From 7c17dd331bb5708152ef2c2dd91c67287f9d821d Mon Sep 17 00:00:00 2001
From: Jason Newcomb <jsnewcomb@pm.me>
Date: Sat, 15 Jun 2024 02:13:32 -0400
Subject: [PATCH] `needless_for_each`: Check HIR tree first.

---
 clippy_lints/src/needless_for_each.rs | 16 +++++-----------
 1 file changed, 5 insertions(+), 11 deletions(-)

diff --git a/clippy_lints/src/needless_for_each.rs b/clippy_lints/src/needless_for_each.rs
index 143acc2b1..6390e51f9 100644
--- a/clippy_lints/src/needless_for_each.rs
+++ b/clippy_lints/src/needless_for_each.rs
@@ -3,7 +3,7 @@ use rustc_hir::intravisit::{walk_expr, Visitor};
 use rustc_hir::{Block, BlockCheckMode, Closure, Expr, ExprKind, Stmt, StmtKind};
 use rustc_lint::{LateContext, LateLintPass};
 use rustc_session::declare_lint_pass;
-use rustc_span::{sym, Span, Symbol};
+use rustc_span::{sym, Span};
 
 use clippy_utils::diagnostics::span_lint_and_then;
 use clippy_utils::is_trait_method;
@@ -55,16 +55,8 @@ declare_lint_pass!(NeedlessForEach => [NEEDLESS_FOR_EACH]);
 
 impl<'tcx> LateLintPass<'tcx> for NeedlessForEach {
     fn check_stmt(&mut self, cx: &LateContext<'tcx>, stmt: &'tcx Stmt<'_>) {
-        let (StmtKind::Expr(expr) | StmtKind::Semi(expr)) = stmt.kind else {
-            return;
-        };
-
-        if let ExprKind::MethodCall(method_name, for_each_recv, [for_each_arg], _) = expr.kind
-            // Check the method name is `for_each`.
-            && method_name.ident.name == Symbol::intern("for_each")
-            // Check `for_each` is an associated function of `Iterator`.
-            && is_trait_method(cx, expr, sym::Iterator)
-            // Checks the receiver of `for_each` is also a method call.
+        if let StmtKind::Expr(expr) | StmtKind::Semi(expr) = stmt.kind
+            && let ExprKind::MethodCall(method_name, for_each_recv, [for_each_arg], _) = expr.kind
             && let ExprKind::MethodCall(_, iter_recv, [], _) = for_each_recv.kind
             // Skip the lint if the call chain is too long. e.g. `v.field.iter().for_each()` or
             // `v.foo().iter().for_each()` must be skipped.
@@ -72,6 +64,8 @@ impl<'tcx> LateLintPass<'tcx> for NeedlessForEach {
                 iter_recv.kind,
                 ExprKind::Array(..) | ExprKind::Call(..) | ExprKind::Path(..)
             )
+            && method_name.ident.name.as_str() == "for_each"
+            && is_trait_method(cx, expr, sym::Iterator)
             // Checks the type of the `iter` method receiver is NOT a user defined type.
             && has_iter_method(cx, cx.typeck_results().expr_ty(iter_recv)).is_some()
             // Skip the lint if the body is not block because this is simpler than `for` loop.