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Test that promotion follows references when looking for drop
Noticed that this wasn't covered by any of existing tests.

The const checking and const qualification, which currently shares the
implementation with promotion, will likely need a different behaviour
here (see issue #90193).
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tmiasko committed Oct 31, 2021
1 parent 38b01d9 commit fadb9cc
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Showing 2 changed files with 100 additions and 9 deletions.
15 changes: 15 additions & 0 deletions src/test/ui/consts/promote-not.rs
Expand Up @@ -39,6 +39,8 @@ const TEST_INTERIOR_MUT: () = {
let _val: &'static _ = &(Cell::new(1), 2).1; //~ ERROR temporary value dropped while borrowed
};

const TEST_DROP: String = String::new();

fn main() {
// We must not promote things with interior mutability. Not even if we "project it away".
let _val: &'static _ = &(Cell::new(1), 2).0; //~ ERROR temporary value dropped while borrowed
Expand All @@ -50,4 +52,17 @@ fn main() {
let _val: &'static _ = &(1%0); //~ ERROR temporary value dropped while borrowed
let _val: &'static _ = &(1%(1-1)); //~ ERROR temporary value dropped while borrowed
let _val: &'static _ = &([1,2,3][4]+1); //~ ERROR temporary value dropped while borrowed

// No promotion of temporaries that need to be dropped.
let _val: &'static _ = &TEST_DROP;
//~^ ERROR temporary value dropped while borrowed
let _val: &'static _ = &&TEST_DROP;
//~^ ERROR temporary value dropped while borrowed
//~| ERROR temporary value dropped while borrowed
let _val: &'static _ = &(&TEST_DROP,);
//~^ ERROR temporary value dropped while borrowed
//~| ERROR temporary value dropped while borrowed
let _val: &'static _ = &[&TEST_DROP; 1];
//~^ ERROR temporary value dropped while borrowed
//~| ERROR temporary value dropped while borrowed
}
94 changes: 85 additions & 9 deletions src/test/ui/consts/promote-not.stderr
Expand Up @@ -59,7 +59,7 @@ LL | };
| - temporary value is freed at the end of this statement

error[E0716]: temporary value dropped while borrowed
--> $DIR/promote-not.rs:44:29
--> $DIR/promote-not.rs:46:29
|
LL | let _val: &'static _ = &(Cell::new(1), 2).0;
| ---------- ^^^^^^^^^^^^^^^^^ creates a temporary which is freed while still in use
Expand All @@ -70,7 +70,7 @@ LL | }
| - temporary value is freed at the end of this statement

error[E0716]: temporary value dropped while borrowed
--> $DIR/promote-not.rs:45:29
--> $DIR/promote-not.rs:47:29
|
LL | let _val: &'static _ = &(Cell::new(1), 2).1;
| ---------- ^^^^^^^^^^^^^^^^^ creates a temporary which is freed while still in use
Expand All @@ -81,7 +81,7 @@ LL | }
| - temporary value is freed at the end of this statement

error[E0716]: temporary value dropped while borrowed
--> $DIR/promote-not.rs:48:29
--> $DIR/promote-not.rs:50:29
|
LL | let _val: &'static _ = &(1/0);
| ---------- ^^^^^ creates a temporary which is freed while still in use
Expand All @@ -92,7 +92,7 @@ LL | }
| - temporary value is freed at the end of this statement

error[E0716]: temporary value dropped while borrowed
--> $DIR/promote-not.rs:49:29
--> $DIR/promote-not.rs:51:29
|
LL | let _val: &'static _ = &(1/(1-1));
| ---------- ^^^^^^^^^ creates a temporary which is freed while still in use
Expand All @@ -103,7 +103,7 @@ LL | }
| - temporary value is freed at the end of this statement

error[E0716]: temporary value dropped while borrowed
--> $DIR/promote-not.rs:50:29
--> $DIR/promote-not.rs:52:29
|
LL | let _val: &'static _ = &(1%0);
| ---------- ^^^^^ creates a temporary which is freed while still in use
Expand All @@ -114,26 +114,102 @@ LL | }
| - temporary value is freed at the end of this statement

error[E0716]: temporary value dropped while borrowed
--> $DIR/promote-not.rs:51:29
--> $DIR/promote-not.rs:53:29
|
LL | let _val: &'static _ = &(1%(1-1));
| ---------- ^^^^^^^^^ creates a temporary which is freed while still in use
| |
| type annotation requires that borrow lasts for `'static`
LL | let _val: &'static _ = &([1,2,3][4]+1);
...
LL | }
| - temporary value is freed at the end of this statement

error[E0716]: temporary value dropped while borrowed
--> $DIR/promote-not.rs:52:29
--> $DIR/promote-not.rs:54:29
|
LL | let _val: &'static _ = &([1,2,3][4]+1);
| ---------- ^^^^^^^^^^^^^^ creates a temporary which is freed while still in use
| |
| type annotation requires that borrow lasts for `'static`
...
LL | }
| - temporary value is freed at the end of this statement

error[E0716]: temporary value dropped while borrowed
--> $DIR/promote-not.rs:57:29
|
LL | let _val: &'static _ = &TEST_DROP;
| ---------- ^^^^^^^^^ creates a temporary which is freed while still in use
| |
| type annotation requires that borrow lasts for `'static`
...
LL | }
| - temporary value is freed at the end of this statement

error[E0716]: temporary value dropped while borrowed
--> $DIR/promote-not.rs:59:29
|
LL | let _val: &'static _ = &&TEST_DROP;
| ---------- ^^^^^^^^^^ creates a temporary which is freed while still in use
| |
| type annotation requires that borrow lasts for `'static`
...
LL | }
| - temporary value is freed at the end of this statement

error[E0716]: temporary value dropped while borrowed
--> $DIR/promote-not.rs:59:30
|
LL | let _val: &'static _ = &&TEST_DROP;
| ---------- ^^^^^^^^^ creates a temporary which is freed while still in use
| |
| type annotation requires that borrow lasts for `'static`
...
LL | }
| - temporary value is freed at the end of this statement

error[E0716]: temporary value dropped while borrowed
--> $DIR/promote-not.rs:62:29
|
LL | let _val: &'static _ = &(&TEST_DROP,);
| ---------- ^^^^^^^^^^^^^ creates a temporary which is freed while still in use
| |
| type annotation requires that borrow lasts for `'static`
...
LL | }
| - temporary value is freed at the end of this statement

error: aborting due to 13 previous errors
error[E0716]: temporary value dropped while borrowed
--> $DIR/promote-not.rs:62:31
|
LL | let _val: &'static _ = &(&TEST_DROP,);
| ---------- ^^^^^^^^^ creates a temporary which is freed while still in use
| |
| type annotation requires that borrow lasts for `'static`
...
LL | }
| - temporary value is freed at the end of this statement

error[E0716]: temporary value dropped while borrowed
--> $DIR/promote-not.rs:65:29
|
LL | let _val: &'static _ = &[&TEST_DROP; 1];
| ---------- ^^^^^^^^^^^^^^^ creates a temporary which is freed while still in use
| |
| type annotation requires that borrow lasts for `'static`
...
LL | }
| - temporary value is freed at the end of this statement

error[E0716]: temporary value dropped while borrowed
--> $DIR/promote-not.rs:65:31
|
LL | let _val: &'static _ = &[&TEST_DROP; 1];
| ---------- ^^^^^^^^^ - temporary value is freed at the end of this statement
| | |
| | creates a temporary which is freed while still in use
| type annotation requires that borrow lasts for `'static`

error: aborting due to 20 previous errors

For more information about this error, try `rustc --explain E0716`.

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