# map_key_type_not_assignable

> Details about the map_key_type_not_assignable diagnostic produced by the Dart analyzer.



_The element type '{0}' can't be assigned to the map key type '{1}'._

## Description

The analyzer produces this diagnostic when a key of a key-value pair in a
map literal has a type that isn't assignable to the key type of the map.

## Example

The following code produces this diagnostic because `2` is an `int`, but
the keys of the map are required to be `String`s:

```dart
var m = <String, String>{[!2!] : 'a'};
```

## Common fixes

If the type of the map is correct, then change the key to have the correct
type:

```dart
var m = <String, String>{'2' : 'a'};
```

If the type of the key is correct, then change the key type of the map:

```dart
var m = <int, String>{2 : 'a'};
```

