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oli-obkoli-obk
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Cover more cases in the test suite
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‎src/test/ui/consts/const-mut-refs/mut_ref_in_final.rs

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

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

+54-3
Original file line numberDiff line numberDiff line change
@@ -1,9 +1,60 @@
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error[E0764]: mutable references are not allowed in the final value of constants
2-
--> $DIR/mut_ref_in_final.rs:10:21
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--> $DIR/mut_ref_in_final.rs:13:21
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|
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LL | const B: *mut i32 = &mut 4;
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| ^^^^^^
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error: aborting due to previous error
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error[E0716]: temporary value dropped while borrowed
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--> $DIR/mut_ref_in_final.rs:19:40
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|
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LL | const B3: Option<&mut i32> = Some(&mut 42);
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| ----------^^-
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| | | |
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| | | temporary value is freed at the end of this statement
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| | creates a temporary which is freed while still in use
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| using this value as a constant requires that borrow lasts for `'static`
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error[E0716]: temporary value dropped while borrowed
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--> $DIR/mut_ref_in_final.rs:32:43
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|
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LL | const B5: Option<&mut i32> = helper2(&mut 42);
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| -------------^^-
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| | | |
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| | | temporary value is freed at the end of this statement
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| | creates a temporary which is freed while still in use
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| using this value as a constant requires that borrow lasts for `'static`
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error[E0716]: temporary value dropped while borrowed
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--> $DIR/mut_ref_in_final.rs:47:65
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|
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LL | const FOO: NotAMutex<&mut i32> = NotAMutex(UnsafeCell::new(&mut 42));
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| -------------------------------^^--
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| | | |
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| | | temporary value is freed at the end of this statement
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| | creates a temporary which is freed while still in use
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| using this value as a constant requires that borrow lasts for `'static`
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error[E0716]: temporary value dropped while borrowed
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--> $DIR/mut_ref_in_final.rs:50:67
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|
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LL | static FOO2: NotAMutex<&mut i32> = NotAMutex(UnsafeCell::new(&mut 42));
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| -------------------------------^^--
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| | | |
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| | | temporary value is freed at the end of this statement
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| | creates a temporary which is freed while still in use
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| using this value as a static requires that borrow lasts for `'static`
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error[E0716]: temporary value dropped while borrowed
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--> $DIR/mut_ref_in_final.rs:53:71
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|
50+
LL | static mut FOO3: NotAMutex<&mut i32> = NotAMutex(UnsafeCell::new(&mut 42));
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| -------------------------------^^--
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| | | |
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| | | temporary value is freed at the end of this statement
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| | creates a temporary which is freed while still in use
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| using this value as a static requires that borrow lasts for `'static`
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error: aborting due to 6 previous errors
858

9-
For more information about this error, try `rustc --explain E0764`.
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Some errors have detailed explanations: E0716, E0764.
60+
For more information about an error, try `rustc --explain E0716`.

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

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This file was deleted.

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

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