There’s only one library here. As Dmytro hinted, many types in the compiler are “path-dependent”; the compiler uses the “cake pattern” heavily internally. Trees#Tree is the general type (that’s a “type projection”), MyComponent.this.global.Tree is the path-dependent type specific to the particular instance of MyComponent. The latter is a subtype of the former.
It’s good that you quoted the exact error message — that helps us give relevant advice.