Port DT fix for dispatchProp arg in mergeProps

Ref: DefinitelyTyped/DefinitelyTyped#59310

Author: markerikson

src/components/connect.tsx

@@ -312,7 +312,7 @@ export interface Connect<DefaultState = unknown> {
   <no_state = {}, no_dispatch = {}, TOwnProps = {}, TMergedProps = {}>(
     mapStateToProps: null | undefined,
     mapDispatchToProps: null | undefined,
-    mergeProps: MergeProps<undefined, undefined, TOwnProps, TMergedProps>
+    mergeProps: MergeProps<undefined, DispatchProp, TOwnProps, TMergedProps>
   ): InferableComponentEnhancerWithProps<TMergedProps, TOwnProps>
 
   /** mapState and mergeProps */
@@ -325,7 +325,7 @@ export interface Connect<DefaultState = unknown> {
   >(
     mapStateToProps: MapStateToPropsParam<TStateProps, TOwnProps, State>,
     mapDispatchToProps: null | undefined,
-    mergeProps: MergeProps<TStateProps, undefined, TOwnProps, TMergedProps>
+    mergeProps: MergeProps<TStateProps, DispatchProp, TOwnProps, TMergedProps>
   ): InferableComponentEnhancerWithProps<TMergedProps, TOwnProps>
 
   /** mapDispatch (as a object) and mergeProps */

test/typetests/connect-options-and-issues.tsx

@@ -103,6 +103,14 @@ function TestMergedPropsInference() {
       merged: 'merged',
     })
   )(MergedPropsComponent)
+
+  const ConnectedWithInferredDispatch = connect(
+    mapStateToProps,
+    undefined,
+    (stateProps, dispatchProps, ownProps) => {
+      expectType<DispatchProp<AnyAction>>(dispatchProps)
+    }
+  )(MergedPropsComponent)
 }
 
 function Issue16652() {