[analysis_server] Fix hover on constructor name declarations

Change-Id: I6254a8a8d82a1f2b12e8fa3589fbe114d9945af6
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/263401
Reviewed-by: Brian Wilkerson <brianwilkerson@google.com>
Commit-Queue: Brian Wilkerson <brianwilkerson@google.com>

pkg/analysis_server/lib/src/computer/computer_hover.dart

@@ -42,6 +42,8 @@ class DartUnitHoverComputer {
       locationEntity = node.name;
     } else if (node is MethodDeclaration) {
       locationEntity = node.name;
+    } else if (node is ConstructorDeclaration) {
+      locationEntity = node.name ?? node.returnType;
     } else if (node is VariableDeclaration) {
       locationEntity = node.name;
     }
@@ -58,22 +60,34 @@ class DartUnitHoverComputer {
     } else if (parent is ConstructorName &&
         grandParent is InstanceCreationExpression) {
       node = grandParent;
+    } else if (node is SimpleIdentifier &&
+        parent is ConstructorDeclaration &&
+        parent.name != null) {
+      node = parent;
     }
     if (node != null &&
         (node is CompilationUnitMember ||
             node is Expression ||
             node is FormalParameter ||
             node is MethodDeclaration ||
+            node is ConstructorDeclaration ||
             node is VariableDeclaration)) {
-      // For constructor calls the whole expression is selected (above) but this
-      // results in the range covering the whole call so narrow it to just the
-      // ConstructorName.
-      var hover = node is InstanceCreationExpression
-          ? HoverInformation(
-              node.constructorName.offset,
-              node.constructorName.length,
-            )
-          : HoverInformation(locationEntity.offset, locationEntity.length);
+      // For constructors, the location should cover the type name and
+      // constructor name (for both calls and declarations).
+      HoverInformation hover;
+      if (node is InstanceCreationExpression) {
+        hover = HoverInformation(
+          node.constructorName.offset,
+          node.constructorName.length,
+        );
+      } else if (node is ConstructorDeclaration) {
+        var offset = node.returnType.offset;
+        var end = node.name?.end ?? node.returnType.end;
+        var length = end - node.returnType.offset;
+        hover = HoverInformation(offset, length);
+      } else {
+        hover = HoverInformation(locationEntity.offset, locationEntity.length);
+      }
       // element
       var element = ElementLocator.locate(node);
       if (element != null) {

pkg/analysis_server/test/analysis/get_hover_test.dart

@@ -97,6 +97,34 @@ void f() {
     }
   }
 
+  Future<void> test_class_constructor_named_declaration() async {
+    newFile(testFilePath, '''
+library my.library;
+class A {
+  /// my doc
+  A.named() {}
+}
+''');
+    void onConstructor(HoverInformation hover) {
+      // range
+      expect(hover.offset, findOffset('A.named'));
+      expect(hover.length, 'A.named'.length);
+      // element
+      expect(hover.dartdoc, 'my doc');
+      expect(hover.elementDescription, 'A A.named()');
+      expect(hover.elementKind, 'constructor');
+    }
+
+    {
+      var hover = await prepareHover('A.');
+      onConstructor(hover);
+    }
+    {
+      var hover = await prepareHover('named()');
+      onConstructor(hover);
+    }
+  }
+
   Future<void> test_class_constructor_noKeyword_const() async {
     newFile(testFilePath, '''
 library my.library;