analysis feedback changes if you include sky_engine in your project

[sethladd]

Repro case and instructions here: https://gist.github.com/sethladd/79b6d1cdcc9d3b29b5e3acc27581944a

We'd expect there to be no warnings for the code in lib/main.dart, however the inclusion of sky_engine package into .packages is enough to trigger the warning.

The warning we get:

[warning] Unsound implicit cast from 'List<dynamic>' to 'List<Bar>'. (/Users/sethladd/tmp/repocase/lib/main.dart, line 8, col 23)

Which, we're told, is something we shouldn't be getting. The code should be valid (we're told).

Tested with:

~/tmp/repocase $ dartanalyzer --version
dartanalyzer version 1.21.0-dev.4.0

[sethladd]

cc @danrubel who might help us understand how the analyzer is constructing its configuration

(maybe we need something like "dartanalyzer --show-configuration" ?)

[sethladd]

cc @yyoon as our customer

[sethladd]

cc @leafpetersen to confirm our code is correct?

[leafpetersen]

That code should be strong mode clean, and I see no errors if I run the regular strong mode analyzer on it (I didn't try to reproduce the sky_engine issue).

I believe that flutter uses their own version of the SDK, so perhaps that has something to do with it? That error is what I would expect to see if List.map was not properly annotated as a generic method.

[sethladd]

I believe that flutter uses their own version of the SDK

I'm analyzing with "dartanalyzer", from homebrew, version 1.21.0-dev.4.0.

The variable here isn't "dartanalyzer" or "flutter analyze", it's "is sky_engine in my .packages".

[leafpetersen]

The variable here isn't "dartanalyzer" or "flutter analyze", it's "is sky_engine in my .packages".

I don't know where the external version of sky_engine lives (the pub.dartlang version looks way out of date, and 404s on the link to the source code), but looking at the internal version I see a copy of the dart sdk. This makes me.... suspicious... :) I don't know why it's there if it's not being used, and if it's being used, then it seems relevant to this problem.

It's possible that this is a general analyzer bug - there was a caching issue that @stereotype441 just fixed that caused some strange inference problems, but this looks pretty unlikely to be related to me.

I know very little about how flutter works, but I know there's some voodoo going on with the "dart:flutter" etc URIs. That seems like the most likely problem to me: that importing sky_engine is causing a different SDK to be used because of some of this voodoo.

[sethladd]

I don't know where the external version of sky_engine lives

Oh, sorry. It comes from the Flutter SDK, which you clone from github.

We can try to track this down with Dan R. Meanwhile, thanks for confirming that the code should be strong mode clean. That helps eliminate a variable.

[leafpetersen]

Here's something you can try: make the following change to the code:

  List<Bar> barList = fooList.map/*<Bar>*/((Foo f) => new Bar(f)).toList();

and see what happens.

If you get an error about number of type parameters, then it is an issue with the definition of Iterable.map that you are picking up.

If that makes the error go away, then you have a correct definition of Iterable.map, but something is causing the inference of the generic type parameter to fail.

[sethladd]

sky_engine's version of iterable.dart has Iterable/*<T>*/ map/*<T>*/(/*=T*/ f(E e)) => new MappedIterable<E, dynamic/*=T*/>(this, f);

which I guess is correct/up-to-date?

[leafpetersen]

Looks right to me.

[leafpetersen]

But there are failure modes that the test that I suggested above might suss out, so I would try it.

For example, something may be causing the sky_engine sdk to be analyzed in a non-strong mode, resulting in an analyzer context which is non-strong, which is then used to analyze lib/main.dart in strong mode. Hijinks ensue.

[yyoon]

I tried adding the /*<Bar>*/ comment as suggested, and here's the result:

youngseokyoon temp$ dartanalyzer .
Analyzing [.]...
[error] The type '((Foo) → dynamic) → Iterable<dynamic>' is declared with 0 type parameters, but 1 type arguments were given. (/usr/local/google/home/youngseokyoon/Programming/temp/lib/foo.dart, line 12, col 31)
[warning] Unsound implicit cast from 'List<dynamic>' to 'List<Bar>'. (/usr/local/google/home/youngseokyoon/Programming/temp/lib/foo.dart, line 12, col 23)
[lint] Document all public members (/usr/local/google/home/youngseokyoon/Programming/temp/lib/foo.dart, line 1, col 7)
1 error, 1 warning and 1 lint found.