Function checkInExpression

test/fixtures/snapshot/typescript.js:78611–78662

(left, right, leftType, rightType)

            return booleanType;
        }
        function checkInExpression(left, right, leftType, rightType) {
            if (leftType === silentNeverType || rightType === silentNeverType) {
                return silentNeverType;
            }
            if (ts.isPrivateIdentifier(left)) {
                if (languageVersion < 99 /* ScriptTarget.ESNext */) {
                    checkExternalEmitHelpers(left, 2097152 /* ExternalEmitHelpers.ClassPrivateFieldIn */);
                }
                // Unlike in 'checkPrivateIdentifierExpression' we now have access to the RHS type
                // which provides us with the opportunity to emit more detailed errors
                if (!getNodeLinks(left).resolvedSymbol && ts.getContainingClass(left)) {
                    var isUncheckedJS = isUncheckedJSSuggestion(left, rightType.symbol, /*excludeClasses*/ true);
                    reportNonexistentProperty(left, rightType, isUncheckedJS);
                }
            }
            else {
                leftType = checkNonNullType(leftType, left);
                // TypeScript 1.0 spec (April 2014): 4.15.5
                // Require the left operand to be of type Any, the String primitive type, or the Number primitive type.
                if (!(allTypesAssignableToKind(leftType, 402653316 /* TypeFlags.StringLike */ | 296 /* TypeFlags.NumberLike */ | 12288 /* TypeFlags.ESSymbolLike */) ||
                    isTypeAssignableToKind(leftType, 4194304 /* TypeFlags.Index */ | 134217728 /* TypeFlags.TemplateLiteral */ | 268435456 /* TypeFlags.StringMapping */ | 262144 /* TypeFlags.TypeParameter */))) {
                    error(left, ts.Diagnostics.The_left_hand_side_of_an_in_expression_must_be_a_private_identifier_or_of_type_any_string_number_or_symbol);
                }
            }
            rightType = checkNonNullType(rightType, right);
            // TypeScript 1.0 spec (April 2014): 4.15.5
            // The in operator requires the right operand to be
            //
            //   1. assignable to the non-primitive type,
            //   2. an unconstrained type parameter,
            //   3. a union or intersection including one or more type parameters, whose constituents are all assignable to the
            //      the non-primitive type, or are unconstrainted type parameters, or have constraints assignable to the
            //      non-primitive type, or
            //   4. a type parameter whose constraint is
            //      i. an object type,
            //     ii. the non-primitive type, or
            //    iii. a union or intersection with at least one constituent assignable to an object or non-primitive type.
            //
            // The divergent behavior for type parameters and unions containing type parameters is a workaround for type
            // parameters not being narrowable. If the right operand is a concrete type, we can error if there is any chance
            // it is a primitive. But if the operand is a type parameter, it cannot be narrowed, so we don't issue an error
            // unless *all* instantiations would result in an error.
            //
            // The result is always of the Boolean primitive type.
            var rightTypeConstraint = getConstraintOfType(rightType);
            if (!allTypesAssignableToKind(rightType, 67108864 /* TypeFlags.NonPrimitive */ | 58982400 /* TypeFlags.InstantiableNonPrimitive */) ||
                rightTypeConstraint && (isTypeAssignableToKind(rightType, 3145728 /* TypeFlags.UnionOrIntersection */) && !allTypesAssignableToKind(rightTypeConstraint, 67108864 /* TypeFlags.NonPrimitive */ | 58982400 /* TypeFlags.InstantiableNonPrimitive */) ||
                    !maybeTypeOfKind(rightTypeConstraint, 67108864 /* TypeFlags.NonPrimitive */ | 58982400 /* TypeFlags.InstantiableNonPrimitive */ | 524288 /* TypeFlags.Object */))) {
                error(right, ts.Diagnostics.The_right_hand_side_of_an_in_expression_must_not_be_a_primitive);
            }
            return booleanType;
        }
        function checkObjectLiteralAssignment(node, sourceType, rightIsThis) {
            var properties = node.properties;
            if (strictNullChecks && properties.length === 0) {