Rollup merge of #51057 - pnkfelix:issue-51025-make-ui-tests-robust-wrt-nll, r=nikomatsakis

make ui tests robust with respect to NLL

This PR revises the `ui` tests that I could quickly identify that:
 1. previously had successful compilations under non-lexical lifetimes (NLL) because they assumed lexical lifetimes, but
 2. such assumption of lexical lifetimes was actually not necessarily part of the spirit of the original issue/bug we want to witness.

In many cases, this is simply a matter of adding a use of a borrow so that it gets extended long enough to observe a conflict.

(In some cases the revision was more subtle, such as adding a destructor, or revising the order of declaration of some variables.)

----

With these test revisions in place, I subsequently updated the expected stderr output under the NLL compiletest mode. So now we should get even more testing of NLL than we were before.

Fix #51025

Author: Mark-Simulacrum

src/test/ui/borrowck/borrowck-report-with-custom-diagnostic.nll.stderr

@@ -1,14 +1,40 @@
-error: compilation successful
-  --> $DIR/borrowck-report-with-custom-diagnostic.rs:12:1
+error[E0502]: cannot borrow `x` as immutable because it is also borrowed as mutable
+  --> $DIR/borrowck-report-with-custom-diagnostic.rs:17:13
    |
-LL | / fn main() { #![rustc_error] // rust-lang/rust#49855
-LL | |     // Original borrow ends at end of function
-LL | |     let mut x = 1;
-LL | |     let y = &mut x;
-...  |
-LL | |     //~^ immutable borrow occurs here
-LL | | }
-   | |_^
+LL |     let y = &mut x;
+   |             ------ mutable borrow occurs here
+LL |     //~^ mutable borrow occurs here
+LL |     let z = &x; //~ ERROR cannot borrow
+   |             ^^ immutable borrow occurs here
+...
+LL |     y.use_mut();
+   |     - borrow later used here
 
-error: aborting due to previous error
+error[E0502]: cannot borrow `x` as mutable because it is also borrowed as immutable
+  --> $DIR/borrowck-report-with-custom-diagnostic.rs:30:21
+   |
+LL |             let y = &x;
+   |                     -- immutable borrow occurs here
+LL |             //~^ immutable borrow occurs here
+LL |             let z = &mut x; //~ ERROR cannot borrow
+   |                     ^^^^^^ mutable borrow occurs here
+...
+LL |             y.use_ref();
+   |             - borrow later used here
+
+error[E0499]: cannot borrow `x` as mutable more than once at a time
+  --> $DIR/borrowck-report-with-custom-diagnostic.rs:45:17
+   |
+LL |         let y = &mut x;
+   |                 ------ first mutable borrow occurs here
+LL |         //~^ first mutable borrow occurs here
+LL |         let z = &mut x; //~ ERROR cannot borrow
+   |                 ^^^^^^ second mutable borrow occurs here
+...
+LL |         y.use_mut();
+   |         - borrow later used here
+
+error: aborting due to 3 previous errors
 
+Some errors occurred: E0499, E0502.
+For more information about an error, try `rustc --explain E0499`.

src/test/ui/borrowck/borrowck-report-with-custom-diagnostic.rs

@@ -16,6 +16,8 @@ fn main() { #![rustc_error] // rust-lang/rust#49855
     //~^ mutable borrow occurs here
     let z = &x; //~ ERROR cannot borrow
     //~^ immutable borrow occurs here
+    z.use_ref();
+    y.use_mut();
 }
 
 fn foo() {
@@ -27,6 +29,8 @@ fn foo() {
             //~^ immutable borrow occurs here
             let z = &mut x; //~ ERROR cannot borrow
             //~^ mutable borrow occurs here
+            z.use_mut();
+            y.use_ref();
         }
         false => ()
     }
@@ -40,5 +44,10 @@ fn bar() {
         //~^ first mutable borrow occurs here
         let z = &mut x; //~ ERROR cannot borrow
         //~^ second mutable borrow occurs here
+        z.use_mut();
+        y.use_mut();
     };
 }
+
+trait Fake { fn use_mut(&mut self) { } fn use_ref(&self) { }  }
+impl<T> Fake for T { }

src/test/ui/borrowck/borrowck-report-with-custom-diagnostic.stderr

@@ -6,31 +6,31 @@ LL |     let y = &mut x;
 LL |     //~^ mutable borrow occurs here
 LL |     let z = &x; //~ ERROR cannot borrow
    |              ^ immutable borrow occurs here
-LL |     //~^ immutable borrow occurs here
+...
 LL | }
    | - mutable borrow ends here
 
 error[E0502]: cannot borrow `x` as mutable because it is also borrowed as immutable
-  --> $DIR/borrowck-report-with-custom-diagnostic.rs:28:26
+  --> $DIR/borrowck-report-with-custom-diagnostic.rs:30:26
    |
 LL |             let y = &x;
    |                      - immutable borrow occurs here
 LL |             //~^ immutable borrow occurs here
 LL |             let z = &mut x; //~ ERROR cannot borrow
    |                          ^ mutable borrow occurs here
-LL |             //~^ mutable borrow occurs here
+...
 LL |         }
    |         - immutable borrow ends here
 
 error[E0499]: cannot borrow `x` as mutable more than once at a time
-  --> $DIR/borrowck-report-with-custom-diagnostic.rs:41:22
+  --> $DIR/borrowck-report-with-custom-diagnostic.rs:45:22
    |
 LL |         let y = &mut x;
    |                      - first mutable borrow occurs here
 LL |         //~^ first mutable borrow occurs here
 LL |         let z = &mut x; //~ ERROR cannot borrow
    |                      ^ second mutable borrow occurs here
-LL |         //~^ second mutable borrow occurs here
+...
 LL |     };
    |     - first borrow ends here
 

src/test/ui/borrowck/mut-borrow-outside-loop.nll.stderr

@@ -1,14 +1,24 @@
-error: compilation successful
-  --> $DIR/mut-borrow-outside-loop.rs:13:1
+error[E0499]: cannot borrow `void` as mutable more than once at a time
+  --> $DIR/mut-borrow-outside-loop.rs:17:18
    |
-LL | / fn main() { #![rustc_error] // rust-lang/rust#49855
-LL | |     let mut void = ();
-LL | |
-LL | |     let first = &mut void;
-...  |
-LL | |     }
-LL | | }
-   | |_^
+LL |     let first = &mut void;
+   |                 --------- first mutable borrow occurs here
+LL |     let second = &mut void; //~ ERROR cannot borrow
+   |                  ^^^^^^^^^ second mutable borrow occurs here
+LL |     first.use_mut();
+   |     ----- borrow later used here
 
-error: aborting due to previous error
+error[E0499]: cannot borrow `inner_void` as mutable more than once at a time
+  --> $DIR/mut-borrow-outside-loop.rs:25:28
+   |
+LL |         let inner_first = &mut inner_void;
+   |                           --------------- first mutable borrow occurs here
+LL |         let inner_second = &mut inner_void; //~ ERROR cannot borrow
+   |                            ^^^^^^^^^^^^^^^ second mutable borrow occurs here
+LL |         inner_second.use_mut();
+LL |         inner_first.use_mut();
+   |         ----------- borrow later used here
+
+error: aborting due to 2 previous errors
 
+For more information about this error, try `rustc --explain E0499`.

src/test/ui/borrowck/mut-borrow-outside-loop.rs

@@ -15,12 +15,18 @@ fn main() { #![rustc_error] // rust-lang/rust#49855
 
     let first = &mut void;
     let second = &mut void; //~ ERROR cannot borrow
+    first.use_mut();
+    second.use_mut();
 
     loop {
         let mut inner_void = ();
 
         let inner_first = &mut inner_void;
         let inner_second = &mut inner_void; //~ ERROR cannot borrow
+        inner_second.use_mut();
+        inner_first.use_mut();
     }
 }
 
+trait Fake { fn use_mut(&mut self) { } fn use_ref(&self) { }  }
+impl<T> Fake for T { }

src/test/ui/borrowck/mut-borrow-outside-loop.stderr

@@ -10,12 +10,13 @@ LL | }
    | - first borrow ends here
 
 error[E0499]: cannot borrow `inner_void` as mutable more than once at a time
-  --> $DIR/mut-borrow-outside-loop.rs:23:33
+  --> $DIR/mut-borrow-outside-loop.rs:25:33
    |
 LL |         let inner_first = &mut inner_void;
    |                                ---------- first mutable borrow occurs here
 LL |         let inner_second = &mut inner_void; //~ ERROR cannot borrow
    |                                 ^^^^^^^^^^ second mutable borrow occurs here
+...
 LL |     }
    |     - first borrow ends here
 

src/test/ui/codemap_tests/issue-11715.nll.stderr

@@ -1,12 +1,14 @@
-error: compilation successful
-  --> $DIR/issue-11715.rs:97:1
+error[E0499]: cannot borrow `x` as mutable more than once at a time
+  --> $DIR/issue-11715.rs:100:13
    |
-LL | / fn main() { #![rustc_error] // rust-lang/rust#49855
-LL | |     let mut x = "foo";
-LL | |     let y = &mut x;
-LL | |     let z = &mut x; //~ ERROR cannot borrow
-LL | | }
-   | |_^
+LL |     let y = &mut x;
+   |             ------ first mutable borrow occurs here
+LL |     let z = &mut x; //~ ERROR cannot borrow
+   |             ^^^^^^ second mutable borrow occurs here
+LL |     z.use_mut();
+LL |     y.use_mut();
+   |     - borrow later used here
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0499`.

src/test/ui/codemap_tests/issue-11715.rs

@@ -98,4 +98,9 @@ fn main() { #![rustc_error] // rust-lang/rust#49855
     let mut x = "foo";
     let y = &mut x;
     let z = &mut x; //~ ERROR cannot borrow
+    z.use_mut();
+    y.use_mut();
 }
+
+trait Fake { fn use_mut(&mut self) { } fn use_ref(&self) { }  }
+impl<T> Fake for T { }

src/test/ui/codemap_tests/issue-11715.stderr

@@ -5,6 +5,7 @@ LL |     let y = &mut x;
    |                  - first mutable borrow occurs here
 LL |     let z = &mut x; //~ ERROR cannot borrow
    |                  ^ second mutable borrow occurs here
+...
 LL | }
    | - first borrow ends here
 

src/test/ui/dropck/dropck-eyepatch-extern-crate.nll.stderr

@@ -1,14 +1,15 @@
-error: compilation successful
-  --> $DIR/dropck-eyepatch-extern-crate.rs:27:1
+error[E0597]: `c_shortest` does not live long enough
+  --> $DIR/dropck-eyepatch-extern-crate.rs:47:19
    |
-LL | / fn main() { #![rustc_error] // rust-lang/rust#49855
-LL | |     use std::cell::Cell;
-LL | |     let c_long;
-LL | |     let (c, mut dt, mut dr, mut pt, mut pr, st, sr)
-...  |
-LL | |     println!("{:?}", (dt.0, dr.0, pt.0, pr.0, st.0, sr.0));
-LL | | }
-   | |_^
+LL |     dt = Dt("dt", &c_shortest);
+   |                   ^^^^^^^^^^^ borrowed value does not live long enough
+...
+LL | }
+   | -
+   | |
+   | borrowed value only lives until here
+   | borrow later used here, when `dt` is dropped
 
 error: aborting due to previous error
 
+For more information about this error, try `rustc --explain E0597`.