Document lifetime of temporaries in conditions of if and while-expr #94
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Explain that temporaries created in the condition expression of an if or if/else are dropped immediately after the condition expression.
Explain that temporaries created in the loop conditional expression of a while expression are freed immediately after the loop conditional expression.
PieterPenninckx
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src/expressions.md
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| When a temporary rvalue is being created that is assigned into a `let` | ||
| declaration, however, the temporary is created with the lifetime of the | ||
| enclosing block instead, as using the enclosing statement (the `let` | ||
| A first exception is when a temporary value is created in the |
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The phrasing here seems odd and opens the possibility that there are more than two exceptions. Perhaps a paragraph stating "There are two exceptions to this rule." prior to the exceptions listings?
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You are right: it is odd. I don't know if there are still some exceptions missing, however.
Can someone confirm that there are no other exceptions missing? Then we can add "There are two exceptions to this rule."
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I'd argue that this is not an exception - the only exception is the let rule. It's just that the conditional of an if or while are counted as a single statement for the purposes of the rule.
Also, side note, you don't have to do the whole taking a reference thing in order to create a temporary object. If an rvalue is not assigned to an lvalue, or is not used to construct an object, then a temporary object is automatically created.
Reformulate text so that dropping of temporaries created in condition expression of an `if` or `if`/`else` or in the loop conditional expression of a `while` is now part of the rule, not an exception. Revert the paragraph concerning the `let` expression to its original form. Move examples. Include an example of a temporary without borrowing.
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Thanks! |
Explain that temporaries created in the condition expression of an
iforif/elseexpression are dropped immediately after the condition expression. Similar forwhile. See rust-lang/rust#12033