Make comma separated lists of anything easier to make for errors

Provide a new function `listify`, meant to be used in cases similar to `pluralize!`. When you have a slice of arbitrary elements that need to be presented to the user, `listify` allows you to turn that into a list of comma separated strings.

This reduces a lot of redundant logic that happens often in diagnostics.

1 files changed, 1 insertions, 13 deletions

diff --git a/compiler/rustc_errors/src/lib.rs b/compiler/rustc_errors/src/lib.rs
index 549729548f5..a6458c9ffdc 100644
--- a/compiler/rustc_errors/src/lib.rs
+++ b/compiler/rustc_errors/src/lib.rs
@@ -65,7 +65,7 @@ pub use rustc_error_messages::{
     SubdiagMessage, fallback_fluent_bundle, fluent_bundle,
 };
 use rustc_lint_defs::LintExpectationId;
-pub use rustc_lint_defs::{Applicability, pluralize};
+pub use rustc_lint_defs::{Applicability, listify, pluralize};
 use rustc_macros::{Decodable, Encodable};
 pub use rustc_span::ErrorGuaranteed;
 pub use rustc_span::fatal_error::{FatalError, FatalErrorMarker};
@@ -1999,18 +1999,6 @@ pub fn a_or_an(s: &str) -> &'static str {
     }
 }
 
-/// Grammatical tool for displaying messages to end users in a nice form.
-///
-/// Take a list ["a", "b", "c"] and output a display friendly version "a, b and c"
-pub fn display_list_with_comma_and<T: std::fmt::Display>(v: &[T]) -> String {
-    match v {
-        [] => "".to_string(),
-        [a] => a.to_string(),
-        [a, b] => format!("{a} and {b}"),
-        [a, v @ ..] => format!("{a}, {}", display_list_with_comma_and(v)),
-    }
-}
-
 #[derive(Clone, Copy, PartialEq, Hash, Debug)]
 pub enum TerminalUrl {
     No,