Expose isTypeReference function in public API

Search Terms

isTypeReference

Suggestion

The public compiler API exposes a getTypeArguments method on the type checker:

https://github.com/microsoft/TypeScript/blob/cc7cb9eadb10a56687513d4fc3a67d5210b387bb/lib/typescript.d.ts#L2107

But provides no way to check if a type is a TypeReference. Users of the TS compiler API have to roll their own, which is error-prone. I suggest that if TypeReference is exposed in the public API, there should be a way to assert whether a type is a TypeReference.

Use Cases

See above

Examples

Currently, public uses of getTypeArguments must do something like this to assert that a type is a TypeReference:

function isTypeReference(ty: ts.Type): ty is ts.TypeReference {
    return 'typeArguments' in ty;
}

const ty = getType();
if (isTypeReference(ty)) {
    getChecker().getTypeArguments(ty);
}

With an exposed type guards, this becomes

const ty = getType();
if (ts.isTypeReference(ty)) {
    getChecker().getTypeArguments(ty);
}

Checklist

My suggestion meets these guidelines:

• This wouldn't be a breaking change in existing TypeScript/JavaScript code
• This wouldn't change the runtime behavior of existing JavaScript code
• This could be implemented without emitting different JS based on the types of the expressions
• This isn't a runtime feature (e.g. library functionality, non-ECMAScript syntax with JavaScript output, etc.)
• This feature would agree with the rest of TypeScript's Design Goals.

Bắt đầu bằng cách kiểm tra lib/typescript.d.ts xung quanh phương thức getTypeArguments được cung cấp và API TypeReference công khai. Xác minh rằng API đã hoàn thiện cung cấp ts.isTypeReference và rằng ví dụ có thể sử dụng nó để bảo vệ các lệnh gọi đến getTypeArguments.