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Dart analyzer type inference with "is" type check #9666

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DartBot opened this issue Apr 4, 2013 · 13 comments
Closed

Dart analyzer type inference with "is" type check #9666

DartBot opened this issue Apr 4, 2013 · 13 comments
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@bwilkerson
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area-analyzer Use area-analyzer for Dart analyzer issues, including the analysis server and code completion. P2 A bug or feature request we're likely to work on type-enhancement A request for a change that isn't a bug

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@DartBot
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DartBot commented Apr 4, 2013

This issue was originally filed by @bp74

What steps will reproduce the problem?

class foo {
}

class oneFoo extends foo {
  bool coolProperty = true;
}

class twoFoo extends foo {
  bool coolProperty = true;
}

void main() {
  foo f = getFoo();

  // case 1:
  if (f is oneFoo)
    if (f.coolProperty)
      print("works fine!");
  
  // case 2:
  if (f is oneFoo && f.coolProperty)
    print("analyzer warning :(");

  // case 3:
  if (f is oneFoo || f is twoFoo)
    if (f.coolProperty)
      print("analyzer warning :(");
}

foo getFoo() {
  return new oneFoo();
}

What is the expected output? What do you see instead?

The source above shows three cases, only case 1 works without an analyzer warning.
I think all those cases should be accepted by the analyzer as valid code, especially because case 1 is supported too.

case 2 and case 3 give the warning:
"coolProperty" is not a member of foo

What version of the product are you using? On what operating system?

Dart Editor version 0.1.2_r20908
Dart SDK version 0.1.2.0_r20908

Please provide any additional information below.
@DartBot
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DartBot commented Apr 7, 2013

This comment was originally written by @bp74

Just tested with the new Dart Analyzer. The test "case 1" doesn't work too. So maybe it's better to write the code in another way anyway.

@bwilkerson
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Just tested with the new Dart Analyzer.

The new analyzer does not yet have any type inferencing in it, but will handle "is" when type inferencing is added.

Set owner to @bwilkerson.
Added this to the M5 milestone.
Added Area-Analyzer, AnalysisEngine, Triaged labels.

@DartBot
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DartBot commented Apr 7, 2013

This comment was originally written by amouravski@google.com

Added Editor-AnalysisEngine label.

@bwilkerson
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Case 1 is now working.

Removed Type-Defect, AnalysisEngine, Editor-AnalysisEngine labels.
Added Type-Enhancement label.

@kevmoo
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kevmoo commented Jun 2, 2013

I think I'm hitting the same issue:

  SwapComponent _getSwap() {
    final Element element = this.query('[is=x-tabs] > [is=x-swap]');
    if(element != null) {
      if(element is SwapComponent) {
        // Warning here:
        // The return type "Element" is not a 'SwapComponent', as defined by the method '_getSwap'
        return element;
      } else if(element.xtag is SwapComponent) {
        return element.xtag;
      }
    }
    return null;
  }

Attachment:
[Screen Shot 2013-06-02 at 3.28.24 PM.png](https://storage.googleapis.com/google-code-attachments/dart/issue-9666/comment-5/Screen Shot 2013-06-02 at 3.28.24 PM.png) (59.45 KB)

@bwilkerson
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Removed this from the M5 milestone.
Added this to the M6 milestone.

@bwilkerson
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Removed this from the M6 milestone.
Added this to the M7 milestone.

@jwren
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jwren commented Sep 19, 2013

M7 -> M8

Removed this from the M7 milestone.
Added this to the M8 milestone.

@bwilkerson
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Removed this from the M8 milestone.
Added this to the Later milestone.

@kasperl
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kasperl commented Jul 10, 2014

Removed this from the Later milestone.
Added Oldschool-Milestone-Later label.

@kasperl
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kasperl commented Aug 4, 2014

Removed Oldschool-Milestone-Later label.

@DartBot DartBot added Type-Enhancement area-analyzer Use area-analyzer for Dart analyzer issues, including the analysis server and code completion. labels Aug 4, 2014
@srawlins
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srawlins commented Oct 9, 2015

Cases 1 and 2 are working now. So it's just the if (f is oneFoo || f is twoFoo) case. Can this be merged into a different issue? I think there's a similar one.

https://dartpad.dartlang.org/df971af508f1de386994

@kevmoo kevmoo added P2 A bug or feature request we're likely to work on type-enhancement A request for a change that isn't a bug and removed triaged labels Feb 29, 2016
@bwilkerson
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Closing as stale.

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area-analyzer Use area-analyzer for Dart analyzer issues, including the analysis server and code completion. P2 A bug or feature request we're likely to work on type-enhancement A request for a change that isn't a bug
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@kevmoo @srawlins @jwren @kasperl @bwilkerson @DartBot