microsoft · ahejlsberg · Apr 23, 2018 · Apr 5, 2018 · Apr 5, 2018 · Apr 6, 2018
diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
diff --git a/src/compiler/commandLineParser.ts b/src/compiler/commandLineParser.ts
@@ -672,6 +672,12 @@ namespace ts {
             category: Diagnostics.Advanced_Options,
             description: Diagnostics.Disable_strict_checking_of_generic_signatures_in_function_types,
         },
+        {
+            name: "keyofStringsOnly",
+            type: "boolean",
+            category: Diagnostics.Advanced_Options,
+            description: Diagnostics.Resolve_keyof_to_string_valued_property_names_only_no_numbers_or_symbols,
+        },
         {
             // A list of plugins to load in the language service
             name: "plugins",

diff --git a/src/compiler/diagnosticMessages.json b/src/compiler/diagnosticMessages.json
@@ -3530,6 +3530,10 @@
         "category": "Message",
         "code": 6194
     },
+    "Resolve 'keyof' to string valued property names only (no numbers or symbols).": {
+        "category": "Message",
+        "code": 6195
+    },
     "Variable '{0}' implicitly has an '{1}' type.": {
         "category": "Error",
         "code": 7005

diff --git a/src/compiler/types.ts b/src/compiler/types.ts
@@ -3373,6 +3373,7 @@ namespace ts {
         /* @internal */ mergeId?: number;       // Merge id (used to look up merged symbol)
         /* @internal */ parent?: Symbol;        // Parent symbol
         /* @internal */ exportSymbol?: Symbol;  // Exported symbol associated with this symbol
+        /* @internal */ nameType?: Type;        // Type associated with a late-bound symbol
         /* @internal */ constEnumOnlyModule?: boolean; // True if module contains only const enums or other modules with only const enums
         /* @internal */ isReferenced?: SymbolFlags; // True if the symbol is referenced elsewhere. Keeps track of the meaning of a reference in case a symbol is both a type parameter and parameter.
         /* @internal */ isReplaceableByMethod?: boolean; // Can this Javascript class property be replaced by a method symbol?
@@ -3407,7 +3408,6 @@ namespace ts {
         enumKind?: EnumKind;                // Enum declaration classification
         originatingImport?: ImportDeclaration | ImportCall; // Import declaration which produced the symbol, present if the symbol is marked as uncallable but had call signatures in `resolveESModuleSymbol`
         lateSymbol?: Symbol;                // Late-bound symbol for a computed property
-        nameType?: Type;                    // Type associate with a late-bound or mapped type property symbol's name
     }
 
     /* @internal */
@@ -3604,7 +3604,7 @@ namespace ts {
         Intrinsic = Any | String | Number | Boolean | BooleanLiteral | ESSymbol | Void | Undefined | Null | Never | NonPrimitive,
         /* @internal */
         Primitive = String | Number | Boolean | Enum | EnumLiteral | ESSymbol | Void | Undefined | Null | Literal | UniqueESSymbol,
-        StringLike = String | StringLiteral | Index,
+        StringLike = String | StringLiteral,
         NumberLike = Number | NumberLiteral | Enum,
         BooleanLike = Boolean | BooleanLiteral,
         EnumLike = Enum | EnumLiteral,
@@ -3761,7 +3761,7 @@ namespace ts {
         /* @internal */
         resolvedIndexType: IndexType;
         /* @internal */
-        resolvedDeclaredIndexType: IndexType;
+        resolvedStringIndexType: IndexType;
         /* @internal */
         resolvedBaseConstraint: Type;
         /* @internal */
@@ -3850,7 +3850,7 @@ namespace ts {
         /* @internal */
         resolvedIndexType?: IndexType;
         /* @internal */
-        resolvedDeclaredIndexType?: IndexType;
+        resolvedStringIndexType?: IndexType;
     }
 
     // Type parameters (TypeFlags.TypeParameter)
@@ -3882,9 +3882,9 @@ namespace ts {
 
     // keyof T types (TypeFlags.Index)
     export interface IndexType extends InstantiableType {
-        /* @internal */
-        isDeclaredType?: boolean;
         type: InstantiableType | UnionOrIntersectionType;
+        /* @internal */
+        stringsOnly: boolean;
     }
 
     export interface ConditionalRoot {
@@ -4043,10 +4043,10 @@ namespace ts {
 
     /* @internal */
     export interface WideningContext {
-        parent?: WideningContext;            // Parent context
-        propertyName?: __String;             // Name of property in parent
-        siblings?: Type[];                   // Types of siblings
-        resolvedPropertyNames?: __String[];  // Property names occurring in sibling object literals
+        parent?: WideningContext;       // Parent context
+        propertyName?: __String;        // Name of property in parent
+        siblings?: Type[];              // Types of siblings
+        resolvedProperties?: Symbol[];  // Properties occurring in sibling object literals
     }
 
     /* @internal */
@@ -4161,6 +4161,7 @@ namespace ts {
         inlineSources?: boolean;
         isolatedModules?: boolean;
         jsx?: JsxEmit;
+        keyofStringsOnly?: boolean;
         lib?: string[];
         /*@internal*/listEmittedFiles?: boolean;
         /*@internal*/listFiles?: boolean;

diff --git a/src/lib/es2015.core.d.ts b/src/lib/es2015.core.d.ts
@@ -1,5 +1,3 @@
-declare type PropertyKey = string | number | symbol;
-
 interface Array<T> {
     /**
      * Returns the value of the first element in the array where predicate is true, and undefined
@@ -258,20 +256,6 @@ interface NumberConstructor {
     parseInt(string: string, radix?: number): number;
 }
 
-interface Object {
-    /**
-     * Determines whether an object has a property with the specified name.
-     * @param v A property name.
-     */
-    hasOwnProperty(v: PropertyKey): boolean;
-
-    /**
-     * Determines whether a specified property is enumerable.
-     * @param v A property name.
-     */
-    propertyIsEnumerable(v: PropertyKey): boolean;
-}
-
 interface ObjectConstructor {
     /**
      * Copy the values of all of the enumerable own properties from one or more source objects to a
@@ -327,25 +311,6 @@ interface ObjectConstructor {
      * @param proto The value of the new prototype or null.
      */
     setPrototypeOf(o: any, proto: object | null): any;
-
-    /**
-     * Gets the own property descriptor of the specified object.
-     * An own property descriptor is one that is defined directly on the object and is not
-     * inherited from the object's prototype.
-     * @param o Object that contains the property.
-     * @param p Name of the property.
-     */
-    getOwnPropertyDescriptor(o: any, propertyKey: PropertyKey): PropertyDescriptor | undefined;
-
-    /**
-     * Adds a property to an object, or modifies attributes of an existing property.
-     * @param o Object on which to add or modify the property. This can be a native JavaScript
-     * object (that is, a user-defined object or a built in object) or a DOM object.
-     * @param p The property name.
-     * @param attributes Descriptor for the property. It can be for a data property or an accessor
-     *  property.
-     */
-    defineProperty(o: any, propertyKey: PropertyKey, attributes: PropertyDescriptor): any;
 }
 
 interface ReadonlyArray<T> {

diff --git a/src/lib/es5.d.ts b/src/lib/es5.d.ts
@@ -74,6 +74,8 @@ declare function escape(string: string): string;
   */
 declare function unescape(string: string): string;
 
+declare type PropertyKey = string | number | symbol;
+
 interface PropertyDescriptor {
     configurable?: boolean;
     enumerable?: boolean;
@@ -104,7 +106,7 @@ interface Object {
       * Determines whether an object has a property with the specified name.
       * @param v A property name.
       */
-    hasOwnProperty(v: string): boolean;
+    hasOwnProperty(v: PropertyKey): boolean;
 
     /**
       * Determines whether an object exists in another object's prototype chain.
@@ -116,7 +118,7 @@ interface Object {
       * Determines whether a specified property is enumerable.
       * @param v A property name.
       */
-    propertyIsEnumerable(v: string): boolean;
+    propertyIsEnumerable(v: PropertyKey): boolean;
 }
 
 interface ObjectConstructor {
@@ -139,7 +141,7 @@ interface ObjectConstructor {
       * @param o Object that contains the property.
       * @param p Name of the property.
     */
-    getOwnPropertyDescriptor(o: any, p: string): PropertyDescriptor | undefined;
+    getOwnPropertyDescriptor(o: any, p: PropertyKey): PropertyDescriptor | undefined;
 
     /**
       * Returns the names of the own properties of an object. The own properties of an object are those that are defined directly
@@ -167,7 +169,7 @@ interface ObjectConstructor {
       * @param p The property name.
       * @param attributes Descriptor for the property. It can be for a data property or an accessor property.
       */
-    defineProperty(o: any, p: string, attributes: PropertyDescriptor & ThisType<any>): any;
+    defineProperty(o: any, p: PropertyKey, attributes: PropertyDescriptor & ThisType<any>): any;
 
     /**
       * Adds one or more properties to an object, and/or modifies attributes of existing properties.
@@ -1340,7 +1342,7 @@ type Pick<T, K extends keyof T> = {
 /**
  * Construct a type with a set of properties K of type T
  */
-type Record<K extends string, T> = {
+type Record<K extends keyof any, T> = {
     [P in K]: T;
 };
 

diff --git a/tests/baselines/reference/api/tsserverlibrary.d.ts b/tests/baselines/reference/api/tsserverlibrary.d.ts
@@ -2099,7 +2099,7 @@ declare namespace ts {
         Unit = 13536,
         StringOrNumberLiteral = 96,
         PossiblyFalsy = 14574,
-        StringLike = 524322,
+        StringLike = 34,
         NumberLike = 84,
         BooleanLike = 136,
         EnumLike = 272,
@@ -2339,6 +2339,7 @@ declare namespace ts {
         inlineSources?: boolean;
         isolatedModules?: boolean;
         jsx?: JsxEmit;
+        keyofStringsOnly?: boolean;
         lib?: string[];
         locale?: string;
         mapRoot?: string;

diff --git a/tests/baselines/reference/api/typescript.d.ts b/tests/baselines/reference/api/typescript.d.ts
@@ -2099,7 +2099,7 @@ declare namespace ts {
         Unit = 13536,
         StringOrNumberLiteral = 96,
         PossiblyFalsy = 14574,
-        StringLike = 524322,
+        StringLike = 34,
         NumberLike = 84,
         BooleanLike = 136,
         EnumLike = 272,
@@ -2339,6 +2339,7 @@ declare namespace ts {
         inlineSources?: boolean;
         isolatedModules?: boolean;
         jsx?: JsxEmit;
+        keyofStringsOnly?: boolean;
         lib?: string[];
         locale?: string;
         mapRoot?: string;

diff --git a/tests/baselines/reference/classAppearsToHaveMembersOfObject.types b/tests/baselines/reference/classAppearsToHaveMembersOfObject.types
@@ -17,9 +17,9 @@ var r = c.toString();
 var r2 = c.hasOwnProperty('');
 >r2 : boolean
 >c.hasOwnProperty('') : boolean
->c.hasOwnProperty : (v: string) => boolean
+>c.hasOwnProperty : (v: string | number | symbol) => boolean
 >c : C
->hasOwnProperty : (v: string) => boolean
+>hasOwnProperty : (v: string | number | symbol) => boolean
 >'' : ""
 
 var o: Object = c;

diff --git a/tests/baselines/reference/complexRecursiveCollections.symbols b/tests/baselines/reference/complexRecursiveCollections.symbols
@@ -1689,7 +1689,7 @@ declare module Immutable {
     export interface Class<T extends Object> {
 >Class : Symbol(Class, Decl(immutable.ts, 214, 70))
 >T : Symbol(T, Decl(immutable.ts, 215, 27))
->Object : Symbol(Object, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --), Decl(lib.es2015.core.d.ts, --, --))
+>Object : Symbol(Object, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
 
       (values?: Partial<T> | Iterable<[string, any]>): Instance<T> & Readonly<T>;
 >values : Symbol(values, Decl(immutable.ts, 216, 7))
@@ -1714,7 +1714,7 @@ declare module Immutable {
     export interface Instance<T extends Object> {
 >Instance : Symbol(Instance, Decl(immutable.ts, 218, 5))
 >T : Symbol(T, Decl(immutable.ts, 219, 30))
->Object : Symbol(Object, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --), Decl(lib.es2015.core.d.ts, --, --))
+>Object : Symbol(Object, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
 
       readonly size: number;
 >size : Symbol(Instance.size, Decl(immutable.ts, 219, 49))
@@ -2005,7 +2005,7 @@ declare module Immutable {
 
       toJS(): Object;
 >toJS : Symbol(Keyed.toJS, Decl(immutable.ts, 269, 76))
->Object : Symbol(Object, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --), Decl(lib.es2015.core.d.ts, --, --))
+>Object : Symbol(Object, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
 
       toJSON(): { [key: string]: V };
 >toJSON : Symbol(Keyed.toJSON, Decl(immutable.ts, 270, 21))
@@ -2594,7 +2594,7 @@ declare module Immutable {
 
       toJS(): Object;
 >toJS : Symbol(Keyed.toJS, Decl(immutable.ts, 340, 59))
->Object : Symbol(Object, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --), Decl(lib.es2015.core.d.ts, --, --))
+>Object : Symbol(Object, Decl(lib.es5.d.ts, --, --), Decl(lib.es5.d.ts, --, --))
 
       toJSON(): { [key: string]: V };
 >toJSON : Symbol(Keyed.toJSON, Decl(immutable.ts, 341, 21))

diff --git a/tests/baselines/reference/computedPropertyNames10_ES5.types b/tests/baselines/reference/computedPropertyNames10_ES5.types
@@ -9,8 +9,8 @@ var a: any;
 >a : any
 
 var v = {
->v : { [x: string]: () => void; [x: number]: () => void; [""](): void; [0](): void; }
->{    [s]() { },    [n]() { },    [s + s]() { },    [s + n]() { },    [+s]() { },    [""]() { },    [0]() { },    [a]() { },    [<any>true]() { },    [`hello bye`]() { },    [`hello ${a} bye`]() { }} : { [x: string]: () => void; [x: number]: () => void; [""](): void; [0](): void; }
+>v : { [x: string]: () => void; [x: number]: () => void; [""](): void; [0](): void; [`hello bye`](): void; }
+>{    [s]() { },    [n]() { },    [s + s]() { },    [s + n]() { },    [+s]() { },    [""]() { },    [0]() { },    [a]() { },    [<any>true]() { },    [`hello bye`]() { },    [`hello ${a} bye`]() { }} : { [x: string]: () => void; [x: number]: () => void; [""](): void; [0](): void; [`hello bye`](): void; }
 
     [s]() { },
 >[s] : () => void

diff --git a/tests/baselines/reference/computedPropertyNames10_ES6.types b/tests/baselines/reference/computedPropertyNames10_ES6.types
@@ -9,8 +9,8 @@ var a: any;
 >a : any
 
 var v = {
->v : { [x: string]: () => void; [x: number]: () => void; [""](): void; [0](): void; }
->{    [s]() { },    [n]() { },    [s + s]() { },    [s + n]() { },    [+s]() { },    [""]() { },    [0]() { },    [a]() { },    [<any>true]() { },    [`hello bye`]() { },    [`hello ${a} bye`]() { }} : { [x: string]: () => void; [x: number]: () => void; [""](): void; [0](): void; }
+>v : { [x: string]: () => void; [x: number]: () => void; [""](): void; [0](): void; [`hello bye`](): void; }
+>{    [s]() { },    [n]() { },    [s + s]() { },    [s + n]() { },    [+s]() { },    [""]() { },    [0]() { },    [a]() { },    [<any>true]() { },    [`hello bye`]() { },    [`hello ${a} bye`]() { }} : { [x: string]: () => void; [x: number]: () => void; [""](): void; [0](): void; [`hello bye`](): void; }
 
     [s]() { },
 >[s] : () => void

diff --git a/tests/baselines/reference/computedPropertyNames28_ES5.types b/tests/baselines/reference/computedPropertyNames28_ES5.types
@@ -12,8 +12,8 @@ class C extends Base {
 >super : typeof Base
 
         var obj = {
->obj : { [x: string]: () => void; }
->{            [(super(), "prop")]() { }        } : { [x: string]: () => void; }
+>obj : { [(super(), "prop")](): void; }
+>{            [(super(), "prop")]() { }        } : { [(super(), "prop")](): void; }
 
             [(super(), "prop")]() { }
 >[(super(), "prop")] : () => void

diff --git a/tests/baselines/reference/computedPropertyNames28_ES6.types b/tests/baselines/reference/computedPropertyNames28_ES6.types
@@ -12,8 +12,8 @@ class C extends Base {
 >super : typeof Base
 
         var obj = {
->obj : { [x: string]: () => void; }
->{            [(super(), "prop")]() { }        } : { [x: string]: () => void; }
+>obj : { [(super(), "prop")](): void; }
+>{            [(super(), "prop")]() { }        } : { [(super(), "prop")](): void; }
 
             [(super(), "prop")]() { }
 >[(super(), "prop")] : () => void

diff --git a/tests/baselines/reference/computedPropertyNames30_ES5.types b/tests/baselines/reference/computedPropertyNames30_ES5.types
@@ -15,8 +15,8 @@ class C extends Base {
 >() => {            var obj = {                // Ideally, we would capture this. But the reference is                // illegal, and not capturing this is consistent with                //treatment of other similar violations.                [(super(), "prop")]() { }            };        } : () => void
 
             var obj = {
->obj : { [x: string]: () => void; }
->{                // Ideally, we would capture this. But the reference is                // illegal, and not capturing this is consistent with                //treatment of other similar violations.                [(super(), "prop")]() { }            } : { [x: string]: () => void; }
+>obj : { [(super(), "prop")](): void; }
+>{                // Ideally, we would capture this. But the reference is                // illegal, and not capturing this is consistent with                //treatment of other similar violations.                [(super(), "prop")]() { }            } : { [(super(), "prop")](): void; }
 
                 // Ideally, we would capture this. But the reference is
                 // illegal, and not capturing this is consistent with

diff --git a/tests/baselines/reference/computedPropertyNames30_ES6.types b/tests/baselines/reference/computedPropertyNames30_ES6.types
@@ -15,8 +15,8 @@ class C extends Base {
 >() => {            var obj = {                // Ideally, we would capture this. But the reference is                // illegal, and not capturing this is consistent with                //treatment of other similar violations.                [(super(), "prop")]() { }            };        } : () => void
 
             var obj = {
->obj : { [x: string]: () => void; }
->{                // Ideally, we would capture this. But the reference is                // illegal, and not capturing this is consistent with                //treatment of other similar violations.                [(super(), "prop")]() { }            } : { [x: string]: () => void; }
+>obj : { [(super(), "prop")](): void; }
+>{                // Ideally, we would capture this. But the reference is                // illegal, and not capturing this is consistent with                //treatment of other similar violations.                [(super(), "prop")]() { }            } : { [(super(), "prop")](): void; }
 
                 // Ideally, we would capture this. But the reference is
                 // illegal, and not capturing this is consistent with

diff --git a/tests/baselines/reference/computedPropertyNames5_ES5.types b/tests/baselines/reference/computedPropertyNames5_ES5.types
@@ -3,8 +3,8 @@ var b: boolean;
 >b : boolean
 
 var v = {
->v : { [x: string]: number; [x: number]: any; [true]: number; }
->{    [b]: 0,    [true]: 1,    [[]]: 0,    [{}]: 0,    [undefined]: undefined,    [null]: null} : { [x: string]: number; [x: number]: null; [true]: number; }
+>v : { [x: number]: any; }
+>{    [b]: 0,    [true]: 1,    [[]]: 0,    [{}]: 0,    [undefined]: undefined,    [null]: null} : { [x: number]: null; }
 
     [b]: 0,
 >[b] : number

diff --git a/tests/baselines/reference/computedPropertyNames5_ES6.types b/tests/baselines/reference/computedPropertyNames5_ES6.types
@@ -3,8 +3,8 @@ var b: boolean;
 >b : boolean
 
 var v = {
->v : { [x: string]: number; [x: number]: any; [true]: number; }
->{    [b]: 0,    [true]: 1,    [[]]: 0,    [{}]: 0,    [undefined]: undefined,    [null]: null} : { [x: string]: number; [x: number]: null; [true]: number; }
+>v : { [x: number]: any; }
+>{    [b]: 0,    [true]: 1,    [[]]: 0,    [{}]: 0,    [undefined]: undefined,    [null]: null} : { [x: number]: null; }
 
     [b]: 0,
 >[b] : number

diff --git a/tests/baselines/reference/computedPropertyNames9_ES5.types b/tests/baselines/reference/computedPropertyNames9_ES5.types
@@ -19,8 +19,8 @@ function f(x): any { }
 >x : any
 
 var v = {
->v : { [x: string]: number; [x: number]: number; [f(true)]: number; }
->{    [f("")]: 0,    [f(0)]: 0,    [f(true)]: 0} : { [x: string]: number; [x: number]: number; [f(true)]: number; }
+>v : { [x: string]: number; [x: number]: number; }
+>{    [f("")]: 0,    [f(0)]: 0,    [f(true)]: 0} : { [x: string]: number; [x: number]: number; }
 
     [f("")]: 0,
 >[f("")] : number