fix(tree): fix type error in tree

src/cdk/tree/nested-node.ts

@@ -17,6 +17,7 @@ import {takeUntil} from 'rxjs/operators/takeUntil';
 
 import {CdkTree, CdkTreeNode} from './tree';
 import {CdkTreeNodeOutlet} from './outlet';
+import {getTreeControlFunctionsMissingError} from './tree-errors';
 
 /**
  * Nested node is a child of `<cdk-tree>`. It works with nested tree.
@@ -62,6 +63,9 @@ export class CdkNestedTreeNode<T> extends CdkTreeNode<T> implements AfterContent
   }
 
   ngAfterContentInit() {
+    if (!this._tree.treeControl.getChildren) {
+      throw getTreeControlFunctionsMissingError();
+    }
     this._tree.treeControl.getChildren(this.data).pipe(takeUntil(this._destroyed))
         .subscribe(result => {
           if (result && result.length) {

src/cdk/tree/tree.spec.ts

@@ -14,11 +14,13 @@ import {Observable} from 'rxjs/Observable';
 import {combineLatest} from 'rxjs/observable/combineLatest';
 import {map} from 'rxjs/operators/map';
 
+import {BaseTreeControl} from './control/base-tree-control';
 import {TreeControl} from './control/tree-control';
 import {FlatTreeControl} from './control/flat-tree-control';
 import {NestedTreeControl} from './control/nested-tree-control';
 import {CdkTreeModule} from './index';
 import {CdkTree} from './tree';
+import {getTreeControlFunctionsMissingError} from './tree-errors';
 
 
 describe('CdkTree', () => {
@@ -587,6 +589,18 @@ describe('CdkTree', () => {
           [`[topping_3] - [cheese_3] + [base_3]`]);
       });
     });
+
+    it('should throw an error when missing function in nested tree', () => {
+      configureCdkTreeTestingModule([NestedCdkErrorTreeApp]);
+      expect(() => TestBed.createComponent(NestedCdkErrorTreeApp).detectChanges())
+          .toThrowError(getTreeControlFunctionsMissingError().message);
+    });
+
+    it('should throw an error when missing function in flat tree', () => {
+      configureCdkTreeTestingModule([FlatCdkErrorTreeApp]);
+      expect(() => TestBed.createComponent(FlatCdkErrorTreeApp).detectChanges())
+        .toThrowError(getTreeControlFunctionsMissingError().message);
+    });
   });
 });
 
@@ -994,3 +1008,56 @@ class ObservableDataSourceNestedCdkTreeApp {
   @ViewChild(CdkTree) tree: CdkTree<TestData>;
 }
 
+@Component({
+  template: `
+    <cdk-tree [dataSource]="dataSource" [treeControl]="treeControl">
+      <cdk-nested-tree-node *cdkTreeNodeDef="let node" class="customNodeClass">
+                     {{node.pizzaTopping}} - {{node.pizzaCheese}} + {{node.pizzaBase}}
+         <ng-template cdkTreeNodeOutlet></ng-template>
+      </cdk-nested-tree-node>
+    </cdk-tree>
+  `
+})
+class NestedCdkErrorTreeApp {
+  getLevel = (node: TestData) => node.level;
+
+  isExpandable = (node: TestData) => node.children.length > 0;
+
+  treeControl: TreeControl<TestData> = new FlatTreeControl(this.getLevel, this.isExpandable);
+
+  dataSource: FakeDataSource | null = new FakeDataSource(this.treeControl);
+
+  @ViewChild(CdkTree) tree: CdkTree<TestData>;
+}
+
+class FakeTreeControl extends BaseTreeControl<TestData> {
+  getDescendants(_: TestData): TestData[] {
+    return this.dataNodes;
+  }
+
+  expandAll(): void {
+    // No op
+  }
+}
+@Component({
+  template: `
+    <cdk-tree [dataSource]="dataSource" [treeControl]="treeControl">
+      <cdk-tree-node *cdkTreeNodeDef="let node" class="customNodeClass">
+                     {{node.pizzaTopping}} - {{node.pizzaCheese}} + {{node.pizzaBase}}
+         <ng-template cdkTreeNodeOutlet></ng-template>
+      </cdk-tree-node>
+    </cdk-tree>
+  `
+})
+class FlatCdkErrorTreeApp {
+
+  getLevel = (node: TestData) => node.level;
+
+  isExpandable = (node: TestData) => node.children.length > 0;
+
+  treeControl: TreeControl<TestData> = new FakeTreeControl();
+
+  dataSource: FakeDataSource | null = new FakeDataSource(this.treeControl);
+
+  @ViewChild(CdkTree) tree: CdkTree<TestData>;
+}

src/cdk/tree/tree.ts

@@ -60,7 +60,7 @@ export class CdkTreeNode<T>  implements FocusableOption, OnDestroy {
    * The most recently created `CdkTreeNode`. We save it in static variable so we can retrieve it
    * in `CdkTree` and set the data to it.
    */
-  static mostRecentTreeNode: CdkTreeNode<any> | null = null;
+  static mostRecentTreeNode: CdkTreeNode<{}> | null = null;
 
   /** Subject that emits when the component has been destroyed. */
   protected _destroyed = new Subject<void>();
@@ -89,7 +89,7 @@ export class CdkTreeNode<T>  implements FocusableOption, OnDestroy {
 
   constructor(protected _elementRef: ElementRef,
               protected _tree: CdkTree<T>) {
-    CdkTreeNode.mostRecentTreeNode = this;
+    CdkTreeNode.mostRecentTreeNode = this as CdkTreeNode<T>;
   }
 
   ngOnDestroy() {
@@ -140,7 +140,7 @@ export class CdkTree<T> implements CollectionViewer, OnInit, OnDestroy {
   private _onDestroy = new Subject<void>();
 
   /** Latest data provided by the data source through the connect interface. */
-  private _data: Array<T> = new Array<T>();
+  private _data = new Array<T>();
 
   /** Differ used to find the changes in the data provided by the data source. */
   private _dataDiffer: IterableDiffer<T>;
@@ -304,7 +304,7 @@ export class CdkTree<T> implements CollectionViewer, OnInit, OnDestroy {
    * definition.
    */
   _getNodeDef(data: T, i: number): CdkTreeNodeDef<T> {
-    if (this._nodeDefs.length == 1) { return this._nodeDefs.first; }
+    if (this._nodeDefs.length === 1) { return this._nodeDefs.first; }
 
     const nodeDef =
       this._nodeDefs.find(def => def.when && def.when(i, data)) || this._defaultNodeDef;
@@ -321,7 +321,7 @@ export class CdkTree<T> implements CollectionViewer, OnInit, OnDestroy {
     const node = this._getNodeDef(nodeData, index);
 
     // Node context that will be provided to created embedded view
-    const context: CdkTreeNodeOutletContext<T> = new CdkTreeNodeOutletContext<T>(nodeData);
+    const context = new CdkTreeNodeOutletContext<T>(nodeData);
 
     // Use default tree nodeOutlet, or nested node's nodeOutlet
     const container = viewContainer ? viewContainer : this._nodeOutlet.viewContainer;

src/demo-app/tree/checklist-tree-demo/checklist-tree-demo.ts

@@ -11,6 +11,7 @@ import {SelectionModel} from '@angular/cdk/collections';
 import {FlatTreeControl} from '@angular/cdk/tree';
 import {MatTreeFlattener, MatTreeFlatDataSource} from '@angular/material/tree';
 import {of as ofObservable} from 'rxjs/observable/of';
+import {Observable} from 'rxjs/Observable';
 import {TodoItemNode, TodoItemFlatNode, ChecklistDatabase} from './checklist-database';
 
 /**
@@ -61,7 +62,9 @@ export class ChecklistTreeDemo {
 
   isExpandable = (node: TodoItemFlatNode) => { return node.expandable; };
 
-  getChildren = (node: TodoItemNode) => { return ofObservable(node.children); };
+  getChildren = (node: TodoItemNode): Observable<TodoItemNode[]> => {
+    return ofObservable(node.children);
+  }
 
   hasChild = (_: number, _nodeData: TodoItemFlatNode) => { return _nodeData.expandable; };
 

src/demo-app/tree/dynamic-tree-demo/dynamic-database.ts

@@ -9,6 +9,7 @@ import {Injectable} from '@angular/core';
 import {FlatTreeControl} from '@angular/cdk/tree';
 import {CollectionViewer, SelectionChange} from '@angular/cdk/collections';
 import {BehaviorSubject} from 'rxjs/BehaviorSubject';
+import {Observable} from 'rxjs/Observable';
 import {merge} from 'rxjs/observable/merge';
 import {map} from 'rxjs/operators/map';
 
@@ -67,12 +68,9 @@ export class DynamicDataSource {
   constructor(private treeControl: FlatTreeControl<DynamicFlatNode>,
               private database: DynamicDatabase) {}
 
-  connect(collectionViewer: CollectionViewer) {
-    const changes = [
-      collectionViewer.viewChange,
-      this.treeControl.expansionModel.onChange!,
-    ];
-    return merge(...changes).pipe(map((change) => {
+  connect(collectionViewer: CollectionViewer): Observable<DynamicFlatNode[]> {
+    return merge(collectionViewer.viewChange, this.treeControl.expansionModel.onChange!)
+        .pipe(map((change) => {
       if ((change as SelectionChange<DynamicFlatNode>).added ||
           (change as SelectionChange<DynamicFlatNode>).removed) {
         this.handleTreeControl(change as SelectionChange<DynamicFlatNode>);

src/demo-app/tree/loadmore-tree-demo/loadmore-tree-demo.ts

@@ -9,6 +9,7 @@
 import {Component} from '@angular/core';
 import {FlatTreeControl} from '@angular/cdk/tree';
 import {MatTreeFlatDataSource, MatTreeFlattener} from '@angular/material/tree';
+import {Observable} from 'rxjs/Observable';
 import {LoadmoreNode, LoadmoreFlatNode, LoadmoreDatabase} from './loadmore-database';
 
 const LOAD_MORE = 'LOAD_MORE';
@@ -50,7 +51,7 @@ export class LoadmoreTreeDemo {
     database.initialize();
   }
 
-  getChildren = (node: LoadmoreNode) => { return node.childrenChange; };
+  getChildren = (node: LoadmoreNode): Observable<LoadmoreNode[]> => { return node.childrenChange; };
 
   transformer = (node: LoadmoreNode, level: number) => {
     if (this.nodeMap.has(node.item)) {