Generic type infering doesn't work

[proven crypt]

I have the type TableColumn and it has 3 generic arguments and I want the last 2 to be inferred by the valueAccessorFn and displayAccessorFn functions. for some reason the 2 arguments stay as "unknown".
help?

  value: TProperty;
  rowValues: TData;
  error?: string;
  onChange: (value: TProperty) => void;
  onBlur: () => void;
}

interface RenderCellValueProps<TProperty> {
  value: TProperty;
  onClick: () => void;
}


export interface TableColumn<TData, TDisplayProp = unknown, TValueProp = unknown> {
  name: string;
  header: string;
  valueAccessorFn: (value: TData) => TValueProp;
  displayAccessorFn: (value: TData) => TDisplayProp;
  renderEditableField?: (props: RenderEditableFieldProps<TData, TValueProp>) => ReactNode;
  renderCellValue?: (props: RenderCellValueProps<TDisplayProp>) => ReactNode;
  renderColumnValue?: (columnName: string) => void;
}


type Foo = {
    name: string
    details: {
        id: number
        str: string
    }
}

const column: TableColumn<Foo> = {
    displayAccessorFn: (value) => value.details.str,
    valueAccessorFn: (value) => value.details.str
}

[green stag]

@proven crypt TS does not do partial inference of arguments.

[proven crypt]

elab?

[green stag]

Either all generics are inferred or all are specified.

And inferring is really only for functions

[proven crypt]

I understand

[green stag]

When you do = unknown that means "if not passed, this will be unknown". It doesn't infer.

The usual pattern is to split the bits that need to be specified from the bits that are meant to be inferred.

function createColumnBuilder<TData>() {
    return function defineColumn<TDisplayProp, TValueProp>(col: TableColumn<TData, TDisplayProp, TValueProp) {
        return col;
    }
}

const columnBuilder = createColumnBuilder<Foo>();
const column = columnBuilder({
    displayAccessorFn: (value) => value.details.str,
    valueAccessorFn: (value) => value.details.str
});

[proven crypt]

interesting

thank you!