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-rw-r--r--src/test/ui/object-lifetime/object-lifetime-default-elision.rs76
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diff --git a/src/test/ui/object-lifetime/object-lifetime-default-elision.rs b/src/test/ui/object-lifetime/object-lifetime-default-elision.rs
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+++ b/src/test/ui/object-lifetime/object-lifetime-default-elision.rs
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+// 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() {
+}