macros: fully specify path to `Fn`

Signed-off-by: David Wood <david.wood@huawei.com>

diff --git a/compiler/rustc_macros/src/diagnostics/subdiagnostic.rs b/compiler/rustc_macros/src/diagnostics/subdiagnostic.rs
index 0b82cb5097eb344e058fb4670399711afabfc6da..5a42a2cd12dd6d264578dce242a20fff90d64405 100644 (file)
--- a/compiler/rustc_macros/src/diagnostics/subdiagnostic.rs
+++ b/compiler/rustc_macros/src/diagnostics/subdiagnostic.rs
@@ -86,7 +86,7 @@ pub(crate) fn into_tokens<'a>(self, mut structure: Structure<'a>) -> TokenStream
             gen impl rustc_errors::AddToDiagnostic for @Self {
                 fn add_to_diagnostic_with<__F>(self, #diag: &mut rustc_errors::Diagnostic, #f: __F)
                 where
-                    __F: Fn(
+                    __F: core::ops::Fn(
                         &mut rustc_errors::Diagnostic,
                         rustc_errors::SubdiagnosticMessage
                     ) -> rustc_errors::SubdiagnosticMessage,