tests/cases/compiler/genericIndexTypeHasSensibleErrorMessage.ts(1,33): error TS1023: An index signature parameter type must be either 'string' or 'number'.


==== tests/cases/compiler/genericIndexTypeHasSensibleErrorMessage.ts (1 errors) ====
    type Wat<T extends string> = { [x: T]: string };
                                    ~
!!! error TS1023: An index signature parameter type must be either 'string' or 'number'.