Adding upstream version 1.68.2+dfsg1.upstream/1.68.2+dfsg1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 37 insertions, 0 deletions

diff --git a/tests/ui/borrowck/two-phase-allow-access-during-reservation.rs b/tests/ui/borrowck/two-phase-allow-access-during-reservation.rs
new file mode 100644
index 000000000..67d084207
--- /dev/null
+++ b/tests/ui/borrowck/two-phase-allow-access-during-reservation.rs
@@ -0,0 +1,37 @@
+// revisions: nll_target
+
+// The following revisions are disabled due to missing support for two_phase_beyond_autoref
+//[nll_beyond] compile-flags: -Z two_phase_beyond_autoref
+
+// This is the second counter-example from Niko's blog post
+// smallcultfollowing.com/babysteps/blog/2017/03/01/nested-method-calls-via-two-phase-borrowing/
+//
+// It is "artificial". It is meant to illustrate directly that we
+// should allow an aliasing access during reservation, but *not* while
+// the mutable borrow is active.
+//
+// The convention for the listed revisions: "lxl" means lexical
+// lifetimes (which can be easier to reason about). "nll" means
+// non-lexical lifetimes. "nll_target" means the initial conservative
+// two-phase borrows that only applies to autoref-introduced borrows.
+// "nll_beyond" means the generalization of two-phase borrows to all
+// `&mut`-borrows (doing so makes it easier to write code for specific
+// corner cases).
+
+fn main() {
+    /*0*/ let mut i = 0;
+
+    /*1*/ let p = &mut i; // (reservation of `i` starts here)
+
+    /*2*/ let j = i;      // OK: `i` is only reserved here
+                          //[nll_target]~^  ERROR cannot use `i` because it was mutably borrowed [E0503]
+
+    /*3*/ *p += 1;        // (mutable borrow of `i` starts here, since `p` is used)
+
+    /*4*/ let k = i;      //[nll_beyond]~  ERROR cannot use `i` because it was mutably borrowed [E0503]
+                          //[nll_target]~^ ERROR cannot use `i` because it was mutably borrowed [E0503]
+
+    /*5*/ *p += 1;
+
+    let _ = (j, k, p);
+}