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Clarify semantics of with expression. (#3690)

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AlekseyTs 2020-07-15 16:02:56 -07:00 committed by GitHub
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proposals/records.md
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@ -275,13 +275,12 @@ A `with` expression allows for "non-destructive mutation", designed to
produce a copy of the receiver expression with modifications in assignments
in the `member_initializer_list`.
A valid `with` expression has a receiver with a non-void type. The receiver type must contain an
accessible synthesized record "clone" method.
A valid `with` expression has a receiver with a non-void type. The receiver type must be a record.
On the right hand side of the `with` expression is a `member_initializer_list` with a sequence
of assignments to *identifier*, which must be an accessible instance field or property of the return
type of the `Clone()` method.
of assignments to *identifier*, which must be an accessible instance field or property of the receiver's
type.
Each `member_initializer` is processed the same way as an assignment to a field or property
access of the return value of the record clone method. The clone method is executed only once
and the assignments are processed in lexical order.
First, receiver's "clone" method (specified above) is invoked and its result is converted to the
receiver's type. Then, each `member_initializer` is processed the same way as an assignment to
a field or property access of the result of the conversion. Assignments are processed in lexical order.