Remove old format_args diagnostic.

Author: m-ou-se

compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs

@@ -3201,14 +3201,6 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
                         let expr_ty: Option<Ty<'_>> =
                             visitor.prop_expr.map(|expr| typeck_results.expr_ty(expr).peel_refs());
 
-                        let is_format_arguments_item = if let Some(expr_ty) = expr_ty
-                            && let ty::Adt(adt, _) = expr_ty.kind()
-                        {
-                            self.infcx.tcx.is_lang_item(adt.did(), LangItem::FormatArguments)
-                        } else {
-                            false
-                        };
-
                         if visitor.found == 0
                             && stmt.span.contains(proper_span)
                             && let Some(p) = sm.span_to_margin(stmt.span)
@@ -3236,25 +3228,17 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
                                 ""
                             };
 
-                            if !is_format_arguments_item {
-                                let addition = format!(
-                                    "let {}binding = {};\n{}",
-                                    mutability,
-                                    s,
-                                    " ".repeat(p)
-                                );
-                                err.multipart_suggestion_verbose(
-                                    msg,
-                                    vec![
-                                        (stmt.span.shrink_to_lo(), addition),
-                                        (proper_span, "binding".to_string()),
-                                    ],
-                                    Applicability::MaybeIncorrect,
-                                );
-                            } else {
-                                err.note("the result of `format_args!` can only be assigned directly if no placeholders in its arguments are used");
-                                err.note("to learn more, visit <https://doc.rust-lang.org/std/macro.format_args.html>");
-                            }
+                            let addition =
+                                format!("let {}binding = {};\n{}", mutability, s, " ".repeat(p));
+                            err.multipart_suggestion_verbose(
+                                msg,
+                                vec![
+                                    (stmt.span.shrink_to_lo(), addition),
+                                    (proper_span, "binding".to_string()),
+                                ],
+                                Applicability::MaybeIncorrect,
+                            );
+
                             suggested = true;
                             break;
                         }