fix: return type lost after type inference (#396)

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

@@ -56,11 +56,13 @@ public class TypeInference extends AbstractVisitor {
 		}
 		ArgType type = assign.getType();
 		for (RegisterArg arg : useList) {
-			ArgType useType = arg.getType();
-			ArgType newType = ArgType.merge(dex, type, useType);
-			if (newType != null) {
-				type = newType;
-			}
+		    ArgType useType = arg.getType();
+            if (!type.isTypeKnown() || !useType.isTypeKnown()) {
+                ArgType newType = ArgType.merge(dex, type, useType);
+                if (newType != null) {
+                    type = newType;
+                }
+            }
 		}
 		return type;
 	}

jadx-core/src/test/java/jadx/tests/integration/arrays/TestArrays4.java

+package jadx.tests.integration.arrays;
+
+import jadx.core.dex.nodes.ClassNode;
+import jadx.tests.api.SmaliTest;
+import static jadx.tests.api.utils.JadxMatchers.containsOne;
+import static org.junit.Assert.assertThat;
+import org.junit.Test;
+
+public class TestArrays4 extends SmaliTest {
+
+    public static class TestCls {
+        char[] payload;
+
+        public TestCls(byte[] bytes) {
+            char[] a = toChars(bytes);
+            this.payload = new char[a.length];
+            System.arraycopy(a, 0, this.payload, 0, bytes.length);
+        }
+
+        private static char[] toChars(byte[] bArr) {
+            return new char[bArr.length];
+        }
+    }
+
+    @Test
+    public void testArrayTypeInference() {
+        noDebugInfo();
+        ClassNode cls = getClassNode(TestCls.class);
+        String code = cls.getCode().toString();
+
+        assertThat(code, containsOne("char[] toChars = toChars(bArr);"));
+    }
+
+}