Analyzer missing error for 'this' access in a constructor assert

[DanTup]

After some refactoring I ended up with code like this:

class Danny {
  int length;
  Danny(String str)
      : length = str.length,
        assert(length != null);
}

I forgot to update the assert to check str, and although this code gives no analysis-time warnings, it fails to run with this compile error:

Compiler message:

lib/src/painter.dart:277:16: Error: Can't access 'this' in a field initializer to read 'length'.
        assert(length != null);
               ^^^^^^

I think there could/should be an analysis error for this if it's not valid.

[devoncarew]

@stereotype441, is this a an issue in the analyzer (for not warning) or in the CFE (for the runtime error)?

[stereotype441]

I believe the error is correct, and the bug is in the analyzer.

[lrhn]

The bug is in the analyzer.
The length in the assert refers to the instance field, making it equivalent to this.length, and you cannot access this (or instance fields) in initializer lists.

The places where you can access instance methods, or this at all, are:

• Instance member bodies.
• Constructor bodies.
  (The this in initializer lists or initializing formals are simply syntactic forms, they do not refer to the object).

If this occurs as an expression anywhere else, it is an error. If an implicit access to an instance field occurs anywhere else, it is an error.
(The C(this.length) : assert(length != 0); constructor assert does not reference the instance field, it references a new final variable with the same name introduced by the initilaizing formal, no this involved)

[lrhn]

Appears to be fixed.