Variant accessors

src/compiler/diagnosticMessages.json

@@ -1706,11 +1706,7 @@
         "category": "Error",
         "code": 2378
     },
-    "Getter and setter accessors do not agree in visibility.": {
-        "category": "Error",
-        "code": 2379
-    },
-    "'get' and 'set' accessor must have the same type.": {
+    "The return type of a 'get' accessor must be assignable to its 'set' accessor type": {
         "category": "Error",
         "code": 2380
     },
@@ -3308,6 +3304,10 @@
         "category": "Error",
         "code": 2807
     },
+    "A get accessor must be at least as accessible as the setter": {
+        "category": "Error",
+        "code": 2808
+    },
 
     "Import declaration '{0}' is using private name '{1}'.": {
         "category": "Error",

src/compiler/parser.ts

@@ -3213,7 +3213,10 @@ namespace ts {
 
         function isTypeMemberStart(): boolean {
             // Return true if we have the start of a signature member
-            if (token() === SyntaxKind.OpenParenToken || token() === SyntaxKind.LessThanToken) {
+            if (token() === SyntaxKind.OpenParenToken ||
+                token() === SyntaxKind.LessThanToken ||
+                token() === SyntaxKind.GetKeyword ||
+                token() === SyntaxKind.SetKeyword) {
                 return true;
             }
             let idToken = false;
@@ -3254,6 +3257,14 @@ namespace ts {
             const pos = getNodePos();
             const hasJSDoc = hasPrecedingJSDocComment();
             const modifiers = parseModifiers();
+            if (parseContextualModifier(SyntaxKind.GetKeyword)) {
+                return parseAccessorDeclaration(pos, hasJSDoc, /*decorators*/ undefined, modifiers, SyntaxKind.GetAccessor);
+            }
+
+            if (parseContextualModifier(SyntaxKind.SetKeyword)) {
+                return parseAccessorDeclaration(pos, hasJSDoc, /*decorators*/ undefined, modifiers, SyntaxKind.SetAccessor);
+            }
+
             if (isIndexSignature()) {
                 return parseIndexSignatureDeclaration(pos, hasJSDoc, /*decorators*/ undefined, modifiers);
             }

src/compiler/types.ts

@@ -1475,19 +1475,19 @@ namespace ts {
 
     // See the comment on MethodDeclaration for the intuition behind GetAccessorDeclaration being a
     // ClassElement and an ObjectLiteralElement.
-    export interface GetAccessorDeclaration extends FunctionLikeDeclarationBase, ClassElement, ObjectLiteralElement, JSDocContainer {
+    export interface GetAccessorDeclaration extends FunctionLikeDeclarationBase, ClassElement, TypeElement, ObjectLiteralElement, JSDocContainer {
         readonly kind: SyntaxKind.GetAccessor;
-        readonly parent: ClassLikeDeclaration | ObjectLiteralExpression;
+        readonly parent: ClassLikeDeclaration | ObjectLiteralExpression | TypeLiteralNode | InterfaceDeclaration;
         readonly name: PropertyName;
         readonly body?: FunctionBody;
         /* @internal */ typeParameters?: NodeArray<TypeParameterDeclaration>; // Present for use with reporting a grammar error
     }
 
     // See the comment on MethodDeclaration for the intuition behind SetAccessorDeclaration being a
     // ClassElement and an ObjectLiteralElement.
-    export interface SetAccessorDeclaration extends FunctionLikeDeclarationBase, ClassElement, ObjectLiteralElement, JSDocContainer {
+    export interface SetAccessorDeclaration extends FunctionLikeDeclarationBase, ClassElement, TypeElement, ObjectLiteralElement, JSDocContainer {
         readonly kind: SyntaxKind.SetAccessor;
-        readonly parent: ClassLikeDeclaration | ObjectLiteralExpression;
+        readonly parent: ClassLikeDeclaration | ObjectLiteralExpression | TypeLiteralNode | InterfaceDeclaration;
         readonly name: PropertyName;
         readonly body?: FunctionBody;
         /* @internal */ typeParameters?: NodeArray<TypeParameterDeclaration>; // Present for use with reporting a grammar error
@@ -4765,6 +4765,7 @@ namespace ts {
         immediateTarget?: Symbol;                   // Immediate target of an alias. May be another alias. Do not access directly, use `checker.getImmediateAliasedSymbol` instead.
         target?: Symbol;                            // Resolved (non-alias) target of an alias
         type?: Type;                                // Type of value symbol
+        writeType?: Type;                           // Type of value symbol in write contexts
         nameType?: Type;                            // Type associated with a late-bound symbol
         uniqueESSymbolType?: Type;                  // UniqueESSymbol type for a symbol
         declaredType?: Type;                        // Type of class, interface, enum, type alias, or type parameter

src/compiler/utilities.ts

@@ -5275,9 +5275,10 @@ namespace ts {
         return symbol.flags & SymbolFlags.Transient ? (<TransientSymbol>symbol).checkFlags : 0;
     }
 
-    export function getDeclarationModifierFlagsFromSymbol(s: Symbol): ModifierFlags {
+    export function getDeclarationModifierFlagsFromSymbol(s: Symbol, isWrite = false): ModifierFlags {
         if (s.valueDeclaration) {
-            const flags = getCombinedModifierFlags(s.valueDeclaration);
+            const declaration = (isWrite && s.declarations && find(s.declarations, d => d.kind === SyntaxKind.SetAccessor)) || s.valueDeclaration;
+            const flags = getCombinedModifierFlags(declaration);
             return s.parent && s.parent.flags & SymbolFlags.Class ? flags : flags & ~ModifierFlags.AccessibilityModifier;
         }
         if (getCheckFlags(s) & CheckFlags.Synthetic) {

tests/baselines/reference/abstractPropertyNegative.errors.txt

@@ -1,5 +1,4 @@
-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(10,18): error TS2380: The return type of a 'get' accessor must be assignable to its 'set' accessor 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'.
@@ -19,7 +18,7 @@ tests/cases/compiler/abstractPropertyNegative.ts(40,9): error TS2676: Accessors
 tests/cases/compiler/abstractPropertyNegative.ts(41,18): error TS2676: Accessors must both be abstract or non-abstract.
 
 
-==== tests/cases/compiler/abstractPropertyNegative.ts (16 errors) ====
+==== tests/cases/compiler/abstractPropertyNegative.ts (15 errors) ====
     interface A {
         prop: string;
         m(): string;
@@ -31,10 +30,8 @@ tests/cases/compiler/abstractPropertyNegative.ts(41,18): error TS2676: Accessors
         abstract m(): string;
         abstract get mismatch(): string;
                      ~~~~~~~~
-!!! error TS2380: 'get' and 'set' accessor must have the same type.
+!!! error TS2380: The return type of a 'get' accessor must be assignable to its 'set' accessor 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 {
           ~

tests/baselines/reference/accessorBodyInTypeContext.errors.txt

@@ -0,0 +1,32 @@
+tests/cases/compiler/accessorBodyInTypeContext.ts(2,15): error TS1183: An implementation cannot be declared in ambient contexts.
+tests/cases/compiler/accessorBodyInTypeContext.ts(6,21): error TS1183: An implementation cannot be declared in ambient contexts.
+tests/cases/compiler/accessorBodyInTypeContext.ts(10,15): error TS1183: An implementation cannot be declared in ambient contexts.
+tests/cases/compiler/accessorBodyInTypeContext.ts(14,21): error TS1183: An implementation cannot be declared in ambient contexts.
+
+
+==== tests/cases/compiler/accessorBodyInTypeContext.ts (4 errors) ====
+    type A = {
+        get foo() { return 0 }
+                  ~~~~~~~~~~~~
+!!! error TS1183: An implementation cannot be declared in ambient contexts.
+    };
+
+    type B = {
+        set foo(v: any) { }
+                        ~~~
+!!! error TS1183: An implementation cannot be declared in ambient contexts.
+    };
+
+    interface X {
+        get foo() { return 0 }
+                  ~~~~~~~~~~~~
+!!! error TS1183: An implementation cannot be declared in ambient contexts.
+    }
+
+    interface Y {
+        set foo(v: any) { }
+                        ~~~
+!!! error TS1183: An implementation cannot be declared in ambient contexts.
+    }
+
+

tests/baselines/reference/accessorBodyInTypeContext.js

@@ -0,0 +1,20 @@
+//// [accessorBodyInTypeContext.ts]
+type A = {
+    get foo() { return 0 }
+};
+
+type B = {
+    set foo(v: any) { }
+};
+
+interface X {
+    get foo() { return 0 }
+}
+
+interface Y {
+    set foo(v: any) { }
+}
+
+
+
+//// [accessorBodyInTypeContext.js]

tests/baselines/reference/accessorBodyInTypeContext.symbols

@@ -0,0 +1,34 @@
+=== tests/cases/compiler/accessorBodyInTypeContext.ts ===
+type A = {
+>A : Symbol(A, Decl(accessorBodyInTypeContext.ts, 0, 0))
+
+    get foo() { return 0 }
+>foo : Symbol(foo, Decl(accessorBodyInTypeContext.ts, 0, 10))
+
+};
+
+type B = {
+>B : Symbol(B, Decl(accessorBodyInTypeContext.ts, 2, 2))
+
+    set foo(v: any) { }
+>foo : Symbol(foo, Decl(accessorBodyInTypeContext.ts, 4, 10))
+>v : Symbol(v, Decl(accessorBodyInTypeContext.ts, 5, 12))
+
+};
+
+interface X {
+>X : Symbol(X, Decl(accessorBodyInTypeContext.ts, 6, 2))
+
+    get foo() { return 0 }
+>foo : Symbol(X.foo, Decl(accessorBodyInTypeContext.ts, 8, 13))
+}
+
+interface Y {
+>Y : Symbol(Y, Decl(accessorBodyInTypeContext.ts, 10, 1))
+
+    set foo(v: any) { }
+>foo : Symbol(Y.foo, Decl(accessorBodyInTypeContext.ts, 12, 13))
+>v : Symbol(v, Decl(accessorBodyInTypeContext.ts, 13, 12))
+}
+
+

tests/baselines/reference/accessorBodyInTypeContext.types

@@ -0,0 +1,32 @@
+=== tests/cases/compiler/accessorBodyInTypeContext.ts ===
+type A = {
+>A : A
+
+    get foo() { return 0 }
+>foo : number
+>0 : 0
+
+};
+
+type B = {
+>B : B
+
+    set foo(v: any) { }
+>foo : any
+>v : any
+
+};
+
+interface X {
+    get foo() { return 0 }
+>foo : number
+>0 : 0
+}
+
+interface Y {
+    set foo(v: any) { }
+>foo : any
+>v : any
+}
+
+

tests/baselines/reference/api/tsserverlibrary.d.ts

@@ -823,15 +823,15 @@ declare namespace ts {
         readonly kind: SyntaxKind.SemicolonClassElement;
         readonly parent: ClassLikeDeclaration;
     }
-    export interface GetAccessorDeclaration extends FunctionLikeDeclarationBase, ClassElement, ObjectLiteralElement, JSDocContainer {
+    export interface GetAccessorDeclaration extends FunctionLikeDeclarationBase, ClassElement, TypeElement, ObjectLiteralElement, JSDocContainer {
         readonly kind: SyntaxKind.GetAccessor;
-        readonly parent: ClassLikeDeclaration | ObjectLiteralExpression;
+        readonly parent: ClassLikeDeclaration | ObjectLiteralExpression | TypeLiteralNode | InterfaceDeclaration;
         readonly name: PropertyName;
         readonly body?: FunctionBody;
     }
-    export interface SetAccessorDeclaration extends FunctionLikeDeclarationBase, ClassElement, ObjectLiteralElement, JSDocContainer {
+    export interface SetAccessorDeclaration extends FunctionLikeDeclarationBase, ClassElement, TypeElement, ObjectLiteralElement, JSDocContainer {
         readonly kind: SyntaxKind.SetAccessor;
-        readonly parent: ClassLikeDeclaration | ObjectLiteralExpression;
+        readonly parent: ClassLikeDeclaration | ObjectLiteralExpression | TypeLiteralNode | InterfaceDeclaration;
         readonly name: PropertyName;
         readonly body?: FunctionBody;
     }

tests/baselines/reference/api/typescript.d.ts

@@ -823,15 +823,15 @@ declare namespace ts {
         readonly kind: SyntaxKind.SemicolonClassElement;
         readonly parent: ClassLikeDeclaration;
     }
-    export interface GetAccessorDeclaration extends FunctionLikeDeclarationBase, ClassElement, ObjectLiteralElement, JSDocContainer {
+    export interface GetAccessorDeclaration extends FunctionLikeDeclarationBase, ClassElement, TypeElement, ObjectLiteralElement, JSDocContainer {
         readonly kind: SyntaxKind.GetAccessor;
-        readonly parent: ClassLikeDeclaration | ObjectLiteralExpression;
+        readonly parent: ClassLikeDeclaration | ObjectLiteralExpression | TypeLiteralNode | InterfaceDeclaration;
         readonly name: PropertyName;
         readonly body?: FunctionBody;
     }
-    export interface SetAccessorDeclaration extends FunctionLikeDeclarationBase, ClassElement, ObjectLiteralElement, JSDocContainer {
+    export interface SetAccessorDeclaration extends FunctionLikeDeclarationBase, ClassElement, TypeElement, ObjectLiteralElement, JSDocContainer {
         readonly kind: SyntaxKind.SetAccessor;
-        readonly parent: ClassLikeDeclaration | ObjectLiteralExpression;
+        readonly parent: ClassLikeDeclaration | ObjectLiteralExpression | TypeLiteralNode | InterfaceDeclaration;
         readonly name: PropertyName;
         readonly body?: FunctionBody;
     }

tests/baselines/reference/divergentAccessors1.js

@@ -0,0 +1,39 @@
+//// [divergentAccessors1.ts]
+// Accessors in interfaces/types
+
+{
+    interface IHasGetSet {
+        get foo(): number;
+        set foo(v: number | string);
+    }
+
+    const ihgs: IHasGetSet = null as any;
+    ihgs.foo = "32";
+    let r_ihgs_foo: number = ihgs.foo;
+}
+
+{
+    type T_HasGetSet = {
+        get foo(): number;
+        set foo(v: number | string);
+    }
+
+    const t_hgs: T_HasGetSet = null as any;
+    t_hgs.foo = "32";
+    let r_t_hgs_foo: number = t_hgs.foo;
+}
+
+
+//// [divergentAccessors1.js]
+"use strict";
+// Accessors in interfaces/types
+{
+    var ihgs = null;
+    ihgs.foo = "32";
+    var r_ihgs_foo = ihgs.foo;
+}
+{
+    var t_hgs = null;
+    t_hgs.foo = "32";
+    var r_t_hgs_foo = t_hgs.foo;
+}