type_literal_in_constant_pattern

Use 'TypeName _' instead of a type literal.

The analyzer produces this diagnostic when a type literal appears as a pattern.

The following code produces this diagnostic because a type literal is used as a constant pattern:

void f(Object? x) {
  if (x case num) {
    // ...
  }
}

If the type literal is intended to match an object of the given type, then use either a variable pattern:

void f(Object? x) {
  if (x case num _) {
    // ...
  }
}

Or an object pattern:

void f(Object? x) {
  if (x case num()) {
    // ...
  }
}

If the type literal is intended to match the type literal, then write it as a constant pattern:

void f(Object? x) {
  if (x case const (num)) {
    // ...
  }
}

Unless stated otherwise, the documentation on this site reflects Dart 3.8.1. Page last updated on 2025-05-08. View source or report an issue.