled incorrectly, please refer to instructions dump. */");
 				ErrorsCounter.methodError(mth, "Inconsistent code");
 			}
+			MethodGen mthGen;
+			if (badCode || mth.contains(AType.JADX_ERROR)) {
+				mthGen = MethodGen.getFallbackMethodGen(mth);
+			} else {
+				mthGen = new MethodGen(this, mth);
+			}
 			if (mthGen.addDefinition(code)) {
 				code.add(' ');
 			}

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

@@ -9,7 +9,6 @@ import jadx.core.dex.instructions.args.ArgType;
 import jadx.core.dex.instructions.args.RegisterArg;
 import jadx.core.dex.nodes.InsnNode;
 import jadx.core.dex.nodes.MethodNode;
-import jadx.core.dex.regions.Region;
 import jadx.core.dex.trycatch.CatchAttr;
 import jadx.core.dex.visitors.DepthTraversal;
 import jadx.core.dex.visitors.FallbackModeVisitor;
@@ -151,49 +150,33 @@ public class MethodGen {
 	}
 
 	public void addInstructions(CodeWriter code) throws CodegenException {
-		if (mth.contains(AType.JADX_ERROR)) {
-			code.startLine("throw new UnsupportedOperationException(\"Method not decompiled: ");
-			code.add(mth.toString());
-			code.add("\");");
-
-			JadxErrorAttr err = mth.get(AType.JADX_ERROR);
-			code.startLine("/* JADX: method processing error */");
-			Throwable cause = err.getCause();
-			if (cause != null) {
-				code.newLine();
-				code.add("/*");
-				code.startLine("Error: ").add(Utils.getStackTrace(cause));
-				code.add("*/");
+		if (mth.contains(AType.JADX_ERROR)
+				|| mth.contains(AFlag.INCONSISTENT_CODE)
+				|| mth.getRegion() == null) {
+			code.startLine("throw new UnsupportedOperationException(\"Method not decompiled: ")
+					.add(mth.toString())
+					.add("\");");
+
+			if (mth.contains(AType.JADX_ERROR)) {
+				JadxErrorAttr err = mth.get(AType.JADX_ERROR);
+				code.startLine("/* JADX: method processing error */");
+				Throwable cause = err.getCause();
+				if (cause != null) {
+					code.newLine();
+					code.add("/*");
+					code.startLine("Error: ").add(Utils.getStackTrace(cause));
+					code.add("*/");
+				}
 			}
-			makeMethodDump(code);
-		} else if (mth.contains(AFlag.INCONSISTENT_CODE)) {
 			code.startLine("/*");
 			addFallbackMethodCode(code);
 			code.startLine("*/");
-			code.newLine();
 		} else {
-			Region startRegion = mth.getRegion();
-			if (startRegion != null) {
-				(new RegionGen(this)).makeRegion(code, startRegion);
-			} else {
-				addFallbackMethodCode(code);
-			}
+			RegionGen regionGen = new RegionGen(this);
+			regionGen.makeRegion(code, mth.getRegion());
 		}
 	}
 
-	private void makeMethodDump(CodeWriter code) {
-		code.startLine("/*");
-		getFallbackMethodGen(mth).addDefinition(code);
-		code.add(" {");
-		code.incIndent();
-
-		addFallbackMethodCode(code);
-
-		code.decIndent();
-		code.startLine('}');
-		code.startLine("*/");
-	}
-
 	public void addFallbackMethodCode(CodeWriter code) {
 		if (mth.getInstructions() == null) {
 			// load original instructions
@@ -212,7 +195,7 @@ public class MethodGen {
 			return;
 		}
 		if (mth.getThisArg() != null) {
-			code.startLine(getFallbackMethodGen(mth).nameGen.useArg(mth.getThisArg())).add(" = this;");
+			code.startLine(nameGen.useArg(mth.getThisArg())).add(" = this;");
 		}
 		addFallbackInsns(code, mth, insnArr, true);
 	}
@@ -248,7 +231,7 @@ public class MethodGen {
 	/**
 	 * Return fallback variant of method codegen
 	 */
-	private static MethodGen getFallbackMethodGen(MethodNode mth) {
+	static MethodGen getFallbackMethodGen(MethodNode mth) {
 		ClassGen clsGen = new ClassGen(mth.getParentClass(), null, true);
 		return new MethodGen(clsGen, mth);
 	}

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

@@ -91,7 +91,7 @@ public class NameGen {
 		String name = arg.getName();
 		if (fallback) {
 			String base = "r" + arg.getRegNum();
-			if (name != null) {
+			if (name != null && !name.equals("this")) {
 				return base + "_" + name;
 			}
 			return base;