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invalid_use_of_null_value

An expression whose value is always 'null' can't be dereferenced.

Description

#

The analyzer produces this diagnostic when an expression whose value will always be null is dereferenced.

Example

#

The following code produces this diagnostic because x will always be null:

dart
int f(Null x) {
  return x.length;
}

Common fixes

#

If the value is allowed to be something other than null, then change the type of the expression:

dart
int f(String? x) {
  return x!.length;
}