invalid_reference_to_this

Invalid reference to 'this' expression.

The analyzer produces this diagnostic when this is used outside of an instance method or a generative constructor. The reserved word this is only defined in the context of an instance method, a generative constructor, or the initializer of a late instance field declaration.

The following code produces this diagnostic because v is a top-level variable:

C f() => this;

class C {}

Use a variable of the appropriate type in place of this, declaring it if necessary:

C f(C c) => c;

class C {}