From 58cc36e69f0a7b67b85692e8dc38a81273b839b9 Mon Sep 17 00:00:00 2001 From: David Tolnay Date: Mon, 4 Nov 2024 22:00:42 -0500 Subject: [PATCH] Improve diagnostic on {_} in format string --- impl/src/fmt.rs | 2 +- tests/ui/display-underscore.stderr | 8 +++++--- 2 files changed, 6 insertions(+), 4 deletions(-) diff --git a/impl/src/fmt.rs b/impl/src/fmt.rs index d984bfd..6b1e7fa 100644 --- a/impl/src/fmt.rs +++ b/impl/src/fmt.rs @@ -78,7 +78,7 @@ impl Display<'_> { let formatvar = match &member { MemberUnraw::Unnamed(index) => IdentUnraw::new(format_ident!("__field{}", index)), MemberUnraw::Named(ident) => { - if user_named_args.contains(ident) { + if user_named_args.contains(ident) || ident == "_" { // Refers to a named argument written by the user, not to field. out += &ident.to_string(); continue; diff --git a/tests/ui/display-underscore.stderr b/tests/ui/display-underscore.stderr index 3935970..36882b9 100644 --- a/tests/ui/display-underscore.stderr +++ b/tests/ui/display-underscore.stderr @@ -1,5 +1,7 @@ -error: in expressions, `_` can only be used on the left-hand side of an assignment - --> tests/ui/display-underscore.rs:4:9 +error: invalid format string: invalid argument name `_` + --> tests/ui/display-underscore.rs:4:11 | 4 | #[error("{_}")] - | ^^^^^ `_` not allowed here + | ^ invalid argument name in format string + | + = note: argument name cannot be a single underscore