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Commit 8ed9589
Auto merge of #143376 - dianne:guard-scope, r=matthewjasper
add a scope for `if let` guard temporaries and bindings
This fixes my concern with `if let` guard drop order, namely that the guard's bindings and temporaries were being dropped after their arm's pattern's bindings, instead of before (rust-lang/rust#141295 (comment)). The guard's bindings and temporaries now live in a new scope, which extends until (but not past) the end of the arm, guaranteeing they're dropped before the arm's pattern's bindings.
This only introduces a new scope for match arms with guards. Perf results (rust-lang/rust#143376 (comment)) seemed to indicate there wasn't a significant hit to introduce a new scope on all match arms, but guard patterns (rust-lang/rust#129967) will likely benefit from only adding new scopes when necessary (with some patterns requiring multiple nested scopes).
Tracking issue for `if_let_guard`: rust-lang/rust#51114
Tests are adapted from examples by `@traviscross,` `@est31,` and myself on rust-lang/rust#141295.File tree
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