rust/tests/ui/borrowck/borrowck-use-uninitialized-in-cast-trait.rs

// Variation on `borrowck-use-uninitialized-in-cast` in which we do a
// trait cast from an uninitialized source. Issue #20791.

trait Foo { fn dummy(&self) { } }
impl Foo for i32 { }

fn main() {
    let x: &i32;
    let y = x as *const dyn Foo; //~ ERROR [E0381]
}
Modify the ExprUseVisitor to walk each part of an AutoRef, and in particular to treat an AutoUnsize as as kind of "instantaneous" borrow of the value being unsized. This prevents us from feeding uninitialized data. This caused a problem for the eager reborrow of comparison traits, because that wound up introducing a "double AutoRef", which was not being thoroughly checked before but turned out not to type check. Fortunately, we can just remove that "eager reborrow" as it is no longer needed now that `PartialEq` doesn't force both LHS and RHS to have the same type (and even if we did have this problem, the better way would be to lean on introducing a common supertype). 2015-04-08 08:31:51 +00:00			// Variation on `borrowck-use-uninitialized-in-cast` in which we do a
			`// trait cast from an uninitialized source. Issue #20791.`

			`trait Foo { fn dummy(&self) { } }`
			`impl Foo for i32 { }`

			`fn main() {`
			`let x: &i32;`
Update ui test suite to use dyn 2019-05-28 18:46:13 +00:00			`let y = x as *const dyn Foo; //~ ERROR [E0381]`
Modify the ExprUseVisitor to walk each part of an AutoRef, and in particular to treat an AutoUnsize as as kind of "instantaneous" borrow of the value being unsized. This prevents us from feeding uninitialized data. This caused a problem for the eager reborrow of comparison traits, because that wound up introducing a "double AutoRef", which was not being thoroughly checked before but turned out not to type check. Fortunately, we can just remove that "eager reborrow" as it is no longer needed now that `PartialEq` doesn't force both LHS and RHS to have the same type (and even if we did have this problem, the better way would be to lean on introducing a common supertype). 2015-04-08 08:31:51 +00:00			`}`