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Broken move semantics in decl_macro #46314
Description
Move semantics with declarative macros 2.0 are broken. Can copy non-copy types.
Playground
#![feature(decl_macro)]
#![allow(unused_macros)]
#[derive(Debug)]
struct NonCopy(String);
struct Foo {
x: NonCopy,
}
macro copy($foo:ident) {
$foo.x
}
macro_rules! copy2 {
($foo:ident) => {
$foo.x
}
}
fn main() {
let foo = Foo { x: NonCopy("foo".into()) };
assert_two_copies(copy!(foo), foo.x);
// A similar old-style macro will not work:
//assert_two_copies(copy2!(foo), foo.x);
}
fn assert_two_copies(a: NonCopy, b: NonCopy) {
println!("Got two copies: {:?}, {:?}", a, b);
}rustc --version --verbose:
rustc 1.23.0-nightly (63739ab7b 2017-11-21)
binary: rustc
commit-hash: 63739ab7b210c1a8c890c2ea5238a3284877daa3
commit-date: 2017-11-21
host: x86_64-unknown-linux-gnu
release: 1.23.0-nightly
LLVM version: 4.0
Reacted by Alex Burka
Activity
kennytm commentedon Nov 27, 2017
The error is caught when enabling MIR borrow-check (pass
-Z borrowck-miror-Z nll), so this is a HIR borrow-check-only issue.petrochenkov commentedon Nov 27, 2017
Probably some fields are compared by name without hygiene adjustments.
pnkfelix commentedon Dec 21, 2017
(tagging with nll labels just so we remember to look at this case when double checking lexical vs NLL.)
nikomatsakis commentedon Apr 3, 2018
We should file this under #47366, seems like?
petrochenkov commentedon Apr 3, 2018
It's very likely this is fixed on my field hygiene branch, I'll check.
valff commentedon Apr 3, 2018
@nikomatsakis Thanks for the reference. I will make a PR with a test for this bug soon.
Regression test for rust-lang#46314
Auto merge of #49642 - kennytm:rollup, r=kennytm
Auto merge of #49718 - petrochenkov:fieldcmp, r=eddyb