core: fix type check for loop over iterable.

jadx-core/src/main/java/jadx/core/dex/visitors/regions/LoopRegionVisitor.java

@@ -224,7 +224,8 @@ public class LoopRegionVisitor extends AbstractVisitor implements IRegionVisitor
 		InsnArg iterableArg = assignInsn.getArg(0);
 		InsnNode hasNextCall = useList.get(0).getParentInsn();
 		InsnNode nextCall = useList.get(1).getParentInsn();
-		if (!checkInvoke(hasNextCall, "java.util.Iterator", "hasNext()Z", 0)
+		if (hasNextCall == null || nextCall == null
+				|| !checkInvoke(hasNextCall, "java.util.Iterator", "hasNext()Z", 0)
 				|| !checkInvoke(nextCall, "java.util.Iterator", "next()Ljava/lang/Object;", 0)) {
 			return false;
 		}
@@ -239,7 +240,7 @@ public class LoopRegionVisitor extends AbstractVisitor implements IRegionVisitor
 				} else {
 					iterVar = parentInsn.getResult();
 					InsnArg castArg = BlockUtils.searchWrappedInsnParent(mth, parentInsn);
-					if (castArg != null) {
+					if (castArg != null && castArg.getParentInsn() != null) {
 						castArg.getParentInsn().replaceArg(castArg, iterVar);
 					} else {
 						// cast not inlined
@@ -266,28 +267,35 @@ public class LoopRegionVisitor extends AbstractVisitor implements IRegionVisitor
 	}
 
 	private static boolean fixIterableType(InsnArg iterableArg, RegisterArg iterVar) {
-		ArgType type = iterableArg.getType();
-		if (type.isGeneric()) {
-			ArgType[] genericTypes = type.getGenericTypes();
-			if (genericTypes != null && genericTypes.length == 1) {
+		ArgType iterableType = iterableArg.getType();
+		ArgType varType = iterVar.getType();
+		if (iterableType.isGeneric()) {
+			ArgType[] genericTypes = iterableType.getGenericTypes();
+			if (genericTypes == null || genericTypes.length != 1) {
+				return false;
+			}
 			ArgType gType = genericTypes[0];
-				if (ArgType.isInstanceOf(gType, iterVar.getType())) {
+			if (gType.equals(varType)) {
 				return true;
-				} else {
-					LOG.warn("Generic type differs: {} and {}", type, iterVar.getType());
 			}
+			if (gType.isGenericType()) {
+				iterVar.setType(gType);
+				return true;
+			}
+			if (ArgType.isInstanceOf(gType, varType)) {
+				return true;
+			}
+			LOG.warn("Generic type differs: {} and {}", gType, varType);
+			return false;
 		}
-		} else {
 		if (!iterableArg.isRegister()) {
 			return true;
 		}
 		// TODO: add checks
-			type = ArgType.generic(type.getObject(), new ArgType[]{iterVar.getType()});
-			iterableArg.setType(type);
+		iterableType = ArgType.generic(iterableType.getObject(), new ArgType[]{varType});
+		iterableArg.setType(iterableType);
 		return true;
 	}
-		return false;
-	}
 
 	/**
 	 * Check if instruction is a interface invoke with corresponding parameters.

jadx-core/src/test/java/jadx/tests/integration/loops/TestIterableForEach3.java

+package jadx.tests.integration.loops;
+
+import jadx.core.dex.nodes.ClassNode;
+import jadx.tests.api.IntegrationTest;
+
+import java.util.Set;
+
+import org.junit.Test;
+
+import static jadx.tests.api.utils.JadxMatchers.containsOne;
+import static org.junit.Assert.assertThat;
+
+public class TestIterableForEach3 extends IntegrationTest {
+
+	public static class TestCls<T extends String> {
+		private Set<T> a;
+		private Set<T> b;
+
+		private void test(T str) {
+			Set<T> set = str.length() == 1 ? a : b;
+			for (T s : set) {
+				if (s.length() == str.length()) {
+					if (str.length() == 0) {
+						set.remove(s);
+					} else {
+						set.add(str);
+					}
+					return;
+				}
+			}
+		}
+	}
+
+	@Test
+	public void test() {
+		ClassNode cls = getClassNode(TestCls.class);
+		String code = cls.getCode().toString();
+
+		assertThat(code, containsOne("for (T s : set) {"));
+		assertThat(code, containsOne("if (str.length() == 0) {"));
+		// TODO move return outside 'if'
+	}
+}