fix: checks for casts in field access, move method inline to visitor (#962)

Signed-off-by: Skylot <skylot@gmail.com>

jadx-core/src/main/java/jadx/core/Consts.java

@@ -2,6 +2,7 @@ package jadx.core;
 
 public class Consts {
 	public static final boolean DEBUG = false;
+	public static final boolean DEBUG_WITH_ERRORS = false; // TODO: fix errors
 	public static final boolean DEBUG_USAGE = false;
 	public static final boolean DEBUG_TYPE_INFERENCE = false;
 	public static final boolean DEBUG_OVERLOADED_CASTS = false;

jadx-core/src/main/java/jadx/core/Jadx.java

@@ -25,8 +25,9 @@ import jadx.core.dex.visitors.FixAccessModifiers;
 import jadx.core.dex.visitors.GenericTypesVisitor;
 import jadx.core.dex.visitors.IDexTreeVisitor;
 import jadx.core.dex.visitors.InitCodeVariables;
+import jadx.core.dex.visitors.InlineMethods;
 import jadx.core.dex.visitors.MarkFinallyVisitor;
-import jadx.core.dex.visitors.MethodInlineVisitor;
+import jadx.core.dex.visitors.MarkMethodsForInline;
 import jadx.core.dex.visitors.MethodInvokeVisitor;
 import jadx.core.dex.visitors.ModVisitor;
 import jadx.core.dex.visitors.MoveInlineVisitor;
@@ -119,6 +120,7 @@ public class Jadx {
 			passes.add(new DebugInfoApplyVisitor());
 		}
 
+		passes.add(new InlineMethods());
 		passes.add(new GenericTypesVisitor());
 		passes.add(new ShadowFieldVisitor());
 		passes.add(new DeboxingVisitor());
@@ -144,9 +146,10 @@ public class Jadx {
 		passes.add(new FixAccessModifiers());
 		passes.add(new ProcessAnonymous());
 		passes.add(new ClassModifier());
-		passes.add(new MethodInlineVisitor());
 		passes.add(new LoopRegionVisitor());
 
+		passes.add(new MarkMethodsForInline());
+
 		passes.add(new ProcessVariables());
 		passes.add(new PrepareForCodeGen());
 		if (args.isCfgOutput()) {

jadx-core/src/main/java/jadx/core/ProcessClass.java

@@ -59,7 +59,11 @@ public final class ProcessClass {
 			cls.setState(NOT_LOADED);
 		}
 		try {
-			cls.getDependencies().forEach(ProcessClass::process);
+			for (ClassNode depCls : cls.getDependencies()) {
+				depCls.startProcessStage();
+				process(depCls);
+			}
+			cls.startCodegenStage();
 			process(cls);
 
 			ICodeInfo code = CodeGen.generate(cls);

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

@@ -1,6 +1,5 @@
 package jadx.core.codegen;
 
-import java.util.ArrayList;
 import java.util.EnumSet;
 import java.util.Iterator;
 import java.util.List;
@@ -10,14 +9,12 @@ import org.jetbrains.annotations.Nullable;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
-import jadx.core.Consts;
 import jadx.core.deobf.NameMapper;
 import jadx.core.dex.attributes.AFlag;
 import jadx.core.dex.attributes.AType;
 import jadx.core.dex.attributes.nodes.FieldReplaceAttr;
 import jadx.core.dex.attributes.nodes.GenericInfoAttr;
 import jadx.core.dex.attributes.nodes.LoopLabelAttr;
-import jadx.core.dex.attributes.nodes.MethodInlineAttr;
 import jadx.core.dex.attributes.nodes.SkipMethodArgsAttr;
 import jadx.core.dex.info.ClassInfo;
 import jadx.core.dex.info.FieldInfo;
@@ -43,7 +40,6 @@ import jadx.core.dex.instructions.args.InsnArg;
 import jadx.core.dex.instructions.args.InsnWrapArg;
 import jadx.core.dex.instructions.args.LiteralArg;
 import jadx.core.dex.instructions.args.Named;
-import jadx.core.dex.instructions.args.NamedArg;
 import jadx.core.dex.instructions.args.RegisterArg;
 import jadx.core.dex.instructions.args.SSAVar;
 import jadx.core.dex.instructions.mods.ConstructorInsn;
@@ -705,12 +701,7 @@ public class InsnGen {
 
 	private void makeInvoke(InvokeNode insn, CodeWriter code) throws CodegenException {
 		MethodInfo callMth = insn.getCallMth();
-
-		// inline method
 		MethodNode callMthNode = mth.root().deepResolveMethod(callMth);
-		if (callMthNode != null && inlineMethod(callMthNode, insn, code)) {
-			return;
-		}
 
 		int k = 0;
 		InvokeType type = insn.getInvokeType();
@@ -844,64 +835,6 @@ public class InsnGen {
 		return true;
 	}
 
-	private boolean inlineMethod(MethodNode callMthNode, InvokeNode insn, CodeWriter code) throws CodegenException {
-		MethodInlineAttr mia = callMthNode.get(AType.METHOD_INLINE);
-		if (mia == null) {
-			return false;
-		}
-		InsnNode inl = mia.getInsn();
-		if (Consts.DEBUG) {
-			code.add("/* inline method: ").add(callMthNode.toString()).add("*/").startLine();
-		}
-		if (forceAssign(inl, insn, callMthNode)) {
-			ArgType varType = callMthNode.getReturnType();
-			useType(code, varType);
-			code.add(' ');
-			code.add(mgen.getNameGen().assignNamedArg(new NamedArg("unused", varType)));
-			code.add(" = ");
-		}
-		if (callMthNode.getMethodInfo().getArgumentsTypes().isEmpty()) {
-			makeInsn(inl, code, Flags.BODY_ONLY);
-		} else {
-			// remap args
-			InsnArg[] regs = new InsnArg[callMthNode.getRegsCount()];
-			int[] regNums = mia.getArgsRegNums();
-			for (int i = 0; i < regNums.length; i++) {
-				InsnArg arg = insn.getArg(i);
-				regs[regNums[i]] = arg;
-			}
-			// replace args
-			InsnNode inlCopy = inl.copyWithoutResult();
-			List<RegisterArg> inlArgs = new ArrayList<>();
-			inlCopy.getRegisterArgs(inlArgs);
-			for (RegisterArg r : inlArgs) {
-				int regNum = r.getRegNum();
-				if (regNum >= regs.length) {
-					LOG.warn("Unknown register number {} in method call: {} from {}", r, callMthNode, mth);
-				} else {
-					InsnArg repl = regs[regNum];
-					if (repl == null) {
-						LOG.warn("Not passed register {} in method call: {} from {}", r, callMthNode, mth);
-					} else {
-						inlCopy.replaceArg(r, repl);
-					}
-				}
-			}
-			makeInsn(inlCopy, code, Flags.BODY_ONLY);
-		}
-		return true;
-	}
-
-	private boolean forceAssign(InsnNode inlineInsn, InvokeNode parentInsn, MethodNode callMthNode) {
-		if (parentInsn.getResult() != null) {
-			return false;
-		}
-		if (parentInsn.contains(AFlag.WRAPPED)) {
-			return false;
-		}
-		return !callMthNode.isVoidReturn();
-	}
-
 	private void makeTernary(TernaryInsn insn, CodeWriter code, Set<Flags> state) throws CodegenException {
 		boolean wrap = state.contains(Flags.BODY_ONLY);
 		if (wrap) {

jadx-core/src/main/java/jadx/core/dex/attributes/AFlag.java

@@ -22,7 +22,9 @@ public enum AFlag {
 
 	HIDDEN, // instruction used inside other instruction but not listed in args
 
-	RESTART_CODEGEN,
+	RESTART_CODEGEN, // codegen must be executed again
+	RELOAD_AT_CODEGEN_STAGE, // class can't be analyzed at 'process' stage => unload before 'codegen' stage
+
 	DONT_RENAME, // do not rename during deobfuscation
 	ADDED_TO_REGION,
 

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

@@ -1,7 +1,10 @@
 package jadx.core.dex.attributes.nodes;
 
 import java.util.List;
+import java.util.Objects;
 
+import jadx.core.Consts;
+import jadx.core.dex.attributes.AFlag;
 import jadx.core.dex.attributes.AType;
 import jadx.core.dex.attributes.IAttribute;
 import jadx.core.dex.instructions.args.RegisterArg;
@@ -10,7 +13,10 @@ import jadx.core.dex.nodes.MethodNode;
 
 public class MethodInlineAttr implements IAttribute {
 
-	public static void markForInline(MethodNode mth, InsnNode replaceInsn) {
+	private static final MethodInlineAttr INLINE_NOT_NEEDED = new MethodInlineAttr(null, null);
+
+	public static MethodInlineAttr markForInline(MethodNode mth, InsnNode replaceInsn) {
+		Objects.requireNonNull(replaceInsn);
 		List<RegisterArg> allArgRegs = mth.getAllArgRegs();
 		int argsCount = allArgRegs.size();
 		int[] regNums = new int[argsCount];
@@ -18,7 +24,19 @@ public class MethodInlineAttr implements IAttribute {
 			RegisterArg reg = allArgRegs.get(i);
 			regNums[i] = reg.getRegNum();
 		}
-		mth.addAttr(new MethodInlineAttr(replaceInsn, regNums));
+		MethodInlineAttr mia = new MethodInlineAttr(replaceInsn, regNums);
+		mth.addAttr(mia);
+		if (Consts.DEBUG) {
+			mth.addAttr(AType.COMMENTS, "Removed for inline");
+		} else {
+			mth.add(AFlag.DONT_GENERATE);
+		}
+		return mia;
+	}
+
+	public static MethodInlineAttr inlineNotNeeded(MethodNode mth) {
+		mth.addAttr(INLINE_NOT_NEEDED);
+		return INLINE_NOT_NEEDED;
 	}
 
 	private final InsnNode insn;
@@ -33,6 +51,10 @@ public class MethodInlineAttr implements IAttribute {
 		this.argsRegNums = argsRegNums;
 	}
 
+	public boolean notNeeded() {
+		return insn == null;
+	}
+
 	public InsnNode getInsn() {
 		return insn;
 	}
@@ -48,6 +70,9 @@ public class MethodInlineAttr implements IAttribute {
 
 	@Override
 	public String toString() {
+		if (notNeeded()) {
+			return "INLINE_NOT_NEEDED";
+		}
 		return "INLINE: " + insn;
 	}
 }

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

@@ -65,6 +65,7 @@ public class ClassNode extends NotificationAttrNode implements ILoadable, ICodeN
 	private ClassNode parentClass;
 
 	private volatile ProcessState state = ProcessState.NOT_LOADED;
+	private LoadStage loadStage = LoadStage.NONE;
 
 	/** Top level classes used in this class (only for top level classes, empty for inners) */
 	private List<ClassNode> dependencies = Collections.emptyList();
@@ -288,6 +289,7 @@ public class ClassNode extends NotificationAttrNode implements ILoadable, ICodeN
 		fields.forEach(FieldNode::unloadAttributes);
 		unloadAttributes();
 		setState(NOT_LOADED);
+		this.loadStage = LoadStage.NONE;
 		this.smali = null;
 	}
 
@@ -577,6 +579,30 @@ public class ClassNode extends NotificationAttrNode implements ILoadable, ICodeN
 		this.state = state;
 	}
 
+	public LoadStage getLoadStage() {
+		return loadStage;
+	}
+
+	public void startProcessStage() {
+		this.loadStage = LoadStage.PROCESS_STAGE;
+	}
+
+	public void startCodegenStage() {
+		this.loadStage = LoadStage.CODEGEN_STAGE;
+		if (contains(AFlag.RELOAD_AT_CODEGEN_STAGE)) {
+			unload();
+			remove(AFlag.RELOAD_AT_CODEGEN_STAGE);
+		}
+	}
+
+	public void reloadAtCodegenStage() {
+		ClassNode topCls = this.getTopParentClass();
+		if (topCls.getLoadStage() == LoadStage.CODEGEN_STAGE) {
+			throw new JadxRuntimeException("Class not yet loaded at codegen stage");
+		}
+		topCls.add(AFlag.RELOAD_AT_CODEGEN_STAGE);
+	}
+
 	public List<ClassNode> getDependencies() {
 		return dependencies;
 	}
@@ -632,4 +658,5 @@ public class ClassNode extends NotificationAttrNode implements ILoadable, ICodeN
 	public String toString() {
 		return clsInfo.getFullName();
 	}
+
 }

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

@@ -0,0 +1,7 @@
+package jadx.core.dex.nodes;
+
+public enum LoadStage {
+	NONE,
+	PROCESS_STAGE, // dependencies not yet loaded
+	CODEGEN_STAGE, // all dependencies loaded
+}

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

@@ -83,7 +83,7 @@ public class FixAccessModifiers extends AbstractVisitor {
 		if (!accessFlags.isPublic()) {
 			// if class is used in inlinable method => make it public
 			for (MethodNode useMth : cls.getUseInMth()) {
-				boolean canInline = MethodInlineVisitor.canInline(useMth) || useMth.contains(AType.METHOD_INLINE);
+				boolean canInline = MarkMethodsForInline.canInline(useMth) || useMth.contains(AType.METHOD_INLINE);
 				if (canInline && !useMth.getUseIn().isEmpty()) {
 					return AccessFlags.PUBLIC;
 				}

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

@@ -0,0 +1,132 @@
+package jadx.core.dex.visitors;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import jadx.core.dex.attributes.AFlag;
+import jadx.core.dex.attributes.nodes.MethodInlineAttr;
+import jadx.core.dex.info.MethodInfo;
+import jadx.core.dex.instructions.InsnType;
+import jadx.core.dex.instructions.InvokeNode;
+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;
+import jadx.core.dex.nodes.BlockNode;
+import jadx.core.dex.nodes.InsnNode;
+import jadx.core.dex.nodes.MethodNode;
+import jadx.core.dex.visitors.typeinference.TypeInferenceVisitor;
+import jadx.core.utils.BlockUtils;
+import jadx.core.utils.exceptions.JadxException;
+import jadx.core.utils.exceptions.JadxRuntimeException;
+
+@JadxVisitor(
+		name = "InlineMethods",
+		desc = "Inline methods (previously marked in MarkMethodsForInline)",
+		runAfter = TypeInferenceVisitor.class,
+		runBefore = ModVisitor.class
+)
+public class InlineMethods extends AbstractVisitor {
+	private static final Logger LOG = LoggerFactory.getLogger(InlineMethods.class);
+
+	@Override
+	public void visit(MethodNode mth) throws JadxException {
+		if (mth.isNoCode()) {
+			return;
+		}
+		for (BlockNode block : mth.getBasicBlocks()) {
+			for (InsnNode insn : block.getInstructions()) {
+				if (insn.getType() == InsnType.INVOKE) {
+					processInvokeInsn(mth, block, ((InvokeNode) insn));
+				}
+			}
+		}
+	}
+
+	private void processInvokeInsn(MethodNode mth, BlockNode block, InvokeNode insn) {
+		MethodInfo callMthInfo = insn.getCallMth();
+		MethodNode callMth = mth.root().deepResolveMethod(callMthInfo);
+		if (callMth == null) {
+			return;
+		}
+		try {
+			// TODO: sort inner classes process order by dependencies!
+			MethodInlineAttr mia = MarkMethodsForInline.process(callMth);
+			if (mia == null) {
+				// method not yet loaded => will retry at codegen stage
+				mth.getParentClass().reloadAtCodegenStage();
+				return;
+			}
+			if (mia.notNeeded()) {
+				return;
+			}
+			inlineMethod(mth, callMth, mia, block, insn);
+		} catch (Exception e) {
+			throw new JadxRuntimeException("Failed to process method for inline", e);
+		}
+	}
+
+	private void inlineMethod(MethodNode mth, MethodNode callMth, MethodInlineAttr mia, BlockNode block, InvokeNode insn) {
+		InsnNode inlCopy = mia.getInsn().copyWithoutResult();
+		RegisterArg resultArg = insn.getResult();
+		if (resultArg != null) {
+			inlCopy.setResult(resultArg.duplicate());
+		} else if (isAssignNeeded(mia.getInsn(), insn, callMth)) {
+			// add fake result to make correct java expression (see test TestGetterInlineNegative)
+			inlCopy.setResult(makeFakeArg(mth, callMth.getReturnType(), "unused"));
+		}
+		if (!callMth.getMethodInfo().getArgumentsTypes().isEmpty()) {
+			// remap args
+			InsnArg[] regs = new InsnArg[callMth.getRegsCount()];
+			int[] regNums = mia.getArgsRegNums();
+			for (int i = 0; i < regNums.length; i++) {
+				InsnArg arg = insn.getArg(i);
+				regs[regNums[i]] = arg;
+			}
+			// replace args
+			List<RegisterArg> inlArgs = new ArrayList<>();
+			inlCopy.getRegisterArgs(inlArgs);
+			for (RegisterArg r : inlArgs) {
+				int regNum = r.getRegNum();
+				if (regNum >= regs.length) {
+					LOG.warn("Unknown register number {} in method call: {} from {}", r, callMth, mth);
+				} else {
+					InsnArg repl = regs[regNum];
+					if (repl == null) {
+						LOG.warn("Not passed register {} in method call: {} from {}", r, callMth, mth);
+					} else {
+						inlCopy.replaceArg(r, repl);
+					}
+				}
+			}
+		}
+		if (!BlockUtils.replaceInsn(mth, block, insn, inlCopy)) {
+			mth.addWarnComment("Failed to inline method: " + callMth);
+		}
+	}
+
+	private boolean isAssignNeeded(InsnNode inlineInsn, InvokeNode parentInsn, MethodNode callMthNode) {
+		if (parentInsn.getResult() != null) {
+			return false;
+		}
+		if (parentInsn.contains(AFlag.WRAPPED)) {
+			return false;
+		}
+		if (inlineInsn.getType() == InsnType.IPUT) {
+			return false;
+		}
+		return !callMthNode.isVoidReturn();
+	}
+
+	private RegisterArg makeFakeArg(MethodNode mth, ArgType varType, String name) {
+		RegisterArg fakeArg = RegisterArg.reg(0, varType);
+		SSAVar ssaVar = mth.makeNewSVar(fakeArg);
+		InitCodeVariables.initCodeVar(ssaVar);
+		fakeArg.setName(name);
+		ssaVar.setType(varType);
+		return fakeArg;
+	}
+}

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

@@ -3,6 +3,8 @@ package jadx.core.dex.visitors;
 import java.util.ArrayList;
 import java.util.List;
 
+import org.jetbrains.annotations.Nullable;
+
 import jadx.api.plugins.input.data.AccessFlags;
 import jadx.core.Consts;
 import jadx.core.dex.attributes.AFlag;
@@ -17,30 +19,50 @@ import jadx.core.dex.instructions.args.InsnArg;
 import jadx.core.dex.instructions.args.InsnWrapArg;
 import jadx.core.dex.instructions.args.RegisterArg;
 import jadx.core.dex.nodes.BlockNode;
-import jadx.core.dex.nodes.FieldNode;
 import jadx.core.dex.nodes.InsnNode;
 import jadx.core.dex.nodes.MethodNode;
 import jadx.core.utils.exceptions.JadxException;
 
 @JadxVisitor(
-		name = "InlineMethods",
-		desc = "Inline synthetic static methods",
+		name = "MarkMethodsForInline",
+		desc = "Mark synthetic static methods for inline",
 		runAfter = {
 				FixAccessModifiers.class,
 				ClassModifier.class
 		}
 )
-public class MethodInlineVisitor extends AbstractVisitor {
+public class MarkMethodsForInline extends AbstractVisitor {
 
 	@Override
 	public void visit(MethodNode mth) throws JadxException {
-		if (canInline(mth) && mth.getBasicBlocks().size() == 2) {
-			BlockNode returnBlock = mth.getBasicBlocks().get(1);
-			if (returnBlock.contains(AFlag.RETURN) || returnBlock.getInstructions().isEmpty()) {
-				BlockNode firstBlock = mth.getBasicBlocks().get(0);
-				inlineMth(mth, firstBlock, returnBlock);
+		process(mth);
+	}
+
+	/**
+	 * @return null if method can't be analyzed (not loaded)
+	 */
+	@Nullable
+	public static MethodInlineAttr process(MethodNode mth) {
+		MethodInlineAttr mia = mth.get(AType.METHOD_INLINE);
+		if (mia != null) {
+			return mia;
+		}
+		if (canInline(mth)) {
+			List<BlockNode> blocks = mth.getBasicBlocks();
+			if (blocks == null) {
+				return null;
+			}
+			if (blocks.size() == 2) {
+				BlockNode returnBlock = blocks.get(1);
+				if (returnBlock.contains(AFlag.RETURN) || returnBlock.getInstructions().isEmpty()) {
+					MethodInlineAttr inlined = inlineMth(mth, blocks.get(0), returnBlock);
+					if (inlined != null) {
+						return inlined;
+					}
+				}
 			}
 		}
+		return MethodInlineAttr.inlineNotNeeded(mth);
 	}
 
 	public static boolean canInline(MethodNode mth) {
@@ -51,41 +73,36 @@ public class MethodInlineVisitor extends AbstractVisitor {
 		return accessFlags.isSynthetic() && accessFlags.isStatic();
 	}
 
-	private static void inlineMth(MethodNode mth, BlockNode firstBlock, BlockNode returnBlock) {
+	@Nullable
+	private static MethodInlineAttr inlineMth(MethodNode mth, BlockNode firstBlock, BlockNode returnBlock) {
 		List<InsnNode> insnList = firstBlock.getInstructions();
 		if (insnList.isEmpty()) {
 			// synthetic field getter
 			BlockNode block = mth.getBasicBlocks().get(1);
 			InsnNode insn = block.getInstructions().get(0);
 			// set arg from 'return' instruction
-			addInlineAttr(mth, InsnNode.wrapArg(insn.getArg(0)));
-			return;
+			return addInlineAttr(mth, InsnNode.wrapArg(insn.getArg(0)));
 		}
 		// synthetic field setter or method invoke
 		if (insnList.size() == 1) {
-			addInlineAttr(mth, insnList.get(0));
-			return;
+			return addInlineAttr(mth, insnList.get(0));
 		}
-
 		// TODO: inline field arithmetics. Disabled tests: TestAnonymousClass3a and TestAnonymousClass5
+		return null;
 	}
 
-	private static void addInlineAttr(MethodNode mth, InsnNode insn) {
-		if (fixVisibilityOfInlineCode(mth, insn)) {
-			if (Consts.DEBUG) {
-				mth.addAttr(AType.COMMENTS, "Removed for inline");
-			} else {
-				InsnNode copy = insn.copyWithoutResult();
-				// unbind SSA variables from copy instruction
-				List<RegisterArg> regArgs = new ArrayList<>();
-				copy.getRegisterArgs(regArgs);
-				for (RegisterArg regArg : regArgs) {
-					copy.replaceArg(regArg, regArg.duplicate(regArg.getRegNum(), null));
-				}
-				MethodInlineAttr.markForInline(mth, copy);
-				mth.add(AFlag.DONT_GENERATE);
-			}
+	private static MethodInlineAttr addInlineAttr(MethodNode mth, InsnNode insn) {
+		if (!fixVisibilityOfInlineCode(mth, insn)) {
+			return null;
 		}
+		InsnNode copy = insn.copyWithoutResult();
+		// unbind SSA variables from copy instruction
+		List<RegisterArg> regArgs = new ArrayList<>();
+		copy.getRegisterArgs(regArgs);
+		for (RegisterArg regArg : regArgs) {
+			copy.replaceArg(regArg, regArg.duplicate(regArg.getRegNum(), null));
+		}
+		return MethodInlineAttr.markForInline(mth, copy);
 	}
 
 	private static boolean fixVisibilityOfInlineCode(MethodNode mth, InsnNode insn) {
@@ -109,10 +126,7 @@ public class MethodInlineVisitor extends AbstractVisitor {
 		if (insn instanceof IndexInsnNode) {
 			Object indexObj = ((IndexInsnNode) insn).getIndex();
 			if (indexObj instanceof FieldInfo) {
-				FieldNode fieldNode = mth.root().deepResolveField(((FieldInfo) indexObj));
-				if (fieldNode != null) {
-					FixAccessModifiers.changeVisibility(fieldNode, newVisFlag);
-				}
+				// field access must be already fixed in ModVisitor.fixFieldUsage method
 				return true;
 			}
 		}

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

@@ -4,6 +4,7 @@ import java.util.Collections;
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.Objects;
 
 import org.jetbrains.annotations.Nullable;
 import org.slf4j.Logger;
@@ -18,6 +19,7 @@ import jadx.core.dex.attributes.AType;
 import jadx.core.dex.attributes.AttrNode;
 import jadx.core.dex.attributes.annotations.AnnotationsList;
 import jadx.core.dex.attributes.nodes.FieldReplaceAttr;
+import jadx.core.dex.info.AccessInfo;
 import jadx.core.dex.info.FieldInfo;
 import jadx.core.dex.info.MethodInfo;
 import jadx.core.dex.instructions.ArithNode;
@@ -148,7 +150,7 @@ public class ModVisitor extends AbstractVisitor {
 
 					case IPUT:
 					case IGET:
-						fixTypeForFieldAccess(mth, (IndexInsnNode) insn);
+						fixFieldUsage(mth, (IndexInsnNode) insn);
 						break;
 
 					default:
@@ -159,7 +161,10 @@ public class ModVisitor extends AbstractVisitor {
 		}
 	}
 
-	private static void fixTypeForFieldAccess(MethodNode mth, IndexInsnNode insn) {
+	/**
+	 * If field is not visible from use site => cast to origin class
+	 */
+	private static void fixFieldUsage(MethodNode mth, IndexInsnNode insn) {
 		InsnArg instanceArg = insn.getArg(insn.getType() == InsnType.IGET ? 0 : 1);
 		if (instanceArg.contains(AFlag.SUPER)) {
 			return;
@@ -170,12 +175,25 @@ public class ModVisitor extends AbstractVisitor {
 		FieldInfo fieldInfo = (FieldInfo) insn.getIndex();
 		ArgType clsType = fieldInfo.getDeclClass().getType();
 		ArgType instanceType = instanceArg.getType();
-		TypeCompareEnum result = mth.root().getTypeCompare().compareTypes(instanceType, clsType);
-		if (result.isEqual() || (result == TypeCompareEnum.NARROW_BY_GENERIC && !instanceType.isGenericType())) {
+		if (Objects.equals(clsType, instanceType)) {
+			// cast not needed
 			return;
 		}
+
+		FieldNode fieldNode = mth.root().resolveField(fieldInfo);
+		if (fieldNode == null) {
+			// unknown field
+			TypeCompareEnum result = mth.root().getTypeCompare().compareTypes(instanceType, clsType);
+			if (result.isEqual() || (result == TypeCompareEnum.NARROW_BY_GENERIC && !instanceType.isGenericType())) {
+				return;
+			}
+		} else if (isFieldVisibleInMethod(fieldNode, mth)) {
+			return;
+		}
+		// insert cast
 		IndexInsnNode castInsn = new IndexInsnNode(InsnType.CAST, clsType, 1);
 		castInsn.addArg(instanceArg.duplicate());
+		castInsn.add(AFlag.SYNTHETIC);
 		castInsn.add(AFlag.EXPLICIT_CAST);
 
 		InsnArg castArg = InsnArg.wrapInsnIntoArg(castInsn);
@@ -184,6 +202,33 @@ public class ModVisitor extends AbstractVisitor {
 		InsnRemover.unbindArgUsage(mth, instanceArg);
 	}
 
+	private static boolean isFieldVisibleInMethod(FieldNode field, MethodNode mth) {
+		AccessInfo accessFlags = field.getAccessFlags();
+		if (accessFlags.isPublic()) {
+			return true;
+		}
+		ClassNode useCls = mth.getParentClass();
+		ClassNode fieldCls = field.getParentClass();
+		boolean sameScope = Objects.equals(useCls, fieldCls) && !mth.getAccessFlags().isStatic();
+		if (sameScope) {
+			return true;
+		}
+		if (accessFlags.isPrivate()) {
+			return false;
+		}
+		// package-private or protected
+		if (Objects.equals(useCls.getClassInfo().getPackage(), fieldCls.getClassInfo().getPackage())) {
+			// same package
+			return true;
+		}
+		if (accessFlags.isPackagePrivate()) {
+			return false;
+		}
+		// protected
+		TypeCompareEnum result = mth.root().getTypeCompare().compareTypes(useCls, fieldCls);
+		return result == TypeCompareEnum.NARROW; // true if use class is subclass of field class
+	}
+
 	private static void replaceConstKeys(ClassNode parentClass, SwitchInsn insn) {
 		int[] keys = insn.getKeys();
 		int len = keys.length;

jadx-core/src/main/java/jadx/core/dex/visitors/typeinference/TypeCompare.java

@@ -12,6 +12,7 @@ import org.slf4j.LoggerFactory;
 import jadx.core.dex.instructions.args.ArgType;
 import jadx.core.dex.instructions.args.ArgType.WildcardBound;
 import jadx.core.dex.instructions.args.PrimitiveType;
+import jadx.core.dex.nodes.ClassNode;
 import jadx.core.dex.nodes.RootNode;
 import jadx.core.utils.exceptions.JadxRuntimeException;
 
@@ -37,6 +38,10 @@ public class TypeCompare {
 		this.reversedComparator = comparator.reversed();
 	}
 
+	public TypeCompareEnum compareTypes(ClassNode first, ClassNode second) {
+		return compareObjects(first.getType(), second.getType());
+	}
+
 	/**
 	 * Compare two type and return result for first argument (narrow, wider or conflict)
 	 */

jadx-core/src/main/java/jadx/core/utils/InsnRemover.java

@@ -135,7 +135,7 @@ public class InsnRemover {
 			mth.removeSVar(ssaVar);
 			return;
 		}
-		if (Consts.DEBUG) { // TODO: enable this
+		if (Consts.DEBUG_WITH_ERRORS) {
 			throw new JadxRuntimeException("Can't remove SSA var, still in use, count: " + useCount + ", list:"
 					+ NL + "  " + ssaVar.getUseList().stream()
 							.map(arg -> arg + " from " + arg.getParentInsn())
@@ -172,7 +172,7 @@ public class InsnRemover {
 					break;
 				}
 			}
-			if (!found && Consts.DEBUG) { // TODO: enable this
+			if (!found && Consts.DEBUG_WITH_ERRORS) {
 				throw new JadxRuntimeException("Can't remove insn:"
 						+ NL + "  " + rem
 						+ NL + " not found in list:"

jadx-core/src/test/java/jadx/tests/integration/types/TestFieldCast.java

@@ -0,0 +1,61 @@
+package jadx.tests.integration.types;
+
+import org.junit.jupiter.api.Test;
+
+import jadx.tests.api.IntegrationTest;
+
+import static jadx.tests.api.utils.assertj.JadxAssertions.assertThat;
+
+/**
+ * Issue #962
+ */
+public class TestFieldCast extends IntegrationTest {
+
+	public static class TestCls {
+		public static class A {
+			public boolean publicField;
+			boolean packagePrivateField;
+			protected boolean protectedField;
+			private boolean privateField;
+		}
+
+		public static class B extends A {
+			public void test() {
+				((A) this).publicField = false;
+				((A) this).protectedField = false;
+				((A) this).packagePrivateField = false;
+				((A) this).privateField = false; // cast to 'A' needed only here
+			}
+		}
+
+		public static class C {
+			public void test(B b) {
+				((A) b).publicField = false;
+				((A) b).protectedField = false;
+				((A) b).packagePrivateField = false;
+				((A) b).privateField = false; // cast to 'A' needed only here
+			}
+		}
+
+		private static class D {
+			public <T extends B> void test(T t) {
+				((A) t).publicField = false;
+				((A) t).protectedField = false;
+				((A) t).packagePrivateField = false;
+				((A) t).privateField = false; // cast to 'A' needed only here
+			}
+		}
+	}
+
+	@Test
+	public void test() {
+		noDebugInfo();
+		assertThat(getClassNode(TestCls.class))
+				.code()
+				.containsOne("((A) this)")
+				.containsOne("((A) b)")
+				.containsOne("((A) t)")
+				.doesNotContain("unused =")
+				.doesNotContain("access modifiers changed");
+	}
+}