Bug: AST-Spec has wrong parent types for MethodDefinition Nodes and others

[SebastianWendorf]

Before You File a Bug Report Please Confirm You Have Done The Following...

• I have tried restarting my IDE and the issue persists.
• I have updated to the latest version of the packages.
• I have searched for related issues and found none that matched my issue.
• I have read the FAQ and my problem is not listed.

Relevant Package

ast-spec

Playground Link

No response

Repro Code

// ES-Lint is used for its parsing capabilities here, to parse external code and analyse it using the provided AST data

import { Node } from "@typescript-eslint/types/dist/generated/ast-spec";
import { AST_NODE_TYPES } from "@typescript-eslint/utils";

let node: Node;

// obtain AST node

if ((node.type === AST_NODE_TYPES.MethodDefinition ||
     node.type === AST_NODE_TYPES.TSAbstractMethodDefinition ||
     node.type === AST_NODE_TYPES.TSMethodSignature) &&
    !node.computed &&
    !!node.parent &&
    (node.parent.type === AST_NODE_TYPES.ClassDeclaration || node.parent.type === AST_NODE_TYPES.TSInterfaceDeclaration)) { ... }

ESLint Config

No response

tsconfig

{
    "include": ["./src/**/*"],
    "compilerOptions": {
        "target": "ESNext",
        "experimentalDecorators": true,
         "module": "Node16",
         "moduleResolution": "node16",
         "paths": {
             "@typescript-eslint/types/dist/generated/ast-spec": ["./node_modules/@typescript-eslint/types/dist/generated/ast-spec"]
         },
        "resolveJsonModule": true,
        "allowJs": true,
        "outDir": "dist",
        "esModuleInterop": true,
        "forceConsistentCasingInFileNames": true,
        "strict": true,
        "noImplicitOverride": true,
        "skipLibCheck": true
    }
}

Expected Result

The code compiles and the check works as expected.

Actual Result

TypeScript reports the following compile error: This comparison appears to be unintentional because the types 'AST_NODE_TYPES.ClassBody | AST_NODE_TYPES.TSInterfaceBody | AST_NODE_TYPES.TSTypeLiteral' and 'AST_NODE_TYPES.ClassDeclaration' have no overlap.

When changing the comparison code the suggested types and debugging to the location in the code during execution, the runtime types match the original version. There's an obvious discrepancy between the runtime types and the types defined for TypeScript. This bug only occurred after upgrading from 7.x to 8.x.

Additional Info

The issue seems to be that @typescript-eslint/types/dist/ts-estree.d.ts seems to provide the wrong type information, e.g.:

interface MethodDefinitionNonComputedName {
parent: TSESTree.ClassBody;
}

See also here for the original source code

Versions

package	version
@typescript-eslint/eslint-plugin	8.1.0
@typescript-eslint/parser	8.1.0
@typescript-eslint/typescript-estree	8.1.0
TypeScript	5.5.4
ESLint	9.9.0
node	22.3.0

[Josh-Cena]

Do you have a sample AST to prove it's wrong? Try

class X {
  foo(): void {}
}

It produces ClassDeclaration > ClassBody > MethodDefinition.

[bradzacher]

Yeah you're expecting that the parent is a ClassDeclaration. But the AST structure is and always has been a ClassBody node around the class members.

This is what the error is telling you.

If you happen to have a repro of the structure you're describing - happy to investigate. But for now closing as a misunderstanding.

[SebastianWendorf]

I ran it on this code:

class CustomClass {
    public x: number;
    public y: number;

    constructor(x: number, y: number) {
        this.x = x;
        this.y = y;
    }
}

When I debug to the location in the code and look a the parsed AST node I get this:

[github-actions]

Uh oh! @SebastianWendorf, the image you shared is missing helpful alt text. Check #9792 (comment).

Alt text is an invisible description that helps screen readers describe images to blind or low-vision users. If you are using markdown to display images, add your alt text inside the brackets of the markdown image.

Learn more about alt text at Basic writing and formatting syntax: images on GitHub Docs.

🤖 Beep boop! This comment was added automatically by github/accessibility-alt-text-bot.

[SebastianWendorf]

May this be an exception with constructors?

EDIT: It also seems to behave this way with regular method definitions.

[Josh-Cena]

@SebastianWendorf Can you reproduce this in our playground? I can't. The AST shape you posted also doesn't make much sense because node.parent doesn't actually contain node?

[bradzacher]

You need to provide us with a reproduction.
A screenshot is not useful to us - we can't reproduce a screenshot.

Either use the playground to reproduce it https://typescript-eslint.io/play/

Or create a new github repo with the code required to reproduce your state.

We cannot help you without a reproduction