Unfortunately, I think there is no way to specify it with mixins helper as the mixin constructors are passed as value.

If anyone come up with the idea to handle this, feel free to put it this thread 🙂

In recent version, passing type information to mixin helper like this worked.

import Vue from 'vue'
import Component, { mixins } from 'vue-class-component'

@Component
class MyMixin extends mixins<GenericMixin<string>>(GenericMixin) {
    created() {
        console.log(this.value('hello'))
    }
}

@Component
class GenericMixin<T=any> extends Vue {
    value(value: T): T {
        return value
    }
}

If think the only way to state the type you are expecting as @garypippi did. So the TS will surely know about what type it should expect since the generic parameter it's not the only one in the mixin types.

In recent version, passing type information to mixin helper like this worked.

import Vue from 'vue'
import Component, { mixins } from 'vue-class-component'

@Component
class MyMixin extends mixins<GenericMixin<string>>(GenericMixin) {
    created() {
        console.log(this.value('hello'))
    }
}

@Component
class GenericMixin<T=any> extends Vue {
    value(value: T): T {
        return value
    }
}

thanks~

Closing as the solution is provided. Thank you for making this discussion!