From 698f8c2f01ea549d77d7dc3338a12e04c11057b9 Mon Sep 17 00:00:00 2001
From: Daniel Baumann <daniel.baumann@progress-linux.org>
Date: Wed, 17 Apr 2024 14:02:58 +0200
Subject: Adding upstream version 1.64.0+dfsg1.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
---
 .../object-lifetime-default-elision.rs             | 76 ++++++++++++++++++++++
 1 file changed, 76 insertions(+)
 create mode 100644 src/test/ui/object-lifetime/object-lifetime-default-elision.rs

(limited to 'src/test/ui/object-lifetime/object-lifetime-default-elision.rs')

diff --git a/src/test/ui/object-lifetime/object-lifetime-default-elision.rs b/src/test/ui/object-lifetime/object-lifetime-default-elision.rs
new file mode 100644
index 000000000..f7c0261cf
--- /dev/null
+++ b/src/test/ui/object-lifetime/object-lifetime-default-elision.rs
@@ -0,0 +1,76 @@
+// Test various cases where the old rules under lifetime elision
+// yield slightly different results than the new rules.
+
+#![allow(dead_code)]
+
+trait SomeTrait {
+    fn dummy(&self) { }
+}
+
+struct SomeStruct<'a> {
+    r: Box<dyn SomeTrait+'a>
+}
+
+fn deref<T>(ss: &T) -> T {
+    // produces the type of a deref without worrying about whether a
+    // move out would actually be legal
+    loop { }
+}
+
+fn load0<'a>(ss: &'a Box<dyn SomeTrait>) -> Box<dyn SomeTrait> {
+    // Under old rules, the fully elaborated types of input/output were:
+    //
+    // for<'a,'b> fn(&'a Box<SomeTrait+'b>) -> Box<SomeTrait+'a>
+    //
+    // Under new rules the result is:
+    //
+    // for<'a> fn(&'a Box<SomeTrait+'static>) -> Box<SomeTrait+'static>
+    //
+    // Therefore, no type error.
+
+    deref(ss)
+}
+
+fn load1(ss: &dyn SomeTrait) -> &dyn SomeTrait {
+    // Under old rules, the fully elaborated types of input/output were:
+    //
+    // for<'a,'b> fn(&'a (SomeTrait+'b)) -> &'a (SomeTrait+'a)
+    //
+    // Under new rules the result is:
+    //
+    // for<'a> fn(&'a (SomeTrait+'a)) -> &'a (SomeTrait+'a)
+    //
+    // In both cases, returning `ss` is legal.
+
+    ss
+}
+
+fn load2<'a>(ss: &'a dyn SomeTrait) -> &dyn SomeTrait {
+    // Same as `load1` but with an explicit name thrown in for fun.
+
+    ss
+}
+
+fn load3<'a,'b>(ss: &'a dyn SomeTrait) -> &'b dyn SomeTrait {
+    // Under old rules, the fully elaborated types of input/output were:
+    //
+    // for<'a,'b,'c>fn(&'a (SomeTrait+'c)) -> &'b (SomeTrait+'a)
+    //
+    // Based on the input/output types, the compiler could infer that
+    //     'c : 'a
+    //     'b : 'a
+    // must hold, and therefore it permitted `&'a (Sometrait+'c)` to be
+    // coerced to `&'b (SomeTrait+'a)`.
+    //
+    // Under the newer defaults, though, we get:
+    //
+    // for<'a,'b> fn(&'a (SomeTrait+'a)) -> &'b (SomeTrait+'b)
+    //
+    // which fails to type check.
+
+    ss
+        //~^ ERROR lifetime may not live long enough
+}
+
+fn main() {
+}
-- 
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