Auto merge of rust-lang#13248 - Alexendoo:format-arg-ast-fallback, r=xFrednet

Remove `find_format_arg_expr` AST fallback

If the function fails where it shouldn't we can fix that directly, but the fallback path is untested as I'm not aware of a case where it would fail

changelog: none

Author: bors

clippy_lints/src/format.rs

@@ -73,7 +73,7 @@ impl<'tcx> LateLintPass<'tcx> for UselessFormat {
                     span_useless_format(cx, call_site, sugg, applicability);
                 },
                 ([arg], [piece]) => {
-                    if let Ok(value) = find_format_arg_expr(expr, arg)
+                    if let Some(value) = find_format_arg_expr(expr, arg)
                         && let FormatArgsPiece::Placeholder(placeholder) = piece
                         && placeholder.format_trait == FormatTrait::Display
                         && placeholder.format_options == FormatOptions::default()

clippy_lints/src/format_args.rs

@@ -224,13 +224,11 @@ impl<'a, 'tcx> FormatArgsExpr<'a, 'tcx> {
             if let FormatArgsPiece::Placeholder(placeholder) = piece
                 && let Ok(index) = placeholder.argument.index
                 && let Some(arg) = self.format_args.arguments.all_args().get(index)
+                && let Some(arg_expr) = find_format_arg_expr(self.expr, arg)
             {
-                let arg_expr = find_format_arg_expr(self.expr, arg);
-
                 self.check_unused_format_specifier(placeholder, arg_expr);
 
-                if let Ok(arg_expr) = arg_expr
-                    && placeholder.format_trait == FormatTrait::Display
+                if placeholder.format_trait == FormatTrait::Display
                     && placeholder.format_options == FormatOptions::default()
                     && !self.is_aliased(index)
                 {
@@ -242,28 +240,13 @@ impl<'a, 'tcx> FormatArgsExpr<'a, 'tcx> {
         }
     }
 
-    fn check_unused_format_specifier(
-        &self,
-        placeholder: &FormatPlaceholder,
-        arg_expr: Result<&Expr<'_>, &rustc_ast::Expr>,
-    ) {
-        let ty_or_ast_expr = arg_expr.map(|expr| self.cx.typeck_results().expr_ty(expr).peel_refs());
-
-        let is_format_args = match ty_or_ast_expr {
-            Ok(ty) => is_type_lang_item(self.cx, ty, LangItem::FormatArguments),
-            Err(expr) => matches!(expr.peel_parens_and_refs().kind, rustc_ast::ExprKind::FormatArgs(_)),
-        };
-
+    fn check_unused_format_specifier(&self, placeholder: &FormatPlaceholder, arg: &Expr<'_>) {
         let options = &placeholder.format_options;
 
-        let arg_span = match arg_expr {
-            Ok(expr) => expr.span,
-            Err(expr) => expr.span,
-        };
-
         if let Some(placeholder_span) = placeholder.span
-            && is_format_args
             && *options != FormatOptions::default()
+            && let ty = self.cx.typeck_results().expr_ty(arg).peel_refs()
+            && is_type_lang_item(self.cx, ty, LangItem::FormatArguments)
         {
             span_lint_and_then(
                 self.cx,
@@ -274,7 +257,7 @@ impl<'a, 'tcx> FormatArgsExpr<'a, 'tcx> {
                     let mut suggest_format = |spec| {
                         let message = format!("for the {spec} to apply consider using `format!()`");
 
-                        if let Some(mac_call) = matching_root_macro_call(self.cx, arg_span, sym::format_args_macro) {
+                        if let Some(mac_call) = matching_root_macro_call(self.cx, arg.span, sym::format_args_macro) {
                             diag.span_suggestion(
                                 self.cx.sess().source_map().span_until_char(mac_call.span, '!'),
                                 message,

clippy_lints/src/format_impl.rs

@@ -196,7 +196,7 @@ impl<'a, 'tcx> FormatImplExpr<'a, 'tcx> {
                     && trait_name == self.format_trait_impl.name
                     && let Ok(index) = placeholder.argument.index
                     && let Some(arg) = format_args.arguments.all_args().get(index)
-                    && let Ok(arg_expr) = find_format_arg_expr(self.expr, arg)
+                    && let Some(arg_expr) = find_format_arg_expr(self.expr, arg)
                 {
                     self.check_format_arg_self(arg_expr);
                 }

clippy_utils/src/macros.rs

@@ -426,12 +426,8 @@ impl FormatArgsStorage {
     }
 }
 
-/// Attempt to find the [`rustc_hir::Expr`] that corresponds to the [`FormatArgument`]'s value, if
-/// it cannot be found it will return the [`rustc_ast::Expr`].
-pub fn find_format_arg_expr<'hir, 'ast>(
-    start: &'hir Expr<'hir>,
-    target: &'ast FormatArgument,
-) -> Result<&'hir Expr<'hir>, &'ast rustc_ast::Expr> {
+/// Attempt to find the [`rustc_hir::Expr`] that corresponds to the [`FormatArgument`]'s value
+pub fn find_format_arg_expr<'hir>(start: &'hir Expr<'hir>, target: &FormatArgument) -> Option<&'hir Expr<'hir>> {
     let SpanData {
         lo,
         hi,
@@ -449,7 +445,6 @@ pub fn find_format_arg_expr<'hir, 'ast>(
             ControlFlow::Continue(())
         }
     })
-    .ok_or(&target.expr)
 }
 
 /// Span of the `:` and format specifiers