Understanding and Fixing TypeScript Error TS2749: "refers to a value, but is being used as a type here"

When working with React and TypeScript, you might encounter the confusing error TS2749: "'TextField' refers to a value, but is being used as a type here." This error typically occurs when TypeScript cannot properly resolve the type information for a component.

Problem Overview

The error occurs when you try to use an imported value as a type, but TypeScript only recognizes it as a runtime value. This commonly happens with:

• Class components that are exported in non-standard ways
• Components imported from third-party libraries like Material-UI
• File extension mismatches (.ts vs .tsx)
• Incorrect import syntax

Here's an example that triggers this error:

import { TextField } from '@material-ui/core';
import React from 'react';

export class MyTextField extends React.Component<MyProps, MyState> {
  private refTextField: React.RefObject<TextField>; // Error: TS2749
  constructor(props: MyProps) {
    super(props);
    this.refTextField = React.createRef();
  }

  render() {
    return <TextField ref={this.refTextField} />;
  }
}

Solutions

1. Use InstanceType with typeof (Recommended)

The most robust solution is to use TypeScript's InstanceType utility type combined with typeof:

private refTextField: React.RefObject<InstanceType<typeof TextField>>;

This approach works because:

• typeof TextField gets the constructor type
• InstanceType<> extracts the instance type from the constructor

For cleaner code, you can create a type alias:

type TextFieldType = InstanceType<typeof TextField>;
private refTextField: React.RefObject<TextFieldType>;

2. Check File Extension

Ensure your React component files use the .tsx extension, not .ts:

WARNING

TypeScript requires .tsx extension for files containing JSX syntax. Using .ts will cause compilation errors.

If you've changed the extension, you may need to reload your TypeScript server/IDE:

1. Change .ts to .tsx
2. Press F1 and select "TypeScript: Restart TS Server" (VS Code)
3. Or reload your editor window

3. Verify Import Syntax

Ensure you're using the correct import syntax:

// Incorrect if TextField isn't default export
import TextField from '@material-ui/core/TextField';

// Correct for named exports
import { TextField } from '@material-ui/core';

TIP

Many Material-UI components are named exports, so using curly braces { } is necessary.

4. Use Type-Only Imports

For better type safety, use type-only imports when you only need the type:

import type { TextFieldProps } from '@material-ui/core';
import { TextField } from '@material-ui/core';

type TextFieldType = InstanceType<typeof TextField>;
private refTextField: React.RefObject<TextFieldType>;

5. Check Component Definition

Ensure you're not accidentally creating a value when you intend to create a type:

// Incorrect - creates a value, not a type
const User = {
  email: string
};

// Correct - creates a type
interface User {
  email?: string | undefined;
}

Complete Working Example

Here's the corrected version of the original problematic code:

import React from 'react';
import { TextField } from '@material-ui/core';

interface MyProps {
  id: string;
  label: string;
  value: string;
}

interface MyState {
  value: string;
}

export class MyTextField extends React.Component<MyProps, MyState> {
  private refTextField: React.RefObject<InstanceType<typeof TextField>>;
  
  constructor(props: MyProps) {
    super(props);
    this.refTextField = React.createRef();
    this.state = { value: props.value };
  }

  render(): JSX.Element {
    const { id, label } = this.props;
    const { value } = this.state;
    
    return (
      <TextField 
        ref={this.refTextField} 
        id={id} 
        label={label} 
        value={value} 
      />
    );
  }
}

Common Pitfalls and Solutions

Incorrect Import

// Wrong - may cause TS2749 if not default export
import TextField from '@material-ui/core/TextField';

Correct Import

// Correct - uses named import syntax
import { TextField } from '@material-ui/core';

Wrong File Extension

// Component.ts - will cause errors with JSX
export const Component = () => <div>Hello</div>;

Correct File Extension

// Component.tsx - correct extension for JSX
export const Component = () => <div>Hello</div>;

When to Use Each Solution

1. Use InstanceType<typeof Component> when working with class components from third-party libraries
2. Check file extensions when you're getting errors in files containing JSX
3. Verify import syntax when working with libraries that use named exports
4. Use type-only imports for better code organization and performance

Conclusion

The TS2749 error typically occurs due to mismatches between TypeScript's understanding of values versus types. The most comprehensive solution is using InstanceType<typeof Component> which explicitly tells TypeScript to treat the component as both a value (for runtime) and extract its type information. Always ensure you're using the correct file extension (.tsx for JSX) and import syntax for your components.

By understanding these patterns, you can avoid this common TypeScript error and write more robust React applications with proper type safety.