diff options
author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-17 12:02:58 +0000 |
---|---|---|
committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-17 12:02:58 +0000 |
commit | 698f8c2f01ea549d77d7dc3338a12e04c11057b9 (patch) | |
tree | 173a775858bd501c378080a10dca74132f05bc50 /compiler/rustc_error_codes/src/error_codes/E0161.md | |
parent | Initial commit. (diff) | |
download | rustc-698f8c2f01ea549d77d7dc3338a12e04c11057b9.tar.xz rustc-698f8c2f01ea549d77d7dc3338a12e04c11057b9.zip |
Adding upstream version 1.64.0+dfsg1.upstream/1.64.0+dfsg1
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'compiler/rustc_error_codes/src/error_codes/E0161.md')
-rw-r--r-- | compiler/rustc_error_codes/src/error_codes/E0161.md | 45 |
1 files changed, 45 insertions, 0 deletions
diff --git a/compiler/rustc_error_codes/src/error_codes/E0161.md b/compiler/rustc_error_codes/src/error_codes/E0161.md new file mode 100644 index 000000000..ebd2c9769 --- /dev/null +++ b/compiler/rustc_error_codes/src/error_codes/E0161.md @@ -0,0 +1,45 @@ +A value was moved whose size was not known at compile time. + +Erroneous code example: + +```compile_fail,E0161 +#![feature(box_syntax)] +trait Bar { + fn f(self); +} + +impl Bar for i32 { + fn f(self) {} +} + +fn main() { + let b: Box<dyn Bar> = box (0 as i32); + b.f(); + // error: cannot move a value of type dyn Bar: the size of dyn Bar cannot + // be statically determined +} +``` + +In Rust, you can only move a value when its size is known at compile time. + +To work around this restriction, consider "hiding" the value behind a reference: +either `&x` or `&mut x`. Since a reference has a fixed size, this lets you move +it around as usual. Example: + +``` +#![feature(box_syntax)] + +trait Bar { + fn f(&self); +} + +impl Bar for i32 { + fn f(&self) {} +} + +fn main() { + let b: Box<dyn Bar> = box (0 as i32); + b.f(); + // ok! +} +``` |