fix: keep types on duplicate cast remove (#1527)

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

@@ -362,8 +362,7 @@ public class ModVisitor extends AbstractVisitor {
 	private static void removeCheckCast(MethodNode mth, BlockNode block, int i, IndexInsnNode insn) {
 		InsnArg castArg = insn.getArg(0);
 		ArgType castType = (ArgType) insn.getIndex();
-		if (!ArgType.isCastNeeded(mth.root(), castArg.getType(), castType)
-				|| isCastDuplicate(insn)) {
+		if (!ArgType.isCastNeeded(mth.root(), castArg.getType(), castType)) {
 			RegisterArg result = insn.getResult();
 			result.setType(castArg.getType());
 
@@ -371,10 +370,19 @@ public class ModVisitor extends AbstractVisitor {
 			move.setResult(result);
 			move.addArg(castArg);
 			replaceInsn(mth, block, i, move);
+			return;
+		}
+		InsnNode prevCast = isCastDuplicate(insn);
+		if (prevCast != null) {
+			// replace previous cast with move
+			InsnNode move = new InsnNode(InsnType.MOVE, 1);
+			move.setResult(prevCast.getResult());
+			move.addArg(prevCast.getArg(0));
+			replaceInsn(mth, block, prevCast, move);
 		}
 	}
 
-	private static boolean isCastDuplicate(IndexInsnNode castInsn) {
+	private static @Nullable InsnNode isCastDuplicate(IndexInsnNode castInsn) {
 		InsnArg arg = castInsn.getArg(0);
 		if (arg.isRegister()) {
 			SSAVar sVar = ((RegisterArg) arg).getSVar();
@@ -382,11 +390,13 @@ public class ModVisitor extends AbstractVisitor {
 				InsnNode assignInsn = sVar.getAssign().getParentInsn();
 				if (assignInsn != null && assignInsn.getType() == InsnType.CHECK_CAST) {
 					ArgType assignCastType = (ArgType) ((IndexInsnNode) assignInsn).getIndex();
-					return assignCastType.equals(castInsn.getIndex());
+					if (assignCastType.equals(castInsn.getIndex())) {
+						return assignInsn;
+					}
 				}
 			}
 		}
-		return false;
+		return null;
 	}
 
 	/**

jadx-core/src/test/java/jadx/tests/integration/types/TestTypeResolver21.java

@@ -0,0 +1,29 @@
+package jadx.tests.integration.types;
+
+import org.junit.jupiter.api.Test;
+
+import jadx.tests.api.SmaliTest;
+
+import static jadx.tests.api.utils.assertj.JadxAssertions.assertThat;
+
+/**
+ * Issue 1527
+ */
+@SuppressWarnings("CommentedOutCode")
+public class TestTypeResolver21 extends SmaliTest {
+	// @formatter:off
+	/*
+		public Number test(Object objectArray) {
+			Object[] arr = (Object[]) objectArray;
+			return (Number) arr[0];
+		}
+	*/
+	// @formatter:on
+
+	@Test
+	public void test() {
+		assertThat(getClassNodeFromSmali())
+				.code()
+				.containsOne("Object[] arr = (Object[]) objectArray;");
+	}
+}

jadx-core/src/test/smali/types/TestTypeResolver21.smali

@@ -0,0 +1,23 @@
+.class public Ltypes/TestTypeResolver21;
+.super Ljava/lang/Object;
+.source "TestTypeResolver21.java"
+
+
+.method public test(Ljava/lang/Object;)Ljava/lang/Number;
+    .registers 4
+    .param p1, "objectArray"    # Ljava/lang/Object;
+
+    .prologue
+    .line 16
+    check-cast p1, [Ljava/lang/Object;
+    .end local p1    # "objectArray":Ljava/lang/Object;
+    move-object v0, p1
+    check-cast v0, [Ljava/lang/Object;
+
+    .line 17
+    .local v0, "arr":[Ljava/lang/Object;
+    const/4 v1, 0x0
+    aget-object v1, v0, v1
+    check-cast v1, Ljava/lang/Number;
+    return-object v1
+.end method