OpenE2K
/
rust
2
0
Fork 0
Code Issues Pull Requests Projects Releases Wiki Activity

Rollup merge of #76059 - GuillaumeGomez:cleanup-e0764, r=Dylan-DPC,pickfire 

Clean up E0764

r? @Dylan-DPC
This commit is contained in:
Tyler Mandry 2020-08-31 19:18:18 -07:00 committed by GitHub
parent 934127cca5 153f966d00
commit 5033203121
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
1 changed files with 13 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

22
compiler/rustc_error_codes/src/error_codes/E0764.md
View File

@ -1,12 +1,4 @@
Mutable references (`&mut`) can only be used in constant functions, not statics
or constants. This limitation exists to prevent the creation of constants that
have a mutable reference in their final value. If you had a constant of `&mut
i32` type, you could modify the value through that reference, making the
constant essentially mutable. While there could be a more fine-grained scheme
in the future that allows mutable references if they are not "leaked" to the
final value, a more conservative approach was chosen for now. `const fn` do not
have this problem, as the borrow checker will prevent the `const fn` from
returning new mutable references.
A mutable reference was used in a constant.
Erroneous code example:
@ -19,6 +11,18 @@ fn main() {
}
```
Mutable references (`&mut`) can only be used in constant functions, not statics
or constants. This limitation exists to prevent the creation of constants that
have a mutable reference in their final value. If you had a constant of
`&mut i32` type, you could modify the value through that reference, making the
constant essentially mutable.
While there could be a more fine-grained scheme in the future that allows
mutable references if they are not "leaked" to the final value, a more
conservative approach was chosen for now. `const fn` do not have this problem,
as the borrow checker will prevent the `const fn` from returning new mutable
references.
Remember: you cannot use a function call inside a constant or static. However,
you can totally use it in constant functions: