Rollup merge of #103382 - compiler-errors:anon-apit-lt-region-ice, r=cjgillot

Don't ICE when reporting borrowck errors involving regions from `anonymous_lifetime_in_impl_trait`

The issue here is that when we have:

```
trait Trait<'a> { .. }

fn foo(arg: impl Trait) { .. }
```

The anonymous lifetime `'_` that we generate for `arg: impl Trait` doesn't end up in the argument type (which is a param) but in a where-clause of the function, in a predicate whose self type is that param ty.

Fixes #101660

r? ``@cjgillot``

2 files changed, 28 insertions, 0 deletions

diff --git a/src/test/ui/borrowck/anonymous-region-in-apit.rs b/src/test/ui/borrowck/anonymous-region-in-apit.rs
new file mode 100644
index 00000000000..7799a7cb151
--- /dev/null
+++ b/src/test/ui/borrowck/anonymous-region-in-apit.rs
@@ -0,0 +1,12 @@
+#![feature(anonymous_lifetime_in_impl_trait)]
+
+trait Foo<T> {
+    fn bar(self, baz: T);
+}
+
+fn qux(foo: impl Foo<&str>) {
+    |baz: &str| foo.bar(baz);
+    //~^ ERROR borrowed data escapes outside of closure
+}
+
+fn main() {}
diff --git a/src/test/ui/borrowck/anonymous-region-in-apit.stderr b/src/test/ui/borrowck/anonymous-region-in-apit.stderr
new file mode 100644
index 00000000000..9e100f8ac3c
--- /dev/null
+++ b/src/test/ui/borrowck/anonymous-region-in-apit.stderr
@@ -0,0 +1,16 @@
+error[E0521]: borrowed data escapes outside of closure
+  --> $DIR/anonymous-region-in-apit.rs:8:17
+   |
+LL | fn qux(foo: impl Foo<&str>) {
+   |        --- lifetime `'2` appears in the type of `foo`
+LL |     |baz: &str| foo.bar(baz);
+   |      ---  -     ^^^^^^^^^^^^
+   |      |    |     |
+   |      |    |     `baz` escapes the closure body here
+   |      |    |     argument requires that `'1` must outlive `'2`
+   |      |    let's call the lifetime of this reference `'1`
+   |      `baz` is a reference that is only valid in the closure body
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0521`.