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use_of_void_result

This expression has a type of 'void' so its value can't be used.

Description

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The analyzer produces this diagnostic when it finds an expression whose type is void, and the expression is used in a place where a value is expected, such as before a member access or on the right-hand side of an assignment.

Example

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The following code produces this diagnostic because f doesn't produce an object on which toString can be invoked:

dart
void f() {}

void g() {
  f().toString();
}

Common fixes

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Either rewrite the code so that the expression has a value or rewrite the code so that it doesn't depend on the value.