45 lines
1.7 KiB
Markdown
45 lines
1.7 KiB
Markdown
# expression variables in initializers
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* [x] Proposed
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* [ ] Prototype: None
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* [ ] Implementation: None
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* [ ] Specification: See below
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## Summary
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[summary]: #summary
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We extend the features introduced in C# 7 to permit expressions containing expression variables (out variable declarations and declaration patterns) in field initializers, property initializers, ctor-initializers, and query clauses.
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## Motivation
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[motivation]: #motivation
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This completes a couple of the rough edges left in the C# language due to lack of time.
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## Detailed design
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[design]: #detailed-design
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We remove the restriction preventing the declaration of expression variables (out variable declarations and declaration patterns) in a ctor-initializer. Such a declared variable is in scope throughout the body of the constructor.
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We remove the restriction preventing the declaration of expression variables (out variable declarations and declaration patterns) in a field or property initializer. Such a declared variable is in scope throughout the initializing expression.
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We remove the restriction preventing the declaration of expression variables (out variable declarations and declaration patterns) in a query expression clause that is translated into the body of a lambda. Such a declared variable is in scope throughout that expression of the query clause.
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## Drawbacks
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[drawbacks]: #drawbacks
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None.
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## Alternatives
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[alternatives]: #alternatives
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The appropriate scope for expression variables declared in these contexts is not obvious, and deserves further LDM discussion.
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## Unresolved questions
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[unresolved]: #unresolved-questions
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- [ ] What is the appropriate scope for these variables?
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## Design meetings
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None.
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