Disallow property/accessor overrides

Unless the base property or accessor is abstract

src/compiler/checker.ts

@@ -29513,14 +29513,27 @@ namespace ts {
                         // either base or derived property is private - not override, skip it
                         continue;
                     }
-
-                    if (isPrototypeProperty(base) || base.flags & SymbolFlags.PropertyOrAccessor && derived.flags & SymbolFlags.PropertyOrAccessor) {
-                        // method is overridden with method or property/accessor is overridden with property/accessor - correct case
+                    if (isPrototypeProperty(base)) {
+                        // method is overridden with method - correct case
                         continue;
                     }
-
                     let errorMessage: DiagnosticMessage;
-                    if (isPrototypeProperty(base)) {
+                    const basePropertyFlags = base.flags & SymbolFlags.PropertyOrAccessor;
+                    const derivedPropertyFlags = derived.flags & SymbolFlags.PropertyOrAccessor;
+                    if (basePropertyFlags && derivedPropertyFlags) {
+                        // property/accessor is overridden with property/accessor
+                        if (!(baseDeclarationFlags & ModifierFlags.Abstract) && basePropertyFlags !== SymbolFlags.Property && derivedPropertyFlags === SymbolFlags.Property) {
+                            errorMessage = Diagnostics.Class_0_defines_instance_member_accessor_1_but_extended_class_2_defines_it_as_instance_member_property;
+                        }
+                        else if (!(baseDeclarationFlags & ModifierFlags.Abstract) && basePropertyFlags === SymbolFlags.Property && derivedPropertyFlags !== SymbolFlags.Property) {
+                            errorMessage = Diagnostics.Class_0_defines_instance_member_property_1_but_extended_class_2_defines_it_as_instance_member_accessor;
+                        }
+                        else {
+                            // correct case
+                            continue;
+                        }
+                    }
+                    else if (isPrototypeProperty(base)) {
                         if (derived.flags & SymbolFlags.Accessor) {
                             errorMessage = Diagnostics.Class_0_defines_instance_member_function_1_but_extended_class_2_defines_it_as_instance_member_accessor;
                         }

src/compiler/diagnosticMessages.json

@@ -2204,6 +2204,15 @@
         "category": "Error",
         "code": 2609
     },
+    "Class '{0}' defines instance member accessor '{1}', but extended class '{2}' defines it as instance member property.": {
+        "category": "Error",
+        "code": 2610
+    },
+    "Class '{0}' defines instance member property '{1}', but extended class '{2}' defines it as instance member accessor.": {
+        "category": "Error",
+        "code": 2611
+    },
+
     "Cannot augment module '{0}' with value exports because it resolves to a non-module entity.": {
         "category": "Error",
         "code": 2649

src/compiler/utilities.ts

@@ -3972,7 +3972,6 @@ namespace ts {
     }
 
     export function getModifierFlagsNoCache(node: Node): ModifierFlags {
-
         let flags = ModifierFlags.None;
         if (node.modifiers) {
             for (const modifier of node.modifiers) {

tests/baselines/reference/accessorsOverrideProperty.errors.txt

@@ -0,0 +1,24 @@
+tests/cases/conformance/classes/propertyMemberDeclarations/accessorsOverrideProperty.ts(5,9): error TS2611: Class 'A' defines instance member property 'p', but extended class 'B' defines it as instance member accessor.
+tests/cases/conformance/classes/propertyMemberDeclarations/accessorsOverrideProperty.ts(12,9): error TS2611: Class 'C' defines instance member property 'p', but extended class 'D' defines it as instance member accessor.
+
+
+==== tests/cases/conformance/classes/propertyMemberDeclarations/accessorsOverrideProperty.ts (2 errors) ====
+    class A {
+        p = 'yep'
+    }
+    class B extends A {
+        get p() { return 'oh no' } // error
+            ~
+!!! error TS2611: Class 'A' defines instance member property 'p', but extended class 'B' defines it as instance member accessor.
+    }
+    class C {
+       p = 101
+    }
+    class D extends C {
+         _secret = 11
+        get p() { return this._secret } // error
+            ~
+!!! error TS2611: Class 'C' defines instance member property 'p', but extended class 'D' defines it as instance member accessor.
+        set p(value) { this._secret = value } // error
+    }
+

tests/baselines/reference/accessorsOverrideProperty.js

@@ -0,0 +1,39 @@
+//// [accessorsOverrideProperty.ts]
+class A {
+    p = 'yep'
+}
+class B extends A {
+    get p() { return 'oh no' } // error
+}
+class C {
+   p = 101
+}
+class D extends C {
+     _secret = 11
+    get p() { return this._secret } // error
+    set p(value) { this._secret = value } // error
+}
+
+
+//// [accessorsOverrideProperty.js]
+class A {
+    constructor() {
+        this.p = 'yep';
+    }
+}
+class B extends A {
+    get p() { return 'oh no'; } // error
+}
+class C {
+    constructor() {
+        this.p = 101;
+    }
+}
+class D extends C {
+    constructor() {
+        super(...arguments);
+        this._secret = 11;
+    }
+    get p() { return this._secret; } // error
+    set p(value) { this._secret = value; } // error
+}

tests/baselines/reference/accessorsOverrideProperty.symbols

@@ -0,0 +1,42 @@
+=== tests/cases/conformance/classes/propertyMemberDeclarations/accessorsOverrideProperty.ts ===
+class A {
+>A : Symbol(A, Decl(accessorsOverrideProperty.ts, 0, 0))
+
+    p = 'yep'
+>p : Symbol(A.p, Decl(accessorsOverrideProperty.ts, 0, 9))
+}
+class B extends A {
+>B : Symbol(B, Decl(accessorsOverrideProperty.ts, 2, 1))
+>A : Symbol(A, Decl(accessorsOverrideProperty.ts, 0, 0))
+
+    get p() { return 'oh no' } // error
+>p : Symbol(B.p, Decl(accessorsOverrideProperty.ts, 3, 19))
+}
+class C {
+>C : Symbol(C, Decl(accessorsOverrideProperty.ts, 5, 1))
+
+   p = 101
+>p : Symbol(C.p, Decl(accessorsOverrideProperty.ts, 6, 9))
+}
+class D extends C {
+>D : Symbol(D, Decl(accessorsOverrideProperty.ts, 8, 1))
+>C : Symbol(C, Decl(accessorsOverrideProperty.ts, 5, 1))
+
+     _secret = 11
+>_secret : Symbol(D._secret, Decl(accessorsOverrideProperty.ts, 9, 19))
+
+    get p() { return this._secret } // error
+>p : Symbol(D.p, Decl(accessorsOverrideProperty.ts, 10, 17), Decl(accessorsOverrideProperty.ts, 11, 35))
+>this._secret : Symbol(D._secret, Decl(accessorsOverrideProperty.ts, 9, 19))
+>this : Symbol(D, Decl(accessorsOverrideProperty.ts, 8, 1))
+>_secret : Symbol(D._secret, Decl(accessorsOverrideProperty.ts, 9, 19))
+
+    set p(value) { this._secret = value } // error
+>p : Symbol(D.p, Decl(accessorsOverrideProperty.ts, 10, 17), Decl(accessorsOverrideProperty.ts, 11, 35))
+>value : Symbol(value, Decl(accessorsOverrideProperty.ts, 12, 10))
+>this._secret : Symbol(D._secret, Decl(accessorsOverrideProperty.ts, 9, 19))
+>this : Symbol(D, Decl(accessorsOverrideProperty.ts, 8, 1))
+>_secret : Symbol(D._secret, Decl(accessorsOverrideProperty.ts, 9, 19))
+>value : Symbol(value, Decl(accessorsOverrideProperty.ts, 12, 10))
+}
+

tests/baselines/reference/accessorsOverrideProperty.types

@@ -0,0 +1,47 @@
+=== tests/cases/conformance/classes/propertyMemberDeclarations/accessorsOverrideProperty.ts ===
+class A {
+>A : A
+
+    p = 'yep'
+>p : string
+>'yep' : "yep"
+}
+class B extends A {
+>B : B
+>A : A
+
+    get p() { return 'oh no' } // error
+>p : string
+>'oh no' : "oh no"
+}
+class C {
+>C : C
+
+   p = 101
+>p : number
+>101 : 101
+}
+class D extends C {
+>D : D
+>C : C
+
+     _secret = 11
+>_secret : number
+>11 : 11
+
+    get p() { return this._secret } // error
+>p : number
+>this._secret : number
+>this : this
+>_secret : number
+
+    set p(value) { this._secret = value } // error
+>p : number
+>value : number
+>this._secret = value : number
+>this._secret : number
+>this : this
+>_secret : number
+>value : number
+}
+

tests/baselines/reference/accessorsOverrideProperty2.errors.txt

@@ -0,0 +1,18 @@
+tests/cases/conformance/classes/propertyMemberDeclarations/accessorsOverrideProperty2.ts(6,7): error TS2611: Class 'Base' defines instance member property 'x', but extended class 'Derived' defines it as instance member accessor.
+
+
+==== tests/cases/conformance/classes/propertyMemberDeclarations/accessorsOverrideProperty2.ts (1 errors) ====
+    class Base {
+      x = 1;
+    }
+
+    class Derived extends Base {
+      get x() { return 2; } // should be an error
+          ~
+!!! error TS2611: Class 'Base' defines instance member property 'x', but extended class 'Derived' defines it as instance member accessor.
+      set x(value) { console.log(`x was set to ${value}`); }
+    }
+
+    const obj = new Derived(); // nothing printed
+    console.log(obj.x); // 1
+

tests/baselines/reference/accessorsOverrideProperty2.js

@@ -0,0 +1,26 @@
+//// [accessorsOverrideProperty2.ts]
+class Base {
+  x = 1;
+}
+
+class Derived extends Base {
+  get x() { return 2; } // should be an error
+  set x(value) { console.log(`x was set to ${value}`); }
+}
+
+const obj = new Derived(); // nothing printed
+console.log(obj.x); // 1
+
+
+//// [accessorsOverrideProperty2.js]
+class Base {
+    constructor() {
+        this.x = 1;
+    }
+}
+class Derived extends Base {
+    get x() { return 2; } // should be an error
+    set x(value) { console.log(`x was set to ${value}`); }
+}
+const obj = new Derived(); // nothing printed
+console.log(obj.x); // 1

tests/baselines/reference/accessorsOverrideProperty2.symbols

@@ -0,0 +1,36 @@
+=== tests/cases/conformance/classes/propertyMemberDeclarations/accessorsOverrideProperty2.ts ===
+class Base {
+>Base : Symbol(Base, Decl(accessorsOverrideProperty2.ts, 0, 0))
+
+  x = 1;
+>x : Symbol(Base.x, Decl(accessorsOverrideProperty2.ts, 0, 12))
+}
+
+class Derived extends Base {
+>Derived : Symbol(Derived, Decl(accessorsOverrideProperty2.ts, 2, 1))
+>Base : Symbol(Base, Decl(accessorsOverrideProperty2.ts, 0, 0))
+
+  get x() { return 2; } // should be an error
+>x : Symbol(Derived.x, Decl(accessorsOverrideProperty2.ts, 4, 28), Decl(accessorsOverrideProperty2.ts, 5, 23))
+
+  set x(value) { console.log(`x was set to ${value}`); }
+>x : Symbol(Derived.x, Decl(accessorsOverrideProperty2.ts, 4, 28), Decl(accessorsOverrideProperty2.ts, 5, 23))
+>value : Symbol(value, Decl(accessorsOverrideProperty2.ts, 6, 8))
+>console.log : Symbol(Console.log, Decl(lib.dom.d.ts, --, --))
+>console : Symbol(console, Decl(lib.dom.d.ts, --, --))
+>log : Symbol(Console.log, Decl(lib.dom.d.ts, --, --))
+>value : Symbol(value, Decl(accessorsOverrideProperty2.ts, 6, 8))
+}
+
+const obj = new Derived(); // nothing printed
+>obj : Symbol(obj, Decl(accessorsOverrideProperty2.ts, 9, 5))
+>Derived : Symbol(Derived, Decl(accessorsOverrideProperty2.ts, 2, 1))
+
+console.log(obj.x); // 1
+>console.log : Symbol(Console.log, Decl(lib.dom.d.ts, --, --))
+>console : Symbol(console, Decl(lib.dom.d.ts, --, --))
+>log : Symbol(Console.log, Decl(lib.dom.d.ts, --, --))
+>obj.x : Symbol(Derived.x, Decl(accessorsOverrideProperty2.ts, 4, 28), Decl(accessorsOverrideProperty2.ts, 5, 23))
+>obj : Symbol(obj, Decl(accessorsOverrideProperty2.ts, 9, 5))
+>x : Symbol(Derived.x, Decl(accessorsOverrideProperty2.ts, 4, 28), Decl(accessorsOverrideProperty2.ts, 5, 23))
+

tests/baselines/reference/accessorsOverrideProperty2.types

@@ -0,0 +1,42 @@
+=== tests/cases/conformance/classes/propertyMemberDeclarations/accessorsOverrideProperty2.ts ===
+class Base {
+>Base : Base
+
+  x = 1;
+>x : number
+>1 : 1
+}
+
+class Derived extends Base {
+>Derived : Derived
+>Base : Base
+
+  get x() { return 2; } // should be an error
+>x : number
+>2 : 2
+
+  set x(value) { console.log(`x was set to ${value}`); }
+>x : number
+>value : number
+>console.log(`x was set to ${value}`) : void
+>console.log : (message?: any, ...optionalParams: any[]) => void
+>console : Console
+>log : (message?: any, ...optionalParams: any[]) => void
+>`x was set to ${value}` : string
+>value : number
+}
+
+const obj = new Derived(); // nothing printed
+>obj : Derived
+>new Derived() : Derived
+>Derived : typeof Derived
+
+console.log(obj.x); // 1
+>console.log(obj.x) : void
+>console.log : (message?: any, ...optionalParams: any[]) => void
+>console : Console
+>log : (message?: any, ...optionalParams: any[]) => void
+>obj.x : number
+>obj : Derived
+>x : number
+

tests/baselines/reference/accessorsOverrideProperty3.errors.txt

@@ -0,0 +1,15 @@
+tests/cases/conformance/classes/propertyMemberDeclarations/accessorsOverrideProperty3.ts(6,9): error TS2611: Class 'Animal' defines instance member property 'sound', but extended class 'Lion' defines it as instance member accessor.
+
+
+==== tests/cases/conformance/classes/propertyMemberDeclarations/accessorsOverrideProperty3.ts (1 errors) ====
+    declare class Animal {
+        sound: string
+    }
+    class Lion extends Animal {
+        _sound = 'grrr'
+        get sound() { return this._sound } // error here
+            ~~~~~
+!!! error TS2611: Class 'Animal' defines instance member property 'sound', but extended class 'Lion' defines it as instance member accessor.
+        set sound(val) { this._sound = val }
+    }
+

tests/baselines/reference/accessorsOverrideProperty3.js

@@ -0,0 +1,20 @@
+//// [accessorsOverrideProperty3.ts]
+declare class Animal {
+    sound: string
+}
+class Lion extends Animal {
+    _sound = 'grrr'
+    get sound() { return this._sound } // error here
+    set sound(val) { this._sound = val }
+}
+
+
+//// [accessorsOverrideProperty3.js]
+class Lion extends Animal {
+    constructor() {
+        super(...arguments);
+        this._sound = 'grrr';
+    }
+    get sound() { return this._sound; } // error here
+    set sound(val) { this._sound = val; }
+}