Create core::fmt::ArgumentV1 with generics instead of fn pointer

Author: nbdd0121

clippy_utils/src/macros.rs

@@ -339,15 +339,13 @@ impl<'tcx> FormatArgsExpn<'tcx> {
         expr_visitor_no_bodies(|e| {
             // if we're still inside of the macro definition...
             if e.span.ctxt() == expr.span.ctxt() {
-                // ArgumnetV1::new(<value>, <format_trait>::fmt)
+                // ArgumnetV1::new_<format_trait>(<value>)
                 if_chain! {
-                    if let ExprKind::Call(callee, [val, fmt_path]) = e.kind;
+                    if let ExprKind::Call(callee, [val]) = e.kind;
                     if let ExprKind::Path(QPath::TypeRelative(ty, seg)) = callee.kind;
-                    if seg.ident.name == sym::new;
                     if let hir::TyKind::Path(QPath::Resolved(_, path)) = ty.kind;
                     if path.segments.last().unwrap().ident.name == sym::ArgumentV1;
-                    if let ExprKind::Path(QPath::Resolved(_, path)) = fmt_path.kind;
-                    if let [.., fmt_trait, _fmt] = path.segments;
+                    if seg.ident.name.as_str().starts_with("new_");
                     then {
                         let val_idx = if_chain! {
                             if val.span.ctxt() == expr.span.ctxt();
@@ -361,7 +359,19 @@ impl<'tcx> FormatArgsExpn<'tcx> {
                                 formatters.len()
                             }
                         };
-                        formatters.push((val_idx, fmt_trait.ident.name));
+                        let fmt_trait = match seg.ident.name.as_str() {
+                            "new_display" => "Display",
+                            "new_debug" => "Debug",
+                            "new_lower_exp" => "LowerExp",
+                            "new_upper_exp" => "UpperExp",
+                            "new_octal" => "Octal",
+                            "new_pointer" => "Pointer",
+                            "new_binary" => "Binary",
+                            "new_lower_hex" => "LowerHex",
+                            "new_upper_hex" => "UpperHex",
+                            _ => unreachable!(),
+                        };
+                        formatters.push((val_idx, Symbol::intern(fmt_trait)));
                     }
                 }
                 if let ExprKind::Struct(QPath::Resolved(_, path), ..) = e.kind {