Fix TypeScript support for custom components with non-standard declar…

…ations (#2181)

* Fix RMWC event handlers

* Add changeset

* Add RMWC-like component test

* Force TS version

* Update .changeset/silent-otters-build.md

Co-authored-by: Mateusz Burzyński <mateuszburzynski@gmail.com>

.changeset/silent-otters-build.md

@@ -0,0 +1,5 @@
+---
+'@emotion/react': patch
+---
+
+Fixed some typing issues with React components with custom generic render functions.

packages/react/types/index.d.ts

@@ -1,5 +1,5 @@
 // Definitions by: Junyoung Clare Jang <https://github.com/Ailrun>
-// TypeScript Version: 3.2
+// TypeScript Version: 3.4
 
 import { EmotionCache } from '@emotion/cache'
 import {

packages/react/types/jsx-namespace.d.ts

@@ -4,9 +4,9 @@ import { Theme } from './index'
 
 type WithConditionalCSSProp<P> = 'className' extends keyof P
   ? string extends P['className' & keyof P]
-    ? P & { css?: Interpolation<Theme> }
-    : P
-  : P
+    ? { css?: Interpolation<Theme> }
+    : {}
+  : {}
 
 // unpack all here to avoid infinite self-referencing when defining our own JSX namespace
 type ReactJSXElement = JSX.Element

packages/react/types/tests.tsx

@@ -231,3 +231,19 @@ const anim1 = keyframes`
     ? true
     : false
 }
+
+// RMWC-like component test
+declare const OtherComponent: {
+  <Tag extends React.ElementType>(
+    props:
+      | React.AllHTMLAttributes<HTMLInputElement>
+      | React.ComponentPropsWithRef<Tag>,
+    ref: any
+  ): JSX.Element
+  displayName?: string
+}
+;<OtherComponent
+  onChange={ev => {
+    console.log(ev.currentTarget.value)
+  }}
+/>