Embrace optional new/const in the language tour #940
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cla: yes
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Hmm, if you open the staged page's Console, there are lots of errors there. |
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Rebasing (to get #941), will help with the Travis errors. |
| // #enddocregion const-context-noconst | ||
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| // Same instances! | ||
| assert(identical(pointAndLine1, pointAndLine2)); |
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Suggestions:
- Use
expect() constvalues are canonicalized, so you can use==
E.g.,
expect(pointAndLine1 == pointAndLine2, isTrue);
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This is what I see in the JS console (maybe these are from the embedded DartPad? cc @jcollins-g): |
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I see what looks like the same console errors in https://www.dartlang.org/guides/language/language-tour. I think we need to remove all the embedded DartPads (in another PR) to fix this (#422). |
| add back the comments that are still relevant. | ||
| 4. Run `./scripts/analyze-and-test-examples.sh` to confirm that | ||
| your changes are good. | ||
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Thanks for adding these helpful instructions.
| {% prettify dart %} | ||
| final p = const ImmutablePoint(2, 2); | ||
| {% endprettify %} | ||
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| Constructing two identical compile-time constants results in a single, |
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I know that this is from before, but maybe we should link to identical() here?
The definition is already given at the end of this file:
[identical()]: {{site.dart_api}}/{{site.data.pkg-vers.SDK.channel}}/dart-core/identical.html
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I'm going to leave this out, because I'd rather not add more words.
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| <aside class="alert alert-info" markdown="1"> | ||
| **Version note:** The `const` keyword became optional | ||
| (within a constant context) in Dart 2. |
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Maybe drop the parentheses?
| @@ -61,7 +66,7 @@ void main() { | |||
| test('const, identical, runtimeType', () { | |||
| _test() { | |||
| // #docregion const | |||
| var p = const ImmutablePoint(2, 2); | |||
| final p = const ImmutablePoint(2, 2); | |||
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Why this change from var to final?
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I was wondering if you'd catch that. :) I don't remember why I changed it. I think it was a side effect of the DartPad changes I was making. I'll change it back.
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@kwalrath Removing all the embedded dartpads seems like an unfortunate consequence. The errors look like they might be a consequence of having an embedded Dartpad, but exactly why isn't clear. Filing an issue. |
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Added more information about the new errors to dart-lang/dart-pad#791. |
Contributes to #870, #507.
Staged: https://kw-www-dartlang-1.firebaseapp.com/guides/language/language-tour#using-constructors