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https://github.com/rust-lang/rust
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4b3ece475d
Derive expansions for packed structs cause move errors because they prefer copying over borrowing since borrowing the fields of a packed struct can result in unaligned access and therefore undefined behaviour. This underlying cause of the errors, however, is not apparent to the user. We add a diagnostic note here to remedy that.
97 lines
3.5 KiB
Rust
97 lines
3.5 KiB
Rust
// Check that deriving builtin traits for a packed struct with
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// non-Copy fields emits move errors along with an additional
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// diagnostic note explaining the reason
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// See issue #117406
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use std::fmt::{Debug, Formatter, Result};
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use std::cmp::Ordering;
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// Packed + derives: additional diagnostic should be emitted
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// for each of Debug, PartialEq and PartialOrd
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#[repr(packed)]
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#[derive(Debug, PartialEq, Eq, PartialOrd, Ord, Hash, Clone, Default)]
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struct StructA(String);
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//~^ ERROR: cannot move out of `self` which is behind a shared reference
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//~| ERROR: cannot move out of `self` which is behind a shared reference
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//~| ERROR: cannot move out of `other` which is behind a shared reference
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//~| ERROR: cannot move out of `self` which is behind a shared reference
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//~| ERROR: cannot move out of `other` which is behind a shared reference
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//~| ERROR: cannot move out of `self` which is behind a shared reference
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//~| ERROR: cannot move out of `other` which is behind a shared reference
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//~| ERROR: cannot move out of `self` which is behind a shared reference
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//~| ERROR: cannot move out of `self` which is behind a shared reference
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// Unrelated impl: additinal diagnostic should NOT be emitted
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impl StructA {
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fn fmt(&self) -> String {
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self.0 //~ ERROR: cannot move out of `self` which is behind a shared reference
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}
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}
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// Packed + manual impls: additional diagnostic should NOT be emitted
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#[repr(packed)]
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struct StructB(String);
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impl Debug for StructB {
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fn fmt(&self, f: &mut Formatter) -> Result {
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let x = &{ self.0 }; //~ ERROR: cannot move out of `self` which is behind a shared reference
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write!(f, "{}", x)
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}
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}
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impl PartialEq for StructB {
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fn eq(&self, other: &StructB) -> bool {
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({ self.0 }) == ({ other.0 })
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//~^ ERROR: cannot move out of `self` which is behind a shared reference
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//~| ERROR: cannot move out of `other` which is behind a shared reference
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}
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}
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impl PartialOrd for StructB {
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fn partial_cmp(&self, other: &StructB) -> Option<Ordering> {
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PartialOrd::partial_cmp(&{ self.0 }, &{ other.0 })
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//~^ ERROR: cannot move out of `self` which is behind a shared reference
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//~| ERROR: cannot move out of `other` which is behind a shared reference
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}
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}
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// NOT packed + derives: additinal diagnostic should NOT be emitted
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#[derive(Debug, PartialEq, Eq, PartialOrd, Ord, Hash, Clone, Default)]
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struct StructC(String);
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// NOT packed + manual impls: additinal dignostic should NOT be emitted
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struct StructD(String);
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impl Debug for StructD {
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fn fmt(&self, f: &mut Formatter) -> Result {
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let x = &{ self.0 }; //~ ERROR: cannot move out of `self` which is behind a shared reference
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write!(f, "{}", x)
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}
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}
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impl PartialEq for StructD {
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fn eq(&self, other: &StructD) -> bool {
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({ self.0 }) == ({ other.0 })
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//~^ ERROR: cannot move out of `self` which is behind a shared reference
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//~| ERROR: cannot move out of `other` which is behind a shared reference
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}
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}
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impl PartialOrd for StructD {
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fn partial_cmp(&self, other: &StructD) -> Option<Ordering> {
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PartialOrd::partial_cmp(&{ self.0 }, &{ other.0 })
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//~^ ERROR: cannot move out of `self` which is behind a shared reference
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//~| ERROR: cannot move out of `other` which is behind a shared reference
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}
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}
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// Packed + derives but the move is outside of a derive
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// expansion: additinal diagnostic should NOT be emitted
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fn func(arg: &StructA) -> String {
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arg.0 //~ ERROR: cannot move out of `arg` which is behind a shared reference
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}
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fn main(){
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}
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