prefix_shadowed_by_local_declaration

The prefix '{0}' can't be used here because it's shadowed by a local declaration.

The analyzer produces this diagnostic when an import prefix is used in a context where it isn't visible because it was shadowed by a local declaration.

The following code produces this diagnostic because the prefix a is being used to access the class Future, but isn't visible because it's shadowed by the parameter a:

import 'dart:async' as a;
​
a.Future? f(int a) {
  a.Future? x;
  return x;
}

Rename either the prefix:

import 'dart:async' as p;
​
p.Future? f(int a) {
  p.Future? x;
  return x;
}

Or rename the local variable:

import 'dart:async' as a;
​
a.Future? f(int p) {
  a.Future? x;
  return x;
}