fix: Fix dropping diamonds on constructor calls (#3362)

src/main/java/spoon/reflect/factory/TypeFactory.java

@@ -93,6 +93,7 @@ public class TypeFactory extends SubFactory {
 	public final CtTypeReference<Set> SET = createReference(Set.class);
 	public final CtTypeReference<Map> MAP = createReference(Map.class);
 	public final CtTypeReference<Enum> ENUM = createReference(Enum.class);
+	public final CtTypeReference<?> OMITTED_TYPE_ARG_TYPE = createReference(CtTypeReference.OMITTED_TYPE_ARG_NAME);
 
 	private final Map<Class<?>, CtType<?>> shadowCache = new ConcurrentHashMap<>();
 

src/main/java/spoon/reflect/reference/CtTypeReference.java

@@ -34,6 +34,11 @@ public interface CtTypeReference<T> extends CtReference, CtActualTypeContainer,
 	 */
 	String NULL_TYPE_NAME = "<nulltype>";
 
+	/**
+	 * Special type used as a type argument when actual type arguments can't be inferred.
+	 */
+	String OMITTED_TYPE_ARG_NAME = "<omitted>";
+
 	/**
 	 * Returns the simple (unqualified) name of this element.
 	 * Following the compilation convention, if the type is a local type,

src/main/java/spoon/support/compiler/jdt/ReferenceBuilder.java

@@ -86,6 +86,7 @@
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collections;
+import java.util.Deque;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
@@ -569,6 +570,47 @@ private <T> void insertGenericTypesInNoClasspathFromJDTInSpoon(TypeReference ori
 				}
 			}
 		}
+
+		if (original.isParameterizedTypeReference() && !type.isParameterized()) {
+			tryRecoverTypeArguments(type);
+		}
+	}
+
+	/**
+	 * In noclasspath mode, empty diamonds in constructor calls on generic types can be lost. This happens if any
+	 * of the following apply:
+	 *
+	 * <ul>
+	 *     <li>The generic type is not on the classpath.</li>
+	 *     <li>The generic type is used in a context where the type arguments cannot be inferred, such as in an
+	 *     unresolved method
+	 *     </li>
+	 * </ul>
+	 *
+	 * See #3360 for details.
+	 */
+	private void tryRecoverTypeArguments(CtTypeReference<?> type) {
+		final Deque<ASTPair> stack = jdtTreeBuilder.getContextBuilder().stack;
+		if (stack.peek() == null || !(stack.peek().node instanceof AllocationExpression)) {
+			// have thus far only ended up here with a generic array type,
+			// don't know if we want or need to deal with those
+			return;
+		}
+
+		AllocationExpression alloc = (AllocationExpression) stack.peek().node;
+		if (alloc.expectedType() == null || !(alloc.expectedType() instanceof ParameterizedTypeBinding)) {
+			// the expected type is not available/parameterized if the constructor call occurred in e.g. an unresolved
+			// method, or in a method that did not expect a parameterized argument
+			type.addActualTypeArgument(jdtTreeBuilder.getFactory().Type().OMITTED_TYPE_ARG_TYPE.clone());
+		} else {
+			ParameterizedTypeBinding expectedType = (ParameterizedTypeBinding) alloc.expectedType();
+			// type arguments can be recovered from the expected type
+			for (TypeBinding binding : expectedType.typeArguments()) {
+				CtTypeReference<?> typeArgRef = getTypeReference(binding);
+				typeArgRef.setImplicit(true);
+				type.addActualTypeArgument(typeArgRef);
+			}
+		}
 	}
 
 	/**

src/test/java/spoon/test/constructorcallnewclass/ConstructorCallTest.java

@@ -19,8 +19,10 @@
 import org.junit.Before;
 import org.junit.Test;
 import spoon.Launcher;
+import spoon.reflect.CtModel;
 import spoon.reflect.code.CtConstructorCall;
 import spoon.reflect.declaration.CtClass;
+import spoon.reflect.declaration.CtElement;
 import spoon.reflect.declaration.CtType;
 import spoon.reflect.factory.Factory;
 import spoon.reflect.reference.CtArrayTypeReference;
@@ -32,8 +34,10 @@
 import spoon.test.constructorcallnewclass.testclasses.Panini;
 
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.List;
 import java.util.TreeSet;
+import java.util.stream.Collectors;
 
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertSame;
@@ -140,4 +144,49 @@ public void testCoreConstructorCall() {
 		assertEquals("new Bar()", call2.toString());
 	}
 
+	@Test
+	public void testParameterizedConstructorCallOmittedTypeArgsNoClasspath() {
+		// contract: omitted type arguments to constructors must be properly resolved if the context allows
+		// the expected type to be known
+		List<String> expectedTypeArgNames = Arrays.asList("Integer", "String");
+		String sourceFile = "./src/test/resources/noclasspath/GenericTypeEmptyDiamond.java";
+
+		CtTypeReference<?> executableType = getConstructorCallTypeFrom("GenericKnownExpectedType", sourceFile);
+
+		assertTrue(executableType.isParameterized());
+		assertEquals(expectedTypeArgNames,
+				executableType.getActualTypeArguments().stream()
+						.map(CtTypeReference::getSimpleName).collect(Collectors.toList()));
+		assertTrue(executableType.getActualTypeArguments().stream().allMatch(CtElement::isImplicit));
+	}
+
+	@Test
+	public void testParameterizedConstructorCallOmittedTypeArgsUnknownExpectedTypeNoClasspath() {
+		// contract: even if the expected type is not known for omitted type arguments the type access must be
+		// detected as parameterized
+		String sourceFile = "./src/test/resources/noclasspath/GenericTypeEmptyDiamond.java";
+		CtTypeReference<?> executableType = getConstructorCallTypeFrom("GenericUnknownExpectedType", sourceFile);
+		assertTrue(executableType.isParameterized());
+		assertTrue(executableType.getActualTypeArguments().stream().allMatch(CtElement::isImplicit));
+	}
+
+	@Test
+	public void testParameterizedConstructorCallOmittedTypeArgsResolvedTypeNoClasspath() {
+		// contract: if a resolved type (here, java.util.ArrayList) is parameterized with empty diamonds in an
+		// unresolved method, the resolved type reference should still be parameterized.
+		String sourceFile = "./src/test/resources/noclasspath/GenericTypeEmptyDiamond.java";
+		CtTypeReference<?> executableType = getConstructorCallTypeFrom("ArrayList", sourceFile);
+		assertTrue(executableType.isParameterized());
+	}
+
+	private CtTypeReference<?> getConstructorCallTypeFrom(String simpleName, String sourceFile) {
+		final Launcher launcher = new Launcher();
+		launcher.getEnvironment().setNoClasspath(true);
+		launcher.addInputResource(sourceFile);
+		CtModel model = launcher.buildModel();
+		List<CtConstructorCall<?>> calls =
+				model.getElements(element -> element.getExecutable().getType().getSimpleName().equals(simpleName));
+		assert calls.size() == 1;
+		return calls.get(0).getExecutable().getType();
+	}
 }

src/test/resources/noclasspath/GenericTypeEmptyDiamond.java

@@ -0,0 +1,13 @@
+// the purpose of this test class is to check that omitted type arguments are properly resolved in noclasspath mode
+import java.util.ArrayList;
+
+class GenericTypeEmptyDiamond {
+    public static void main(String[] args) {
+        // the context should allow the type arguments for this constructor call to be recovered
+        GenericKnownExpectedType<Integer, String> someGeneric = new GenericKnownExpectedType<>();
+        // meth is an unresolved method, so there is no context to allow for inference of type arguments
+        meth(new GenericUnknownExpectedType<>());
+        // same as the above, but with a generic type that is available on the classpath
+        meth(new ArrayList<>());
+    }
+}