Add new nonInferrableType with ObjectFlags.NonInferrableType

Author: ahejlsberg

src/compiler/checker.ts

@@ -404,10 +404,10 @@ namespace ts {
         const wildcardType = createIntrinsicType(TypeFlags.Any, "any");
         const errorType = createIntrinsicType(TypeFlags.Any, "error");
         const unknownType = createIntrinsicType(TypeFlags.Unknown, "unknown");
-        const undefinedType = createNullableType(TypeFlags.Undefined, "undefined", 0);
-        const undefinedWideningType = strictNullChecks ? undefinedType : createNullableType(TypeFlags.Undefined, "undefined", ObjectFlags.ContainsWideningType);
-        const nullType = createNullableType(TypeFlags.Null, "null", 0);
-        const nullWideningType = strictNullChecks ? nullType : createNullableType(TypeFlags.Null, "null", ObjectFlags.ContainsWideningType);
+        const undefinedType = createIntrinsicType(TypeFlags.Undefined, "undefined");
+        const undefinedWideningType = strictNullChecks ? undefinedType : createIntrinsicType(TypeFlags.Undefined, "undefined", ObjectFlags.ContainsWideningType);
+        const nullType = createIntrinsicType(TypeFlags.Null, "null");
+        const nullWideningType = strictNullChecks ? nullType : createIntrinsicType(TypeFlags.Null, "null", ObjectFlags.ContainsWideningType);
         const stringType = createIntrinsicType(TypeFlags.String, "string");
         const numberType = createIntrinsicType(TypeFlags.Number, "number");
         const bigintType = createIntrinsicType(TypeFlags.BigInt, "bigint");
@@ -433,6 +433,7 @@ namespace ts {
         const voidType = createIntrinsicType(TypeFlags.Void, "void");
         const neverType = createIntrinsicType(TypeFlags.Never, "never");
         const silentNeverType = createIntrinsicType(TypeFlags.Never, "never");
+        const nonInferrableType = createIntrinsicType(TypeFlags.Never, "never", ObjectFlags.NonInferrableType);
         const implicitNeverType = createIntrinsicType(TypeFlags.Never, "never");
         const nonPrimitiveType = createIntrinsicType(TypeFlags.NonPrimitive, "object");
         const stringNumberSymbolType = getUnionType([stringType, numberType, esSymbolType]);
@@ -453,7 +454,7 @@ namespace ts {
         const anyFunctionType = createAnonymousType(undefined, emptySymbols, emptyArray, emptyArray, undefined, undefined);
         // The anyFunctionType contains the anyFunctionType by definition. The flag is further propagated
         // in getPropagatingFlagsOfTypes, and it is checked in inferFromTypes.
-        anyFunctionType.objectFlags |= ObjectFlags.ContainsAnyFunctionType;
+        anyFunctionType.objectFlags |= ObjectFlags.NonInferrableType;
 
         const noConstraintType = createAnonymousType(undefined, emptySymbols, emptyArray, emptyArray, undefined, undefined);
         const circularConstraintType = createAnonymousType(undefined, emptySymbols, emptyArray, emptyArray, undefined, undefined);
@@ -2797,14 +2798,9 @@ namespace ts {
             return result;
         }
 
-        function createIntrinsicType(kind: TypeFlags, intrinsicName: string): IntrinsicType {
+        function createIntrinsicType(kind: TypeFlags, intrinsicName: string, objectFlags: ObjectFlags = 0): IntrinsicType {
             const type = <IntrinsicType>createType(kind);
             type.intrinsicName = intrinsicName;
-            return type;
-        }
-
-        function createNullableType(kind: TypeFlags, intrinsicName: string, objectFlags: ObjectFlags): NullableType {
-            const type = createIntrinsicType(kind, intrinsicName);
             type.objectFlags = objectFlags;
             return type;
         }
@@ -14513,7 +14509,7 @@ namespace ts {
             // If any property contains context sensitive functions that have been skipped, the source type
             // is incomplete and we can't infer a meaningful input type.
             for (const prop of properties) {
-                if (getObjectFlags(getTypeOfSymbol(prop)) & ObjectFlags.ContainsAnyFunctionType) {
+                if (getObjectFlags(getTypeOfSymbol(prop)) & ObjectFlags.NonInferrableType) {
                     return undefined;
                 }
             }
@@ -14670,7 +14666,7 @@ namespace ts {
                     // not contain anyFunctionType when we come back to this argument for its second round
                     // of inference. Also, we exclude inferences for silentNeverType (which is used as a wildcard
                     // when constructing types from type parameters that had no inference candidates).
-                    if (getObjectFlags(source) & ObjectFlags.ContainsAnyFunctionType || source === silentNeverType || (priority & InferencePriority.ReturnType && (source === autoType || source === autoArrayType))) {
+                    if (getObjectFlags(source) & ObjectFlags.NonInferrableType || source === silentNeverType || (priority & InferencePriority.ReturnType && (source === autoType || source === autoArrayType))) {
                         return;
                     }
                     const inference = getInferenceInfoForType(target);
@@ -14991,7 +14987,7 @@ namespace ts {
                 const sourceLen = sourceSignatures.length;
                 const targetLen = targetSignatures.length;
                 const len = sourceLen < targetLen ? sourceLen : targetLen;
-                const skipParameters = !!(getObjectFlags(source) & ObjectFlags.ContainsAnyFunctionType);
+                const skipParameters = !!(getObjectFlags(source) & ObjectFlags.NonInferrableType);
                 for (let i = 0; i < len; i++) {
                     inferFromSignature(getBaseSignature(sourceSignatures[sourceLen - len + i]), getBaseSignature(targetSignatures[targetLen - len + i]), skipParameters);
                 }
@@ -21120,7 +21116,7 @@ namespace ts {
             // returns a function type, we choose to defer processing. This narrowly permits function composition
             // operators to flow inferences through return types, but otherwise processes calls right away. We
             // use the resolvingSignature singleton to indicate that we deferred processing. This result will be
-            // propagated out and eventually turned into silentNeverType (a type that is assignable to anything and
+            // propagated out and eventually turned into nonInferrableType (a type that is assignable to anything and
             // from which we never make inferences).
             if (checkMode & CheckMode.SkipGenericFunctions && !node.typeArguments && callSignatures.some(isGenericFunctionReturningFunction)) {
                 skippedGenericFunction(node, checkMode);
@@ -21603,8 +21599,8 @@ namespace ts {
             const signature = getResolvedSignature(node, /*candidatesOutArray*/ undefined, checkMode);
             if (signature === resolvingSignature) {
                 // CheckMode.SkipGenericFunctions is enabled and this is a call to a generic function that
-                // returns a function type. We defer checking and return anyFunctionType.
-                return silentNeverType;
+                // returns a function type. We defer checking and return nonInferrableType.
+                return nonInferrableType;
             }
 
             if (node.expression.kind === SyntaxKind.SuperKeyword) {
@@ -22411,7 +22407,7 @@ namespace ts {
                     const returnType = getReturnTypeFromBody(node, checkMode);
                     const returnOnlySignature = createSignature(undefined, undefined, undefined, emptyArray, returnType, /*resolvedTypePredicate*/ undefined, 0, /*hasRestParameter*/ false, /*hasLiteralTypes*/ false);
                     const returnOnlyType = createAnonymousType(node.symbol, emptySymbols, [returnOnlySignature], emptyArray, undefined, undefined);
-                    returnOnlyType.objectFlags |= ObjectFlags.ContainsAnyFunctionType;
+                    returnOnlyType.objectFlags |= ObjectFlags.NonInferrableType;
                     return links.contextFreeType = returnOnlyType;
                 }
                 return anyFunctionType;

src/compiler/types.ts

@@ -3944,7 +3944,7 @@ namespace ts {
         Instantiable = InstantiableNonPrimitive | InstantiablePrimitive,
         StructuredOrInstantiable = StructuredType | Instantiable,
         /* @internal */
-        ObjectFlagsType = Nullable | Object | Union | Intersection,
+        ObjectFlagsType = Nullable | Never | Object | Union | Intersection,
         // 'Narrowable' types are types where narrowing actually narrows.
         // This *should* be every type other than null, undefined, void, and never
         Narrowable = Any | Unknown | StructuredOrInstantiable | StringLike | NumberLike | BigIntLike | BooleanLike | ESSymbol | UniqueESSymbol | NonPrimitive,
@@ -4064,12 +4064,12 @@ namespace ts {
         /* @internal */
         ContainsObjectLiteral = 1 << 18, // Type is or contains object literal type
         /* @internal */
-        ContainsAnyFunctionType = 1 << 19, // Type is or contains the anyFunctionType
+        NonInferrableType = 1 << 19, // Type is or contains anyFunctionType or silentNeverType
         ClassOrInterface = Class | Interface,
         /* @internal */
         RequiresWidening = ContainsWideningType | ContainsObjectLiteral,
         /* @internal */
-        PropagatingFlags = ContainsWideningType | ContainsObjectLiteral | ContainsAnyFunctionType
+        PropagatingFlags = ContainsWideningType | ContainsObjectLiteral | NonInferrableType
     }
 
     /* @internal */