Fix bug: symbol.valueDeclaration not guaranteed to be defined (#26267)

src/compiler/checker.ts

@@ -20861,7 +20861,7 @@ namespace ts {
                     // If func.parent is a class and symbol is a (readonly) property of that class, or
                     // if func is a constructor and symbol is a (readonly) parameter property declared in it,
                     // then symbol is writeable here.
-                    return !(func.parent === symbol.valueDeclaration.parent || func === symbol.valueDeclaration.parent);
+                    return !symbol.valueDeclaration || !(func.parent === symbol.valueDeclaration.parent || func === symbol.valueDeclaration.parent);
                 }
                 return true;
             }

tests/baselines/reference/readonlyAssignmentInSubclassOfClassExpression.errors.txt

@@ -0,0 +1,13 @@
+tests/cases/compiler/readonlyAssignmentInSubclassOfClassExpression.ts(4,14): error TS2540: Cannot assign to 'attrib' because it is a constant or a read-only property.
+
+
+==== tests/cases/compiler/readonlyAssignmentInSubclassOfClassExpression.ts (1 errors) ====
+    class C extends (class {} as new () => Readonly<{ attrib: number }>) {
+        constructor() {
+            super()
+            this.attrib = 2
+                 ~~~~~~
+!!! error TS2540: Cannot assign to 'attrib' because it is a constant or a read-only property.
+        }
+    }
+    

tests/baselines/reference/readonlyAssignmentInSubclassOfClassExpression.js

@@ -0,0 +1,36 @@
+//// [readonlyAssignmentInSubclassOfClassExpression.ts]
+class C extends (class {} as new () => Readonly<{ attrib: number }>) {
+    constructor() {
+        super()
+        this.attrib = 2
+    }
+}
+
+
+//// [readonlyAssignmentInSubclassOfClassExpression.js]
+var __extends = (this && this.__extends) || (function () {
+    var extendStatics = function (d, b) {
+        extendStatics = Object.setPrototypeOf ||
+            ({ __proto__: [] } instanceof Array && function (d, b) { d.__proto__ = b; }) ||
+            function (d, b) { for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p]; };
+        return extendStatics(d, b);
+    }
+    return function (d, b) {
+        extendStatics(d, b);
+        function __() { this.constructor = d; }
+        d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
+    };
+})();
+var C = /** @class */ (function (_super) {
+    __extends(C, _super);
+    function C() {
+        var _this = _super.call(this) || this;
+        _this.attrib = 2;
+        return _this;
+    }
+    return C;
+}(/** @class */ (function () {
+    function class_1() {
+    }
+    return class_1;
+}())));

tests/baselines/reference/readonlyAssignmentInSubclassOfClassExpression.symbols

@@ -0,0 +1,17 @@
+=== tests/cases/compiler/readonlyAssignmentInSubclassOfClassExpression.ts ===
+class C extends (class {} as new () => Readonly<{ attrib: number }>) {
+>C : Symbol(C, Decl(readonlyAssignmentInSubclassOfClassExpression.ts, 0, 0))
+>Readonly : Symbol(Readonly, Decl(lib.es5.d.ts, --, --))
+>attrib : Symbol(attrib, Decl(readonlyAssignmentInSubclassOfClassExpression.ts, 0, 49))
+
+    constructor() {
+        super()
+>super : Symbol(__type, Decl(readonlyAssignmentInSubclassOfClassExpression.ts, 0, 28))
+
+        this.attrib = 2
+>this.attrib : Symbol(attrib, Decl(readonlyAssignmentInSubclassOfClassExpression.ts, 0, 49))
+>this : Symbol(C, Decl(readonlyAssignmentInSubclassOfClassExpression.ts, 0, 0))
+>attrib : Symbol(attrib, Decl(readonlyAssignmentInSubclassOfClassExpression.ts, 0, 49))
+    }
+}
+

tests/baselines/reference/readonlyAssignmentInSubclassOfClassExpression.types

@@ -0,0 +1,22 @@
+=== tests/cases/compiler/readonlyAssignmentInSubclassOfClassExpression.ts ===
+class C extends (class {} as new () => Readonly<{ attrib: number }>) {
+>C : C
+>(class {} as new () => Readonly<{ attrib: number }>) : Readonly<{ attrib: number; }>
+>class {} as new () => Readonly<{ attrib: number }> : new () => Readonly<{ attrib: number; }>
+>class {} : typeof (Anonymous class)
+>attrib : number
+
+    constructor() {
+        super()
+>super() : void
+>super : new () => Readonly<{ attrib: number; }>
+
+        this.attrib = 2
+>this.attrib = 2 : 2
+>this.attrib : any
+>this : this
+>attrib : any
+>2 : 2
+    }
+}
+

tests/cases/compiler/readonlyAssignmentInSubclassOfClassExpression.ts

@@ -0,0 +1,6 @@
+class C extends (class {} as new () => Readonly<{ attrib: number }>) {
+    constructor() {
+        super()
+        this.attrib = 2
+    }
+}