Refactor absolute_paths:

* Check the path length first
* Use `is_from_proc_macro`
* Use symbols instead of strings when checking crate names

clippy_lints/src/absolute_paths.rs

@@ -1,13 +1,14 @@
 use clippy_config::Conf;
 use clippy_utils::diagnostics::span_lint;
-use clippy_utils::source::snippet_opt;
+use clippy_utils::is_from_proc_macro;
 use rustc_data_structures::fx::FxHashSet;
 use rustc_hir::def::{DefKind, Res};
 use rustc_hir::def_id::{DefId, CRATE_DEF_INDEX};
 use rustc_hir::{HirId, ItemKind, Node, Path};
 use rustc_lint::{LateContext, LateLintPass};
 use rustc_session::impl_lint_pass;
 use rustc_span::symbol::kw;
+use rustc_span::Symbol;
 
 declare_clippy_lint! {
     /// ### What it does
@@ -24,6 +25,13 @@ declare_clippy_lint! {
     /// Note: One exception to this is code from macro expansion - this does not lint such cases, as
     /// using absolute paths is the proper way of referencing items in one.
     ///
+    /// ### Known issues
+    ///
+    /// There are currently a few cases which are not caught by this lint:
+    /// * Macro calls. e.g. `path::to::macro!()`
+    /// * Derive macros. e.g. `#[derive(path::to::macro)]`
+    /// * Attribute macros. e.g. `#[path::to::macro]`
+    ///
     /// ### Example
     /// ```no_run
     /// let x = std::f64::consts::PI;
@@ -48,63 +56,65 @@ impl_lint_pass!(AbsolutePaths => [ABSOLUTE_PATHS]);
 
 pub struct AbsolutePaths {
     pub absolute_paths_max_segments: u64,
-    pub absolute_paths_allowed_crates: &'static FxHashSet<String>,
+    pub absolute_paths_allowed_crates: FxHashSet<Symbol>,
 }
 
 impl AbsolutePaths {
     pub fn new(conf: &'static Conf) -> Self {
         Self {
             absolute_paths_max_segments: conf.absolute_paths_max_segments,
-            absolute_paths_allowed_crates: &conf.absolute_paths_allowed_crates,
+            absolute_paths_allowed_crates: conf.absolute_paths_allowed_crates
+                .iter()
+                .map(|x| Symbol::intern(x))
+                .collect(),
         }
     }
 }
 
-impl LateLintPass<'_> for AbsolutePaths {
+impl<'tcx> LateLintPass<'tcx> for AbsolutePaths {
     // We should only lint `QPath::Resolved`s, but since `Path` is only used in `Resolved` and `UsePath`
     // we don't need to use a visitor or anything as we can just check if the `Node` for `hir_id` isn't
     // a `Use`
-    #[expect(clippy::cast_possible_truncation)]
-    fn check_path(&mut self, cx: &LateContext<'_>, path: &Path<'_>, hir_id: HirId) {
-        let Self {
-            absolute_paths_max_segments,
-            absolute_paths_allowed_crates,
-        } = self;
-
-        if !path.span.from_expansion()
-            && let node = cx.tcx.hir_node(hir_id)
-            && !matches!(node, Node::Item(item) if matches!(item.kind, ItemKind::Use(_, _)))
-            && let [first, rest @ ..] = path.segments
-            // Handle `::std`
-            && let (segment, len) = if first.ident.name == kw::PathRoot {
-                // Indexing is fine as `PathRoot` must be followed by another segment. `len() - 1`
-                // is fine here for the same reason
-                (&rest[0], path.segments.len() - 1)
-            } else {
-                (first, path.segments.len())
-            }
-            && len > *absolute_paths_max_segments as usize
-            && let Some(segment_snippet) = snippet_opt(cx, segment.ident.span)
-            && segment_snippet == segment.ident.as_str()
-        {
-            let is_abs_external =
-                matches!(segment.res, Res::Def(DefKind::Mod, DefId { index, .. }) if index == CRATE_DEF_INDEX);
-            let is_abs_crate = segment.ident.name == kw::Crate;
-
-            if is_abs_external && absolute_paths_allowed_crates.contains(segment.ident.name.as_str())
-                || is_abs_crate && absolute_paths_allowed_crates.contains("crate")
+    fn check_path(&mut self, cx: &LateContext<'tcx>, path: &Path<'tcx>, hir_id: HirId) {
+        let segments = match path.segments {
+            [] | [_] => return,
+            // Don't count enum variants and trait items as part of the length.
+            [rest @ .., _]
+                if let [.., s] = rest
+                    && matches!(s.res, Res::Def(DefKind::Enum | DefKind::Trait | DefKind::TraitAlias, _)) =>
+            {
+                rest
+            },
+            path => path,
+        };
+        if let [s1, s2, ..] = segments
+            && let has_root = s1.ident.name == kw::PathRoot
+            && let first = if has_root { s2 } else { s1 }
+            && let len = segments.len() - usize::from(has_root)
+            && len as u64 > self.absolute_paths_max_segments
+            && let crate_name = if let Res::Def(DefKind::Mod, DefId { index, .. }) = first.res
+                && index == CRATE_DEF_INDEX
             {
+                // `other_crate::foo` or `::other_crate::foo`
+                first.ident.name
+            } else if first.ident.name == kw::Crate || has_root {
+                // `::foo` or `crate::foo`
+                kw::Crate
+            } else {
                 return;
             }
-
-            if is_abs_external || is_abs_crate {
-                span_lint(
-                    cx,
-                    ABSOLUTE_PATHS,
-                    path.span,
-                    "consider bringing this path into scope with the `use` keyword",
-                );
-            }
+            && !path.span.from_expansion()
+            && let node = cx.tcx.hir_node(hir_id)
+            && !matches!(node, Node::Item(item) if matches!(item.kind, ItemKind::Use(..)))
+            && !self.absolute_paths_allowed_crates.contains(&crate_name)
+            && !is_from_proc_macro(cx, path)
+        {
+            span_lint(
+                cx,
+                ABSOLUTE_PATHS,
+                path.span,
+                "consider bringing this path into scope with the `use` keyword",
+            );
         }
     }
 }

clippy_utils/src/check_proc_macro.rs

@@ -123,16 +123,14 @@ fn qpath_search_pat(path: &QPath<'_>) -> (Pat, Pat) {
 
 fn path_search_pat(path: &Path<'_>) -> (Pat, Pat) {
     let (head, tail) = match path.segments {
-        [head, .., tail] => (head, tail),
-        [p] => (p, p),
         [] => return (Pat::Str(""), Pat::Str("")),
+        [p] => (Pat::Sym(p.ident.name), p),
+        // QPath::Resolved can have a path that looks like `<Foo as Bar>::baz` where
+        // the path (`Bar::baz`) has it's span covering the whole QPath.
+        [.., tail] => (Pat::Str(""), tail),
     };
     (
-        if head.ident.name == kw::PathRoot {
-            Pat::Str("::")
-        } else {
-            Pat::Sym(head.ident.name)
-        },
+        head,
         if tail.args.is_some() {
             Pat::Str(">")
         } else {

tests/ui-toml/absolute_paths/absolute_paths.allow_crates.stderr

@@ -1,29 +1,44 @@
 error: consider bringing this path into scope with the `use` keyword
-  --> tests/ui-toml/absolute_paths/absolute_paths.rs:40:5
+  --> tests/ui-toml/absolute_paths/absolute_paths.rs:14:13
    |
-LL |     std::f32::MAX;
-   |     ^^^^^^^^^^^^^
+LL |     let _ = std::path::is_separator(' ');
+   |             ^^^^^^^^^^^^^^^^^^^^^^^
    |
-   = note: `-D clippy::absolute-paths` implied by `-D warnings`
-   = help: to override `-D warnings` add `#[allow(clippy::absolute_paths)]`
+note: the lint level is defined here
+  --> tests/ui-toml/absolute_paths/absolute_paths.rs:7:9
+   |
+LL | #![deny(clippy::absolute_paths)]
+   |         ^^^^^^^^^^^^^^^^^^^^^^
+
+error: consider bringing this path into scope with the `use` keyword
+  --> tests/ui-toml/absolute_paths/absolute_paths.rs:20:13
+   |
+LL |     let _ = ::std::path::MAIN_SEPARATOR;
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: consider bringing this path into scope with the `use` keyword
+  --> tests/ui-toml/absolute_paths/absolute_paths.rs:25:13
+   |
+LL |     let _ = std::collections::hash_map::HashMap::<i32, i32>::new();
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: consider bringing this path into scope with the `use` keyword
-  --> tests/ui-toml/absolute_paths/absolute_paths.rs:41:5
+  --> tests/ui-toml/absolute_paths/absolute_paths.rs:28:31
    |
-LL |     core::f32::MAX;
-   |     ^^^^^^^^^^^^^^
+LL |     let _: &std::path::Path = std::path::Path::new("");
+   |                               ^^^^^^^^^^^^^^^
 
 error: consider bringing this path into scope with the `use` keyword
-  --> tests/ui-toml/absolute_paths/absolute_paths.rs:42:5
+  --> tests/ui-toml/absolute_paths/absolute_paths.rs:28:13
    |
-LL |     ::core::f32::MAX;
-   |     ^^^^^^^^^^^^^^^^
+LL |     let _: &std::path::Path = std::path::Path::new("");
+   |             ^^^^^^^^^^^^^^^
 
 error: consider bringing this path into scope with the `use` keyword
-  --> tests/ui-toml/absolute_paths/absolute_paths.rs:58:5
+  --> tests/ui-toml/absolute_paths/absolute_paths.rs:43:13
    |
-LL |     ::std::f32::MAX;
-   |     ^^^^^^^^^^^^^^^
+LL |     let _ = std::option::Option::None::<i32>;
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error: aborting due to 4 previous errors
+error: aborting due to 6 previous errors
 

tests/ui-toml/absolute_paths/absolute_paths.allow_long.stderr

@@ -0,0 +1,14 @@
+error: consider bringing this path into scope with the `use` keyword
+  --> tests/ui-toml/absolute_paths/absolute_paths.rs:25:13
+   |
+LL |     let _ = std::collections::hash_map::HashMap::<i32, i32>::new();
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+note: the lint level is defined here
+  --> tests/ui-toml/absolute_paths/absolute_paths.rs:7:9
+   |
+LL | #![deny(clippy::absolute_paths)]
+   |         ^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 1 previous error
+

tests/ui-toml/absolute_paths/absolute_paths.default.stderr

@@ -0,0 +1,80 @@
+error: consider bringing this path into scope with the `use` keyword
+  --> tests/ui-toml/absolute_paths/absolute_paths.rs:14:13
+   |
+LL |     let _ = std::path::is_separator(' ');
+   |             ^^^^^^^^^^^^^^^^^^^^^^^
+   |
+note: the lint level is defined here
+  --> tests/ui-toml/absolute_paths/absolute_paths.rs:7:9
+   |
+LL | #![deny(clippy::absolute_paths)]
+   |         ^^^^^^^^^^^^^^^^^^^^^^
+
+error: consider bringing this path into scope with the `use` keyword
+  --> tests/ui-toml/absolute_paths/absolute_paths.rs:20:13
+   |
+LL |     let _ = ::std::path::MAIN_SEPARATOR;
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: consider bringing this path into scope with the `use` keyword
+  --> tests/ui-toml/absolute_paths/absolute_paths.rs:25:13
+   |
+LL |     let _ = std::collections::hash_map::HashMap::<i32, i32>::new();
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: consider bringing this path into scope with the `use` keyword
+  --> tests/ui-toml/absolute_paths/absolute_paths.rs:28:31
+   |
+LL |     let _: &std::path::Path = std::path::Path::new("");
+   |                               ^^^^^^^^^^^^^^^
+
+error: consider bringing this path into scope with the `use` keyword
+  --> tests/ui-toml/absolute_paths/absolute_paths.rs:28:13
+   |
+LL |     let _: &std::path::Path = std::path::Path::new("");
+   |             ^^^^^^^^^^^^^^^
+
+error: consider bringing this path into scope with the `use` keyword
+  --> tests/ui-toml/absolute_paths/absolute_paths.rs:37:13
+   |
+LL |     let _ = ::core::clone::Clone::clone(&0i32);
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: consider bringing this path into scope with the `use` keyword
+  --> tests/ui-toml/absolute_paths/absolute_paths.rs:40:13
+   |
+LL |     let _ = <i32 as core::clone::Clone>::clone(&0i32);
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: consider bringing this path into scope with the `use` keyword
+  --> tests/ui-toml/absolute_paths/absolute_paths.rs:43:13
+   |
+LL |     let _ = std::option::Option::None::<i32>;
+   |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: consider bringing this path into scope with the `use` keyword
+  --> tests/ui-toml/absolute_paths/absolute_paths.rs:65:17
+   |
+LL |         impl<T: core::cmp::Eq> core::fmt::Display for X<T>
+   |                 ^^^^^^^^^^^^^
+
+error: consider bringing this path into scope with the `use` keyword
+  --> tests/ui-toml/absolute_paths/absolute_paths.rs:70:18
+   |
+LL |         where T: core::clone::Clone
+   |                  ^^^^^^^^^^^^^^^^^^
+
+error: consider bringing this path into scope with the `use` keyword
+  --> tests/ui-toml/absolute_paths/absolute_paths.rs:65:32
+   |
+LL |         impl<T: core::cmp::Eq> core::fmt::Display for X<T>
+   |                                ^^^^^^^^^^^^^^^^^^
+
+error: consider bringing this path into scope with the `use` keyword
+  --> tests/ui-toml/absolute_paths/absolute_paths.rs:116:5
+   |
+LL |     crate::m1::S
+   |     ^^^^^^^^^^^^
+
+error: aborting due to 12 previous errors
+