feat: support inner class contruction with outer instance (#2253)

jadx-core/src/main/java/jadx/core/codegen/ClassGen.java

@@ -652,6 +652,13 @@ public class ClassGen {
 		code.add(clsName);
 	}
 
+	public void addClsShortNameForced(ICodeWriter code, ClassInfo classInfo) {
+		code.add(classInfo.getAliasShortName());
+		if (!isBothClassesInOneTopClass(cls.getClassInfo(), classInfo)) {
+			addImport(classInfo);
+		}
+	}
+
 	private String useClassInternal(ClassInfo useCls, ClassInfo extClsInfo) {
 		String fullName = extClsInfo.getAliasFullName();
 		if (fallback || !useImports) {

jadx-core/src/main/java/jadx/core/codegen/InsnGen.java

@@ -749,6 +749,7 @@ public class InsnGen {
 			code.attachAnnotation(refMth);
 			code.add("this");
 		} else {
+			boolean forceShortName = addOuterClassInstance(insn, code, callMth);
 			code.add("new ");
 			if (refMth == null || refMth.contains(AFlag.DONT_GENERATE)) {
 				// use class reference if constructor method is missing (default constructor)
@@ -756,7 +757,11 @@ public class InsnGen {
 			} else {
 				code.attachAnnotation(refMth);
 			}
-			mgen.getClassGen().addClsName(code, insn.getClassType());
+			if (forceShortName) {
+				mgen.getClassGen().addClsShortNameForced(code, insn.getClassType());
+			} else {
+				mgen.getClassGen().addClsName(code, insn.getClassType());
+			}
 			GenericInfoAttr genericInfoAttr = insn.get(AType.GENERIC_INFO);
 			if (genericInfoAttr != null) {
 				code.add('<');
@@ -777,6 +782,27 @@ public class InsnGen {
 		generateMethodArguments(code, insn, 0, callMth);
 	}
 
+	private boolean addOuterClassInstance(ConstructorInsn insn, ICodeWriter code, MethodNode callMth) throws CodegenException {
+		if (callMth == null || !callMth.contains(AFlag.SKIP_FIRST_ARG)) {
+			return false;
+		}
+		ClassNode ctrCls = callMth.getDeclaringClass();
+		if (!ctrCls.isInner() || insn.getArgsCount() == 0) {
+			return false;
+		}
+		InsnArg instArg = insn.getArg(0);
+		if (instArg.isThis()) {
+			return false;
+		}
+		// instance arg should be of an outer class type
+		if (!instArg.getType().equals(ctrCls.getDeclaringClass().getType())) {
+			return false;
+		}
+		addArgDot(code, instArg);
+		// can't use another dot, force short name of class
+		return true;
+	}
+
 	private void inlineAnonymousConstructor(ICodeWriter code, ClassNode cls, ConstructorInsn insn) throws CodegenException {
 		cls.ensureProcessed();
 		if (this.mth.getParentClass() == cls) {

jadx-core/src/test/java/jadx/tests/integration/inner/TestInnerConstructorCall.java

@@ -0,0 +1,33 @@
+package jadx.tests.integration.inner;
+
+import org.junit.jupiter.api.Test;
+
+import jadx.tests.api.IntegrationTest;
+
+import static jadx.tests.api.utils.assertj.JadxAssertions.assertThat;
+
+public class TestInnerConstructorCall extends IntegrationTest {
+
+	public static class TestCls {
+		@SuppressWarnings("InnerClassMayBeStatic")
+		public class A {
+			public class AA {
+				public void test() {
+				}
+			}
+		}
+
+		public void test() {
+			A a = new A();
+			A.AA aa = a.new AA();
+			aa.test();
+		}
+	}
+
+	@Test
+	public void test() {
+		assertThat(getClassNode(TestCls.class))
+				.code()
+				.containsOne("A.AA aa = a.new AA();");
+	}
+}