Fix call hierarchy position resolution #2771

Author: gayanper

org.eclipse.jdt.ls.core/src/org/eclipse/jdt/ls/core/internal/handlers/CallHierarchyHandler.java

@@ -75,7 +75,7 @@ public List<CallHierarchyItem> prepareCallHierarchy(CallHierarchyPrepareParams p
 		int character = params.getPosition().getCharacter();
 
 		try {
-			IMember candidate = getCallHierarchyElement(uri, line, character, monitor);
+			IMember candidate = getCallHierarchyElement(uri, line, character, true, monitor);
 			if (candidate == null) {
 				return null;
 			}
@@ -140,7 +140,7 @@ public List<CallHierarchyOutgoingCall> callHierarchyOutgoingCalls(CallHierarchyO
 		return null;
 	}
 
-	private IMember getCallHierarchyElement(String uri, int line, int character, IProgressMonitor monitor) throws JavaModelException {
+	private IMember getCallHierarchyElement(String uri, int line, int character, boolean prepare, IProgressMonitor monitor) throws JavaModelException {
 		Assert.isNotNull(uri, "uri");
 
 		ITypeRoot root = JDTUtils.resolveTypeRoot(uri);
@@ -162,7 +162,12 @@ private IMember getCallHierarchyElement(String uri, int line, int character, IPr
 		int offset = JsonRpcHelpers.toOffset(root, line, character);
 		List<IJavaElement> selectedElements = codeResolve(root, offset);
 		Stream<IJavaElement> possibleElements = selectedElements.stream().filter(CallHierarchyCore::isPossibleInputElement);
-		Optional<IJavaElement> firstElement = possibleElements.findFirst();
+		Optional<IJavaElement> firstElement = possibleElements.findFirst().flatMap(element -> {
+			if (!prepare && element instanceof IType) {
+				return Optional.ofNullable(getEnclosingMember(root, offset)).map(IJavaElement.class::cast).filter(e -> !element.equals(e)).or(() -> Optional.of(element));
+			}
+			return Optional.of(element);
+		});
 		if (firstElement.isPresent() && firstElement.get() instanceof IMember member) {
 			candidate = member;
 		}
@@ -177,7 +182,7 @@ private IMember getCallHierarchyElement(String uri, int line, int character, IPr
 
 	private List<CallHierarchyIncomingCall> getIncomingCallItemsAt(String uri, int line, int character, IProgressMonitor monitor) throws JavaModelException {
 		SubMonitor sub = SubMonitor.convert(monitor, 2);
-		IMember candidate = getCallHierarchyElement(uri, line, character, sub.split(1));
+		IMember candidate = getCallHierarchyElement(uri, line, character, false, sub.split(1));
 		if (candidate == null) {
 			return null;
 		}
@@ -228,7 +233,7 @@ private Range getRange(IOpenable openable, CallLocation location) {
 
 	private List<CallHierarchyOutgoingCall> getOutgoingCallItemsAt(String uri, int line, int character, IProgressMonitor monitor) throws JavaModelException {
 		SubMonitor sub = SubMonitor.convert(monitor, 2);
-		IMember candidate = getCallHierarchyElement(uri, line, character, sub.split(1));
+		IMember candidate = getCallHierarchyElement(uri, line, character, false, sub.split(1));
 		if (candidate == null) {
 			return null;
 		}

org.eclipse.jdt.ls.tests/projects/eclipse/hello/src/org/sample/CallHierarchyGH2771.java

@@ -0,0 +1,11 @@
+package org.sample;
+
+public interface CallHierarchyGH2771 {
+    Opt<String> name();
+
+    public static class Opt<T> {
+        public static <T> Opt<T> of(T t) {
+            return new Opt();
+        }
+    }
+}

org.eclipse.jdt.ls.tests/src/org/eclipse/jdt/ls/core/internal/handlers/CallHierarchyHandlerTest.java

@@ -193,6 +193,35 @@ public void outgoing_jar() throws Exception {
 		assertTrue(jarUri.contains("WordUtils.class"));
 	}
 
+	@Test
+	public void incomingCalls_OnInterfaceMethod() throws Exception {
+		// Line 27 from `CallHierarchy`
+		//    public void <|>bar() {
+		String uri = getUriFromSrcProject("org.sample.CallHierarchyGH2771");
+		List<CallHierarchyItem> items = prepareCallHierarchy(uri, 3, 17);
+		assertNotNull(items);
+		assertEquals(1, items.size());
+		assertItem(items.get(0), "name()" + JavaElementLabels.DECL_STRING + "Opt<String>", Method, "org.sample.CallHierarchyGH2771", false, 3);
+
+		List<CallHierarchyIncomingCall> calls = getIncomingCalls(items.get(0));
+		assertNotNull(calls);
+		assertEquals(0, calls.size());
+	}
+
+	@Test
+	public void incomingCalls_OnInterfaceMethodReturnType() throws Exception {
+		// Line 27 from `CallHierarchy`
+		//    public void <|>bar() {
+		String uri = getUriFromSrcProject("org.sample.CallHierarchyGH2771");
+		List<CallHierarchyItem> items = prepareCallHierarchy(uri, 3, 6);
+		assertNotNull(items);
+		assertEquals(1, items.size());
+		assertItem(items.get(0), "Opt<T>", Class, "org.sample.CallHierarchyGH2771", false, 5);
+
+		List<CallHierarchyIncomingCall> calls = getIncomingCalls(items.get(0));
+		assertNotNull(calls);
+		assertEquals(1, calls.size());
+	}
 	// @Test
 	// public void outgoing_recursive() throws Exception {
 	// 	// Line 60 from `CallHierarchy`