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Specify temporary for this as an input parameter #927

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Merged
merged 4 commits into from
Sep 20, 2023
Merged

Specify temporary for this as an input parameter #927

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8a20540
Specify temporary for `this` as an input parameter
BillWagner Sep 12, 2023
12f2e79
Specify defensive copy for other readonly variables
BillWagner Sep 12, 2023
34f77e6
fix formatting of nested list.
BillWagner Sep 14, 2023
0ecb733
Update expressions.md
BillWagner Sep 19, 2023
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7 changes: 6 additions & 1 deletion standard/expressions.md
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Expand Up @@ -1211,7 +1211,12 @@ The run-time processing of a function member invocation consists of the followin
- `M` is invoked.
- Otherwise, if the type of `E` is a value-type `V`, and `M` is declared or overridden in `V`:
- `E` is evaluated. If this evaluation causes an exception, then no further steps are executed. For an instance constructor, this evaluation consists of allocating storage (typically from an execution stack) for the new object. In this case `E` is classified as a variable.
- If `E` is not classified as a variable, then a temporary local variable of `E`’s type is created and the value of `E` is assigned to that variable. `E` is then reclassified as a reference to that temporary local variable. The temporary variable is accessible as `this` within `M`, but not in any other way. Thus, only when `E` is a true variable is it possible for the caller to observe the changes that `M` makes to `this`.
- If `E` is not classified as a variable, or if `V` is not a readonly struct type (§16.2.2), and `E` is one of:
- an input parameter (§15.6.2.3), or
- a `readonly` field (§15.5.3), or
- a `readonly` reference variable or return (§9.7),

then a temporary local variable of `E`’s type is created and the value of `E` is assigned to that variable. `E` is then reclassified as a reference to that temporary local variable. The temporary variable is accessible as `this` within `M`, but not in any other way. Thus, only when `E` can be written is it possible for the caller to observe the changes that `M` makes to `this`.
- The argument list is evaluated as described in [§12.6.2](expressions.md#1262-argument-lists).
- `M` is invoked. The variable referenced by `E` becomes the variable referenced by `this`.
- Otherwise:
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