promote-not: add test that distinguishes promotion from outer scope rule

2 files changed, 42 insertions, 22 deletions

diff --git a/tests/ui/consts/promote-not.rs b/tests/ui/consts/promote-not.rs
index e0f02354354..9b16f32532a 100644
--- a/tests/ui/consts/promote-not.rs
+++ b/tests/ui/consts/promote-not.rs
@@ -40,7 +40,16 @@ const TEST_INTERIOR_MUT: () = {
     let _val: &'static _ = &(Cell::new(1), 2).1; //~ ERROR temporary value dropped while borrowed
 };
 
-const TEST_DROP: String = String::new();
+// This gets accepted by the "outer scope" rule, not promotion.
+const TEST_DROP_OUTER_SCOPE: &String = &String::new();
+// To demonstrate that, we can rewrite it as follows. If this was promotion it would still work.
+const TEST_DROP_NOT_PROMOTE: &String = {
+    let x = &String::new(); //~ ERROR destructor of `String` cannot be evaluated at compile-time
+    // The "dropped while borrowed" error seems to be suppressed, but the key point is that this
+    // fails to compile.
+    x
+};
+
 
 fn main() {
     // We must not promote things with interior mutability. Not even if we "project it away".
@@ -59,6 +68,7 @@ fn main() {
     let _val: &'static _ = &([1,2,3][4]+1); //~ ERROR temporary value dropped while borrowed
 
     // No promotion of temporaries that need to be dropped.
+    const TEST_DROP: String = String::new();
     let _val: &'static _ = &TEST_DROP;
     //~^ ERROR temporary value dropped while borrowed
     let _val: &'static _ = &&TEST_DROP;
diff --git a/tests/ui/consts/promote-not.stderr b/tests/ui/consts/promote-not.stderr
index 9dbd703d489..07d4a135ed4 100644
--- a/tests/ui/consts/promote-not.stderr
+++ b/tests/ui/consts/promote-not.stderr
@@ -38,6 +38,15 @@ LL |     let _val: &'static _ = &(Cell::new(1), 2).1;
 LL | };
    | - temporary value is freed at the end of this statement
 
+error[E0493]: destructor of `String` cannot be evaluated at compile-time
+  --> $DIR/promote-not.rs:47:14
+   |
+LL |     let x = &String::new();
+   |              ^^^^^^^^^^^^^ the destructor for this type cannot be evaluated in constants
+...
+LL | };
+   | - value is dropped here
+
 error[E0716]: temporary value dropped while borrowed
   --> $DIR/promote-not.rs:21:32
    |
@@ -59,7 +68,7 @@ LL | }
    | - temporary value is freed at the end of this statement
 
 error[E0716]: temporary value dropped while borrowed
-  --> $DIR/promote-not.rs:47:29
+  --> $DIR/promote-not.rs:56:29
    |
 LL |     let _val: &'static _ = &(Cell::new(1), 2).0;
    |               ----------    ^^^^^^^^^^^^^^^^^ creates a temporary value which is freed while still in use
@@ -70,7 +79,7 @@ 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:57:29
    |
 LL |     let _val: &'static _ = &(Cell::new(1), 2).1;
    |               ----------    ^^^^^^^^^^^^^^^^^ creates a temporary value which is freed while still in use
@@ -81,7 +90,7 @@ 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:60:29
    |
 LL |     let _val: &'static _ = &(1/0);
    |               ----------    ^^^^^ creates a temporary value which is freed while still in use
@@ -92,7 +101,7 @@ 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:61:29
    |
 LL |     let _val: &'static _ = &(1/(1-1));
    |               ----------    ^^^^^^^^^ creates a temporary value which is freed while still in use
@@ -103,7 +112,7 @@ LL | }
    | - temporary value is freed at the end of this statement
 
 error[E0716]: temporary value dropped while borrowed
-  --> $DIR/promote-not.rs:53:29
+  --> $DIR/promote-not.rs:62:29
    |
 LL |     let _val: &'static _ = &((1+1)/(1-1));
    |               ----------    ^^^^^^^^^^^^^ creates a temporary value which is freed while still in use
@@ -114,7 +123,7 @@ LL | }
    | - temporary value is freed at the end of this statement
 
 error[E0716]: temporary value dropped while borrowed
-  --> $DIR/promote-not.rs:54:29
+  --> $DIR/promote-not.rs:63:29
    |
 LL |     let _val: &'static _ = &(i32::MIN/-1);
    |               ----------    ^^^^^^^^^^^^^ creates a temporary value which is freed while still in use
@@ -125,7 +134,7 @@ LL | }
    | - temporary value is freed at the end of this statement
 
 error[E0716]: temporary value dropped while borrowed
-  --> $DIR/promote-not.rs:55:29
+  --> $DIR/promote-not.rs:64:29
    |
 LL |     let _val: &'static _ = &(i32::MIN/(0-1));
    |               ----------    ^^^^^^^^^^^^^^^^ creates a temporary value which is freed while still in use
@@ -136,7 +145,7 @@ LL | }
    | - temporary value is freed at the end of this statement
 
 error[E0716]: temporary value dropped while borrowed
-  --> $DIR/promote-not.rs:56:29
+  --> $DIR/promote-not.rs:65:29
    |
 LL |     let _val: &'static _ = &(-128i8/-1);
    |               ----------    ^^^^^^^^^^^ creates a temporary value which is freed while still in use
@@ -147,7 +156,7 @@ LL | }
    | - temporary value is freed at the end of this statement
 
 error[E0716]: temporary value dropped while borrowed
-  --> $DIR/promote-not.rs:57:29
+  --> $DIR/promote-not.rs:66:29
    |
 LL |     let _val: &'static _ = &(1%0);
    |               ----------    ^^^^^ creates a temporary value which is freed while still in use
@@ -158,7 +167,7 @@ LL | }
    | - temporary value is freed at the end of this statement
 
 error[E0716]: temporary value dropped while borrowed
-  --> $DIR/promote-not.rs:58:29
+  --> $DIR/promote-not.rs:67:29
    |
 LL |     let _val: &'static _ = &(1%(1-1));
    |               ----------    ^^^^^^^^^ creates a temporary value which is freed while still in use
@@ -169,7 +178,7 @@ LL | }
    | - temporary value is freed at the end of this statement
 
 error[E0716]: temporary value dropped while borrowed
-  --> $DIR/promote-not.rs:59:29
+  --> $DIR/promote-not.rs:68:29
    |
 LL |     let _val: &'static _ = &([1,2,3][4]+1);
    |               ----------    ^^^^^^^^^^^^^^ creates a temporary value which is freed while still in use
@@ -180,7 +189,7 @@ LL | }
    | - temporary value is freed at the end of this statement
 
 error[E0716]: temporary value dropped while borrowed
-  --> $DIR/promote-not.rs:62:29
+  --> $DIR/promote-not.rs:72:29
    |
 LL |     let _val: &'static _ = &TEST_DROP;
    |               ----------    ^^^^^^^^^ creates a temporary value which is freed while still in use
@@ -191,7 +200,7 @@ LL | }
    | - temporary value is freed at the end of this statement
 
 error[E0716]: temporary value dropped while borrowed
-  --> $DIR/promote-not.rs:64:29
+  --> $DIR/promote-not.rs:74:29
    |
 LL |     let _val: &'static _ = &&TEST_DROP;
    |               ----------    ^^^^^^^^^^ creates a temporary value which is freed while still in use
@@ -202,7 +211,7 @@ LL | }
    | - temporary value is freed at the end of this statement
 
 error[E0716]: temporary value dropped while borrowed
-  --> $DIR/promote-not.rs:64:30
+  --> $DIR/promote-not.rs:74:30
    |
 LL |     let _val: &'static _ = &&TEST_DROP;
    |               ----------     ^^^^^^^^^ creates a temporary value which is freed while still in use
@@ -213,7 +222,7 @@ LL | }
    | - temporary value is freed at the end of this statement
 
 error[E0716]: temporary value dropped while borrowed
-  --> $DIR/promote-not.rs:67:29
+  --> $DIR/promote-not.rs:77:29
    |
 LL |     let _val: &'static _ = &(&TEST_DROP,);
    |               ----------    ^^^^^^^^^^^^^ creates a temporary value which is freed while still in use
@@ -224,7 +233,7 @@ LL | }
    | - temporary value is freed at the end of this statement
 
 error[E0716]: temporary value dropped while borrowed
-  --> $DIR/promote-not.rs:67:31
+  --> $DIR/promote-not.rs:77:31
    |
 LL |     let _val: &'static _ = &(&TEST_DROP,);
    |               ----------      ^^^^^^^^^ creates a temporary value which is freed while still in use
@@ -235,7 +244,7 @@ LL | }
    | - temporary value is freed at the end of this statement
 
 error[E0716]: temporary value dropped while borrowed
-  --> $DIR/promote-not.rs:70:29
+  --> $DIR/promote-not.rs:80:29
    |
 LL |     let _val: &'static _ = &[&TEST_DROP; 1];
    |               ----------    ^^^^^^^^^^^^^^^ creates a temporary value which is freed while still in use
@@ -246,7 +255,7 @@ LL | }
    | - temporary value is freed at the end of this statement
 
 error[E0716]: temporary value dropped while borrowed
-  --> $DIR/promote-not.rs:70:31
+  --> $DIR/promote-not.rs:80:31
    |
 LL |     let _val: &'static _ = &[&TEST_DROP; 1];
    |               ----------      ^^^^^^^^^    - temporary value is freed at the end of this statement
@@ -255,7 +264,7 @@ LL |     let _val: &'static _ = &[&TEST_DROP; 1];
    |               type annotation requires that borrow lasts for `'static`
 
 error[E0716]: temporary value dropped while borrowed
-  --> $DIR/promote-not.rs:79:26
+  --> $DIR/promote-not.rs:89:26
    |
 LL |     let x: &'static _ = &UnionWithCell { f1: 0 };
    |            ----------    ^^^^^^^^^^^^^^^^^^^^^^^ creates a temporary value which is freed while still in use
@@ -265,6 +274,7 @@ LL |
 LL | }
    | - temporary value is freed at the end of this statement
 
-error: aborting due to 25 previous errors
+error: aborting due to 26 previous errors
 
-For more information about this error, try `rustc --explain E0716`.
+Some errors have detailed explanations: E0493, E0716.
+For more information about an error, try `rustc --explain E0493`.