tsc, tsserver: hangs with large union type and object spread in React HOC (strict mode)

TypeScript Version: 3.4.0-dev.20190216

Search Terms: hang higher order union strictFunctionTypes

Code

Note that this code has compilation errors, but that’s not important. When invoking tsc or loading in an editor that uses tsserver, the compilation hangs/never completes.

import * as React from "react";

const animated: {
  [Tag in keyof JSX.IntrinsicElements]: React.ForwardRefExoticComponent<
    React.ComponentPropsWithRef<Tag>
  >
} = {};

function makeAnimated<T extends React.ReactType>(
  comp: T
): React.ForwardRefExoticComponent<React.ComponentPropsWithRef<T>> {
  return null as any; // not important
}

export interface UpgradedProps {
  show: boolean;
}

export function test<P>(
  component: React.ComponentType<P> | keyof React.ReactHTML
): React.ComponentType<P & UpgradedProps> {
  // changing to `const Comp: any` un-hangs tsserver
  const Comp =
    typeof component === "string"
      ? animated[component]
      : makeAnimated(component);

  return React.forwardRef<any, P & UpgradeProps>((props, ref) => {
    const { show, ...ownProps } = props; // addition of this line causes the hang
    return show ? <Comp {...ownProps} ref={ref} /> : null;
  });
}

Expected behavior:

Compilation completes (optionally with errors).

Actual behavior:

Compilation hangs.

Repro Link: https://github.com/jgoz/typescript-bug

Related Issues: Didn’t find anything recent

[natew]

@aleclarson oh! Is anyone else getting what I’m getting the ? Last couple months VSCode as been nearly unusable (with no extensions), autocomplete takes a couple seconds, cursor and text input lags often and sometimes they spike to a freeze. This is on a pretty powerful new laptop.

[jgoz]

@RyanCavanaugh I just disabled all options and re-enabled one-by-one. The server will hang when strict: true is set.

{
  "compileOnSave": false,
  "compilerOptions": {
    "jsx": "react",
    "skipLibCheck": true,
    "strict": true
  }
}