react-redux type inference is broken since v3.1

[Torvin]

TypeScript Version: 3.1.0-dev.20180810

Search Terms: react-redux connect type inference

I've noticed this issue while upgrading from v3.0.3. Type inferrence got broken on some of redux's connect calls. I was able to isolate the issue (see the code below). The issue is reproducible on @next and @latest. I ran some regression tests and was able to narrow it down to 3.1.0-dev.20180810 where the bug was introduced. The last version where the code works as expected was 3.1.0-dev.20180809.

Code

type MapStateToProps<TStateProps> = () => TStateProps;

type MergeProps<TStateProps, TMergedProps> = (stateProps: TStateProps) => TMergedProps;

function connect<TStateProps = {}, TMergedProps = {}>(
   mapStateToProps: MapStateToProps<TStateProps>,
   mergeProps: MergeProps<TStateProps, TMergedProps>) {
}

connect(() => ({ time: 123 }), ({ time }) => ({
   time,
   doSomething() {
   },
}))

Expected behavior: compiles without errors

Actual behavior: error TS2459: Type 'TStateProps' has no property 'time' and no string index signature.

Playground Link: here

Somehow these examples compile without problem though:

// no 'expression body' in C# terms
connect(() => ({ time: 123 }), ({ time }) => {
   return {
      time,
      doSomething() {
      },
   }
})

// no 'time' on TMergedProps
connect(() => ({ time: 123 }), ({ time }) => ({
   doSomething() {
   },
}))

// property instead of a function
connect(() => ({ time: 123 }), ({ time }) => ({
   time,
   doSomething: () => {
   },
}))

[Dudeonyx]

Connect works fine for me,

Have you tried updating @types/react-redux ?

[Torvin]

Can't reproduce anymore on 3.6.0-dev.20190730. Fixed?

[jakebailey]

This was fixed by #31574, but could probably use an explicit test.