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VM allows assignment in assert. #17682

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lrhn opened this issue Mar 21, 2014 · 4 comments
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VM allows assignment in assert. #17682

lrhn opened this issue Mar 21, 2014 · 4 comments
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@floitschG
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area-vm Use area-vm for VM related issues, including code coverage, FFI, and the AOT and JIT backends. type-bug Incorrect behavior (everything from a crash to more subtle misbehavior)

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@lrhn
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lrhn commented Mar 21, 2014 •
edited

Grammar of assert statements is:

'assert' '(' conditionalExpression ')' ';'

This does not allow assignment expressions directly as the expression.
The VM allows the syntax:

assert(x = true);

Analyzer now catches the syntax error.
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DartBot commented Apr 26, 2014

This comment was originally written by @chalin

Related: https://code.google.com/p/dart/issues/detail?id=12289

@lrhn lrhn added Type-Defect area-vm Use area-vm for VM related issues, including code coverage, FFI, and the AOT and JIT backends. labels Apr 26, 2014
@kevmoo kevmoo added type-bug Incorrect behavior (everything from a crash to more subtle misbehavior) and removed priority-unassigned labels Feb 29, 2016
@mhausner
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dart2js also allows assert(x = true). Both implementations are wrong. I suspect that there is code that may depend on this, maybe on purpose. For example, tests/standalone/io/file_constructor_test.dart.

void main() {
  bool developerMode = false;
  assert(developerMode = true);
  ....
  if (developerMode) ....

@mhausner
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@floitschG, please determine whether the language spec should be updated, or the two implementations should be fixed.

@eernstg
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eernstg commented Jul 12, 2016 •
edited

We discussed this issue in the language team and came up with the following analysis which concludes that we will switch to assert(expression): https://gist.github.com/eernstg/50a327addd96035d5393a507c0ea2d9a.

This means that the vm and dart2js already implement the right semantics, but the analyzer should be adjusted. Created a new issue for the adjustment of the analyzer and one for the spec.

@eernstg eernstg closed this as completed Jul 12, 2016
This was referenced Jul 12, 2016
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@munificent munificent mentioned this issue Dec 16, 2016
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@kevmoo @lrhn @mhausner @floitschG @DartBot @eernstg