Fix naming and update comment

Author: JsonFreeman

src/compiler/checker.ts

@@ -114,7 +114,7 @@ namespace ts {
 
         let anyFunctionType = createAnonymousType(undefined, emptySymbols, emptyArray, emptyArray, undefined, undefined);
         // The anyFunctionType contains the anyFunctionType by definition. The flag is further propagated
-        // in getContainsLiteralFlagsOfTypes, and it is checked in inferFromTypes.
+        // in getPropagatingFlagsOfTypes, and it is checked in inferFromTypes.
         anyFunctionType.flags |= TypeFlags.ContainsAnyFunctionType;
 
         let noConstraintType = createAnonymousType(undefined, emptySymbols, emptyArray, emptyArray, undefined, undefined);
@@ -3761,22 +3761,23 @@ namespace ts {
             }
         }
 
-        // This function is used to propagate widening flags when creating new object types references and union types.
-        // It is only necessary to do so if a constituent type might be the undefined type, the null type, or the type
-        // of an object literal (since those types have widening related information we need to track).
-        function getContainsLiteralFlagsOfTypes(types: Type[]): TypeFlags {
+        // This function is used to propagate certain flags when creating new object type references and union types.
+        // It is only necessary to do so if a constituent type might be the undefined type, the null type, the type
+        // of an object literal or the anyFunctionType. This is because there are operations in the type checker
+        // that care about the presence of such types at arbitrary depth in a containing type.
+        function getPropagatingFlagsOfTypes(types: Type[]): TypeFlags {
             let result: TypeFlags = 0;
             for (let type of types) {
                 result |= type.flags;
             }
-            return result & TypeFlags.ContainsLiteralFlags;
+            return result & TypeFlags.PropagatingFlags;
         }
 
         function createTypeReference(target: GenericType, typeArguments: Type[]): TypeReference {
             let id = getTypeListId(typeArguments);
             let type = target.instantiations[id];
             if (!type) {
-                let flags = TypeFlags.Reference | getContainsLiteralFlagsOfTypes(typeArguments);
+                let flags = TypeFlags.Reference | getPropagatingFlagsOfTypes(typeArguments);
                 type = target.instantiations[id] = <TypeReference>createObjectType(flags, target.symbol);
                 type.target = target;
                 type.typeArguments = typeArguments;
@@ -4030,7 +4031,7 @@ namespace ts {
             let id = getTypeListId(elementTypes);
             let type = tupleTypes[id];
             if (!type) {
-                type = tupleTypes[id] = <TupleType>createObjectType(TypeFlags.Tuple | getContainsLiteralFlagsOfTypes(elementTypes));
+                type = tupleTypes[id] = <TupleType>createObjectType(TypeFlags.Tuple | getPropagatingFlagsOfTypes(elementTypes));
                 type.elementTypes = elementTypes;
             }
             return type;
@@ -4179,7 +4180,7 @@ namespace ts {
             let id = getTypeListId(typeSet);
             let type = unionTypes[id];
             if (!type) {
-                type = unionTypes[id] = <UnionType>createObjectType(TypeFlags.Union | getContainsLiteralFlagsOfTypes(typeSet));
+                type = unionTypes[id] = <UnionType>createObjectType(TypeFlags.Union | getPropagatingFlagsOfTypes(typeSet));
                 type.types = typeSet;
             }
             return type;
@@ -4213,7 +4214,7 @@ namespace ts {
             let id = getTypeListId(typeSet);
             let type = intersectionTypes[id];
             if (!type) {
-                type = intersectionTypes[id] = <IntersectionType>createObjectType(TypeFlags.Intersection | getContainsLiteralFlagsOfTypes(typeSet));
+                type = intersectionTypes[id] = <IntersectionType>createObjectType(TypeFlags.Intersection | getPropagatingFlagsOfTypes(typeSet));
                 type.types = typeSet;
             }
             return type;
@@ -7103,7 +7104,7 @@ namespace ts {
             let stringIndexType = getIndexType(IndexKind.String);
             let numberIndexType = getIndexType(IndexKind.Number);
             let result = createAnonymousType(node.symbol, propertiesTable, emptyArray, emptyArray, stringIndexType, numberIndexType);
-            result.flags |= TypeFlags.ObjectLiteral | TypeFlags.FreshObjectLiteral | TypeFlags.ContainsObjectLiteral | (typeFlags & TypeFlags.ContainsLiteralFlags);
+            result.flags |= TypeFlags.ObjectLiteral | TypeFlags.FreshObjectLiteral | TypeFlags.ContainsObjectLiteral | (typeFlags & TypeFlags.PropagatingFlags);
             return result;
 
             function getIndexType(kind: IndexKind) {

src/compiler/types.ts

@@ -1784,7 +1784,7 @@ namespace ts {
         /* @internal */
         RequiresWidening = ContainsUndefinedOrNull | ContainsObjectLiteral,
         /* @internal */
-        ContainsLiteralFlags = ContainsUndefinedOrNull | ContainsObjectLiteral | ContainsAnyFunctionType
+        PropagatingFlags = ContainsUndefinedOrNull | ContainsObjectLiteral | ContainsAnyFunctionType
     }
 
     // Properties common to all types