TypeScript: Feb 2019 Definitely Typed failures on typescript@next

Found by trying to change a whole bunch of package’s project URLs in DefinitelyTyped/DefinitelyTyped#32977

d3-array

Error: C:/Users/nathansa/DefinitelyTyped/types/d3-array/d3-array-tests.ts:611:7
ERROR: 611:7  expect  TypeScript@next compile error:
Type '(string | number | number[] | Date)[]' is not assignable to type '(number[] | Date)[]'.
  Type 'string | number | number[] | Date' is not assignable to type 'number[] | Date'.
    Type 'string' is not assignable to type 'number[] | Date'.

Looks like a possible change in index access types

ember

Error: C:/Users/nathansa/DefinitelyTyped/types/ember/test/observable.ts:106:32
ERROR: 106:32  expect  TypeScript@next compile error:
Argument of type 'Pick<UnwrapComputedPropertyGetters<any>, string>' is not assignable to parameter of type '{ dummy: any; }'.
  Property 'dummy' is missing in type 'Pick<UnwrapComputedPropertyGetters<any>, string>' but required in type '{ dummy: any; }'.

Same.

petit-dom

Error: C:/Users/nathansa/DefinitelyTyped/types/petit-dom/petit-dom-tests.tsx:190:10
ERROR: 190:10  expect  TypeScript@next compile error:
Type '{ content: (string | Element)[]; name: string; count: number; onSomeEvent: (event: Event) => void; }' is not assignable to type 'IntrinsicAttributes & CustomProps'.
  Property 'content' does not exist on type 'IntrinsicAttributes & CustomProps'.
ERROR: 354:10  expect  TypeScript@next compile error:
Type '{ content: (string | Element)[]; name: string; count: number; onSomeEvent: (event: Event) => void; }' is not assignable to type 'IntrinsicAttributes & IntrinsicClassAttributes<ComponentClassWithChildren> & CustomProps'.
  Property 'content' does not exist on type 'IntrinsicAttributes & IntrinsicClassAttributes<ComponentClassWithChildren> & CustomProps'.

Something to do with JSX? Not sure.