Merge #9572

9572: fix: Work around older synstructure derives r=lnicola a=flodiebold

Fixes #9562, until the proper fix rust-lang/chalk#717 works which requires mystor/synstructure#47 to be released.

Also add an unrelated test, for #9560.

Co-authored-by: Florian Diebold <flodiebold@gmail.com>

crates/hir_def/src/item_tree/lower.rs

@@ -448,7 +448,12 @@ impl<'a> Ctx<'a> {
     }
 
     fn lower_const(&mut self, konst: &ast::Const) -> FileItemTreeId<Const> {
-        let name = konst.name().map(|it| it.as_name());
+        let mut name = konst.name().map(|it| it.as_name());
+        if name.as_ref().map_or(false, |n| n.to_string().starts_with("_DERIVE_")) {
+            // FIXME: this is a hack to treat consts generated by synstructure as unnamed
+            // remove this some time in the future
+            name = None;
+        }
         let type_ref = self.lower_type_ref_opt(konst.ty());
         let visibility = self.lower_visibility(konst);
         let ast_id = self.source_ast_id_map.ast_id(konst);

crates/hir_ty/src/tests/coercion.rs

@@ -500,7 +500,7 @@ fn main() {
 }
 
 #[test]
-fn coerce_unsize_expected_type() {
+fn coerce_unsize_expected_type_1() {
     check_no_mismatches(
         r#"
 //- minicore: coerce_unsized
@@ -520,6 +520,32 @@ fn main() {
     );
 }
 
+#[test]
+fn coerce_unsize_expected_type_2() {
+    // FIXME: this is wrong, #9560
+    check(
+        r#"
+//- minicore: coerce_unsized
+struct InFile<T>;
+impl<T> InFile<T> {
+    fn with_value<U>(self, value: U) -> InFile<U> { InFile }
+}
+struct RecordField;
+trait AstNode {}
+impl AstNode for RecordField {}
+
+fn takes_dyn(it: InFile<&dyn AstNode>) {}
+
+fn test() {
+    let x: InFile<()> = InFile;
+    let n = &RecordField;
+    takes_dyn(x.with_value(n));
+           // ^^^^^^^^^^^^^^^ expected InFile<&dyn AstNode>, got InFile<&RecordField>
+}
+        "#,
+    );
+}
+
 #[test]
 fn coerce_array_elems_lub() {
     check_no_mismatches(