Abstract properties

src/compiler/checker.ts

@@ -12051,6 +12051,9 @@ namespace ts {
                         if (((node.flags & NodeFlags.AccessibilityModifier) !== (otherAccessor.flags & NodeFlags.AccessibilityModifier))) {
                             error(node.name, Diagnostics.Getter_and_setter_accessors_do_not_agree_in_visibility);
                         }
+                        if (((node.flags & NodeFlags.Abstract) !== (otherAccessor.flags & NodeFlags.Abstract))) {
+                            error(node.name, Diagnostics.Accessors_must_both_be_abstract_or_non_abstract);
+                        }
 
                         const currentAccessorType = getAnnotatedAccessorType(node);
                         const otherAccessorType = getAnnotatedAccessorType(otherAccessor);
@@ -16498,8 +16501,11 @@ namespace ts {
                             return grammarErrorOnNode(modifier, Diagnostics._0_modifier_already_seen, "abstract");
                         }
                         if (node.kind !== SyntaxKind.ClassDeclaration) {
-                            if (node.kind !== SyntaxKind.MethodDeclaration) {
-                                return grammarErrorOnNode(modifier, Diagnostics.abstract_modifier_can_only_appear_on_a_class_or_method_declaration);
+                            if (node.kind !== SyntaxKind.MethodDeclaration &&
+                                node.kind !== SyntaxKind.PropertyDeclaration &&
+                                node.kind !== SyntaxKind.GetAccessor &&
+                                node.kind !== SyntaxKind.SetAccessor) {
+                                return grammarErrorOnNode(modifier, Diagnostics.abstract_modifier_can_only_appear_on_a_class_method_or_property_declaration);
                             }
                             if (!(node.parent.kind === SyntaxKind.ClassDeclaration && node.parent.flags & NodeFlags.Abstract)) {
                                 return grammarErrorOnNode(modifier, Diagnostics.Abstract_methods_can_only_appear_within_an_abstract_class);
@@ -16993,7 +16999,7 @@ namespace ts {
             else if (isInAmbientContext(accessor)) {
                 return grammarErrorOnNode(accessor.name, Diagnostics.An_accessor_cannot_be_declared_in_an_ambient_context);
             }
-            else if (accessor.body === undefined) {
+            else if (accessor.body === undefined && !(accessor.flags & NodeFlags.Abstract)) {
                 return grammarErrorAtPos(getSourceFileOfNode(accessor), accessor.end - 1, ";".length, Diagnostics._0_expected, "{");
             }
             else if (accessor.typeParameters) {

src/compiler/diagnosticMessages.json

@@ -779,7 +779,7 @@
         "category": "Error",
         "code": 1241
     },
-    "'abstract' modifier can only appear on a class or method declaration.": {
+    "'abstract' modifier can only appear on a class, method, or property declaration.": {
         "category": "Error",
         "code": 1242
     },
@@ -1843,6 +1843,10 @@
         "category": "Error",
         "code": 2675
     },
+    "Accessors must both be abstract or non-abstract.": {
+        "category": "Error",
+        "code": 2676
+    },
     "Import declaration '{0}' is using private name '{1}'.": {
         "category": "Error",
         "code": 4000

tests/baselines/reference/abstractProperty.js

@@ -0,0 +1,56 @@
+//// [abstractProperty.ts]
+interface A {
+    prop: string;
+    raw: string;
+    m(): void;
+}
+abstract class B implements A {
+    abstract prop: string;
+    abstract raw: string;
+    abstract readonly ro: string;
+    abstract get readonlyProp(): string;
+    abstract set readonlyProp(val: string);
+    abstract m(): void;
+}
+class C extends B {
+    get prop() { return "foo"; }
+    set prop(v) { }
+    raw = "edge";
+    readonly ro = "readonly please";
+    readonlyProp: string; // don't have to give a value, in fact
+    m() { }
+}
+
+//// [abstractProperty.js]
+var __extends = (this && this.__extends) || function (d, b) {
+    for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p];
+    function __() { this.constructor = d; }
+    d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
+};
+var B = (function () {
+    function B() {
+    }
+    Object.defineProperty(B.prototype, "readonlyProp", {
+        get: function () { },
+        set: function (val) { },
+        enumerable: true,
+        configurable: true
+    });
+    return B;
+}());
+var C = (function (_super) {
+    __extends(C, _super);
+    function C() {
+        _super.apply(this, arguments);
+        this.raw = "edge";
+        this.ro = "readonly please";
+    }
+    Object.defineProperty(C.prototype, "prop", {
+        get: function () { return "foo"; },
+        set: function (v) { },
+        enumerable: true,
+        configurable: true
+    });
+    C.prototype.m = function () { };
+    return C;
+}(B));

tests/baselines/reference/abstractProperty.symbols

@@ -0,0 +1,59 @@
+=== tests/cases/compiler/abstractProperty.ts ===
+interface A {
+>A : Symbol(A, Decl(abstractProperty.ts, 0, 0))
+
+    prop: string;
+>prop : Symbol(prop, Decl(abstractProperty.ts, 0, 13))
+
+    raw: string;
+>raw : Symbol(raw, Decl(abstractProperty.ts, 1, 17))
+
+    m(): void;
+>m : Symbol(m, Decl(abstractProperty.ts, 2, 16))
+}
+abstract class B implements A {
+>B : Symbol(B, Decl(abstractProperty.ts, 4, 1))
+>A : Symbol(A, Decl(abstractProperty.ts, 0, 0))
+
+    abstract prop: string;
+>prop : Symbol(prop, Decl(abstractProperty.ts, 5, 31))
+
+    abstract raw: string;
+>raw : Symbol(raw, Decl(abstractProperty.ts, 6, 26))
+
+    abstract readonly ro: string;
+>ro : Symbol(ro, Decl(abstractProperty.ts, 7, 25))
+
+    abstract get readonlyProp(): string;
+>readonlyProp : Symbol(readonlyProp, Decl(abstractProperty.ts, 8, 33), Decl(abstractProperty.ts, 9, 40))
+
+    abstract set readonlyProp(val: string);
+>readonlyProp : Symbol(readonlyProp, Decl(abstractProperty.ts, 8, 33), Decl(abstractProperty.ts, 9, 40))
+>val : Symbol(val, Decl(abstractProperty.ts, 10, 30))
+
+    abstract m(): void;
+>m : Symbol(m, Decl(abstractProperty.ts, 10, 43))
+}
+class C extends B {
+>C : Symbol(C, Decl(abstractProperty.ts, 12, 1))
+>B : Symbol(B, Decl(abstractProperty.ts, 4, 1))
+
+    get prop() { return "foo"; }
+>prop : Symbol(prop, Decl(abstractProperty.ts, 13, 19), Decl(abstractProperty.ts, 14, 32))
+
+    set prop(v) { }
+>prop : Symbol(prop, Decl(abstractProperty.ts, 13, 19), Decl(abstractProperty.ts, 14, 32))
+>v : Symbol(v, Decl(abstractProperty.ts, 15, 13))
+
+    raw = "edge";
+>raw : Symbol(raw, Decl(abstractProperty.ts, 15, 19))
+
+    readonly ro = "readonly please";
+>ro : Symbol(ro, Decl(abstractProperty.ts, 16, 17))
+
+    readonlyProp: string; // don't have to give a value, in fact
+>readonlyProp : Symbol(readonlyProp, Decl(abstractProperty.ts, 17, 36))
+
+    m() { }
+>m : Symbol(m, Decl(abstractProperty.ts, 18, 25))
+}

tests/baselines/reference/abstractProperty.types

@@ -0,0 +1,62 @@
+=== tests/cases/compiler/abstractProperty.ts ===
+interface A {
+>A : A
+
+    prop: string;
+>prop : string
+
+    raw: string;
+>raw : string
+
+    m(): void;
+>m : () => void
+}
+abstract class B implements A {
+>B : B
+>A : A
+
+    abstract prop: string;
+>prop : string
+
+    abstract raw: string;
+>raw : string
+
+    abstract readonly ro: string;
+>ro : string
+
+    abstract get readonlyProp(): string;
+>readonlyProp : string
+
+    abstract set readonlyProp(val: string);
+>readonlyProp : string
+>val : string
+
+    abstract m(): void;
+>m : () => void
+}
+class C extends B {
+>C : C
+>B : B
+
+    get prop() { return "foo"; }
+>prop : string
+>"foo" : string
+
+    set prop(v) { }
+>prop : string
+>v : string
+
+    raw = "edge";
+>raw : string
+>"edge" : string
+
+    readonly ro = "readonly please";
+>ro : string
+>"readonly please" : string
+
+    readonlyProp: string; // don't have to give a value, in fact
+>readonlyProp : string
+
+    m() { }
+>m : () => void
+}

tests/baselines/reference/abstractPropertyNegative.errors.txt

@@ -0,0 +1,106 @@
+tests/cases/compiler/abstractPropertyNegative.ts(10,18): error TS2380: 'get' and 'set' accessor must have the same type.
+tests/cases/compiler/abstractPropertyNegative.ts(11,18): error TS2380: 'get' and 'set' accessor must have the same type.
+tests/cases/compiler/abstractPropertyNegative.ts(13,7): error TS2515: Non-abstract class 'C' does not implement inherited abstract member 'm' from class 'B'.
+tests/cases/compiler/abstractPropertyNegative.ts(13,7): error TS2515: Non-abstract class 'C' does not implement inherited abstract member 'mismatch' from class 'B'.
+tests/cases/compiler/abstractPropertyNegative.ts(13,7): error TS2515: Non-abstract class 'C' does not implement inherited abstract member 'prop' from class 'B'.
+tests/cases/compiler/abstractPropertyNegative.ts(13,7): error TS2515: Non-abstract class 'C' does not implement inherited abstract member 'readonlyProp' from class 'B'.
+tests/cases/compiler/abstractPropertyNegative.ts(15,5): error TS1244: Abstract methods can only appear within an abstract class.
+tests/cases/compiler/abstractPropertyNegative.ts(16,37): error TS1005: '{' expected.
+tests/cases/compiler/abstractPropertyNegative.ts(19,1): error TS2450: Left-hand side of assignment expression cannot be a constant or a read-only property.
+tests/cases/compiler/abstractPropertyNegative.ts(24,7): error TS2415: Class 'WrongTypePropertyImpl' incorrectly extends base class 'WrongTypeProperty'.
+  Types of property 'num' are incompatible.
+    Type 'string' is not assignable to type 'number'.
+tests/cases/compiler/abstractPropertyNegative.ts(30,7): error TS2415: Class 'WrongTypeAccessorImpl' incorrectly extends base class 'WrongTypeAccessor'.
+  Types of property 'num' are incompatible.
+    Type 'string' is not assignable to type 'number'.
+tests/cases/compiler/abstractPropertyNegative.ts(33,7): error TS2415: Class 'WrongTypeAccessorImpl2' incorrectly extends base class 'WrongTypeAccessor'.
+  Types of property 'num' are incompatible.
+    Type 'string' is not assignable to type 'number'.
+tests/cases/compiler/abstractPropertyNegative.ts(38,18): error TS2676: Accessors must both be abstract or non-abstract.
+tests/cases/compiler/abstractPropertyNegative.ts(39,9): error TS2676: Accessors must both be abstract or non-abstract.
+tests/cases/compiler/abstractPropertyNegative.ts(40,9): error TS2676: Accessors must both be abstract or non-abstract.
+tests/cases/compiler/abstractPropertyNegative.ts(41,18): error TS2676: Accessors must both be abstract or non-abstract.
+
+
+==== tests/cases/compiler/abstractPropertyNegative.ts (16 errors) ====
+    interface A {
+        prop: string;
+        m(): string;
+    }
+    abstract class B implements A {
+        abstract prop: string;
+        public abstract readonly ro: string;
+        abstract get readonlyProp(): string;
+        abstract m(): string;
+        abstract get mismatch(): string;
+                     ~~~~~~~~
+!!! error TS2380: 'get' and 'set' accessor must have the same type.
+        abstract set mismatch(val: number); // error, not same type
+                     ~~~~~~~~
+!!! error TS2380: 'get' and 'set' accessor must have the same type.
+    }
+    class C extends B {
+          ~
+!!! error TS2515: Non-abstract class 'C' does not implement inherited abstract member 'm' from class 'B'.
+          ~
+!!! error TS2515: Non-abstract class 'C' does not implement inherited abstract member 'mismatch' from class 'B'.
+          ~
+!!! error TS2515: Non-abstract class 'C' does not implement inherited abstract member 'prop' from class 'B'.
+          ~
+!!! error TS2515: Non-abstract class 'C' does not implement inherited abstract member 'readonlyProp' from class 'B'.
+        readonly ro = "readonly please";
+        abstract notAllowed: string;
+        ~~~~~~~~
+!!! error TS1244: Abstract methods can only appear within an abstract class.
+        get concreteWithNoBody(): string;
+                                        ~
+!!! error TS1005: '{' expected.
+    }
+    let c = new C();
+    c.ro = "error: lhs of assignment can't be readonly";
+    ~~~~
+!!! error TS2450: Left-hand side of assignment expression cannot be a constant or a read-only property.
+
+    abstract class WrongTypeProperty {
+        abstract num: number;
+    }
+    class WrongTypePropertyImpl extends WrongTypeProperty {
+          ~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2415: Class 'WrongTypePropertyImpl' incorrectly extends base class 'WrongTypeProperty'.
+!!! error TS2415:   Types of property 'num' are incompatible.
+!!! error TS2415:     Type 'string' is not assignable to type 'number'.
+        num = "nope, wrong";
+    }
+    abstract class WrongTypeAccessor {
+        abstract get num(): number;
+    }
+    class WrongTypeAccessorImpl extends WrongTypeAccessor {
+          ~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2415: Class 'WrongTypeAccessorImpl' incorrectly extends base class 'WrongTypeAccessor'.
+!!! error TS2415:   Types of property 'num' are incompatible.
+!!! error TS2415:     Type 'string' is not assignable to type 'number'.
+        get num() { return "nope, wrong"; }
+    }
+    class WrongTypeAccessorImpl2 extends WrongTypeAccessor {
+          ~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2415: Class 'WrongTypeAccessorImpl2' incorrectly extends base class 'WrongTypeAccessor'.
+!!! error TS2415:   Types of property 'num' are incompatible.
+!!! error TS2415:     Type 'string' is not assignable to type 'number'.
+        num = "nope, wrong";
+    }
+
+    abstract class AbstractAccessorMismatch {
+        abstract get p1(): string;
+                     ~~
+!!! error TS2676: Accessors must both be abstract or non-abstract.
+        set p1(val: string) { };
+            ~~
+!!! error TS2676: Accessors must both be abstract or non-abstract.
+        get p2(): string { return "should work"; }
+            ~~
+!!! error TS2676: Accessors must both be abstract or non-abstract.
+        abstract set p2(val: string);
+                     ~~
+!!! error TS2676: Accessors must both be abstract or non-abstract.
+    }
+