specify lifetime extension of pin! and format_args! arguments
#1980
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- Removes an unused trait and impl from the successful tests. - Adds uses following all tests so they test lifetime extension.
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| @@ -434,6 +434,7 @@ expression which is one of the following: | |||
| expression], [braced struct][struct expression], or [tuple][tuple expression] | |||
| expression. | |||
| * The arguments to an extending [tuple struct] or [tuple variant] constructor expression. | |||
| * The argument(s) to an extending [`pin!`] or [`format_args!`] [macro invocation] expression. | |||
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Ideally this should be clearer about the format arguments being extended, not the format string (which doesn't need extension), but I've had trouble including that detail without breaking the flow/clarity of the section
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| r[destructors.scope.lifetime-extension.exprs.borrow] | ||
| The operand of any extending borrow expression has its temporary scope | ||
| extended. | ||
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| r[destructors.scope.lifetime-extension.exprs.macros] | ||
| The built-in macros [`pin!`] and [`format_args!`] create temporaries. | ||
| Any extending [`pin!`] or [`format_args!`] [macro invocation] expression has an extended temporary scope. |
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Fourth pass: I've broken up destructors.scope.lifetime-extension.exprs to match destructors.scope.lifetime-extension.patterns and to put the rule for built-in macros' temporaries in a subsection. I've also moved the rule for arguments' extension back into the the newly-delimited rule destructors.scope.lifetime-extension.exprs.extending. I'm not satisfied with the wording yet, but structurally I think it's an improvement.
I'm doing a bit of conflation here. The "temporaries" here are both:
super letbindings; since they have (extended) temporary scopes, I feel like referring to them as "temporaries" is most fitting for the moment.- The borrowed temporaries created when a value expression is passed to
format_args!.
Let me know if it needs further clarification. My hope is that it's a suitable level of detail for how these macros behave, to avoid specifying their exact expansion.
Reference PR for rust-lang/rust#145838, given the
format_args!change in rust-lang/rust#145882. cc @m-ou-seBased on #1979; the first commit is the commit from that PR.