stringToComponent type that works with ppx

Author: rickyvetter

src/ReactDOM.res

@@ -2100,8 +2100,9 @@ module Props = {
 
 include Props
 
-// As we've removed `ReactDOMRe.createElement`, this enables patterns like
-// React.createElement(ReactDOM.stringToComponent(multiline ? "textarea" : "input"), ...)
-external stringToComponent: string => React.component<domProps> = "%identity"
+// Used by the ppx to generate primitive components like "div".
+// Intentionally unsafe because typechecking is enforced by the ppx.
+@deprecated("Please use JSX syntax directly.")
+external stringToComponent: string => React.component<'a> = "%identity"
 
 module Style = ReactDOMStyle