Merge pull request microsoft#13791 from Microsoft/typeof-string-literal-union-type

`typeof x` now has a string literal union type

Author: sandersn

src/compiler/checker.ts

@@ -326,7 +326,6 @@ namespace ts {
             "object": TypeFacts.TypeofEQObject,
             "function": TypeFacts.TypeofEQFunction
         });
-
         const typeofNEFacts = createMapFromTemplate({
             "string": TypeFacts.TypeofNEString,
             "number": TypeFacts.TypeofNENumber,
@@ -336,14 +335,14 @@ namespace ts {
             "object": TypeFacts.TypeofNEObject,
             "function": TypeFacts.TypeofNEFunction
         });
-
         const typeofTypesByName = createMapFromTemplate<Type>({
             "string": stringType,
             "number": numberType,
             "boolean": booleanType,
             "symbol": esSymbolType,
             "undefined": undefinedType
         });
+        const typeofType = createTypeofType();
 
         let jsxElementType: Type;
         let _jsxNamespace: string;
@@ -1727,6 +1726,10 @@ namespace ts {
             return type;
         }
 
+        function createTypeofType() {
+            return getUnionType(convertToArray(typeofEQFacts.keys(), s => getLiteralTypeForText(TypeFlags.StringLiteral, s)));
+        }
+
         // A reserved member name starts with two underscores, but the third character cannot be an underscore
         // or the @ symbol. A third underscore indicates an escaped form of an identifer that started
         // with at least two underscores. The @ character indicates that the name is denoted by a well known ES
@@ -14626,7 +14629,7 @@ namespace ts {
 
         function checkTypeOfExpression(node: TypeOfExpression): Type {
             checkExpression(node.expression);
-            return stringType;
+            return typeofType;
         }
 
         function checkVoidExpression(node: VoidExpression): Type {

src/compiler/core.ts

@@ -895,6 +895,14 @@ namespace ts {
         return result;
     }
 
+    export function convertToArray<T, U>(iterator: Iterator<T>, f: (value: T) => U) {
+        const result: U[] = [];
+        for (let { value, done } = iterator.next(); !done; { value, done } = iterator.next()) {
+            result.push(f(value));
+        }
+        return result;
+    }
+
     /**
      * Calls `callback` for each entry in the map, returning the first truthy result.
      * Use `map.forEach` instead for normal iteration.

tests/baselines/reference/TypeGuardWithEnumUnion.types

@@ -12,7 +12,7 @@ function f1(x: Color | string) {
 
     if (typeof x === "number") {
 >typeof x === "number" : boolean
->typeof x : string
+>typeof x : "string" | "number" | "boolean" | "symbol" | "undefined" | "object" | "function"
 >x : string | Color
 >"number" : "number"
 
@@ -41,7 +41,7 @@ function f2(x: Color | string | string[]) {
 
     if (typeof x === "object") {
 >typeof x === "object" : boolean
->typeof x : string
+>typeof x : "string" | "number" | "boolean" | "symbol" | "undefined" | "object" | "function"
 >x : string | Color | string[]
 >"object" : "object"
 
@@ -54,7 +54,7 @@ function f2(x: Color | string | string[]) {
     }
     if (typeof x === "number") {
 >typeof x === "number" : boolean
->typeof x : string
+>typeof x : "string" | "number" | "boolean" | "symbol" | "undefined" | "object" | "function"
 >x : string | Color | string[]
 >"number" : "number"
 
@@ -76,7 +76,7 @@ function f2(x: Color | string | string[]) {
     }
     if (typeof x === "string") {
 >typeof x === "string" : boolean
->typeof x : string
+>typeof x : "string" | "number" | "boolean" | "symbol" | "undefined" | "object" | "function"
 >x : string | Color | string[]
 >"string" : "string"
 

tests/baselines/reference/anonymousClassExpression1.types

@@ -4,7 +4,7 @@ function f() {
 
     return typeof class {} === "function";
 >typeof class {} === "function" : boolean
->typeof class {} : string
+>typeof class {} : "string" | "number" | "boolean" | "symbol" | "undefined" | "object" | "function"
 >class {} : typeof (Anonymous class)
 >"function" : "function"
 }

tests/baselines/reference/callSignatureWithoutReturnTypeAnnotationInference.types

@@ -103,17 +103,17 @@ var r6 = foo6(1);
 >1 : 1
 
 function foo7(x) {
->foo7 : (x: any) => string
+>foo7 : (x: any) => "string" | "number" | "boolean" | "symbol" | "undefined" | "object" | "function"
 >x : any
 
     return typeof x;
->typeof x : string
+>typeof x : "string" | "number" | "boolean" | "symbol" | "undefined" | "object" | "function"
 >x : any
 }
 var r7 = foo7(1);
->r7 : string
->foo7(1) : string
->foo7 : (x: any) => string
+>r7 : "string" | "number" | "boolean" | "symbol" | "undefined" | "object" | "function"
+>foo7(1) : "string" | "number" | "boolean" | "symbol" | "undefined" | "object" | "function"
+>foo7 : (x: any) => "string" | "number" | "boolean" | "symbol" | "undefined" | "object" | "function"
 >1 : 1
 
 // object types

tests/baselines/reference/castExpressionParentheses.types

@@ -182,7 +182,7 @@ declare var A;
 >(<any>typeof A).x : any
 >(<any>typeof A) : any
 ><any>typeof A : any
->typeof A : string
+>typeof A : "string" | "number" | "boolean" | "symbol" | "undefined" | "object" | "function"
 >A : any
 >x : any
 

tests/baselines/reference/castOfAwait.types

@@ -8,7 +8,7 @@ async function f() {
 >0 : 0
 
     typeof await 0;
->typeof await 0 : string
+>typeof await 0 : "string" | "number" | "boolean" | "symbol" | "undefined" | "object" | "function"
 >await 0 : 0
 >0 : 0
 
@@ -21,7 +21,7 @@ async function f() {
 >await void <string> typeof <number> void await 0 : any
 >void <string> typeof <number> void await 0 : undefined
 ><string> typeof <number> void await 0 : string
->typeof <number> void await 0 : string
+>typeof <number> void await 0 : "string" | "number" | "boolean" | "symbol" | "undefined" | "object" | "function"
 ><number> void await 0 : number
 >void await 0 : undefined
 >await 0 : 0

tests/baselines/reference/classDoesNotDependOnBaseTypes.types

@@ -5,7 +5,7 @@ var x: StringTree;
 
 if (typeof x !== "string") {
 >typeof x !== "string" : boolean
->typeof x : string
+>typeof x : "string" | "number" | "boolean" | "symbol" | "undefined" | "object" | "function"
 >x : StringTree
 >"string" : "string"
 

tests/baselines/reference/conditionalOperatorConditionIsBooleanType.types

@@ -120,7 +120,7 @@ true ? exprString1 : exprBoolean1; // union
 typeof "123" == "string" ? exprBoolean1 : exprBoolean2;
 >typeof "123" == "string" ? exprBoolean1 : exprBoolean2 : boolean
 >typeof "123" == "string" : boolean
->typeof "123" : string
+>typeof "123" : "string" | "number" | "boolean" | "symbol" | "undefined" | "object" | "function"
 >"123" : "123"
 >"string" : "string"
 >exprBoolean1 : boolean
@@ -262,7 +262,7 @@ var resultIsBoolean3 = typeof "123" == "string" ? exprBoolean1 : exprBoolean2;
 >resultIsBoolean3 : boolean
 >typeof "123" == "string" ? exprBoolean1 : exprBoolean2 : boolean
 >typeof "123" == "string" : boolean
->typeof "123" : string
+>typeof "123" : "string" | "number" | "boolean" | "symbol" | "undefined" | "object" | "function"
 >"123" : "123"
 >"string" : "string"
 >exprBoolean1 : boolean
@@ -299,7 +299,7 @@ var resultIsStringOrBoolean4 = typeof "123" === "string" ? exprString1 : exprBoo
 >resultIsStringOrBoolean4 : string | boolean
 >typeof "123" === "string" ? exprString1 : exprBoolean1 : string | boolean
 >typeof "123" === "string" : boolean
->typeof "123" : string
+>typeof "123" : "string" | "number" | "boolean" | "symbol" | "undefined" | "object" | "function"
 >"123" : "123"
 >"string" : "string"
 >exprString1 : string

tests/baselines/reference/conditionalOperatorConditoinIsStringType.types

@@ -123,7 +123,7 @@ var array = ["1", "2", "3"];
 
 typeof condString ? exprAny1 : exprAny2;
 >typeof condString ? exprAny1 : exprAny2 : any
->typeof condString : string
+>typeof condString : "string" | "number" | "boolean" | "symbol" | "undefined" | "object" | "function"
 >condString : string
 >exprAny1 : any
 >exprAny2 : any
@@ -254,7 +254,7 @@ var resultIsStringOrBoolean2 = "hello" ? exprString1 : exprBoolean1; // union
 var resultIsAny3 = typeof condString ? exprAny1 : exprAny2;
 >resultIsAny3 : any
 >typeof condString ? exprAny1 : exprAny2 : any
->typeof condString : string
+>typeof condString : "string" | "number" | "boolean" | "symbol" | "undefined" | "object" | "function"
 >condString : string
 >exprAny1 : any
 >exprAny2 : any
@@ -297,7 +297,7 @@ var resultIsObject3 = array[1] ? exprIsObject1 : exprIsObject2;
 var resultIsStringOrBoolean3 = typeof condString ? exprString1 : exprBoolean1; // union
 >resultIsStringOrBoolean3 : string | boolean
 >typeof condString ? exprString1 : exprBoolean1 : string | boolean
->typeof condString : string
+>typeof condString : "string" | "number" | "boolean" | "symbol" | "undefined" | "object" | "function"
 >condString : string
 >exprString1 : string
 >exprBoolean1 : boolean