microsoft · ahejlsberg · Nov 17, 2022 · Nov 16, 2022 · Nov 16, 2022 · Nov 16, 2022
diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
@@ -386,6 +386,7 @@ export const enum CheckMode {
 
 /** @internal */
 export const enum SignatureCheckMode {
+    None              = 0,
     BivariantCallback = 1 << 0,
     StrictCallback    = 1 << 1,
     IgnoreReturnTypes = 1 << 2,
@@ -476,7 +477,7 @@ function SymbolLinks(this: SymbolLinks) {
 }
 
 function NodeLinks(this: NodeLinks) {
-    this.flags = 0;
+    this.flags = NodeCheckFlags.None;
 }
 
 /** @internal */
@@ -1473,7 +1474,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
     function createSymbol(flags: SymbolFlags, name: __String, checkFlags?: CheckFlags) {
         symbolCount++;
         const symbol = (new Symbol(flags | SymbolFlags.Transient, name) as TransientSymbol);
-        symbol.checkFlags = checkFlags || 0;
+        symbol.checkFlags = checkFlags || CheckFlags.None;
         return symbol;
     }
 
@@ -4543,7 +4544,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
         return new Type(checker, flags);
     }
 
-    function createIntrinsicType(kind: TypeFlags, intrinsicName: string, objectFlags: ObjectFlags = 0): IntrinsicType {
+    function createIntrinsicType(kind: TypeFlags, intrinsicName: string, objectFlags = ObjectFlags.None): IntrinsicType {
         const type = createType(kind) as IntrinsicType;
         type.intrinsicName = intrinsicName;
         type.objectFlags = objectFlags;
@@ -8659,7 +8660,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
 
     function formatUnionTypes(types: readonly Type[]): Type[] {
         const result: Type[] = [];
-        let flags: TypeFlags = 0;
+        let flags = 0 as TypeFlags;
         for (let i = 0; i < types.length; i++) {
             const t = types[i];
             flags |= t.flags;
@@ -14750,7 +14751,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
         const minLength = countWhere(elementFlags, f => !!(f & (ElementFlags.Required | ElementFlags.Variadic)));
         let typeParameters: TypeParameter[] | undefined;
         const properties: Symbol[] = [];
-        let combinedFlags: ElementFlags = 0;
+        let combinedFlags = 0 as ElementFlags;
         if (arity) {
             typeParameters = new Array(arity);
             for (let i = 0; i < arity; i++) {
@@ -15114,7 +15115,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
             return types[0];
         }
         let typeSet: Type[] | undefined = [];
-        const includes = addTypesToUnion(typeSet, 0, types);
+        const includes = addTypesToUnion(typeSet, 0 as TypeFlags, types);
         if (unionReduction !== UnionReduction.None) {
             if (includes & TypeFlags.AnyOrUnknown) {
                 return includes & TypeFlags.Any ?
@@ -15429,7 +15430,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
     // for intersections of types with signatures can be deterministic.
     function getIntersectionType(types: readonly Type[], aliasSymbol?: Symbol, aliasTypeArguments?: readonly Type[], noSupertypeReduction?: boolean): Type {
         const typeMembershipMap: Map<string, Type> = new Map();
-        const includes = addTypesToIntersection(typeMembershipMap, 0, types);
+        const includes = addTypesToIntersection(typeMembershipMap, 0 as TypeFlags, types);
         const typeSet: Type[] = arrayFrom(typeMembershipMap.values());
         // An intersection type is considered empty if it contains
         // the type never, or
@@ -18441,7 +18442,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
     function isSignatureAssignableTo(source: Signature,
         target: Signature,
         ignoreReturnTypes: boolean): boolean {
-        return compareSignaturesRelated(source, target, ignoreReturnTypes ? SignatureCheckMode.IgnoreReturnTypes : 0, /*reportErrors*/ false,
+        return compareSignaturesRelated(source, target, ignoreReturnTypes ? SignatureCheckMode.IgnoreReturnTypes : SignatureCheckMode.None, /*reportErrors*/ false,
             /*errorReporter*/ undefined, /*errorReporter*/ undefined, compareTypesAssignable, /*reportUnreliableMarkers*/ undefined) !== Ternary.False;
     }
 
@@ -18757,11 +18758,13 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
         if (s & TypeFlags.Object && t & TypeFlags.NonPrimitive && !(relation === strictSubtypeRelation && isEmptyAnonymousObjectType(source) && !(getObjectFlags(source) & ObjectFlags.FreshLiteral))) return true;
         if (relation === assignableRelation || relation === comparableRelation) {
             if (s & TypeFlags.Any) return true;
-            // Type number or any numeric literal type is assignable to any numeric enum type or any
-            // numeric enum literal type. This rule exists for backwards compatibility reasons because
-            // bit-flag enum types sometimes look like literal enum types with numeric literal values.
-            if (s & (TypeFlags.Number | TypeFlags.NumberLiteral) && !(s & TypeFlags.EnumLiteral) && (
-                t & TypeFlags.Enum || relation === assignableRelation && t & TypeFlags.NumberLiteral && t & TypeFlags.EnumLiteral)) return true;
+            // Type number is assignable to any computed numeric enum type or any numeric enum literal type, and
+            // a numeric literal type is assignable any computed numeric enum type or any numeric enum literal type
+            // with a matching value. These rules exist such that enums can be used for bit-flag purposes.
+            if (s & TypeFlags.Number && (t & TypeFlags.Enum || t & TypeFlags.NumberLiteral && t & TypeFlags.EnumLiteral)) return true;
+            if (s & TypeFlags.NumberLiteral && !(s & TypeFlags.EnumLiteral) && (t & TypeFlags.Enum ||
+                t & TypeFlags.NumberLiteral && t & TypeFlags.EnumLiteral &&
+                (source as NumberLiteralType).value === (target as NumberLiteralType).value)) return true;
             // Anything is assignable to a union containing undefined, null, and {}
             if (isUnknownLikeUnionType(target)) return true;
         }
@@ -19745,7 +19748,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
                 if (!(expandingFlags & ExpandingFlags.Target) && isDeeplyNestedType(target, targetStack, targetDepth)) expandingFlags |= ExpandingFlags.Target;
             }
             let originalHandler: typeof outofbandVarianceMarkerHandler;
-            let propagatingVarianceFlags: RelationComparisonResult = 0;
+            let propagatingVarianceFlags = 0 as RelationComparisonResult;
             if (outofbandVarianceMarkerHandler) {
                 originalHandler = outofbandVarianceMarkerHandler;
                 outofbandVarianceMarkerHandler = onlyUnreliable => {
@@ -22863,7 +22866,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
         }
     }
 
-    function inferTypes(inferences: InferenceInfo[], originalSource: Type, originalTarget: Type, priority: InferencePriority = 0, contravariant = false) {
+    function inferTypes(inferences: InferenceInfo[], originalSource: Type, originalTarget: Type, priority = InferencePriority.None, contravariant = false) {
         let bivariant = false;
         let propagationType: Type;
         let inferencePriority: number = InferencePriority.MaxValue;

diff --git a/src/compiler/transformers/es2015.ts b/src/compiler/transformers/es2015.ts
@@ -88,6 +88,7 @@ interface LoopOutParameter {
 }
 
 const enum LoopOutParameterFlags {
+    None = 0,
     Body = 1 << 0,          // Modified in the body of the iteration statement
     Initializer = 1 << 1,   // Set in the initializer of a ForStatement
 }
@@ -3488,7 +3489,7 @@ export function transformES2015(context: TransformationContext): (x: SourceFile
             const checkFlags = resolver.getNodeCheckFlags(decl);
             if (checkFlags & NodeCheckFlags.NeedsLoopOutParameter || hasCapturedBindingsInForHead) {
                 const outParamName = factory.createUniqueName("out_" + idText(name));
-                let flags: LoopOutParameterFlags = 0;
+                let flags = LoopOutParameterFlags.None;
                 if (checkFlags & NodeCheckFlags.NeedsLoopOutParameter) {
                     flags |= LoopOutParameterFlags.Body;
                 }

diff --git a/src/compiler/transformers/es2017.ts b/src/compiler/transformers/es2017.ts
@@ -25,6 +25,7 @@ const enum ES2017SubstitutionFlags {
 }
 
 const enum ContextFlags {
+    None = 0,
     NonTopLevel = 1 << 0,
     HasLexicalThis = 1 << 1
 }
@@ -66,7 +67,7 @@ export function transformES2017(context: TransformationContext): (x: SourceFile
     /** A set of node IDs for generated super accessors (variable statements). */
     const substitutedSuperAccessors: boolean[] = [];
 
-    let contextFlags: ContextFlags = 0;
+    let contextFlags = ContextFlags.None;
 
     // Save the previous transformation hooks.
     const previousOnEmitNode = context.onEmitNode;

diff --git a/src/compiler/types.ts b/src/compiler/types.ts
@@ -5514,6 +5514,7 @@ export const enum EnumKind {
 
 /** @internal */
 export const enum CheckFlags {
+    None              = 0,
     Instantiated      = 1 << 0,         // Instantiated symbol
     SyntheticProperty = 1 << 1,         // Property in union or intersection type
     SyntheticMethod   = 1 << 2,         // Method in union or intersection type
@@ -5611,31 +5612,32 @@ export interface PatternAmbientModule {
 
 /** @internal */
 export const enum NodeCheckFlags {
-    TypeChecked                              = 0x00000001,  // Node has been type checked
-    LexicalThis                              = 0x00000002,  // Lexical 'this' reference
-    CaptureThis                              = 0x00000004,  // Lexical 'this' used in body
-    CaptureNewTarget                         = 0x00000008,  // Lexical 'new.target' used in body
-    SuperInstance                            = 0x00000100,  // Instance 'super' reference
-    SuperStatic                              = 0x00000200,  // Static 'super' reference
-    ContextChecked                           = 0x00000400,  // Contextual types have been assigned
-    MethodWithSuperPropertyAccessInAsync     = 0x00000800,  // A method that contains a SuperProperty access in an async context.
-    MethodWithSuperPropertyAssignmentInAsync = 0x00001000,  // A method that contains a SuperProperty assignment in an async context.
-    CaptureArguments                         = 0x00002000,  // Lexical 'arguments' used in body
-    EnumValuesComputed                       = 0x00004000,  // Values for enum members have been computed, and any errors have been reported for them.
-    LexicalModuleMergesWithClass             = 0x00008000,  // Instantiated lexical module declaration is merged with a previous class declaration.
-    LoopWithCapturedBlockScopedBinding       = 0x00010000,  // Loop that contains block scoped variable captured in closure
-    ContainsCapturedBlockScopeBinding        = 0x00020000,  // Part of a loop that contains block scoped variable captured in closure
-    CapturedBlockScopedBinding               = 0x00040000,  // Block-scoped binding that is captured in some function
-    BlockScopedBindingInLoop                 = 0x00080000,  // Block-scoped binding with declaration nested inside iteration statement
-    ClassWithBodyScopedClassBinding          = 0x00100000,  // Decorated class that contains a binding to itself inside of the class body.
-    BodyScopedClassBinding                   = 0x00200000,  // Binding to a decorated class inside of the class's body.
-    NeedsLoopOutParameter                    = 0x00400000,  // Block scoped binding whose value should be explicitly copied outside of the converted loop
-    AssignmentsMarked                        = 0x00800000,  // Parameter assignments have been marked
-    ClassWithConstructorReference            = 0x01000000,  // Class that contains a binding to its constructor inside of the class body.
-    ConstructorReferenceInClass              = 0x02000000,  // Binding to a class constructor inside of the class's body.
-    ContainsClassWithPrivateIdentifiers      = 0x04000000,  // Marked on all block-scoped containers containing a class with private identifiers.
-    ContainsSuperPropertyInStaticInitializer = 0x08000000,  // Marked on all block-scoped containers containing a static initializer with 'super.x' or 'super[x]'.
-    InCheckIdentifier                        = 0x10000000,
+    None                                     = 0,
+    TypeChecked                              = 1 << 0,   // Node has been type checked
+    LexicalThis                              = 1 << 1,   // Lexical 'this' reference
+    CaptureThis                              = 1 << 2,   // Lexical 'this' used in body
+    CaptureNewTarget                         = 1 << 3,   // Lexical 'new.target' used in body
+    SuperInstance                            = 1 << 4,   // Instance 'super' reference
+    SuperStatic                              = 1 << 5,   // Static 'super' reference
+    ContextChecked                           = 1 << 6,   // Contextual types have been assigned
+    MethodWithSuperPropertyAccessInAsync     = 1 << 7,   // A method that contains a SuperProperty access in an async context.
+    MethodWithSuperPropertyAssignmentInAsync = 1 << 8,   // A method that contains a SuperProperty assignment in an async context.
+    CaptureArguments                         = 1 << 9,   // Lexical 'arguments' used in body
+    EnumValuesComputed                       = 1 << 10,  // Values for enum members have been computed, and any errors have been reported for them.
+    LexicalModuleMergesWithClass             = 1 << 11,  // Instantiated lexical module declaration is merged with a previous class declaration.
+    LoopWithCapturedBlockScopedBinding       = 1 << 12,  // Loop that contains block scoped variable captured in closure
+    ContainsCapturedBlockScopeBinding        = 1 << 13,  // Part of a loop that contains block scoped variable captured in closure
+    CapturedBlockScopedBinding               = 1 << 14,  // Block-scoped binding that is captured in some function
+    BlockScopedBindingInLoop                 = 1 << 15,  // Block-scoped binding with declaration nested inside iteration statement
+    ClassWithBodyScopedClassBinding          = 1 << 16,  // Decorated class that contains a binding to itself inside of the class body.
+    BodyScopedClassBinding                   = 1 << 17,  // Binding to a decorated class inside of the class's body.
+    NeedsLoopOutParameter                    = 1 << 18,  // Block scoped binding whose value should be explicitly copied outside of the converted loop
+    AssignmentsMarked                        = 1 << 19,  // Parameter assignments have been marked
+    ClassWithConstructorReference            = 1 << 20,  // Class that contains a binding to its constructor inside of the class body.
+    ConstructorReferenceInClass              = 1 << 21,  // Binding to a class constructor inside of the class's body.
+    ContainsClassWithPrivateIdentifiers      = 1 << 22,  // Marked on all block-scoped containers containing a class with private identifiers.
+    ContainsSuperPropertyInStaticInitializer = 1 << 23,  // Marked on all block-scoped containers containing a static initializer with 'super.x' or 'super[x]'.
+    InCheckIdentifier                        = 1 << 24,
 }
 
 /** @internal */
@@ -5842,6 +5844,7 @@ export interface EnumType extends Type {
 // are specific to certain types and reuse the same bit position. Those ObjectFlags require a check
 // for a certain TypeFlags value to determine their meaning.
 export const enum ObjectFlags {
+    None             = 0,
     Class            = 1 << 0,  // Class
     Interface        = 1 << 1,  // Interface
     Reference        = 1 << 2,  // Generic type reference
@@ -6384,6 +6387,7 @@ export type TypeMapper =
     | { kind: TypeMapKind.Composite | TypeMapKind.Merged, mapper1: TypeMapper, mapper2: TypeMapper };
 
 export const enum InferencePriority {
+    None                         = 0,
     NakedTypeVariable            = 1 << 0,  // Naked type variable in union or intersection type
     SpeculativeTuple             = 1 << 1,  // Speculative tuple inference
     SubstituteSource             = 1 << 2,  // Source of inference originated within a substitution type's substitute

diff --git a/src/services/formatting/rule.ts b/src/services/formatting/rule.ts
@@ -17,6 +17,7 @@ export const anyContext: readonly ContextPredicate[] = emptyArray;
 
 /** @internal */
 export const enum RuleAction {
+    None                       = 0,
     StopProcessingSpaceActions = 1 << 0,
     StopProcessingTokenActions = 1 << 1,
     InsertSpace                = 1 << 2,

diff --git a/src/services/formatting/rulesMap.ts b/src/services/formatting/rulesMap.ts
@@ -22,7 +22,7 @@ function getRulesMap(): RulesMap {
  * cannot be applied at the same position.
  */
 function getRuleActionExclusion(ruleAction: RuleAction): RuleAction {
-    let mask: RuleAction = 0;
+    let mask = RuleAction.None;
     if (ruleAction & RuleAction.StopProcessingSpaceActions) {
         mask |= RuleAction.ModifySpaceAction;
     }

diff --git a/src/testRunner/unittests/helpers.ts b/src/testRunner/unittests/helpers.ts
@@ -1,6 +1,7 @@
 import * as ts from "../_namespaces/ts";
 
 const enum ChangedPart {
+    none = 0,
     references = 1 << 0,
     importsAndExports = 1 << 1,
     program = 1 << 2
@@ -32,7 +33,7 @@ export class SourceText implements ts.IScriptSnapshot {
     constructor(private references: string,
         private importsAndExports: string,
         private program: string,
-        private changedPart: ChangedPart = 0,
+        private changedPart = ChangedPart.none,
         private version = 0) {
     }
 

diff --git a/tests/baselines/reference/api/tsserverlibrary.d.ts b/tests/baselines/reference/api/tsserverlibrary.d.ts
@@ -6719,6 +6719,7 @@ declare namespace ts {
     interface EnumType extends Type {
     }
     enum ObjectFlags {
+        None = 0,
         Class = 1,
         Interface = 2,
         Reference = 4,
@@ -6889,6 +6890,7 @@ declare namespace ts {
         declaration?: IndexSignatureDeclaration;
     }
     enum InferencePriority {
+        None = 0,
         NakedTypeVariable = 1,
         SpeculativeTuple = 2,
         SubstituteSource = 4,

diff --git a/tests/baselines/reference/api/typescript.d.ts b/tests/baselines/reference/api/typescript.d.ts
@@ -2783,6 +2783,7 @@ declare namespace ts {
     interface EnumType extends Type {
     }
     enum ObjectFlags {
+        None = 0,
         Class = 1,
         Interface = 2,
         Reference = 4,
@@ -2953,6 +2954,7 @@ declare namespace ts {
         declaration?: IndexSignatureDeclaration;
     }
     enum InferencePriority {
+        None = 0,
         NakedTypeVariable = 1,
         SpeculativeTuple = 2,
         SubstituteSource = 4,