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mraleph opened this issue May 23, 2018 · 8 comments
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errors thrown by constant evaluator are unreadable #33216

mraleph opened this issue May 23, 2018 · 8 comments
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@a-siva
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area-vm Use area-vm for VM related issues, including code coverage, and the AOT and JIT backends. P2 A bug or feature request we're likely to work on
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Dart 2.1.1

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@mraleph
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mraleph commented May 23, 2018 

 class B {
   const B(int v);
 }

 const dynamic c = "";

 void foo([x = const B(c)]) { }

 void main() {
   foo();
 }

results in

$ out/ReleaseX64/dart --preview-dart-2 /tmp/error.dart
Unhandled exception:
'file:///tmp/error.dart': error: Not a constant expression:  is not an instance of Type: class 'int'
#0      main (file:///tmp/error.dart:11:3)
#1      _startIsolate.<anonymous closure> (dart:isolate/runtime/libisolate_patch.dart:279:19)
#2      _RawReceivePortImpl._handleMessage (dart:isolate/runtime/libisolate_patch.dart:165:12)

Not that the top-most frame does not actually point to the location of the type error - it points to the invocation of foo within the main.

The type error itself is very different from how VM reports other similar type errors.

Other cases:

 class A {
   const A(int v);
 }

 class C {
   const C(int v);
 }

 class B extends C {
   const B._(v) : super(v);

   const B(v) : this._(v);
 }

 const dynamic c = "";

 void foo([x = const B(c)]) { }

 void main() {
   foo();
 }

produces unreadable (notice double "Unhandled exception" and no location information on frame #1)

$ out/ReleaseX64/dart --preview-dart-2 /tmp/error.dart
Unhandled exception:
Unhandled exception:
type 'String' is not a subtype of type 'int'
#0      new B._ (file:///tmp/error.dart:11:24)
#1      new B (file:///tmp/error.dart)
#2      main (file:///tmp/error.dart:21:3)
#3      _startIsolate.<anonymous closure> (dart:isolate/runtime/libisolate_patch.dart:279:19)
#4      _RawReceivePortImpl._handleMessage (dart:isolate/runtime/libisolate_patch.dart:165:12)
error: error evaluating constant constructor
#0      main (file:///tmp/error.dart:21:3)
#1      _startIsolate.<anonymous closure> (dart:isolate/runtime/libisolate_patch.dart:279:19)
#2      _RawReceivePortImpl._handleMessage (dart:isolate/runtime/libisolate_patch.dart:165:12)

while

class A {
   const A(int v);
 }

 class C {
   const C(int v);
 }

 class B extends C {
   const B._(v, {x: const C(c)}) : super(v);

   const B(v) : this._(v);
 }

 const dynamic c = "";

 void foo([x = const B(c)]) { }

 void main() {
   foo();
 }

produces

$ out/ReleaseX64/dart --preview-dart-2 /tmp/error.dart
Unhandled exception:
Unhandled exception:
'file:///tmp/error.dart': error: Not a constant expression:  is not an instance of Type: class 'int'
#0      new B (file:///tmp/error.dart)
#1      main (file:///tmp/error.dart:21:3)
#2      _startIsolate.<anonymous closure> (dart:isolate/runtime/libisolate_patch.dart:279:19)
#3      _RawReceivePortImpl._handleMessage (dart:isolate/runtime/libisolate_patch.dart:165:12)
error: error evaluating constant constructor
#0      main (file:///tmp/error.dart:21:3)
#1      _startIsolate.<anonymous closure> (dart:isolate/runtime/libisolate_patch.dart:279:19)
#2      _RawReceivePortImpl._handleMessage (dart:isolate/runtime/libisolate_patch.dart:165:12)
@mraleph mraleph added area-vm Use area-vm for VM related issues, including code coverage, and the AOT and JIT backends. P0 A serious issue requiring immediate resolution area-kernel labels May 23, 2018
@mraleph mraleph added this to the Dart2Stable milestone May 23, 2018
@mraleph
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mraleph commented May 23, 2018

@kmillikin please select priority

@matanlurey
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THank you @mraleph (and @kmillikin)!

@kmillikin kmillikin added P2 A bug or feature request we're likely to work on and removed P0 A serious issue requiring immediate resolution labels May 24, 2018
@kmillikin kmillikin assigned a-siva and unassigned kmillikin Jun 15, 2018
@kmillikin
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I don't think there's anything we need to put in Kernel for the VM to generate a better error. @a-siva can you reassign to someone on the VM team? (Also, consider whether this is in scope for Dart2Stable.)

If it turns out we need to change something in Kernel, let us know.

@jensjoha
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jensjoha commented Jul 6, 2018

With https://dart-review.googlesource.com/c/sdk/+/63883 I get

Unhandled exception:
'[...]/issue_33216.dart': error: line 7 pos 24: Not a constant expression: Type 'String' is not a subtype of type 'int'
 void foo([x = const B(c)]) { }
                       ^

#0      main ([...]/issue_33216.dart:10:4)
#1      _startIsolate.<anonymous closure> (dart:isolate/runtime/libisolate_patch.dart:279:19)
#2      _RawReceivePortImpl._handleMessage (dart:isolate/runtime/libisolate_patch.dart:165:12)

then

Unhandled exception:
Unhandled exception:
type 'String' is not a subtype of type 'int'
#0      new B._ ([...]/issue_33216.dart:10:25)
#1      new B ([...]/issue_33216.dart:12:22)
#2      main ([...]/issue_33216.dart:20:4)
#3      _startIsolate.<anonymous closure> (dart:isolate/runtime/libisolate_patch.dart:279:19)
#4      _RawReceivePortImpl._handleMessage (dart:isolate/runtime/libisolate_patch.dart:165:12)
'[...]/issue_33216.dart': error: line 17 pos 22: error evaluating constant constructor
 void foo([x = const B(c)]) { }
                     ^

#0      main ([...]/issue_33216.dart:20:4)
#1      _startIsolate.<anonymous closure> (dart:isolate/runtime/libisolate_patch.dart:279:19)
#2      _RawReceivePortImpl._handleMessage (dart:isolate/runtime/libisolate_patch.dart:165:12)

and finally

Unhandled exception:
Unhandled exception:
'[...]/issue_33216.dart': error: line 10 pos 29: Not a constant expression: Type 'String' is not a subtype of type 'int'
   const B._(v, {x: const C(c)}) : super(v);
                            ^

#0      new B ([...]/issue_33216.dart:12:22)
#1      main ([...]/issue_33216.dart:20:4)
#2      _startIsolate.<anonymous closure> (dart:isolate/runtime/libisolate_patch.dart:279:19)
#3      _RawReceivePortImpl._handleMessage (dart:isolate/runtime/libisolate_patch.dart:165:12)
'[...]/issue_33216.dart': error: line 17 pos 22: error evaluating constant constructor
 void foo([x = const B(c)]) { }
                     ^

#0      main ([...]/issue_33216.dart:20:4)
#1      _startIsolate.<anonymous closure> (dart:isolate/runtime/libisolate_patch.dart:279:19)
#2      _RawReceivePortImpl._handleMessage (dart:isolate/runtime/libisolate_patch.dart:165:12)

Stuff like

Unhandled exception:
Unhandled exception:

might not be great, but --no-preview-dart-2 --checked does that too.

dart-bot pushed a commit that referenced this issue Jul 9, 2018
@jensjoha
More positions in dart2 constant evaluator
d26dba1 
Use positions already available in for instance AsExpressions,
also adds new offsets in the kernel format to
SuperInitializer and RedirectingInitializer.

Bug: #33216
Change-Id: I542967ddc6ec782e6513d62fce038a49239e1622
Reviewed-on: https://dart-review.googlesource.com/63883
Commit-Queue: Jens Johansen <jensj@google.com>
Reviewed-by: Vyacheslav Egorov <vegorov@google.com>
@dgrove
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dgrove commented Jul 9, 2018

After talking with @kevmoo:

  • Dart Analyzer messages are fine for these cases
  • Dart VM messages are not too bad (given @jensjoha 's report)

Moving to Dart 2.1

@dgrove dgrove modified the milestones: Dart2Stable, Dart2.1 Jul 9, 2018
@a-siva
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a-siva commented Jul 9, 2018

The error messages reported by Dart VM after the changes made by @jensjoha are consistent with what was being generated by Dart 1.
I would close this and open a new enhancement issue with more details on generating consistent error messages across the different tools.

@zoechi zoechi mentioned this issue Jul 17, 2018
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@dgrove
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dgrove commented Oct 9, 2018

@a-siva any updates for 2.1?

@a-siva
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a-siva commented Oct 11, 2018

See comment above, I believe this issue can be closed unless somebody disagrees with that.

@dgrove dgrove closed this as completed Oct 11, 2018
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@mraleph @matanlurey @kmillikin @dgrove @a-siva @jensjoha