1 files changed, 18 insertions, 5 deletions
diff --git a/compiler/rustc_builtin_macros/src/concat.rs b/compiler/rustc_builtin_macros/src/concat.rs
index 7da9bdc38..b92964d03 100644
--- a/compiler/rustc_builtin_macros/src/concat.rs
+++ b/compiler/rustc_builtin_macros/src/concat.rs
@@ -4,6 +4,8 @@ use rustc_expand::base::{self, DummyResult};
 use rustc_session::errors::report_lit_error;
 use rustc_span::symbol::Symbol;
 
+use crate::errors;
+
 pub fn expand_concat(
     cx: &mut base::ExtCtxt<'_>,
     sp: rustc_span::Span,
@@ -31,7 +33,7 @@ pub fn expand_concat(
                     accumulator.push_str(&b.to_string());
                 }
                 Ok(ast::LitKind::Byte(..) | ast::LitKind::ByteStr(..)) => {
-                    cx.span_err(e.span, "cannot concatenate a byte string literal");
+                    cx.emit_err(errors::ConcatBytestr { span: e.span });
                     has_errors = true;
                 }
                 Ok(ast::LitKind::Err) => {
@@ -42,8 +44,20 @@ pub fn expand_concat(
                     has_errors = true;
                 }
             },
+            // We also want to allow negative numeric literals.
+            ast::ExprKind::Unary(ast::UnOp::Neg, ref expr) if let ast::ExprKind::Lit(token_lit) = expr.kind => {
+                match ast::LitKind::from_token_lit(token_lit) {
+                    Ok(ast::LitKind::Int(i, _)) => accumulator.push_str(&format!("-{i}")),
+                    Ok(ast::LitKind::Float(f, _)) => accumulator.push_str(&format!("-{f}")),
+                    Err(err) => {
+                        report_lit_error(&cx.sess.parse_sess, err, token_lit, e.span);
+                        has_errors = true;
+                    }
+                    _ => missing_literal.push(e.span),
+                }
+            }
             ast::ExprKind::IncludedBytes(..) => {
-                cx.span_err(e.span, "cannot concatenate a byte string literal")
+                cx.emit_err(errors::ConcatBytestr { span: e.span });
             }
             ast::ExprKind::Err => {
                 has_errors = true;
@@ -53,10 +67,9 @@ pub fn expand_concat(
             }
         }
     }
+
     if !missing_literal.is_empty() {
-        let mut err = cx.struct_span_err(missing_literal, "expected a literal");
-        err.note("only literals (like `\"foo\"`, `42` and `3.14`) can be passed to `concat!()`");
-        err.emit();
+        cx.emit_err(errors::ConcatMissingLiteral { spans: missing_literal });
         return DummyResult::any(sp);
     } else if has_errors {
         return DummyResult::any(sp);