Port PR 62923: Fix crash in abstract property checking for unnamed class expressions

[Copilot]

Ports TypeScript PR #62923 which fixes a crash when checking abstract properties in unnamed class expressions. The compiler previously crashed with Cannot read properties of undefined (reading 'kind') when encountering abstract properties in class expressions without names.

Changes

• internal/checker/checker.go: Modified checkPropertyAccessibilityAtLocation to check parent symbol flags directly instead of calling GetClassLikeDeclarationOfSymbol, which returns nil for unnamed class expressions. Now uses symbolToString(parentSymbol) for error messages, handling both named and unnamed classes.

• testdata/tests/cases/compiler/errorInUnnamedClassExpression.ts: Added test case covering the crash scenario.

Example

Previously crashed:

let Foo = class {
    constructor() {
        this.bar++;  // Compiler crashes here
    }
    abstract bar;
};

Now produces proper error:

error TS2715: Abstract property 'bar' in class 'Foo' cannot be accessed in the constructor.

Original prompt

Port PR 62923

---

✨ Let Copilot coding agent set things up for you — coding agent works faster and does higher quality work when set up for your repo.