Make enum literal type identical to the union of its values

src/compiler/checker.ts

@@ -21573,6 +21573,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
             const t = isFreshLiteralType(type) ? (type as FreshableType).regularType :
                 isGenericTupleType(type) ? getNormalizedTupleType(type, writing) :
                 getObjectFlags(type) & ObjectFlags.Reference ? (type as TypeReference).node ? createTypeReference((type as TypeReference).target, getTypeArguments(type as TypeReference)) : getSingleBaseForNonAugmentingSubtype(type) || type :
+                type.flags & TypeFlags.EnumLiteral && type.flags & TypeFlags.Union ? getUnionType((type as UnionType).types) :
                 type.flags & TypeFlags.UnionOrIntersection ? getNormalizedUnionOrIntersectionType(type as UnionOrIntersectionType, writing) :
                 type.flags & TypeFlags.Substitution ? writing ? (type as SubstitutionType).baseType : getSubstitutionIntersection(type as SubstitutionType) :
                 type.flags & TypeFlags.Simplifiable ? getSimplifiedType(type, writing) :

tests/baselines/reference/enumAssignmentCompat3.errors.txt

@@ -1,23 +1,27 @@
 enumAssignmentCompat3.ts(68,1): error TS2322: Type 'Abcd.E' is not assignable to type 'First.E'.
-  Property 'd' is missing in type 'First.E'.
+  Type 'E.a' is not assignable to type 'E'.
 enumAssignmentCompat3.ts(70,1): error TS2322: Type 'Cd.E' is not assignable to type 'First.E'.
-  Each declaration of 'E.c' differs in its value, where '2' was expected but '0' was given.
+  Type 'E.c' is not assignable to type 'E'.
 enumAssignmentCompat3.ts(71,1): error TS2322: Type 'Nope' is not assignable to type 'E'.
+  Type 'Nope.a' is not assignable to type 'E'.
 enumAssignmentCompat3.ts(72,1): error TS2322: Type 'Decl.E' is not assignable to type 'First.E'.
-  Each declaration of 'E.c' differs in its value, where '2' was expected but '3' was given.
+  Type 'E.a' is not assignable to type 'E'.
 enumAssignmentCompat3.ts(75,1): error TS2322: Type 'First.E' is not assignable to type 'Ab.E'.
-  Property 'c' is missing in type 'Ab.E'.
+  Type 'E.a' is not assignable to type 'E'.
 enumAssignmentCompat3.ts(76,1): error TS2322: Type 'First.E' is not assignable to type 'Cd.E'.
-  Property 'a' is missing in type 'Cd.E'.
+  Type 'E.a' is not assignable to type 'E'.
 enumAssignmentCompat3.ts(77,1): error TS2322: Type 'E' is not assignable to type 'Nope'.
+  Type 'E.a' is not assignable to type 'Nope'.
 enumAssignmentCompat3.ts(78,1): error TS2322: Type 'First.E' is not assignable to type 'Decl.E'.
-  Each declaration of 'E.c' differs in its value, where '3' was expected but '2' was given.
+  Type 'E.a' is not assignable to type 'E'.
 enumAssignmentCompat3.ts(82,1): error TS2322: Type 'Const.E' is not assignable to type 'First.E'.
+  Type 'E.a' is not assignable to type 'E'.
 enumAssignmentCompat3.ts(83,1): error TS2322: Type 'First.E' is not assignable to type 'Const.E'.
+  Type 'E.a' is not assignable to type 'E'.
 enumAssignmentCompat3.ts(86,1): error TS2322: Type 'Merged.E' is not assignable to type 'First.E'.
-  Each declaration of 'E.c' differs in its value, where '2' was expected but '3' was given.
+  Type 'E.a' is not assignable to type 'E'.
 enumAssignmentCompat3.ts(87,1): error TS2322: Type 'First.E' is not assignable to type 'Merged.E'.
-  Each declaration of 'E.c' differs in its value, where '3' was expected but '2' was given.
+  Type 'E.a' is not assignable to type 'E'.
 
 
 ==== enumAssignmentCompat3.ts (12 errors) ====
@@ -91,54 +95,58 @@ enumAssignmentCompat3.ts(87,1): error TS2322: Type 'First.E' is not assignable t
     abc = secondAbcd; // missing 'd'
     ~~~
 !!! error TS2322: Type 'Abcd.E' is not assignable to type 'First.E'.
-!!! error TS2322:   Property 'd' is missing in type 'First.E'.
+!!! error TS2322:   Type 'E.a' is not assignable to type 'E'.
     abc = secondAb; // ok
     abc = secondCd; // missing 'd'
     ~~~
 !!! error TS2322: Type 'Cd.E' is not assignable to type 'First.E'.
-!!! error TS2322:   Each declaration of 'E.c' differs in its value, where '2' was expected but '0' was given.
+!!! error TS2322:   Type 'E.c' is not assignable to type 'E'.
     abc = nope; // nope!
     ~~~
 !!! error TS2322: Type 'Nope' is not assignable to type 'E'.
+!!! error TS2322:   Type 'Nope.a' is not assignable to type 'E'.
     abc = decl; // bad - value of 'c' differs between these enums
     ~~~
 !!! error TS2322: Type 'Decl.E' is not assignable to type 'First.E'.
-!!! error TS2322:   Each declaration of 'E.c' differs in its value, where '2' was expected but '3' was given.
+!!! error TS2322:   Type 'E.a' is not assignable to type 'E'.
     secondAbc = abc; // ok
     secondAbcd = abc; // ok
     secondAb = abc; // missing 'c'
     ~~~~~~~~
 !!! error TS2322: Type 'First.E' is not assignable to type 'Ab.E'.
-!!! error TS2322:   Property 'c' is missing in type 'Ab.E'.
+!!! error TS2322:   Type 'E.a' is not assignable to type 'E'.
     secondCd = abc; // missing 'a' and 'b'
     ~~~~~~~~
 !!! error TS2322: Type 'First.E' is not assignable to type 'Cd.E'.
-!!! error TS2322:   Property 'a' is missing in type 'Cd.E'.
+!!! error TS2322:   Type 'E.a' is not assignable to type 'E'.
     nope = abc; // nope!
     ~~~~
 !!! error TS2322: Type 'E' is not assignable to type 'Nope'.
+!!! error TS2322:   Type 'E.a' is not assignable to type 'Nope'.
     decl = abc; // bad - value of 'c' differs between these enums
     ~~~~
 !!! error TS2322: Type 'First.E' is not assignable to type 'Decl.E'.
-!!! error TS2322:   Each declaration of 'E.c' differs in its value, where '3' was expected but '2' was given.
+!!! error TS2322:   Type 'E.a' is not assignable to type 'E'.
 
     // const is only assignable to itself
     k = k;
     abc = k; // error
     ~~~
 !!! error TS2322: Type 'Const.E' is not assignable to type 'First.E'.
+!!! error TS2322:   Type 'E.a' is not assignable to type 'E'.
     k = abc;
     ~
 !!! error TS2322: Type 'First.E' is not assignable to type 'Const.E'.
+!!! error TS2322:   Type 'E.a' is not assignable to type 'E'.
 
     // merged enums compare all their members
     abc = merged; // missing 'd'
     ~~~
 !!! error TS2322: Type 'Merged.E' is not assignable to type 'First.E'.
-!!! error TS2322:   Each declaration of 'E.c' differs in its value, where '2' was expected but '3' was given.
+!!! error TS2322:   Type 'E.a' is not assignable to type 'E'.
     merged = abc; // bad - value of 'c' differs between these enums
     ~~~~~~
 !!! error TS2322: Type 'First.E' is not assignable to type 'Merged.E'.
-!!! error TS2322:   Each declaration of 'E.c' differs in its value, where '3' was expected but '2' was given.
+!!! error TS2322:   Type 'E.a' is not assignable to type 'E'.
     abc = merged2; // ok
     merged2 = abc; // ok

tests/baselines/reference/enumAssignmentCompat6.errors.txt

@@ -1,17 +1,19 @@
 a.ts(36,5): error TS2322: Type 'strings.DiagnosticCategory' is not assignable to type 'numerics.DiagnosticCategory'.
-  Each declaration of 'DiagnosticCategory.Warning' differs in its value, where '0' was expected but '"Warning"' was given.
+  Type 'DiagnosticCategory.Warning' is not assignable to type 'DiagnosticCategory'.
 a.ts(37,5): error TS2322: Type 'numerics.DiagnosticCategory' is not assignable to type 'strings.DiagnosticCategory'.
-  Each declaration of 'DiagnosticCategory.Warning' differs in its value, where '"Warning"' was expected but '0' was given.
+  Type 'DiagnosticCategory.Warning' is not assignable to type 'DiagnosticCategory'.
 a.ts(41,5): error TS2322: Type 'DiagnosticCategory' is not assignable to type 'DiagnosticCategory2'.
+  Type 'DiagnosticCategory.Warning' is not assignable to type 'DiagnosticCategory2'.
 a.ts(42,5): error TS2322: Type 'DiagnosticCategory2' is not assignable to type 'DiagnosticCategory'.
+  Type 'DiagnosticCategory2.Warning' is not assignable to type 'DiagnosticCategory'.
 a.ts(51,5): error TS2322: Type 'ambients.DiagnosticCategory' is not assignable to type 'strings.DiagnosticCategory'.
-  One value of 'DiagnosticCategory.Warning' is the string '"Warning"', and the other is assumed to be an unknown numeric value.
+  Type 'DiagnosticCategory.Warning' is not assignable to type 'DiagnosticCategory'.
 a.ts(52,5): error TS2322: Type 'strings.DiagnosticCategory' is not assignable to type 'ambients.DiagnosticCategory'.
-  One value of 'DiagnosticCategory.Warning' is the string '"Warning"', and the other is assumed to be an unknown numeric value.
+  Type 'DiagnosticCategory.Warning' is not assignable to type 'DiagnosticCategory'.
 f.ts(18,9): error TS2322: Type 'DiagnosticCategory' is not assignable to type 'import("f").DiagnosticCategory'.
-  Each declaration of 'DiagnosticCategory.Warning' differs in its value, where '0' was expected but '"Warning"' was given.
+  Type 'DiagnosticCategory.Warning' is not assignable to type 'DiagnosticCategory'.
 f.ts(19,9): error TS2322: Type 'import("f").DiagnosticCategory' is not assignable to type 'DiagnosticCategory'.
-  Each declaration of 'DiagnosticCategory.Warning' differs in its value, where '"Warning"' was expected but '0' was given.
+  Type 'DiagnosticCategory.Warning' is not assignable to type 'DiagnosticCategory'.
 
 
 ==== a.ts (6 errors) ====
@@ -53,20 +55,22 @@ f.ts(19,9): error TS2322: Type 'import("f").DiagnosticCategory' is not assignabl
         x = y;
         ~
 !!! error TS2322: Type 'strings.DiagnosticCategory' is not assignable to type 'numerics.DiagnosticCategory'.
-!!! error TS2322:   Each declaration of 'DiagnosticCategory.Warning' differs in its value, where '0' was expected but '"Warning"' was given.
+!!! error TS2322:   Type 'DiagnosticCategory.Warning' is not assignable to type 'DiagnosticCategory'.
         y = x;
         ~
 !!! error TS2322: Type 'numerics.DiagnosticCategory' is not assignable to type 'strings.DiagnosticCategory'.
-!!! error TS2322:   Each declaration of 'DiagnosticCategory.Warning' differs in its value, where '"Warning"' was expected but '0' was given.
+!!! error TS2322:   Type 'DiagnosticCategory.Warning' is not assignable to type 'DiagnosticCategory'.
     }
 
     function g(x: numerics.DiagnosticCategory2, y: strings.DiagnosticCategory) {
         x = y;
         ~
 !!! error TS2322: Type 'DiagnosticCategory' is not assignable to type 'DiagnosticCategory2'.
+!!! error TS2322:   Type 'DiagnosticCategory.Warning' is not assignable to type 'DiagnosticCategory2'.
         y = x;
         ~
 !!! error TS2322: Type 'DiagnosticCategory2' is not assignable to type 'DiagnosticCategory'.
+!!! error TS2322:   Type 'DiagnosticCategory2.Warning' is not assignable to type 'DiagnosticCategory'.
     }
 
     function h(x: numerics.DiagnosticCategory, y: ambients.DiagnosticCategory) {
@@ -78,11 +82,11 @@ f.ts(19,9): error TS2322: Type 'import("f").DiagnosticCategory' is not assignabl
         x = y;
         ~
 !!! error TS2322: Type 'ambients.DiagnosticCategory' is not assignable to type 'strings.DiagnosticCategory'.
-!!! error TS2322:   One value of 'DiagnosticCategory.Warning' is the string '"Warning"', and the other is assumed to be an unknown numeric value.
+!!! error TS2322:   Type 'DiagnosticCategory.Warning' is not assignable to type 'DiagnosticCategory'.
         y = x;
         ~
 !!! error TS2322: Type 'strings.DiagnosticCategory' is not assignable to type 'ambients.DiagnosticCategory'.
-!!! error TS2322:   One value of 'DiagnosticCategory.Warning' is the string '"Warning"', and the other is assumed to be an unknown numeric value.
+!!! error TS2322:   Type 'DiagnosticCategory.Warning' is not assignable to type 'DiagnosticCategory'.
     }
 
 ==== f.ts (2 errors) ====
@@ -106,10 +110,10 @@ f.ts(19,9): error TS2322: Type 'import("f").DiagnosticCategory' is not assignabl
             x = y;
             ~
 !!! error TS2322: Type 'DiagnosticCategory' is not assignable to type 'import("f").DiagnosticCategory'.
-!!! error TS2322:   Each declaration of 'DiagnosticCategory.Warning' differs in its value, where '0' was expected but '"Warning"' was given.
+!!! error TS2322:   Type 'DiagnosticCategory.Warning' is not assignable to type 'DiagnosticCategory'.
             y = x;
             ~
 !!! error TS2322: Type 'import("f").DiagnosticCategory' is not assignable to type 'DiagnosticCategory'.
-!!! error TS2322:   Each declaration of 'DiagnosticCategory.Warning' differs in its value, where '"Warning"' was expected but '0' was given.
+!!! error TS2322:   Type 'DiagnosticCategory.Warning' is not assignable to type 'DiagnosticCategory'.
         }
     })()

tests/baselines/reference/enumLiteralTypes3.errors.txt

@@ -3,9 +3,11 @@ enumLiteralTypes3.ts(10,5): error TS2322: Type 'YesNo' is not assignable to type
 enumLiteralTypes3.ts(11,5): error TS2322: Type 'UnknownYesNo' is not assignable to type 'Choice.Yes'.
   Type 'Choice.Unknown' is not assignable to type 'Choice.Yes'.
 enumLiteralTypes3.ts(12,5): error TS2322: Type 'Choice' is not assignable to type 'Choice.Yes'.
+  Type 'Choice.Unknown' is not assignable to type 'Choice.Yes'.
 enumLiteralTypes3.ts(18,5): error TS2322: Type 'UnknownYesNo' is not assignable to type 'YesNo'.
   Type 'Choice.Unknown' is not assignable to type 'YesNo'.
 enumLiteralTypes3.ts(19,5): error TS2322: Type 'Choice' is not assignable to type 'YesNo'.
+  Type 'Choice.Unknown' is not assignable to type 'YesNo'.
 enumLiteralTypes3.ts(37,5): error TS2322: Type 'Choice.Unknown' is not assignable to type 'Choice.Yes'.
 enumLiteralTypes3.ts(39,5): error TS2322: Type 'Choice.No' is not assignable to type 'Choice.Yes'.
 enumLiteralTypes3.ts(40,5): error TS2322: Type 'Choice.Unknown' is not assignable to type 'YesNo'.
@@ -38,6 +40,7 @@ enumLiteralTypes3.ts(96,14): error TS2678: Type 'Choice.Unknown' is not comparab
         a = d;
         ~
 !!! error TS2322: Type 'Choice' is not assignable to type 'Choice.Yes'.
+!!! error TS2322:   Type 'Choice.Unknown' is not assignable to type 'Choice.Yes'.
     }
 
     function f2(a: Yes, b: YesNo, c: UnknownYesNo, d: Choice) {
@@ -50,6 +53,7 @@ enumLiteralTypes3.ts(96,14): error TS2678: Type 'Choice.Unknown' is not comparab
         b = d;
         ~
 !!! error TS2322: Type 'Choice' is not assignable to type 'YesNo'.
+!!! error TS2322:   Type 'Choice.Unknown' is not assignable to type 'YesNo'.
     }
 
     function f3(a: Yes, b: YesNo, c: UnknownYesNo, d: Choice) {

tests/baselines/reference/identityRelationEnumTypes.js

@@ -0,0 +1,41 @@
+//// [tests/cases/compiler/identityRelationEnumTypes.ts] ////
+
+//// [identityRelationEnumTypes.ts]
+namespace identityRelationEnumTypes {
+    export type Equals<A, B> = (<T>() => T extends B ? 1 : 0) extends (<T>() => T extends A ? 1 : 0) ? true : false;
+
+    export enum Enum {
+        A = 'a',
+        B = 'b',
+    }
+
+    export type EnumValues = typeof Enum[keyof typeof Enum];
+
+    type Result = identityRelationEnumTypes.Equals<
+        identityRelationEnumTypes.Enum,
+        identityRelationEnumTypes.EnumValues
+    >;  // true
+}
+
+
+//// [identityRelationEnumTypes.js]
+"use strict";
+var identityRelationEnumTypes;
+(function (identityRelationEnumTypes) {
+    var Enum;
+    (function (Enum) {
+        Enum["A"] = "a";
+        Enum["B"] = "b";
+    })(Enum = identityRelationEnumTypes.Enum || (identityRelationEnumTypes.Enum = {}));
+})(identityRelationEnumTypes || (identityRelationEnumTypes = {}));
+
+
+//// [identityRelationEnumTypes.d.ts]
+declare namespace identityRelationEnumTypes {
+    type Equals<A, B> = (<T>() => T extends B ? 1 : 0) extends (<T>() => T extends A ? 1 : 0) ? true : false;
+    enum Enum {
+        A = "a",
+        B = "b"
+    }
+    type EnumValues = typeof Enum[keyof typeof Enum];
+}

tests/baselines/reference/identityRelationEnumTypes.symbols

@@ -0,0 +1,48 @@
+//// [tests/cases/compiler/identityRelationEnumTypes.ts] ////
+
+=== identityRelationEnumTypes.ts ===
+namespace identityRelationEnumTypes {
+>identityRelationEnumTypes : Symbol(identityRelationEnumTypes, Decl(identityRelationEnumTypes.ts, 0, 0))
+
+    export type Equals<A, B> = (<T>() => T extends B ? 1 : 0) extends (<T>() => T extends A ? 1 : 0) ? true : false;
+>Equals : Symbol(Equals, Decl(identityRelationEnumTypes.ts, 0, 37))
+>A : Symbol(A, Decl(identityRelationEnumTypes.ts, 1, 23))
+>B : Symbol(B, Decl(identityRelationEnumTypes.ts, 1, 25))
+>T : Symbol(T, Decl(identityRelationEnumTypes.ts, 1, 33))
+>T : Symbol(T, Decl(identityRelationEnumTypes.ts, 1, 33))
+>B : Symbol(B, Decl(identityRelationEnumTypes.ts, 1, 25))
+>T : Symbol(T, Decl(identityRelationEnumTypes.ts, 1, 72))
+>T : Symbol(T, Decl(identityRelationEnumTypes.ts, 1, 72))
+>A : Symbol(A, Decl(identityRelationEnumTypes.ts, 1, 23))
+
+    export enum Enum {
+>Enum : Symbol(Enum, Decl(identityRelationEnumTypes.ts, 1, 116))
+
+        A = 'a',
+>A : Symbol(Enum.A, Decl(identityRelationEnumTypes.ts, 3, 22))
+
+        B = 'b',
+>B : Symbol(Enum.B, Decl(identityRelationEnumTypes.ts, 4, 16))
+    }
+
+    export type EnumValues = typeof Enum[keyof typeof Enum];
+>EnumValues : Symbol(EnumValues, Decl(identityRelationEnumTypes.ts, 6, 5))
+>Enum : Symbol(Enum, Decl(identityRelationEnumTypes.ts, 1, 116))
+>Enum : Symbol(Enum, Decl(identityRelationEnumTypes.ts, 1, 116))
+
+    type Result = identityRelationEnumTypes.Equals<
+>Result : Symbol(Result, Decl(identityRelationEnumTypes.ts, 8, 60))
+>identityRelationEnumTypes : Symbol(identityRelationEnumTypes, Decl(identityRelationEnumTypes.ts, 0, 0))
+>Equals : Symbol(Equals, Decl(identityRelationEnumTypes.ts, 0, 37))
+
+        identityRelationEnumTypes.Enum,
+>identityRelationEnumTypes : Symbol(identityRelationEnumTypes, Decl(identityRelationEnumTypes.ts, 0, 0))
+>Enum : Symbol(Enum, Decl(identityRelationEnumTypes.ts, 1, 116))
+
+        identityRelationEnumTypes.EnumValues
+>identityRelationEnumTypes : Symbol(identityRelationEnumTypes, Decl(identityRelationEnumTypes.ts, 0, 0))
+>EnumValues : Symbol(EnumValues, Decl(identityRelationEnumTypes.ts, 6, 5))
+
+    >;  // true
+}
+

tests/baselines/reference/identityRelationEnumTypes.types

@@ -0,0 +1,57 @@
+//// [tests/cases/compiler/identityRelationEnumTypes.ts] ////
+
+=== identityRelationEnumTypes.ts ===
+namespace identityRelationEnumTypes {
+>identityRelationEnumTypes : typeof identityRelationEnumTypes
+>                          : ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+    export type Equals<A, B> = (<T>() => T extends B ? 1 : 0) extends (<T>() => T extends A ? 1 : 0) ? true : false;
+>Equals : Equals<A, B>
+>       : ^^^^^^^^^^^^
+>true : true
+>     : ^^^^
+>false : false
+>      : ^^^^^
+
+    export enum Enum {
+>Enum : Enum
+>     : ^^^^
+
+        A = 'a',
+>A : Enum.A
+>  : ^^^^^^
+>'a' : "a"
+>    : ^^^
+
+        B = 'b',
+>B : Enum.B
+>  : ^^^^^^
+>'b' : "b"
+>    : ^^^
+    }
+
+    export type EnumValues = typeof Enum[keyof typeof Enum];
+>EnumValues : EnumValues
+>           : ^^^^^^^^^^
+>Enum : typeof Enum
+>     : ^^^^^^^^^^^
+>Enum : typeof Enum
+>     : ^^^^^^^^^^^
+
+    type Result = identityRelationEnumTypes.Equals<
+>Result : true
+>       : ^^^^
+>identityRelationEnumTypes : any
+>                          : ^^^
+
+        identityRelationEnumTypes.Enum,
+>identityRelationEnumTypes : any
+>                          : ^^^
+
+        identityRelationEnumTypes.EnumValues
+>identityRelationEnumTypes : any
+>                          : ^^^
+
+    >;  // true
+}
+