bug(mat-tree): mat-tree reports a compilation error wher used with a trackBy option in NestedTreeControl

[POFerro]

Hi,

I have a mat-tree associated with the tree control:
public readonly mainMenuTreeControl = new NestedTreeControl<IMainMenuNode, string>(node => node.children, { trackBy: this.mainMenuItemTrackBy });

where this.mainMenuItemTrackBy is defined as (menuNode: IMainMenuNode): string{ ... }
when used in a view like <mat-tree [dataSource]="..." [treeControl]="mainMenuTreeControl">...</mat-tree>

compiler reports an error:
error TS2322: Type 'NestedTreeControl<IMainMenuNode, string>' is not assignable to type 'TreeControl<IMainMenuNode, IMainMenuNode>'.
31 [treeControl]="mainMenuTreeControl"

from what I have seen in code I believe MatTree should in fact be MatTree<T, K =T> as is NestedTreeControl defined and the property treeControl should also be: @Input() treeControl: TreeControl<T, K>;

Can you help me?
Thanks in advance
POFerro

[crisbeto]

An identical issue was reported with the framework a few days ago (angular/angular#40125), could it be the same as this one? Can you try the solution from the last comment to see if it resolves it?

[POFerro]

Hi @crisbeto ,

No, this case is different, I'll explain:
As of commit: #19602
TreeControl is defined as two argument generic: TreeControl<T, K = T> this change was to include the ability of having a trackBy function defined in the control itself and K is the return type of this function.

While this change happened in the TreeControl classes the class MatTree didn't change to reflect the second generic parameter so now if K != T in TreeControl class the property type in MatTree will mismatch since it is defining the property type as being TreeControl<T, T> (second generic parameter type is being inferred by default value K = T).