fix: resolve generic type vars for instance field get instruction (#918)

jadx-core/src/main/java/jadx/core/dex/nodes/utils/TypeUtils.java

@@ -61,6 +61,9 @@ public class TypeUtils {
 	}
 
 	private void expandTypeVar(NotificationAttrNode node, ArgType type, Collection<ArgType> typeVars) {
+		if (typeVars.isEmpty()) {
+			return;
+		}
 		boolean allExtendsEmpty = true;
 		for (ArgType argType : typeVars) {
 			if (notEmpty(argType.getExtendTypes())) {

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

@@ -0,0 +1,83 @@
+package jadx.core.dex.visitors.typeinference;
+
+import jadx.core.dex.info.FieldInfo;
+import jadx.core.dex.instructions.IndexInsnNode;
+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.nodes.RootNode;
+
+/**
+ * Dynamic bound for instance field get of generic type.
+ * Bound type calculated using instance generic type.
+ */
+public final class TypeBoundFieldGetAssign implements ITypeBoundDynamic {
+	private final RootNode root;
+	private final IndexInsnNode getNode;
+	private final FieldInfo fieldInfo;
+	private final ArgType initType;
+
+	public TypeBoundFieldGetAssign(RootNode root, IndexInsnNode getNode, ArgType initType) {
+		this.root = root;
+		this.getNode = getNode;
+		this.fieldInfo = ((FieldInfo) getNode.getIndex());
+		this.initType = initType;
+	}
+
+	@Override
+	public BoundEnum getBound() {
+		return BoundEnum.ASSIGN;
+	}
+
+	@Override
+	public ArgType getType(TypeUpdateInfo updateInfo) {
+		return getResultType(updateInfo.getType(getInstanceArg()));
+	}
+
+	@Override
+	public ArgType getType() {
+		return getResultType(getInstanceArg().getType());
+	}
+
+	private ArgType getResultType(ArgType instanceType) {
+		ArgType resultGeneric = root.getTypeUtils().replaceClassGenerics(instanceType, initType);
+		if (resultGeneric != null && !resultGeneric.isWildcard()) {
+			return resultGeneric;
+		}
+		return initType; // TODO: check if this type is allowed in current scope
+	}
+
+	private InsnArg getInstanceArg() {
+		return getNode.getArg(0);
+	}
+
+	@Override
+	public RegisterArg getArg() {
+		return getNode.getResult();
+	}
+
+	@Override
+	public boolean equals(Object o) {
+		if (this == o) {
+			return true;
+		}
+		if (o == null || getClass() != o.getClass()) {
+			return false;
+		}
+		TypeBoundFieldGetAssign that = (TypeBoundFieldGetAssign) o;
+		return getNode.equals(that.getNode);
+	}
+
+	@Override
+	public int hashCode() {
+		return getNode.hashCode();
+	}
+
+	@Override
+	public String toString() {
+		return "FieldGetAssign{" + fieldInfo
+				+ ", type=" + getType()
+				+ ", instanceArg=" + getInstanceArg()
+				+ '}';
+	}
+}

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

@@ -293,6 +293,10 @@ public final class TypeInferenceVisitor extends AbstractVisitor {
 				addBound(typeInfo, makeAssignInvokeBound((InvokeNode) insn));
 				break;
 
+			case IGET:
+				addBound(typeInfo, makeAssignFieldGetBound((IndexInsnNode) insn));
+				break;
+
 			case CHECK_CAST:
 				addBound(typeInfo, new TypeBoundCheckCastAssign(root, (IndexInsnNode) insn));
 				break;
@@ -304,6 +308,14 @@ public final class TypeInferenceVisitor extends AbstractVisitor {
 		}
 	}
 
+	private ITypeBound makeAssignFieldGetBound(IndexInsnNode insn) {
+		ArgType initType = insn.getResult().getInitType();
+		if (initType.containsTypeVariable()) {
+			return new TypeBoundFieldGetAssign(root, insn, initType);
+		}
+		return new TypeBoundConst(BoundEnum.ASSIGN, initType);
+	}
+
 	private ITypeBound makeAssignInvokeBound(InvokeNode invokeNode) {
 		ArgType boundType = invokeNode.getCallMth().getReturnType();
 		ArgType genericReturnType = root.getMethodUtils().getMethodGenericReturnType(invokeNode);

jadx-core/src/test/java/jadx/tests/integration/generics/TestGenericFields.java

@@ -0,0 +1,40 @@
+package jadx.tests.integration.generics;
+
+import org.junit.jupiter.api.Test;
+
+import jadx.tests.api.IntegrationTest;
+
+import static jadx.tests.api.utils.assertj.JadxAssertions.assertThat;
+
+public class TestGenericFields extends IntegrationTest {
+
+	public static class TestCls {
+
+		public static class Summary {
+			Value<Amount> price;
+		}
+
+		public static class Value<T> {
+			T value;
+		}
+
+		public static class Amount {
+			String cur;
+			int val;
+		}
+
+		public String test(Summary summary) {
+			Amount amount = summary.price.value;
+			return amount.val + " " + amount.cur;
+		}
+	}
+
+	@Test
+	public void test() {
+		noDebugInfo();
+		assertThat(getClassNode(TestCls.class))
+				.code()
+				.doesNotContain("T t = ")
+				.containsOne("Amount amount =");
+	}
+}