avoid_single_cascade_in_expression_statements

Unnecessary cascade expression.

The analyzer produces this diagnostic when a single cascade operator is used and the value of the expression isn't being used for anything (such as being assigned to a variable or being passed as an argument).

The following code produces this diagnostic because the value of the cascade expression s..length isn't being used:

void f(String s) {
  s..length;
}

Replace the cascade operator with a simple access operator:

void f(String s) {
  s.length;
}