@lysdexic@programming.dev to Rust@programming.devEnglish • 8 months agoCommon Rust Lifetime Misconceptions (2020)github.commessage-square5fedilinkarrow-up138arrow-down11cross-posted to: rust@lemmy.ml
arrow-up137arrow-down1external-linkCommon Rust Lifetime Misconceptions (2020)github.com@lysdexic@programming.dev to Rust@programming.devEnglish • 8 months agomessage-square5fedilinkcross-posted to: rust@lemmy.ml
minus-square@hairyballs@programming.devlinkfedilink1•edit-28 months agoThere are still obvious things the BC cannot get. For example: struct Foo; impl Foo { fn num(&mut self) -> usize { 0 } fn index(&mut self, _i: usize) { } } let foo = Foo; foo.index(foo.num()); //error
minus-square@sirdorius@programming.devlinkfedilink2•edit-28 months agoThis looks like a pretty easy fix that the compiler could do by extracting the argument to a temp variable to improve the syntax of the language.
minus-square@KillTheMule@programming.devlinkfedilink1•edit-28 months agoNote that when you change num to take &self instead, this works out (you also need to mark foo as mutable, of course).
minus-square@hairyballs@programming.devlinkfedilink1•8 months agoIt’s a toy example. In that case, the solution is to assign the expression to a variable to compute its result upfront.
There are still obvious things the BC cannot get. For example:
struct Foo; impl Foo { fn num(&mut self) -> usize { 0 } fn index(&mut self, _i: usize) { } } let foo = Foo; foo.index(foo.num()); //errorThis looks like a pretty easy fix that the compiler could do by extracting the argument to a temp variable to improve the syntax of the language.
Note that when you change
numto take&selfinstead, this works out (you also need to markfooas mutable, of course).It’s a toy example. In that case, the solution is to assign the expression to a variable to compute its result upfront.