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Syntax for readonly and T #476

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jclark opened this issue Apr 5, 2020 · 4 comments
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Syntax for readonly and T #476

jclark opened this issue Apr 5, 2020 · 4 comments
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enhancement Enhancement to language design implementation/done Implementation Done lang Relates to the Ballerina language specification
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Swan Lake preview 1

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jclark commented Apr 5, 2020

We need to a syntax to specify that something is readonly and belongs to type T.

The immutability proposal uses readonly<T>.

Another approach is to add intersection types using & as the intersection operator, so you would say readonly & T.

This is part of #189.
@jclark jclark added enhancement Enhancement to language design lang Relates to the Ballerina language specification labels Apr 5, 2020
@jclark jclark added this to the 2020R2 milestone Apr 5, 2020
@jclark jclark self-assigned this Apr 5, 2020
@jclark jclark mentioned this issue Apr 5, 2020
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jclark commented Apr 5, 2020

A couple of questions to consider:

  • are there existing features that could be expressed with intersection?
  • how does this interact with the *T; feature of records and objects?

@jclark jclark mentioned this issue Apr 6, 2020
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jclark commented Apr 7, 2020

Current consensus is to use T & readonly.

@MaryamZi MaryamZi mentioned this issue Apr 8, 2020
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@jclark jclark mentioned this issue Apr 13, 2020
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jclark commented Apr 13, 2020

I think it might be possible to express lax static typing in terms of intersection. See #488.

@jclark jclark modified the milestones: 2020R3, 2020R2 Apr 24, 2020
@hasithaa hasithaa added the implementation/inprogress Implementation inprogress label Apr 27, 2020
@jclark jclark added the status/inprogress Fixes are in the process of being added label May 1, 2020
jclark added a commit that referenced this issue May 1, 2020
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Add section on intersection types
b81c657 
Part of #476.
jclark added a commit that referenced this issue May 1, 2020
@jclark
Add intersection to type descriptor table
5d5da03 
Part of #476
jclark added a commit that referenced this issue May 1, 2020
@jclark
Note that readonly can be used with intersection
1d0d996 
Part of #476.
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jclark commented May 1, 2020

This is now done.

@jclark jclark closed this as completed May 1, 2020
@jclark jclark removed the status/inprogress Fixes are in the process of being added label May 1, 2020
@jclark jclark mentioned this issue May 1, 2020
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jclark added a commit that referenced this issue May 1, 2020
@jclark
Mention intersection types in changes
bdce017 
Part of #476
This was referenced May 14, 2020
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@hasithaa hasithaa added the implementation/done Implementation Done label Jun 17, 2020
@hasithaa hasithaa removed the implementation/inprogress Implementation inprogress label Jun 17, 2020
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