The common front-end should give better error messages for the >>> operator.

[lrhn]

The >>> operator was added back to the Dart language specification for Dart 2.0.
It should be implemented as a valid overridable operator (#30888).

The current implementation still doesn't do so, and gives very odd error messages.

Example:

class C {                                                                       
  operator>>>(o) => this;
}
main() {
  C() >>> 42;
}

gives the errors:

tsh2.dart:2:11: Error: A method declaration needs an explicit list of parameters.
Try adding a parameter list to the method declaration.
  operator>>>(o) => this;
          ^^
tsh2.dart:2:13: Error: Expected '{' before this.
  operator>>>(o) => this;
            ^
tsh2.dart:2:11: Error: Operator '>>' should have exactly one parameter.
  operator>>>(o) => this;
          ^^
tsh2.dart:2:13: Error: Operator declarations must be preceeded by the keyword 'operator'.
Try adding the keyword 'operator'.
  operator>>>(o) => this;
            ^
tsh2.dart:5:9: Error: Expected an identifier, but got '>'.
  C() >>> 42;
        ^
tsh2.dart:1: Error: Too many positional arguments: 0 allowed, but 1 found.
Try removing the extra positional arguments.