fix: check bases does not contain reference to loop index

Author: granddaifuku

clippy_lints/src/loops/manual_memcpy.rs

@@ -3,6 +3,7 @@ use clippy_utils::diagnostics::span_lint_and_sugg;
 use clippy_utils::source::snippet;
 use clippy_utils::sugg::Sugg;
 use clippy_utils::ty::is_copy;
+use clippy_utils::usage::local_used_in;
 use clippy_utils::{get_enclosing_block, higher, path_to_local, sugg};
 use rustc_ast::ast;
 use rustc_errors::Applicability;
@@ -59,13 +60,13 @@ pub(super) fn check<'tcx>(
                         let rhs = fetch_cloned_expr(rhs);
                         if let ExprKind::Index(base_left, idx_left, _) = lhs.kind
                             && let ExprKind::Index(base_right, idx_right, _) = rhs.kind
-                            && is_index_suggestable(base_left) && is_index_suggestable(base_right)
                             && let Some(ty) = get_slice_like_element_ty(cx, cx.typeck_results().expr_ty(base_left))
                             && get_slice_like_element_ty(cx, cx.typeck_results().expr_ty(base_right)).is_some()
                             && let Some((start_left, offset_left)) = get_details_from_idx(cx, idx_left, &starts)
                             && let Some((start_right, offset_right)) = get_details_from_idx(cx, idx_right, &starts)
-
-                            // Source and destination must be different
+							&& !local_used_in(cx, canonical_id, base_left)
+							&& !local_used_in(cx, canonical_id, base_right)
+                        // Source and destination must be different
                             && path_to_local(base_left) != path_to_local(base_right)
                         {
                             Some((
@@ -487,19 +488,3 @@ fn is_array_length_equal_to_range(cx: &LateContext<'_>, start: &Expr<'_>, end: &
         false
     }
 }
-
-// Returns true if index is suggestable
-// i.e. Returns false if patterns are Index(Path(_), Path(_)) or Index(Index(_, _, _), Path(_))
-fn is_index_suggestable(expr: &Expr<'_>) -> bool {
-    if let ExprKind::Index(left_expr, right_expr, _) = expr.kind {
-        // Index(Path(_), Path(_), _) returns false
-        if matches!(left_expr.kind, ExprKind::Path(_)) {
-            return !matches!(right_expr.kind, ExprKind::Path(_));
-        }
-
-        // Nested Index pattern
-        return is_index_suggestable(left_expr) && !matches!(right_expr.kind, ExprKind::Path(_));
-    }
-
-    true
-}

tests/ui/manual_memcpy/without_loop_counters.rs

@@ -161,6 +161,9 @@ pub fn manual_copy(src: &[i32], dst: &mut [i32], dst2: &mut [i32]) {
 
     // Don't trigger lint for following multi-dimension arrays
     let src = [[0; 5]; 5];
+    for i in 0..4 {
+        dst[i] = src[i + 1][i];
+    }
     for i in 0..5 {
         dst[i] = src[i][i];
     }

tests/ui/manual_memcpy/without_loop_counters.stderr

@@ -145,7 +145,7 @@ LL | |     }
    | |_____^ help: try replacing the loop by: `dst.copy_from_slice(&src);`
 
 error: it looks like you're manually copying between slices
-  --> tests/ui/manual_memcpy/without_loop_counters.rs:201:5
+  --> tests/ui/manual_memcpy/without_loop_counters.rs:204:5
    |
 LL | /     for i in 0..5 {
 LL | |
@@ -154,7 +154,7 @@ LL | |     }
    | |_____^ help: try replacing the loop by: `dst.copy_from_slice(&src[0]);`
 
 error: it looks like you're manually copying between slices
-  --> tests/ui/manual_memcpy/without_loop_counters.rs:207:5
+  --> tests/ui/manual_memcpy/without_loop_counters.rs:210:5
    |
 LL | /     for i in 0..5 {
 LL | |
@@ -163,7 +163,7 @@ LL | |     }
    | |_____^ help: try replacing the loop by: `dst.copy_from_slice(&src[0][1]);`
 
 error: it looks like you're manually copying between slices
-  --> tests/ui/manual_memcpy/without_loop_counters.rs:215:5
+  --> tests/ui/manual_memcpy/without_loop_counters.rs:218:5
    |
 LL | /     for i in 0..src.len() {
 LL | |