core: use flag for mark 'this' register

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

@@ -26,6 +26,7 @@ public enum AFlag {
 	SKIP_ARG, // skip argument in invoke call
 	ANONYMOUS_CONSTRUCTOR,
 	ANONYMOUS_CLASS,
+	THIS,
 
 	ELSE_IF_CHAIN,
 

jadx-core/src/main/java/jadx/core/dex/instructions/args/InsnArg.java

@@ -140,7 +140,7 @@ public abstract class InsnArg extends Typed {
 	}
 
 	public boolean isThis() {
-		// must be implemented in RegisterArg and MthParameterArg
+		// must be implemented in RegisterArg
 		return false;
 	}
 }

jadx-core/src/main/java/jadx/core/dex/instructions/args/RegisterArg.java

@@ -4,6 +4,7 @@ import java.util.Objects;
 
 import org.jetbrains.annotations.NotNull;
 
+import jadx.core.dex.attributes.AFlag;
 import jadx.core.dex.instructions.InsnType;
 import jadx.core.dex.instructions.PhiInsn;
 import jadx.core.dex.nodes.DexNode;
@@ -118,7 +119,7 @@ public class RegisterArg extends InsnArg implements Named {
 
 	@Override
 	public boolean isThis() {
-		if ("this".equals(getName())) {
+		if (contains(AFlag.THIS)) {
 			return true;
 		}
 		// maybe it was moved from 'this' register

jadx-core/src/main/java/jadx/core/dex/instructions/args/TypeImmutableArg.java

@@ -4,7 +4,7 @@ import org.jetbrains.annotations.NotNull;
 
 public class TypeImmutableArg extends RegisterArg {
 
-	private boolean isThis;
+	public static final String THIS_ARG_NAME = "this";
 
 	public TypeImmutableArg(int rn, ArgType type) {
 		super(rn, type);
@@ -20,48 +20,20 @@ public class TypeImmutableArg extends RegisterArg {
 		// not allowed
 	}
 
-	public void markAsThis() {
-		this.isThis = true;
-	}
-
-	@Override
-	public boolean isThis() {
-		return isThis;
-	}
-
 	@Override
 	public String getName() {
-		if (isThis) {
-			return "this";
+		if (isThis()) {
+			return THIS_ARG_NAME;
 		}
 		return super.getName();
 	}
 
 	@Override
 	void setSVar(@NotNull SSAVar sVar) {
-		if (isThis) {
-			sVar.setName("this");
+		if (isThis()) {
+			sVar.setName(THIS_ARG_NAME);
 		}
 		sVar.setTypeImmutable(type);
 		super.setSVar(sVar);
 	}
-
-	@Override
-	public boolean equals(Object obj) {
-		if (this == obj) {
-			return true;
-		}
-		if (!(obj instanceof TypeImmutableArg)) {
-			return false;
-		}
-		if (!super.equals(obj)) {
-			return false;
-		}
-		return isThis == ((TypeImmutableArg) obj).isThis;
-	}
-
-	@Override
-	public int hashCode() {
-		return 31 * super.hashCode() + (isThis ? 1 : 0);
-	}
 }

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

@@ -193,11 +193,11 @@ public class MethodNode extends LineAttrNode implements ILoadable, IDexNode {
 				}
 			}
 			initArguments(argsTypes);
+			return true;
 		} catch (JadxRuntimeException e) {
 			LOG.error("Method signature parse error: {}", this, e);
 			return false;
 		}
-		return true;
 	}
 
 	private void initArguments(List<ArgType> args) {
@@ -214,7 +214,7 @@ public class MethodNode extends LineAttrNode implements ILoadable, IDexNode {
 			thisArg = null;
 		} else {
 			TypeImmutableArg arg = InsnArg.typeImmutableReg(pos - 1, parentClass.getClassInfo().getType());
-			arg.markAsThis();
+			arg.add(AFlag.THIS);
 			thisArg = arg;
 		}
 		if (args.isEmpty()) {
@@ -243,6 +243,7 @@ public class MethodNode extends LineAttrNode implements ILoadable, IDexNode {
 		return argsList.remove(0);
 	}
 
+	@Nullable
 	public RegisterArg getThisArg() {
 		return thisArg;
 	}

jadx-core/src/main/java/jadx/core/dex/visitors/ssa/SSATransform.java

@@ -53,6 +53,7 @@ public class SSATransform extends AbstractVisitor {
 
 		fixLastAssignInTry(mth);
 		removeBlockerInsns(mth);
+		markThisArg(mth);
 
 		boolean repeatFix;
 		int k = 0;
@@ -405,4 +406,11 @@ public class SSATransform extends AbstractVisitor {
 		InstructionRemover.unbindInsn(mth, phi);
 		return true;
 	}
+
+	private static void markThisArg(MethodNode mth) {
+		RegisterArg thisArg = mth.getThisArg();
+		if (thisArg != null) {
+			thisArg.getSVar().getUseList().forEach(arg -> arg.add(AFlag.THIS));
+		}
+	}
 }