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Cover more cases in the test suite

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This commit is contained in:
oli 2021-01-23 11:58:58 +00:00
parent 14f39aa81a
commit cd09871157
4 changed files with 99 additions and 38 deletions
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45
src/test/ui/consts/const-mut-refs/mut_ref_in_final.rs
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@ -1,6 +1,9 @@
#![feature(const_mut_refs)]
#![feature(const_fn)]
#![feature(const_transmute)]
#![feature(raw_ref_op)]
#![feature(const_raw_ptr_deref)]
const NULL: *mut i32 = std::ptr::null_mut();
const A: *const i32 = &4;
@ -9,6 +12,25 @@ const A: *const i32 = &4;
// as that would be an enormous footgun in oli-obk's opinion.
const B: *mut i32 = &mut 4; //~ ERROR mutable references are not allowed
// Ok, no actual mutable allocation exists
const B2: Option<&mut i32> = None;
// Not ok, can't prove that no mutable allocation ends up in final value
const B3: Option<&mut i32> = Some(&mut 42); //~ ERROR temporary value dropped while borrowed
const fn helper() -> Option<&'static mut i32> { unsafe {
// Undefined behaviour, who doesn't love tests like this.
// This code never gets executed, because the static checks fail before that.
Some(&mut *(42 as *mut i32))
} }
// Check that we do not look into function bodies.
// We treat all functions as not returning a mutable reference, because there is no way to
// do that without causing the borrow checker to complain (see the B5/helper2 test below).
const B4: Option<&mut i32> = helper();
const fn helper2(x: &mut i32) -> Option<&mut i32> { Some(x) }
const B5: Option<&mut i32> = helper2(&mut 42); //~ ERROR temporary value dropped while borrowed
// Ok, because no references to mutable data exist here, since the `{}` moves
// its value and then takes a reference to that.
const C: *const i32 = &{
@ -17,7 +39,30 @@ const C: *const i32 = &{
x
};
use std::cell::UnsafeCell;
struct NotAMutex<T>(UnsafeCell<T>);
unsafe impl<T> Sync for NotAMutex<T> {}
const FOO: NotAMutex<&mut i32> = NotAMutex(UnsafeCell::new(&mut 42));
//~^ ERROR temporary value dropped while borrowed
static FOO2: NotAMutex<&mut i32> = NotAMutex(UnsafeCell::new(&mut 42));
//~^ ERROR temporary value dropped while borrowed
static mut FOO3: NotAMutex<&mut i32> = NotAMutex(UnsafeCell::new(&mut 42));
//~^ ERROR temporary value dropped while borrowed
// `BAR` works, because `&42` promotes immediately instead of relying on
// the enclosing scope rule.
const BAR: NotAMutex<&i32> = NotAMutex(UnsafeCell::new(&42));
fn main() {
println!("{}", unsafe { *A });
unsafe { *B = 4 } // Bad news
unsafe {
**FOO.0.get() = 99;
assert_eq!(**FOO.0.get(), 99);
}
}

57
src/test/ui/consts/const-mut-refs/mut_ref_in_final.stderr
View file

@ -1,9 +1,60 @@
error[E0764]: mutable references are not allowed in the final value of constants
--> $DIR/mut_ref_in_final.rs:10:21
--> $DIR/mut_ref_in_final.rs:13:21
|
LL | const B: *mut i32 = &mut 4;
| ^^^^^^
error: aborting due to previous error
error[E0716]: temporary value dropped while borrowed
--> $DIR/mut_ref_in_final.rs:19:40
|
LL | const B3: Option<&mut i32> = Some(&mut 42);
| ----------^^-
| | | |
| | | temporary value is freed at the end of this statement
| | creates a temporary which is freed while still in use
| using this value as a constant requires that borrow lasts for `'static`
For more information about this error, try `rustc --explain E0764`.
error[E0716]: temporary value dropped while borrowed
--> $DIR/mut_ref_in_final.rs:32:43
|
LL | const B5: Option<&mut i32> = helper2(&mut 42);
| -------------^^-
| | | |
| | | temporary value is freed at the end of this statement
| | creates a temporary which is freed while still in use
| using this value as a constant requires that borrow lasts for `'static`
error[E0716]: temporary value dropped while borrowed
--> $DIR/mut_ref_in_final.rs:47:65
|
LL | const FOO: NotAMutex<&mut i32> = NotAMutex(UnsafeCell::new(&mut 42));
| -------------------------------^^--
| | | |
| | | temporary value is freed at the end of this statement
| | creates a temporary which is freed while still in use
| using this value as a constant requires that borrow lasts for `'static`
error[E0716]: temporary value dropped while borrowed
--> $DIR/mut_ref_in_final.rs:50:67
|
LL | static FOO2: NotAMutex<&mut i32> = NotAMutex(UnsafeCell::new(&mut 42));
| -------------------------------^^--
| | | |
| | | temporary value is freed at the end of this statement
| | creates a temporary which is freed while still in use
| using this value as a static requires that borrow lasts for `'static`
error[E0716]: temporary value dropped while borrowed
--> $DIR/mut_ref_in_final.rs:53:71
|
LL | static mut FOO3: NotAMutex<&mut i32> = NotAMutex(UnsafeCell::new(&mut 42));
| -------------------------------^^--
| | | |
| | | temporary value is freed at the end of this statement
| | creates a temporary which is freed while still in use
| using this value as a static requires that borrow lasts for `'static`
error: aborting due to 6 previous errors
Some errors have detailed explanations: E0716, E0764.
For more information about an error, try `rustc --explain E0716`.

22
src/test/ui/consts/const-mut-refs/mut_ref_in_final_ok.rs
View file

@ -1,22 +0,0 @@
#![feature(const_mut_refs)]
#![feature(const_fn)]
#![feature(raw_ref_op)]
use std::cell::UnsafeCell;
struct NotAMutex<T>(UnsafeCell<T>);
unsafe impl<T> Sync for NotAMutex<T> {}
const FOO: NotAMutex<&mut i32> = NotAMutex(UnsafeCell::new(&mut 42));
//~^ ERROR temporary value dropped while borrowed
// `BAR` works, because `&42` promotes immediately instead of relying on
// "final value lifetime extension".
const BAR: NotAMutex<&i32> = NotAMutex(UnsafeCell::new(&42));
fn main() {
unsafe {
**FOO.0.get() = 99;
assert_eq!(**FOO.0.get(), 99);
}
}

13
src/test/ui/consts/const-mut-refs/mut_ref_in_final_ok.stderr
View file

@ -1,13 +0,0 @@
error[E0716]: temporary value dropped while borrowed
--> $DIR/mut_ref_in_final_ok.rs:10:65
|
LL | const FOO: NotAMutex<&mut i32> = NotAMutex(UnsafeCell::new(&mut 42));
| -------------------------------^^--
| | | |
| | | temporary value is freed at the end of this statement
| | creates a temporary which is freed while still in use
| using this value as a constant requires that borrow lasts for `'static`
error: aborting due to previous error
For more information about this error, try `rustc --explain E0716`.