1 files changed, 44 insertions, 47 deletions

diff --git a/src/tools/clippy/clippy_lints/src/format.rs b/src/tools/clippy/clippy_lints/src/format.rs
index d0fab6949..d34d6e927 100644
--- a/src/tools/clippy/clippy_lints/src/format.rs
+++ b/src/tools/clippy/clippy_lints/src/format.rs
@@ -1,14 +1,13 @@
 use clippy_utils::diagnostics::span_lint_and_sugg;
-use clippy_utils::macros::{root_macro_call_first_node, FormatArgsExpn};
-use clippy_utils::source::snippet_with_applicability;
+use clippy_utils::macros::{find_format_arg_expr, find_format_args, root_macro_call_first_node};
+use clippy_utils::source::{snippet_opt, snippet_with_context};
 use clippy_utils::sugg::Sugg;
-use if_chain::if_chain;
+use rustc_ast::{FormatArgsPiece, FormatOptions, FormatTrait};
 use rustc_errors::Applicability;
 use rustc_hir::{Expr, ExprKind};
 use rustc_lint::{LateContext, LateLintPass};
 use rustc_middle::ty;
 use rustc_session::{declare_lint_pass, declare_tool_lint};
-use rustc_span::symbol::kw;
 use rustc_span::{sym, Span};
 
 declare_clippy_lint! {
@@ -44,55 +43,53 @@ declare_lint_pass!(UselessFormat => [USELESS_FORMAT]);
 
 impl<'tcx> LateLintPass<'tcx> for UselessFormat {
     fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
-        let (format_args, call_site) = if_chain! {
-            if let Some(macro_call) = root_macro_call_first_node(cx, expr);
-            if cx.tcx.is_diagnostic_item(sym::format_macro, macro_call.def_id);
-            if let Some(format_args) = FormatArgsExpn::find_nested(cx, expr, macro_call.expn);
-            then {
-                (format_args, macro_call.span)
-            } else {
-                return
-            }
-        };
+        let Some(macro_call) = root_macro_call_first_node(cx, expr) else { return };
+        if !cx.tcx.is_diagnostic_item(sym::format_macro, macro_call.def_id) {
+            return;
+        }
+
+        find_format_args(cx, expr, macro_call.expn, |format_args| {
+            let mut applicability = Applicability::MachineApplicable;
+            let call_site = macro_call.span;
 
-        let mut applicability = Applicability::MachineApplicable;
-        if format_args.args.is_empty() {
-            match *format_args.format_string.parts {
-                [] => span_useless_format_empty(cx, call_site, "String::new()".to_owned(), applicability),
-                [_] => {
+            match (format_args.arguments.all_args(), &format_args.template[..]) {
+                ([], []) => span_useless_format_empty(cx, call_site, "String::new()".to_owned(), applicability),
+                ([], [_]) => {
                     // Simulate macro expansion, converting {{ and }} to { and }.
-                    let s_expand = format_args.format_string.snippet.replace("{{", "{").replace("}}", "}");
+                    let Some(snippet) = snippet_opt(cx, format_args.span) else { return };
+                    let s_expand = snippet.replace("{{", "{").replace("}}", "}");
                     let sugg = format!("{s_expand}.to_string()");
                     span_useless_format(cx, call_site, sugg, applicability);
                 },
-                [..] => {},
-            }
-        } else if let [arg] = &*format_args.args {
-            let value = arg.param.value;
-            if_chain! {
-                if format_args.format_string.parts == [kw::Empty];
-                if arg.format.is_default();
-                if match cx.typeck_results().expr_ty(value).peel_refs().kind() {
-                    ty::Adt(adt, _) => Some(adt.did()) == cx.tcx.lang_items().string(),
-                    ty::Str => true,
-                    _ => false,
-                };
-                then {
-                    let is_new_string = match value.kind {
-                        ExprKind::Binary(..) => true,
-                        ExprKind::MethodCall(path, ..) => path.ident.name == sym::to_string,
-                        _ => false,
-                    };
-                    let sugg = if is_new_string {
-                        snippet_with_applicability(cx, value.span, "..", &mut applicability).into_owned()
-                    } else {
-                        let sugg = Sugg::hir_with_applicability(cx, value, "<arg>", &mut applicability);
-                        format!("{}.to_string()", sugg.maybe_par())
-                    };
-                    span_useless_format(cx, call_site, sugg, applicability);
-                }
+                ([arg], [piece]) => {
+                    if let Ok(value) = find_format_arg_expr(expr, arg)
+                        && let FormatArgsPiece::Placeholder(placeholder) = piece
+                        && placeholder.format_trait == FormatTrait::Display
+                        && placeholder.format_options == FormatOptions::default()
+                        && match cx.typeck_results().expr_ty(value).peel_refs().kind() {
+                            ty::Adt(adt, _) => Some(adt.did()) == cx.tcx.lang_items().string(),
+                            ty::Str => true,
+                            _ => false,
+                        }
+                    {
+                        let is_new_string = match value.kind {
+                            ExprKind::Binary(..) => true,
+                            ExprKind::MethodCall(path, ..) => path.ident.name == sym::to_string,
+                            _ => false,
+                        };
+                        let sugg = if is_new_string {
+                            snippet_with_context(cx, value.span, call_site.ctxt(), "..", &mut applicability).0.into_owned()
+                        } else {
+                            let sugg = Sugg::hir_with_context(cx, value, call_site.ctxt(), "<arg>", &mut applicability);
+                            format!("{}.to_string()", sugg.maybe_par())
+                        };
+                        span_useless_format(cx, call_site, sugg, applicability);
+
+                    }
+                },
+                _ => {},
             }
-        };
+        });
     }
 }