Crash: TypeError: Cannot read properties of undefined (reading 'kind') in checkPropertyAccessibility when using abstract in Class Expression

[na7ure-a]

🔎 Search Terms

"Cannot read properties of undefined (reading 'kind')"

"isMemberName crash"

"abstract property class expression crash"

"checkPropertyAccessibilityAtLocation crash"

🕗 Version & Regression Information

Versions tested: 5.7.3, 5.8.3, 5.9.3, Nightly (typescript@5.10.0-dev.20251221)

Is this a regression? No, this appears to be a long-standing issue in the checker's handling of illegal abstract modifiers within class expressions.

Does it occur in nightly? Yes.

⏯ Playground Link

https://www.typescriptlang.org/zh/play/?target=7&outFile=mylib.js&ts=5.8.3#code/DYUwLgBAYg9jEF4IGNgEMDOGIG8BQEhKMAdhmAE4CuyYMFAFAJS4FHtgAWAlhgHQAjNBQDUIgNxtCAXykQ0A8hTS0IQipOmS8QA

💻 Code

let Foo = class {
    constructor() {
        this.bar++;
    }
    abstract bar;
};

🙁 Actual behavior

.\ts-versions\5.9.3\node_modules\.bin\tsc.cmd --noEmit  .\bugfind\mute1.ts
D:\do\tscFuzz\ts-versions\5.9.3\node_modules\typescript\lib\_tsc.js:123168
      throw e;
      ^

TypeError: Cannot read properties of undefined (reading 'kind')
    at isMemberName (D:\do\tscFuzz\ts-versions\5.9.3\node_modules\typescript\lib\_tsc.js:11830:15)                                                                                                       
    at getTextOfIdentifierOrLiteral (D:\do\tscFuzz\ts-versions\5.9.3\node_modules\typescript\lib\_tsc.js:15842:10)                                                                                       
    at checkPropertyAccessibilityAtLocation (D:\do\tscFuzz\ts-versions\5.9.3\node_modules\typescript\lib\_tsc.js:74766:132)                                                                              
    at checkPropertyAccessibility (D:\do\tscFuzz\ts-versions\5.9.3\node_modules\typescript\lib\_tsc.js:74735:12)                                                                                         
    at checkPropertyAccessExpressionOrQualifiedName (D:\do\tscFuzz\ts-versions\5.9.3\node_modules\typescript\lib\_tsc.js:75176:7)                                                                        
    at checkPropertyAccessExpression (D:\do\tscFuzz\ts-versions\5.9.3\node_modules\typescript\lib\_tsc.js:74932:94)                                                                                      
    at checkExpressionWorker (D:\do\tscFuzz\ts-versions\5.9.3\node_modules\typescript\lib\_tsc.js:80937:16)                                                                                              
    at checkExpression (D:\do\tscFuzz\ts-versions\5.9.3\node_modules\typescript\lib\_tsc.js:80846:32)                                                                                                    
    at checkPostfixUnaryExpression (D:\do\tscFuzz\ts-versions\5.9.3\node_modules\typescript\lib\_tsc.js:79348:25)                                                                                        
    at checkExpressionWorker (D:\do\tscFuzz\ts-versions\5.9.3\node_modules\typescript\lib\_tsc.js:80980:16)  

🙂 Expected behavior

The compiler should not crash

Additional information about the issue

No response

[ahejlsberg]

The code that crashes assumes all class-like declarations have a name, which is not necessarily the case for class expressions.