2 files changed, 56 insertions, 0 deletions
diff --git a/tests/ui/typeck/issue-107775.rs b/tests/ui/typeck/issue-107775.rs
new file mode 100644
index 00000000000..6fbac2ee975
--- /dev/null
+++ b/tests/ui/typeck/issue-107775.rs
@@ -0,0 +1,40 @@
+// edition: 2021
+
+use std::collections::HashMap;
+use std::future::Future;
+use std::pin::Pin;
+
+pub trait Trait {
+    fn do_something<'async_trait>(byte: u8)
+    ->
+        Pin<Box<dyn Future<Output = ()> +
+        Send + 'async_trait>>;
+}
+
+pub struct Struct;
+
+impl Trait for Struct {
+    fn do_something<'async_trait>(byte: u8)
+        ->
+            Pin<Box<dyn Future<Output = ()> +
+            Send + 'async_trait>> {
+        Box::pin(
+
+            async move { let byte = byte; let _: () = {}; })
+    }
+}
+
+pub struct Map {
+    map: HashMap<u16, fn(u8) -> Pin<Box<dyn Future<Output = ()> + Send>>>,
+}
+
+impl Map {
+    pub fn new() -> Self {
+        let mut map = HashMap::new();
+        map.insert(1, Struct::do_something);
+        Self { map }
+        //~^ ERROR mismatched types
+    }
+}
+
+fn main() {}
diff --git a/tests/ui/typeck/issue-107775.stderr b/tests/ui/typeck/issue-107775.stderr
new file mode 100644
index 00000000000..9ee9c022c6e
--- /dev/null
+++ b/tests/ui/typeck/issue-107775.stderr
@@ -0,0 +1,16 @@
+error[E0308]: mismatched types
+  --> $DIR/issue-107775.rs:35:16
+   |
+LL |         map.insert(1, Struct::do_something);
+   |                    -  -------------------- this is of type `fn(u8) -> Pin<Box<dyn Future<Output = ()> + Send>> {<Struct as Trait>::do_something::<'_>}`, which causes `map` to be inferred as `HashMap<{integer}, fn(u8) -> Pin<Box<dyn Future<Output = ()> + Send>> {<Struct as Trait>::do_something::<'_>}>`
+   |                    |
+   |                    this is of type `{integer}`, which causes `map` to be inferred as `HashMap<{integer}, fn(u8) -> Pin<Box<dyn Future<Output = ()> + Send>> {<Struct as Trait>::do_something::<'_>}>`
+LL |         Self { map }
+   |                ^^^ expected `HashMap<u16, fn(u8) -> Pin<...>>`, found `HashMap<{integer}, ...>`
+   |
+   = note: expected struct `HashMap<u16, fn(_) -> Pin<Box<(dyn Future<Output = ()> + Send + 'static)>>>`
+              found struct `HashMap<{integer}, fn(_) -> Pin<Box<dyn Future<Output = ()> + Send>> {<Struct as Trait>::do_something::<'_>}>`
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0308`.