- Qt 6.12
- Qt Qml
- Qt Qml Tooling
- qmllint
- QML Lint Warning and Errors
- Syntax
- Qt 6.12.0 Reference Documentation

Signal handler parameters ◦ Duplicate id

# Syntax

This warning category is spelled `[syntax]` by qmllint.

## Nested inline components are not supported

### What happened?

You defined an inline component inside another inline component.

### Why is this bad?

The QML language does not allow nested inline components. Always define inline components inside the root item of the QML file.

### Example

     import QtQuick

     Item {
         component Correct: Item {
             component Evil: Item { ... }
             ...
         }
     }

To fix this warning, move all components to the root item of the QML file.

     import QtQuick

     Item {
         component NotEvilAnymore: Item { ... }
         component Correct: Item {
             ...
         }
     }

## Inline component declaration must be followed by a typename

### What happened?

You defined an inline component with an invalid base type.

### Why is this bad?

Inline components need a base type to inherit from.

### Example

     import QtQuick

     Item {
         property Item someProperty
         component InlineComponent: someProperty {}
     }

In this case, `someProperty` is not a valid type name, as it is a property name. To fix this warning, use a valid Type as the component's base type:

     import QtQuick

     Item {
         property Item someProperty
         component InlineComponent: Item { ... }
     }

## Invalid alias expression: an initializer is needed

### What happened?

You defined a property alias without its aliased property.

### Why is this bad?

Alias properties always need to have their aliased property or id in their definition.

### Example

     import QtQuick

     Item {
         id: root
         property int someProperty
         property alias aliasProperty
     }

To fix this warning, replace the alias with a normal property, or add the missing aliased property:

     import QtQuick

     Item {
         id: root
         property int someProperty
         property alias withAliasedProperty: root.someProperty
     }

## Invalid alias expression: only ids and field member expressions can be aliased

### What happened?

You defined a property alias that aliases an expression other than an ID or a field member expression.

A field member expression is an expression of the form `someId.someProperty`.

### Why is this bad?

Alias properties always need to have their aliased property in their definition, and can't bind to other expressions than IDs and field member expressions.

### Example

     import QtQuick

     Item {
         property int p
         property alias someProperty: p + 1
     }

To fix this warning, replace the alias with a normal property or bind it to an id or field member expression:

     import QtQuick

     Item {
         id: root
         property int p
         property int someProperty: p + 1
         property alias alternative: root.p
     }

## Id must be followed by an identifier

### What happened?

You defined an id without a value.

### Why is this bad?

The QML language does not allow empty ids.

### Example

     import QtQuick

     Item {
         id:;
     }

To fix this warning, bind the id to a valid name:

     import QtQuick

     Item {
         id: root;
     }

## Failed to parse id

### What happened?

You bound an id to an expression other than a name.

### Why is this bad?

The QML language only allows names as bindings to ids; more complex expressions can't be used.

### Example

     import QtQuick

     Item {
         property int a
         property int b
         function f() {
             if (true)
                 return a
             return b
         }

         id: f()
     }

To fix this warning, bind the id to a valid name or declare a property and set up a binding:

     import QtQuick

     Item {
         property int a
         property int b
         function f() {
             if (true)
                 return a
             return b
         }

         id: someItem // it would be confusing to call it `f` like the function
         property int alternative: f()
     }

## Declaring an object which is not a QML object as a list member

### What happened?

You added an expression other than an object into a list of objects.

### Why is this bad?

The QML language only allows objects in object lists.

### Example

     import QtQuick

     Item {
         property int hello
         property list<Item> myList: [
             Item {}, hello{}
         ]
     }

To fix this warning, use a valid object type, or remove the item from the list:

     import QtQuick

     Item {
         component Hello: Item {}
         property list<Item> myList: [
             Item {}, Hello{}
         ]
     }

## Unknown argument to pragma

### What happened?

You specified an invalid argument to a pragma.

### Why is this bad?

The pragma will have no effect.

### Example

     pragma ComponentBehavior: Buond
     import QtQuick

     Item {
     }

You can fix this warning by removing the pragma or fixing a potential typo:

     pragma ComponentBehavior: Bound
     import QtQuick

     Item {
     }

Signal handler parameters ◦ Duplicate id