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Initialization by assignment not allowed for "drop-ful" types in constants. #62273
Description
In the following example, FOO and ASSIGN are allowed but FOO_ASSIGN isn't:
pub struct Foo;
impl Drop for Foo {
fn drop(&mut self) {}
}
pub const FOO: Foo = { let x = Foo; x };
pub const ASSIGN: i32 = { let x; x = 0; x };
pub const FOO_ASSIGN: Foo = { let x; x = Foo; x };The reason is that x = Foo; is lowered to DropAndReplace in MIR, and that's not handled in const-checking as a Drop and an assignment (which it functionally is).
cc @davidtwco This might also break the [constant; N] promotion (while &T promotion would never encounter DropAndReplace because &T is always Copy).
EDIT: nevermind, promotion works based on temporaries, so it shouldn't be affected.
Activity
Centril commentedon Jul 1, 2019
I'm going to label this as a bug since it seems covered by #57175 from a T-Lang perspective.
Rollup merge of rust-lang#62275 - eddyb:const-drop-replace, r=pnkfelix