Merge pull request #24310 from Microsoft/nonWideningLiteralInferences

Non-widening literal type inferences

src/compiler/checker.ts

@@ -9286,8 +9286,10 @@ namespace ts {
             return type;
         }
 
-        function getRegularTypeOfLiteralType(type: Type) {
-            return type.flags & TypeFlags.StringOrNumberLiteral && type.flags & TypeFlags.FreshLiteral ? (<LiteralType>type).regularType : type;
+        function getRegularTypeOfLiteralType(type: Type): Type {
+            return type.flags & TypeFlags.StringOrNumberLiteral && type.flags & TypeFlags.FreshLiteral ? (<LiteralType>type).regularType :
+                type.flags & TypeFlags.Union ? getUnionType(sameMap((<UnionType>type).types, getRegularTypeOfLiteralType)) :
+                type;
         }
 
         function getLiteralType(value: string | number, enumId?: number, symbol?: Symbol) {
@@ -12774,10 +12776,12 @@ namespace ts {
             // all inferences were made to top-level occurrences of the type parameter, and
             // the type parameter has no constraint or its constraint includes no primitive or literal types, and
             // the type parameter was fixed during inference or does not occur at top-level in the return type.
-            const widenLiteralTypes = inference.topLevel &&
-                !hasPrimitiveConstraint(inference.typeParameter) &&
+            const primitiveConstraint = hasPrimitiveConstraint(inference.typeParameter);
+            const widenLiteralTypes = !primitiveConstraint && inference.topLevel &&
                 (inference.isFixed || !isTypeParameterAtTopLevel(getReturnTypeOfSignature(signature), inference.typeParameter));
-            const baseCandidates = widenLiteralTypes ? sameMap(candidates, getWidenedLiteralType) : candidates;
+            const baseCandidates = primitiveConstraint ? sameMap(candidates, getRegularTypeOfLiteralType) :
+                widenLiteralTypes ? sameMap(candidates, getWidenedLiteralType) :
+                candidates;
             // If all inferences were made from contravariant positions, infer a common subtype. Otherwise, if
             // union types were requested or if all inferences were made from the return type position, infer a
             // union type. Otherwise, infer a common supertype.

tests/baselines/reference/bestCommonTypeOfConditionalExpressions2.types

@@ -30,7 +30,7 @@ var derived2: Derived2;
 
 var r2 = true ? 1 : '';
 >r2 : string | number
->true ? 1 : '' : 1 | ""
+>true ? 1 : '' : "" | 1
 >true : true
 >1 : 1
 >'' : ""

tests/baselines/reference/callExpressionWithTypeParameterConstrainedToOuterTypeParameter.types

@@ -15,7 +15,7 @@ var i: I<string>;
 >I : I<T>
 
 var y = i(""); // y should be string
->y : string
+>y : ""
 >i("") : ""
 >i : I<string>
 >"" : ""

tests/baselines/reference/conditionalExpression1.types

@@ -1,8 +1,8 @@
 === tests/cases/compiler/conditionalExpression1.ts ===
 var x: boolean = (true ? 1 : ""); // should be an error
 >x : boolean
->(true ? 1 : "") : 1 | ""
->true ? 1 : "" : 1 | ""
+>(true ? 1 : "") : "" | 1
+>true ? 1 : "" : "" | 1
 >true : true
 >1 : 1
 >"" : ""

tests/baselines/reference/conditionalExpressions2.types

@@ -15,7 +15,7 @@ var b = false ? undefined : 0;
 
 var c = false ? 1 : 0;
 >c : number
->false ? 1 : 0 : 1 | 0
+>false ? 1 : 0 : 0 | 1
 >false : false
 >1 : 1
 >0 : 0

tests/baselines/reference/conditionalOperatorWithIdenticalBCT.types

@@ -218,7 +218,7 @@ var result10: (t: X) => any = true ? (m) => m.propertyX1 : (n) => n.propertyX2;
 //Expr1 and Expr2 are literals
 var result11: any = true ? 1 : 'string';
 >result11 : any
->true ? 1 : 'string' : 1 | "string"
+>true ? 1 : 'string' : "string" | 1
 >true : true
 >1 : 1
 >'string' : "string"

tests/baselines/reference/conditionalTypes1.types

@@ -589,8 +589,8 @@ function zeroOf<T extends number | string | boolean>(value: T) {
 ><ZeroOf<T>>(typeof value === "number" ? 0 : typeof value === "string" ? "" : false) : ZeroOf<T>
 >ZeroOf : ZeroOf<T>
 >T : T
->(typeof value === "number" ? 0 : typeof value === "string" ? "" : false) : false | 0 | ""
->typeof value === "number" ? 0 : typeof value === "string" ? "" : false : false | 0 | ""
+>(typeof value === "number" ? 0 : typeof value === "string" ? "" : false) : false | "" | 0
+>typeof value === "number" ? 0 : typeof value === "string" ? "" : false : false | "" | 0
 >typeof value === "number" : boolean
 >typeof value : "string" | "number" | "boolean" | "symbol" | "undefined" | "object" | "function"
 >value : T

tests/baselines/reference/declFileTypeAnnotationParenType.types

@@ -24,7 +24,7 @@ var y = [() => new c()];
 var k: (() => c) | string = (() => new c()) || "";
 >k : string | (() => c)
 >c : c
->(() => new c()) || "" : (() => c) | ""
+>(() => new c()) || "" : "" | (() => c)
 >(() => new c()) : () => c
 >() => new c() : () => c
 >new c() : c

tests/baselines/reference/literalTypeWidening.js

@@ -60,6 +60,18 @@ function f5() {
     let v4 = c4;
 }
 
+declare function widening<T>(x: T): T;
+declare function nonWidening<T extends string | number | symbol>(x: T): T;
+
+function f6(cond: boolean) {
+    let x1 = widening('a');
+    let x2 = widening(10);
+    let x3 = widening(cond ? 'a' : 10);
+    let y1 = nonWidening('a');
+    let y2 = nonWidening(10);
+    let y3 = nonWidening(cond ? 'a' : 10);
+}
+
 // Repro from #10898
 
 type FAILURE = "FAILURE";
@@ -95,10 +107,33 @@ type TestEvent = "onmouseover" | "onmouseout";
 
 function onMouseOver(): TestEvent { return "onmouseover"; }
 
-let x = onMouseOver();
+let x = onMouseOver();
+
+// Repro from #23649
+
+export function Set<K extends string>(...keys: K[]): Record<K, true | undefined> {
+  const result = {} as Record<K, true | undefined>
+  keys.forEach(key => result[key] = true)
+  return result
+}
+
+export function keys<K extends string, V>(obj: Record<K, V>): K[] {
+  return Object.keys(obj) as K[]
+}
+
+type Obj = { code: LangCode }
+
+const langCodeSet = Set('fr', 'en', 'es', 'it', 'nl')
+export type LangCode = keyof typeof langCodeSet
+export const langCodes = keys(langCodeSet)
+
+const arr: Obj[] = langCodes.map(code => ({ code }))
+
 
 //// [literalTypeWidening.js]
+"use strict";
 // Widening vs. non-widening literal types
+exports.__esModule = true;
 function f1() {
     var c1 = "hello"; // Widening type "hello"
     var v1 = c1; // Type string
@@ -153,6 +188,14 @@ function f5() {
     var c4 = "foo";
     var v4 = c4;
 }
+function f6(cond) {
+    var x1 = widening('a');
+    var x2 = widening(10);
+    var x3 = widening(cond ? 'a' : 10);
+    var y1 = nonWidening('a');
+    var y2 = nonWidening(10);
+    var y3 = nonWidening(cond ? 'a' : 10);
+}
 var FAILURE = "FAILURE";
 function doWork() {
     return FAILURE;
@@ -172,3 +215,21 @@ if (isSuccess(result)) {
 }
 function onMouseOver() { return "onmouseover"; }
 var x = onMouseOver();
+// Repro from #23649
+function Set() {
+    var keys = [];
+    for (var _i = 0; _i < arguments.length; _i++) {
+        keys[_i] = arguments[_i];
+    }
+    var result = {};
+    keys.forEach(function (key) { return result[key] = true; });
+    return result;
+}
+exports.Set = Set;
+function keys(obj) {
+    return Object.keys(obj);
+}
+exports.keys = keys;
+var langCodeSet = Set('fr', 'en', 'es', 'it', 'nl');
+exports.langCodes = keys(langCodeSet);
+var arr = exports.langCodes.map(function (code) { return ({ code: code }); });

tests/baselines/reference/literalTypeWidening.symbols

@@ -197,89 +197,206 @@ function f5() {
 >c4 : Symbol(c4, Decl(literalTypeWidening.ts, 57, 9))
 }
 
+declare function widening<T>(x: T): T;
+>widening : Symbol(widening, Decl(literalTypeWidening.ts, 59, 1))
+>T : Symbol(T, Decl(literalTypeWidening.ts, 61, 26))
+>x : Symbol(x, Decl(literalTypeWidening.ts, 61, 29))
+>T : Symbol(T, Decl(literalTypeWidening.ts, 61, 26))
+>T : Symbol(T, Decl(literalTypeWidening.ts, 61, 26))
+
+declare function nonWidening<T extends string | number | symbol>(x: T): T;
+>nonWidening : Symbol(nonWidening, Decl(literalTypeWidening.ts, 61, 38))
+>T : Symbol(T, Decl(literalTypeWidening.ts, 62, 29))
+>x : Symbol(x, Decl(literalTypeWidening.ts, 62, 65))
+>T : Symbol(T, Decl(literalTypeWidening.ts, 62, 29))
+>T : Symbol(T, Decl(literalTypeWidening.ts, 62, 29))
+
+function f6(cond: boolean) {
+>f6 : Symbol(f6, Decl(literalTypeWidening.ts, 62, 74))
+>cond : Symbol(cond, Decl(literalTypeWidening.ts, 64, 12))
+
+    let x1 = widening('a');
+>x1 : Symbol(x1, Decl(literalTypeWidening.ts, 65, 7))
+>widening : Symbol(widening, Decl(literalTypeWidening.ts, 59, 1))
+
+    let x2 = widening(10);
+>x2 : Symbol(x2, Decl(literalTypeWidening.ts, 66, 7))
+>widening : Symbol(widening, Decl(literalTypeWidening.ts, 59, 1))
+
+    let x3 = widening(cond ? 'a' : 10);
+>x3 : Symbol(x3, Decl(literalTypeWidening.ts, 67, 7))
+>widening : Symbol(widening, Decl(literalTypeWidening.ts, 59, 1))
+>cond : Symbol(cond, Decl(literalTypeWidening.ts, 64, 12))
+
+    let y1 = nonWidening('a');
+>y1 : Symbol(y1, Decl(literalTypeWidening.ts, 68, 7))
+>nonWidening : Symbol(nonWidening, Decl(literalTypeWidening.ts, 61, 38))
+
+    let y2 = nonWidening(10);
+>y2 : Symbol(y2, Decl(literalTypeWidening.ts, 69, 7))
+>nonWidening : Symbol(nonWidening, Decl(literalTypeWidening.ts, 61, 38))
+
+    let y3 = nonWidening(cond ? 'a' : 10);
+>y3 : Symbol(y3, Decl(literalTypeWidening.ts, 70, 7))
+>nonWidening : Symbol(nonWidening, Decl(literalTypeWidening.ts, 61, 38))
+>cond : Symbol(cond, Decl(literalTypeWidening.ts, 64, 12))
+}
+
 // Repro from #10898
 
 type FAILURE = "FAILURE";
->FAILURE : Symbol(FAILURE, Decl(literalTypeWidening.ts, 59, 1), Decl(literalTypeWidening.ts, 64, 5))
+>FAILURE : Symbol(FAILURE, Decl(literalTypeWidening.ts, 71, 1), Decl(literalTypeWidening.ts, 76, 5))
 
 const FAILURE = "FAILURE";
->FAILURE : Symbol(FAILURE, Decl(literalTypeWidening.ts, 59, 1), Decl(literalTypeWidening.ts, 64, 5))
+>FAILURE : Symbol(FAILURE, Decl(literalTypeWidening.ts, 71, 1), Decl(literalTypeWidening.ts, 76, 5))
 
 type Result<T> = T | FAILURE;
->Result : Symbol(Result, Decl(literalTypeWidening.ts, 64, 26))
->T : Symbol(T, Decl(literalTypeWidening.ts, 66, 12))
->T : Symbol(T, Decl(literalTypeWidening.ts, 66, 12))
->FAILURE : Symbol(FAILURE, Decl(literalTypeWidening.ts, 59, 1), Decl(literalTypeWidening.ts, 64, 5))
+>Result : Symbol(Result, Decl(literalTypeWidening.ts, 76, 26))
+>T : Symbol(T, Decl(literalTypeWidening.ts, 78, 12))
+>T : Symbol(T, Decl(literalTypeWidening.ts, 78, 12))
+>FAILURE : Symbol(FAILURE, Decl(literalTypeWidening.ts, 71, 1), Decl(literalTypeWidening.ts, 76, 5))
 
 function doWork<T>(): Result<T> {
->doWork : Symbol(doWork, Decl(literalTypeWidening.ts, 66, 29))
->T : Symbol(T, Decl(literalTypeWidening.ts, 68, 16))
->Result : Symbol(Result, Decl(literalTypeWidening.ts, 64, 26))
->T : Symbol(T, Decl(literalTypeWidening.ts, 68, 16))
+>doWork : Symbol(doWork, Decl(literalTypeWidening.ts, 78, 29))
+>T : Symbol(T, Decl(literalTypeWidening.ts, 80, 16))
+>Result : Symbol(Result, Decl(literalTypeWidening.ts, 76, 26))
+>T : Symbol(T, Decl(literalTypeWidening.ts, 80, 16))
 
   return FAILURE;
->FAILURE : Symbol(FAILURE, Decl(literalTypeWidening.ts, 59, 1), Decl(literalTypeWidening.ts, 64, 5))
+>FAILURE : Symbol(FAILURE, Decl(literalTypeWidening.ts, 71, 1), Decl(literalTypeWidening.ts, 76, 5))
 }
 
 function isSuccess<T>(result: Result<T>): result is T {
->isSuccess : Symbol(isSuccess, Decl(literalTypeWidening.ts, 70, 1))
->T : Symbol(T, Decl(literalTypeWidening.ts, 72, 19))
->result : Symbol(result, Decl(literalTypeWidening.ts, 72, 22))
->Result : Symbol(Result, Decl(literalTypeWidening.ts, 64, 26))
->T : Symbol(T, Decl(literalTypeWidening.ts, 72, 19))
->result : Symbol(result, Decl(literalTypeWidening.ts, 72, 22))
->T : Symbol(T, Decl(literalTypeWidening.ts, 72, 19))
+>isSuccess : Symbol(isSuccess, Decl(literalTypeWidening.ts, 82, 1))
+>T : Symbol(T, Decl(literalTypeWidening.ts, 84, 19))
+>result : Symbol(result, Decl(literalTypeWidening.ts, 84, 22))
+>Result : Symbol(Result, Decl(literalTypeWidening.ts, 76, 26))
+>T : Symbol(T, Decl(literalTypeWidening.ts, 84, 19))
+>result : Symbol(result, Decl(literalTypeWidening.ts, 84, 22))
+>T : Symbol(T, Decl(literalTypeWidening.ts, 84, 19))
 
   return !isFailure(result);
->isFailure : Symbol(isFailure, Decl(literalTypeWidening.ts, 74, 1))
->result : Symbol(result, Decl(literalTypeWidening.ts, 72, 22))
+>isFailure : Symbol(isFailure, Decl(literalTypeWidening.ts, 86, 1))
+>result : Symbol(result, Decl(literalTypeWidening.ts, 84, 22))
 }
 
 function isFailure<T>(result: Result<T>): result is FAILURE {
->isFailure : Symbol(isFailure, Decl(literalTypeWidening.ts, 74, 1))
->T : Symbol(T, Decl(literalTypeWidening.ts, 76, 19))
->result : Symbol(result, Decl(literalTypeWidening.ts, 76, 22))
->Result : Symbol(Result, Decl(literalTypeWidening.ts, 64, 26))
->T : Symbol(T, Decl(literalTypeWidening.ts, 76, 19))
->result : Symbol(result, Decl(literalTypeWidening.ts, 76, 22))
->FAILURE : Symbol(FAILURE, Decl(literalTypeWidening.ts, 59, 1), Decl(literalTypeWidening.ts, 64, 5))
+>isFailure : Symbol(isFailure, Decl(literalTypeWidening.ts, 86, 1))
+>T : Symbol(T, Decl(literalTypeWidening.ts, 88, 19))
+>result : Symbol(result, Decl(literalTypeWidening.ts, 88, 22))
+>Result : Symbol(Result, Decl(literalTypeWidening.ts, 76, 26))
+>T : Symbol(T, Decl(literalTypeWidening.ts, 88, 19))
+>result : Symbol(result, Decl(literalTypeWidening.ts, 88, 22))
+>FAILURE : Symbol(FAILURE, Decl(literalTypeWidening.ts, 71, 1), Decl(literalTypeWidening.ts, 76, 5))
 
   return result === FAILURE;
->result : Symbol(result, Decl(literalTypeWidening.ts, 76, 22))
->FAILURE : Symbol(FAILURE, Decl(literalTypeWidening.ts, 59, 1), Decl(literalTypeWidening.ts, 64, 5))
+>result : Symbol(result, Decl(literalTypeWidening.ts, 88, 22))
+>FAILURE : Symbol(FAILURE, Decl(literalTypeWidening.ts, 71, 1), Decl(literalTypeWidening.ts, 76, 5))
 }
 
 function increment(x: number): number {
->increment : Symbol(increment, Decl(literalTypeWidening.ts, 78, 1))
->x : Symbol(x, Decl(literalTypeWidening.ts, 80, 19))
+>increment : Symbol(increment, Decl(literalTypeWidening.ts, 90, 1))
+>x : Symbol(x, Decl(literalTypeWidening.ts, 92, 19))
 
   return x + 1;
->x : Symbol(x, Decl(literalTypeWidening.ts, 80, 19))
+>x : Symbol(x, Decl(literalTypeWidening.ts, 92, 19))
 }
 
 let result = doWork<number>();
->result : Symbol(result, Decl(literalTypeWidening.ts, 84, 3))
->doWork : Symbol(doWork, Decl(literalTypeWidening.ts, 66, 29))
+>result : Symbol(result, Decl(literalTypeWidening.ts, 96, 3))
+>doWork : Symbol(doWork, Decl(literalTypeWidening.ts, 78, 29))
 
 if (isSuccess(result)) {
->isSuccess : Symbol(isSuccess, Decl(literalTypeWidening.ts, 70, 1))
->result : Symbol(result, Decl(literalTypeWidening.ts, 84, 3))
+>isSuccess : Symbol(isSuccess, Decl(literalTypeWidening.ts, 82, 1))
+>result : Symbol(result, Decl(literalTypeWidening.ts, 96, 3))
 
   increment(result);
->increment : Symbol(increment, Decl(literalTypeWidening.ts, 78, 1))
->result : Symbol(result, Decl(literalTypeWidening.ts, 84, 3))
+>increment : Symbol(increment, Decl(literalTypeWidening.ts, 90, 1))
+>result : Symbol(result, Decl(literalTypeWidening.ts, 96, 3))
 }
 
 // Repro from #10898
 
 type TestEvent = "onmouseover" | "onmouseout";
->TestEvent : Symbol(TestEvent, Decl(literalTypeWidening.ts, 88, 1))
+>TestEvent : Symbol(TestEvent, Decl(literalTypeWidening.ts, 100, 1))
 
 function onMouseOver(): TestEvent { return "onmouseover"; }
->onMouseOver : Symbol(onMouseOver, Decl(literalTypeWidening.ts, 92, 46))
->TestEvent : Symbol(TestEvent, Decl(literalTypeWidening.ts, 88, 1))
+>onMouseOver : Symbol(onMouseOver, Decl(literalTypeWidening.ts, 104, 46))
+>TestEvent : Symbol(TestEvent, Decl(literalTypeWidening.ts, 100, 1))
 
 let x = onMouseOver();
->x : Symbol(x, Decl(literalTypeWidening.ts, 96, 3))
->onMouseOver : Symbol(onMouseOver, Decl(literalTypeWidening.ts, 92, 46))
+>x : Symbol(x, Decl(literalTypeWidening.ts, 108, 3))
+>onMouseOver : Symbol(onMouseOver, Decl(literalTypeWidening.ts, 104, 46))
+
+// Repro from #23649
+
+export function Set<K extends string>(...keys: K[]): Record<K, true | undefined> {
+>Set : Symbol(Set, Decl(literalTypeWidening.ts, 108, 22))
+>K : Symbol(K, Decl(literalTypeWidening.ts, 112, 20))
+>keys : Symbol(keys, Decl(literalTypeWidening.ts, 112, 38))
+>K : Symbol(K, Decl(literalTypeWidening.ts, 112, 20))
+>Record : Symbol(Record, Decl(lib.d.ts, --, --))
+>K : Symbol(K, Decl(literalTypeWidening.ts, 112, 20))
+
+  const result = {} as Record<K, true | undefined>
+>result : Symbol(result, Decl(literalTypeWidening.ts, 113, 7))
+>Record : Symbol(Record, Decl(lib.d.ts, --, --))
+>K : Symbol(K, Decl(literalTypeWidening.ts, 112, 20))
+
+  keys.forEach(key => result[key] = true)
+>keys.forEach : Symbol(Array.forEach, Decl(lib.d.ts, --, --))
+>keys : Symbol(keys, Decl(literalTypeWidening.ts, 112, 38))
+>forEach : Symbol(Array.forEach, Decl(lib.d.ts, --, --))
+>key : Symbol(key, Decl(literalTypeWidening.ts, 114, 15))
+>result : Symbol(result, Decl(literalTypeWidening.ts, 113, 7))
+>key : Symbol(key, Decl(literalTypeWidening.ts, 114, 15))
+
+  return result
+>result : Symbol(result, Decl(literalTypeWidening.ts, 113, 7))
+}
+
+export function keys<K extends string, V>(obj: Record<K, V>): K[] {
+>keys : Symbol(keys, Decl(literalTypeWidening.ts, 116, 1))
+>K : Symbol(K, Decl(literalTypeWidening.ts, 118, 21))
+>V : Symbol(V, Decl(literalTypeWidening.ts, 118, 38))
+>obj : Symbol(obj, Decl(literalTypeWidening.ts, 118, 42))
+>Record : Symbol(Record, Decl(lib.d.ts, --, --))
+>K : Symbol(K, Decl(literalTypeWidening.ts, 118, 21))
+>V : Symbol(V, Decl(literalTypeWidening.ts, 118, 38))
+>K : Symbol(K, Decl(literalTypeWidening.ts, 118, 21))
+
+  return Object.keys(obj) as K[]
+>Object.keys : Symbol(ObjectConstructor.keys, Decl(lib.d.ts, --, --))
+>Object : Symbol(Object, Decl(lib.d.ts, --, --), Decl(lib.d.ts, --, --))
+>keys : Symbol(ObjectConstructor.keys, Decl(lib.d.ts, --, --))
+>obj : Symbol(obj, Decl(literalTypeWidening.ts, 118, 42))
+>K : Symbol(K, Decl(literalTypeWidening.ts, 118, 21))
+}
+
+type Obj = { code: LangCode }
+>Obj : Symbol(Obj, Decl(literalTypeWidening.ts, 120, 1))
+>code : Symbol(code, Decl(literalTypeWidening.ts, 122, 12))
+>LangCode : Symbol(LangCode, Decl(literalTypeWidening.ts, 124, 53))
+
+const langCodeSet = Set('fr', 'en', 'es', 'it', 'nl')
+>langCodeSet : Symbol(langCodeSet, Decl(literalTypeWidening.ts, 124, 5))
+>Set : Symbol(Set, Decl(literalTypeWidening.ts, 108, 22))
+
+export type LangCode = keyof typeof langCodeSet
+>LangCode : Symbol(LangCode, Decl(literalTypeWidening.ts, 124, 53))
+>langCodeSet : Symbol(langCodeSet, Decl(literalTypeWidening.ts, 124, 5))
+
+export const langCodes = keys(langCodeSet)
+>langCodes : Symbol(langCodes, Decl(literalTypeWidening.ts, 126, 12))
+>keys : Symbol(keys, Decl(literalTypeWidening.ts, 116, 1))
+>langCodeSet : Symbol(langCodeSet, Decl(literalTypeWidening.ts, 124, 5))
+
+const arr: Obj[] = langCodes.map(code => ({ code }))
+>arr : Symbol(arr, Decl(literalTypeWidening.ts, 128, 5))
+>Obj : Symbol(Obj, Decl(literalTypeWidening.ts, 120, 1))
+>langCodes.map : Symbol(Array.map, Decl(lib.d.ts, --, --))
+>langCodes : Symbol(langCodes, Decl(literalTypeWidening.ts, 126, 12))
+>map : Symbol(Array.map, Decl(lib.d.ts, --, --))
+>code : Symbol(code, Decl(literalTypeWidening.ts, 128, 33))
+>code : Symbol(code, Decl(literalTypeWidening.ts, 128, 43))
 

tests/baselines/reference/literalTypeWidening.types

@@ -219,6 +219,67 @@ function f5() {
 >c4 : "foo"
 }
 
+declare function widening<T>(x: T): T;
+>widening : <T>(x: T) => T
+>T : T
+>x : T
+>T : T
+>T : T
+
+declare function nonWidening<T extends string | number | symbol>(x: T): T;
+>nonWidening : <T extends string | number | symbol>(x: T) => T
+>T : T
+>x : T
+>T : T
+>T : T
+
+function f6(cond: boolean) {
+>f6 : (cond: boolean) => void
+>cond : boolean
+
+    let x1 = widening('a');
+>x1 : string
+>widening('a') : "a"
+>widening : <T>(x: T) => T
+>'a' : "a"
+
+    let x2 = widening(10);
+>x2 : number
+>widening(10) : 10
+>widening : <T>(x: T) => T
+>10 : 10
+
+    let x3 = widening(cond ? 'a' : 10);
+>x3 : string | number
+>widening(cond ? 'a' : 10) : "a" | 10
+>widening : <T>(x: T) => T
+>cond ? 'a' : 10 : "a" | 10
+>cond : boolean
+>'a' : "a"
+>10 : 10
+
+    let y1 = nonWidening('a');
+>y1 : "a"
+>nonWidening('a') : "a"
+>nonWidening : <T extends string | number | symbol>(x: T) => T
+>'a' : "a"
+
+    let y2 = nonWidening(10);
+>y2 : 10
+>nonWidening(10) : 10
+>nonWidening : <T extends string | number | symbol>(x: T) => T
+>10 : 10
+
+    let y3 = nonWidening(cond ? 'a' : 10);
+>y3 : "a" | 10
+>nonWidening(cond ? 'a' : 10) : "a" | 10
+>nonWidening : <T extends string | number | symbol>(x: T) => T
+>cond ? 'a' : 10 : "a" | 10
+>cond : boolean
+>'a' : "a"
+>10 : 10
+}
+
 // Repro from #10898
 
 type FAILURE = "FAILURE";
@@ -316,3 +377,97 @@ let x = onMouseOver();
 >onMouseOver() : TestEvent
 >onMouseOver : () => TestEvent
 
+// Repro from #23649
+
+export function Set<K extends string>(...keys: K[]): Record<K, true | undefined> {
+>Set : <K extends string>(...keys: K[]) => Record<K, true>
+>K : K
+>keys : K[]
+>K : K
+>Record : Record<K, T>
+>K : K
+>true : true
+
+  const result = {} as Record<K, true | undefined>
+>result : Record<K, true>
+>{} as Record<K, true | undefined> : Record<K, true>
+>{} : {}
+>Record : Record<K, T>
+>K : K
+>true : true
+
+  keys.forEach(key => result[key] = true)
+>keys.forEach(key => result[key] = true) : void
+>keys.forEach : (callbackfn: (value: K, index: number, array: K[]) => void, thisArg?: any) => void
+>keys : K[]
+>forEach : (callbackfn: (value: K, index: number, array: K[]) => void, thisArg?: any) => void
+>key => result[key] = true : (key: K) => boolean
+>key : K
+>result[key] = true : true
+>result[key] : Record<K, true>[K]
+>result : Record<K, true>
+>key : K
+>true : true
+
+  return result
+>result : Record<K, true>
+}
+
+export function keys<K extends string, V>(obj: Record<K, V>): K[] {
+>keys : <K extends string, V>(obj: Record<K, V>) => K[]
+>K : K
+>V : V
+>obj : Record<K, V>
+>Record : Record<K, T>
+>K : K
+>V : V
+>K : K
+
+  return Object.keys(obj) as K[]
+>Object.keys(obj) as K[] : K[]
+>Object.keys(obj) : string[]
+>Object.keys : (o: {}) => string[]
+>Object : ObjectConstructor
+>keys : (o: {}) => string[]
+>obj : Record<K, V>
+>K : K
+}
+
+type Obj = { code: LangCode }
+>Obj : Obj
+>code : "fr" | "en" | "es" | "it" | "nl"
+>LangCode : "fr" | "en" | "es" | "it" | "nl"
+
+const langCodeSet = Set('fr', 'en', 'es', 'it', 'nl')
+>langCodeSet : Record<"fr" | "en" | "es" | "it" | "nl", true>
+>Set('fr', 'en', 'es', 'it', 'nl') : Record<"fr" | "en" | "es" | "it" | "nl", true>
+>Set : <K extends string>(...keys: K[]) => Record<K, true>
+>'fr' : "fr"
+>'en' : "en"
+>'es' : "es"
+>'it' : "it"
+>'nl' : "nl"
+
+export type LangCode = keyof typeof langCodeSet
+>LangCode : "fr" | "en" | "es" | "it" | "nl"
+>langCodeSet : Record<"fr" | "en" | "es" | "it" | "nl", true>
+
+export const langCodes = keys(langCodeSet)
+>langCodes : ("fr" | "en" | "es" | "it" | "nl")[]
+>keys(langCodeSet) : ("fr" | "en" | "es" | "it" | "nl")[]
+>keys : <K extends string, V>(obj: Record<K, V>) => K[]
+>langCodeSet : Record<"fr" | "en" | "es" | "it" | "nl", true>
+
+const arr: Obj[] = langCodes.map(code => ({ code }))
+>arr : Obj[]
+>Obj : Obj
+>langCodes.map(code => ({ code })) : { code: "fr" | "en" | "es" | "it" | "nl"; }[]
+>langCodes.map : <U>(callbackfn: (value: "fr" | "en" | "es" | "it" | "nl", index: number, array: ("fr" | "en" | "es" | "it" | "nl")[]) => U, thisArg?: any) => U[]
+>langCodes : ("fr" | "en" | "es" | "it" | "nl")[]
+>map : <U>(callbackfn: (value: "fr" | "en" | "es" | "it" | "nl", index: number, array: ("fr" | "en" | "es" | "it" | "nl")[]) => U, thisArg?: any) => U[]
+>code => ({ code }) : (code: "fr" | "en" | "es" | "it" | "nl") => { code: "fr" | "en" | "es" | "it" | "nl"; }
+>code : "fr" | "en" | "es" | "it" | "nl"
+>({ code }) : { code: "fr" | "en" | "es" | "it" | "nl"; }
+>{ code } : { code: "fr" | "en" | "es" | "it" | "nl"; }
+>code : "fr" | "en" | "es" | "it" | "nl"
+

tests/baselines/reference/literalTypes2.types

@@ -555,7 +555,7 @@ class C2 {
 >bar : () => 1 | 0
 
         return cond ? 0 : 1;
->cond ? 0 : 1 : 1 | 0
+>cond ? 0 : 1 : 0 | 1
 >cond : boolean
 >0 : 0
 >1 : 1

tests/baselines/reference/literalTypes3.types

@@ -107,7 +107,7 @@ function f5(x: number, y: 1 | 2) {
 >y : 1 | 2
 
         x;  // 0 | 1 | 2
->x : 1 | 2 | 0
+>x : 0 | 1 | 2
     }
 }
 
@@ -126,7 +126,7 @@ function f6(x: number, y: 1 | 2) {
 >x : number
 
         x;  // 0 | 1 | 2
->x : 1 | 2 | 0
+>x : 0 | 1 | 2
     }
 }
 

tests/baselines/reference/newExpressionWithTypeParameterConstrainedToOuterTypeParameter.types

@@ -15,7 +15,7 @@ var i: I<string>;
 >I : I<T>
 
 var y = new i(""); // y should be string
->y : string
+>y : ""
 >new i("") : ""
 >i : I<string>
 >"" : ""

tests/baselines/reference/parserArgumentList1.types

@@ -26,7 +26,7 @@ export function removeClass (node:HTMLElement, className:string) {
 >rightDelimiter : any
 
 		return leftDelimiter.length + rightDelimiter.length === 2 ? ' ' : '';
->leftDelimiter.length + rightDelimiter.length === 2 ? ' ' : '' : " " | ""
+>leftDelimiter.length + rightDelimiter.length === 2 ? ' ' : '' : "" | " "
 >leftDelimiter.length + rightDelimiter.length === 2 : boolean
 >leftDelimiter.length + rightDelimiter.length : any
 >leftDelimiter.length : any

tests/baselines/reference/subtypesOfTypeParameter.types

@@ -144,14 +144,14 @@ function f2<T, U>(x: T, y: U) {
 
     var r2 = true ? '' : x;
 >r2 : string | T
->true ? '' : x : T | ""
+>true ? '' : x : "" | T
 >true : true
 >'' : ""
 >x : T
 
     var r2 = true ? x : '';
 >r2 : string | T
->true ? x : '' : T | ""
+>true ? x : '' : "" | T
 >true : true
 >x : T
 >'' : ""

tests/baselines/reference/subtypesOfTypeParameterWithConstraints2.types

@@ -259,14 +259,14 @@ function f6<T extends String>(x: T) {
 
     var r2 = true ? '' : x; // ok
 >r2 : string | T
->true ? '' : x : T | ""
+>true ? '' : x : "" | T
 >true : true
 >'' : ""
 >x : T
 
     var r2 = true ? x : ''; // ok
 >r2 : string | T
->true ? x : '' : T | ""
+>true ? x : '' : "" | T
 >true : true
 >x : T
 >'' : ""

tests/baselines/reference/uniqueSymbols.types

@@ -699,19 +699,19 @@ g(N["s"]);
 
 // falsy expressions
 s || "";
->s || "" : unique symbol | ""
+>s || "" : "" | unique symbol
 >s : unique symbol
 >"" : ""
 
 N.s || "";
->N.s || "" : unique symbol | ""
+>N.s || "" : "" | unique symbol
 >N.s : unique symbol
 >N : typeof N
 >s : unique symbol
 >"" : ""
 
 N["s"] || "";
->N["s"] || "" : unique symbol | ""
+>N["s"] || "" : "" | unique symbol
 >N["s"] : unique symbol
 >N : typeof N
 >"s" : "s"

tests/baselines/reference/uniqueSymbolsDeclarations.types

@@ -699,19 +699,19 @@ g(N["s"]);
 
 // falsy expressions
 s || "";
->s || "" : unique symbol | ""
+>s || "" : "" | unique symbol
 >s : unique symbol
 >"" : ""
 
 N.s || "";
->N.s || "" : unique symbol | ""
+>N.s || "" : "" | unique symbol
 >N.s : unique symbol
 >N : typeof N
 >s : unique symbol
 >"" : ""
 
 N["s"] || "";
->N["s"] || "" : unique symbol | ""
+>N["s"] || "" : "" | unique symbol
 >N["s"] : unique symbol
 >N : typeof N
 >"s" : "s"

tests/cases/conformance/types/literal/literalTypeWidening.ts

@@ -59,6 +59,18 @@ function f5() {
     let v4 = c4;
 }
 
+declare function widening<T>(x: T): T;
+declare function nonWidening<T extends string | number | symbol>(x: T): T;
+
+function f6(cond: boolean) {
+    let x1 = widening('a');
+    let x2 = widening(10);
+    let x3 = widening(cond ? 'a' : 10);
+    let y1 = nonWidening('a');
+    let y2 = nonWidening(10);
+    let y3 = nonWidening(cond ? 'a' : 10);
+}
+
 // Repro from #10898
 
 type FAILURE = "FAILURE";
@@ -94,4 +106,24 @@ type TestEvent = "onmouseover" | "onmouseout";
 
 function onMouseOver(): TestEvent { return "onmouseover"; }
 
-let x = onMouseOver();
+let x = onMouseOver();
+
+// Repro from #23649
+
+export function Set<K extends string>(...keys: K[]): Record<K, true | undefined> {
+  const result = {} as Record<K, true | undefined>
+  keys.forEach(key => result[key] = true)
+  return result
+}
+
+export function keys<K extends string, V>(obj: Record<K, V>): K[] {
+  return Object.keys(obj) as K[]
+}
+
+type Obj = { code: LangCode }
+
+const langCodeSet = Set('fr', 'en', 'es', 'it', 'nl')
+export type LangCode = keyof typeof langCodeSet
+export const langCodes = keys(langCodeSet)
+
+const arr: Obj[] = langCodes.map(code => ({ code }))