1 files changed, 41 insertions, 0 deletions
diff --git a/src/test/ui/traits/issue-77982.rs b/src/test/ui/traits/issue-77982.rs
new file mode 100644
index 000000000..f5be6cf21
--- /dev/null
+++ b/src/test/ui/traits/issue-77982.rs
@@ -0,0 +1,41 @@
+use std::collections::HashMap;
+
+fn what() {
+    let descr = String::new();
+    let mut opts = HashMap::<String, ()>::new();
+    let opt = String::new();
+
+    opts.get(opt.as_ref()); //~ ERROR type annotations needed
+    //~^ ERROR type annotations needed
+}
+
+fn main() {
+    let ips: Vec<_> = (0..100_000).map(|_| u32::from(0u32.into())).collect();
+    //~^ ERROR type annotations needed
+}
+
+trait Foo<'a, T: ?Sized> {
+    fn foo(&self) -> Box<T> {
+        todo!()
+    }
+}
+
+trait Bar<'a, T: ?Sized> {
+    fn bar(&self) -> Box<T> {
+        todo!()
+    }
+}
+
+impl Foo<'static, u32> for () {}
+impl<'a> Foo<'a, i16> for () {}
+
+impl<'a> Bar<'static, u32> for &'a () {}
+impl<'a> Bar<'a, i16> for &'a () {}
+
+fn foo() {
+    let _ = ().foo(); //~ ERROR type annotations needed
+}
+
+fn bar() {
+    let _ = (&()).bar(); //~ ERROR type annotations needed
+}