Use diagnostic items for `Into`, `IntoIterator`, `LinkedList`, `ptr::null`, `prt::null_mut`

11 files changed, 45 insertions, 26 deletions

diff --git a/clippy_lints/src/from_over_into.rs b/clippy_lints/src/from_over_into.rs
index 3560672a748..48316c3a61d 100644
--- a/clippy_lints/src/from_over_into.rs
+++ b/clippy_lints/src/from_over_into.rs
@@ -1,11 +1,11 @@
 use clippy_utils::diagnostics::span_lint_and_help;
-use clippy_utils::paths::INTO;
-use clippy_utils::{match_def_path, meets_msrv, msrvs};
+use clippy_utils::{meets_msrv, msrvs};
 use if_chain::if_chain;
 use rustc_hir as hir;
 use rustc_lint::{LateContext, LateLintPass, LintContext};
 use rustc_semver::RustcVersion;
 use rustc_session::{declare_tool_lint, impl_lint_pass};
+use rustc_span::symbol::sym;
 
 declare_clippy_lint! {
     /// **What it does:** Searches for implementations of the `Into<..>` trait and suggests to implement `From<..>` instead.
@@ -62,7 +62,7 @@ impl LateLintPass<'_> for FromOverInto {
         if_chain! {
             if let hir::ItemKind::Impl{ .. } = &item.kind;
             if let Some(impl_trait_ref) = cx.tcx.impl_trait_ref(item.def_id);
-            if match_def_path(cx, impl_trait_ref.def_id, &INTO);
+            if cx.tcx.is_diagnostic_item(sym::into_trait, impl_trait_ref.def_id);
 
             then {
                 span_lint_and_help(
diff --git a/clippy_lints/src/loops/explicit_into_iter_loop.rs b/clippy_lints/src/loops/explicit_into_iter_loop.rs
index c7a28f42ea1..1bab0d99b69 100644
--- a/clippy_lints/src/loops/explicit_into_iter_loop.rs
+++ b/clippy_lints/src/loops/explicit_into_iter_loop.rs
@@ -1,16 +1,17 @@
 use super::EXPLICIT_INTO_ITER_LOOP;
 use clippy_utils::diagnostics::span_lint_and_sugg;
+use clippy_utils::is_trait_method;
 use clippy_utils::source::snippet_with_applicability;
-use clippy_utils::{match_trait_method, paths};
 use rustc_errors::Applicability;
 use rustc_hir::Expr;
 use rustc_lint::LateContext;
 use rustc_middle::ty::TyS;
+use rustc_span::symbol::sym;
 
 pub(super) fn check(cx: &LateContext<'_>, self_arg: &'hir Expr<'hir>, call_expr: &Expr<'_>) {
     let self_ty = cx.typeck_results().expr_ty(self_arg);
     let self_ty_adjusted = cx.typeck_results().expr_ty_adjusted(self_arg);
-    if !(TyS::same_type(self_ty, self_ty_adjusted) && match_trait_method(cx, call_expr, &paths::INTO_ITERATOR)) {
+    if !(TyS::same_type(self_ty, self_ty_adjusted) && is_trait_method(cx, call_expr, sym::IntoIterator)) {
         return;
     }
 
diff --git a/clippy_lints/src/loops/explicit_iter_loop.rs b/clippy_lints/src/loops/explicit_iter_loop.rs
index 3ba56a9294f..50bc096ba22 100644
--- a/clippy_lints/src/loops/explicit_iter_loop.rs
+++ b/clippy_lints/src/loops/explicit_iter_loop.rs
@@ -1,8 +1,8 @@
 use super::EXPLICIT_ITER_LOOP;
 use clippy_utils::diagnostics::span_lint_and_sugg;
+use clippy_utils::is_trait_method;
 use clippy_utils::source::snippet_with_applicability;
-use clippy_utils::ty::{is_type_diagnostic_item, match_type};
-use clippy_utils::{match_trait_method, paths};
+use clippy_utils::ty::is_type_diagnostic_item;
 use rustc_errors::Applicability;
 use rustc_hir::{Expr, Mutability};
 use rustc_lint::LateContext;
@@ -12,7 +12,7 @@ use rustc_span::sym;
 pub(super) fn check(cx: &LateContext<'_>, self_arg: &Expr<'_>, arg: &Expr<'_>, method_name: &str) {
     let should_lint = match method_name {
         "iter" | "iter_mut" => is_ref_iterable_type(cx, self_arg),
-        "into_iter" if match_trait_method(cx, arg, &paths::INTO_ITERATOR) => {
+        "into_iter" if is_trait_method(cx, arg, sym::IntoIterator) => {
             let receiver_ty = cx.typeck_results().expr_ty(self_arg);
             let receiver_ty_adjusted = cx.typeck_results().expr_ty_adjusted(self_arg);
             let ref_receiver_ty = cx.tcx.mk_ref(
@@ -55,7 +55,7 @@ fn is_ref_iterable_type(cx: &LateContext<'_>, e: &Expr<'_>) -> bool {
     let ty = cx.typeck_results().expr_ty(e);
     is_iterable_array(ty, cx) ||
     is_type_diagnostic_item(cx, ty, sym::vec_type) ||
-    match_type(cx, ty, &paths::LINKED_LIST) ||
+    is_type_diagnostic_item(cx, ty, sym::LinkedList) ||
     is_type_diagnostic_item(cx, ty, sym::hashmap_type) ||
     is_type_diagnostic_item(cx, ty, sym::hashset_type) ||
     is_type_diagnostic_item(cx, ty, sym::vecdeque_type) ||
diff --git a/clippy_lints/src/matches.rs b/clippy_lints/src/matches.rs
index de73af8bf60..e4f6aae7f82 100644
--- a/clippy_lints/src/matches.rs
+++ b/clippy_lints/src/matches.rs
@@ -1794,7 +1794,7 @@ mod redundant_pattern_match {
             || is_type_diagnostic_item(cx, ty, sym::Arc)
             || is_type_diagnostic_item(cx, ty, sym::cstring_type)
             || is_type_diagnostic_item(cx, ty, sym::BTreeMap)
-            || match_type(cx, ty, &paths::LINKED_LIST)
+            || is_type_diagnostic_item(cx, ty, sym::LinkedList)
             || match_type(cx, ty, &paths::WEAK_RC)
             || match_type(cx, ty, &paths::WEAK_ARC)
         {
diff --git a/clippy_lints/src/methods/iter_count.rs b/clippy_lints/src/methods/iter_count.rs
index f8a38e67d00..b69f57f50e0 100644
--- a/clippy_lints/src/methods/iter_count.rs
+++ b/clippy_lints/src/methods/iter_count.rs
@@ -1,8 +1,7 @@
 use super::utils::derefs_to_slice;
 use clippy_utils::diagnostics::span_lint_and_sugg;
-use clippy_utils::paths;
 use clippy_utils::source::snippet_with_applicability;
-use clippy_utils::ty::{is_type_diagnostic_item, match_type};
+use clippy_utils::ty::is_type_diagnostic_item;
 use rustc_errors::Applicability;
 use rustc_hir::Expr;
 use rustc_lint::LateContext;
@@ -26,7 +25,7 @@ pub(crate) fn check<'tcx>(cx: &LateContext<'tcx>, expr: &Expr<'_>, recv: &'tcx E
         "BTreeMap"
     } else if is_type_diagnostic_item(cx, ty, sym::BTreeSet) {
         "BTreeSet"
-    } else if match_type(cx, ty, &paths::LINKED_LIST) {
+    } else if is_type_diagnostic_item(cx, ty, sym::LinkedList) {
         "LinkedList"
     } else if is_type_diagnostic_item(cx, ty, sym::BinaryHeap) {
         "BinaryHeap"
diff --git a/clippy_lints/src/ptr.rs b/clippy_lints/src/ptr.rs
index dba3b1805cd..b15447622a8 100644
--- a/clippy_lints/src/ptr.rs
+++ b/clippy_lints/src/ptr.rs
@@ -4,7 +4,7 @@ use clippy_utils::diagnostics::{span_lint, span_lint_and_sugg, span_lint_and_the
 use clippy_utils::ptr::get_spans;
 use clippy_utils::source::snippet_opt;
 use clippy_utils::ty::{is_type_diagnostic_item, match_type, walk_ptrs_hir_ty};
-use clippy_utils::{expr_path_res, is_lint_allowed, match_any_def_paths, paths};
+use clippy_utils::{expr_path_res, is_lint_allowed, match_any_diagnostic_items, paths};
 use if_chain::if_chain;
 use rustc_errors::Applicability;
 use rustc_hir::{
@@ -419,7 +419,7 @@ fn get_rptr_lm<'tcx>(ty: &'tcx Ty<'tcx>) -> Option<(&'tcx Lifetime, Mutability,
 fn is_null_path(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool {
     if let ExprKind::Call(pathexp, []) = expr.kind {
         expr_path_res(cx, pathexp).opt_def_id().map_or(false, |id| {
-            match_any_def_paths(cx, id, &[&paths::PTR_NULL, &paths::PTR_NULL_MUT]).is_some()
+            match_any_diagnostic_items(cx, id, &[sym::ptr_null, sym::ptr_null_mut]).is_some()
         })
     } else {
         false
diff --git a/clippy_lints/src/transmuting_null.rs b/clippy_lints/src/transmuting_null.rs
index b57d158293d..5bbaeedad5f 100644
--- a/clippy_lints/src/transmuting_null.rs
+++ b/clippy_lints/src/transmuting_null.rs
@@ -1,12 +1,13 @@
 use clippy_utils::consts::{constant_context, Constant};
 use clippy_utils::diagnostics::span_lint;
-use clippy_utils::{is_expr_path_def_path, paths};
+use clippy_utils::{is_expr_diagnostic_item, is_expr_path_def_path, paths};
 use if_chain::if_chain;
 use rustc_ast::LitKind;
 use rustc_hir::{Expr, ExprKind};
 use rustc_lint::{LateContext, LateLintPass, LintContext};
 use rustc_middle::lint::in_external_macro;
 use rustc_session::{declare_lint_pass, declare_tool_lint};
+use rustc_span::symbol::sym;
 
 declare_clippy_lint! {
     /// **What it does:** Checks for transmute calls which would receive a null pointer.
@@ -67,7 +68,7 @@ impl<'tcx> LateLintPass<'tcx> for TransmutingNull {
                 // `std::mem::transmute(std::ptr::null::<i32>())`
                 if_chain! {
                     if let ExprKind::Call(func1, []) = arg.kind;
-                    if is_expr_path_def_path(cx, func1, &paths::PTR_NULL);
+                    if is_expr_diagnostic_item(cx, func1, sym::ptr_null);
                     then {
                         span_lint(cx, TRANSMUTING_NULL, expr.span, LINT_MSG)
                     }
diff --git a/clippy_lints/src/types/linked_list.rs b/clippy_lints/src/types/linked_list.rs
index a9fbe7aa315..5fb708741e5 100644
--- a/clippy_lints/src/types/linked_list.rs
+++ b/clippy_lints/src/types/linked_list.rs
@@ -1,12 +1,12 @@
 use clippy_utils::diagnostics::span_lint_and_help;
-use clippy_utils::{match_def_path, paths};
 use rustc_hir::{self as hir, def_id::DefId};
 use rustc_lint::LateContext;
+use rustc_span::symbol::sym;
 
 use super::LINKEDLIST;
 
 pub(super) fn check(cx: &LateContext<'_>, hir_ty: &hir::Ty<'_>, def_id: DefId) -> bool {
-    if match_def_path(cx, def_id, &paths::LINKED_LIST) {
+    if cx.tcx.is_diagnostic_item(sym::LinkedList, def_id) {
         span_lint_and_help(
             cx,
             LINKEDLIST,
diff --git a/clippy_lints/src/useless_conversion.rs b/clippy_lints/src/useless_conversion.rs
index c97f7e1626e..a4bc8c09f53 100644
--- a/clippy_lints/src/useless_conversion.rs
+++ b/clippy_lints/src/useless_conversion.rs
@@ -2,7 +2,7 @@ use clippy_utils::diagnostics::{span_lint_and_help, span_lint_and_sugg};
 use clippy_utils::source::{snippet, snippet_with_macro_callsite};
 use clippy_utils::sugg::Sugg;
 use clippy_utils::ty::{is_type_diagnostic_item, same_type_and_consts};
-use clippy_utils::{get_parent_expr, match_def_path, match_trait_method, paths};
+use clippy_utils::{get_parent_expr, is_trait_method, match_def_path, match_trait_method, paths};
 use if_chain::if_chain;
 use rustc_errors::Applicability;
 use rustc_hir::{Expr, ExprKind, HirId, MatchSource};
@@ -64,7 +64,7 @@ impl<'tcx> LateLintPass<'tcx> for UselessConversion {
             },
 
             ExprKind::MethodCall(name, .., args, _) => {
-                if match_trait_method(cx, e, &paths::INTO) && &*name.ident.as_str() == "into" {
+                if is_trait_method(cx, e, sym::into_trait) && &*name.ident.as_str() == "into" {
                     let a = cx.typeck_results().expr_ty(e);
                     let b = cx.typeck_results().expr_ty(&args[0]);
                     if same_type_and_consts(a, b) {
@@ -80,7 +80,7 @@ impl<'tcx> LateLintPass<'tcx> for UselessConversion {
                         );
                     }
                 }
-                if match_trait_method(cx, e, &paths::INTO_ITERATOR) && name.ident.name == sym::into_iter {
+                if is_trait_method(cx, e, sym::IntoIterator) && name.ident.name == sym::into_iter {
                     if let Some(parent_expr) = get_parent_expr(cx, e) {
                         if let ExprKind::MethodCall(parent_name, ..) = parent_expr.kind {
                             if parent_name.ident.name != sym::into_iter {
diff --git a/clippy_utils/src/lib.rs b/clippy_utils/src/lib.rs
index 364ae536ecd..b19d1430b6e 100644
--- a/clippy_utils/src/lib.rs
+++ b/clippy_utils/src/lib.rs
@@ -411,12 +411,22 @@ pub fn is_qpath_def_path(cx: &LateContext<'_>, path: &QPath<'_>, hir_id: HirId,
 }
 
 /// If the expression is a path, resolves it to a `DefId` and checks if it matches the given path.
+///
+/// Please use `is_expr_diagnostic_item` if the target is a diagnostic item.
 pub fn is_expr_path_def_path(cx: &LateContext<'_>, expr: &Expr<'_>, segments: &[&str]) -> bool {
     expr_path_res(cx, expr)
         .opt_def_id()
         .map_or(false, |id| match_def_path(cx, id, segments))
 }
 
+/// If the expression is a path, resolves it to a `DefId` and checks if it matches the given
+/// diagnostic item.
+pub fn is_expr_diagnostic_item(cx: &LateContext<'_>, expr: &Expr<'_>, diag_item: Symbol) -> bool {
+    expr_path_res(cx, expr)
+        .opt_def_id()
+        .map_or(false, |id| cx.tcx.is_diagnostic_item(diag_item, id))
+}
+
 /// THIS METHOD IS DEPRECATED and will eventually be removed since it does not match against the
 /// entire path or resolved `DefId`. Prefer using `match_def_path`. Consider getting a `DefId` from
 /// `QPath::Resolved.1.res.opt_def_id()`.
@@ -1249,6 +1259,8 @@ pub fn match_function_call<'tcx>(
 
 /// Checks if the given `DefId` matches any of the paths. Returns the index of matching path, if
 /// any.
+///
+/// Please use `match_any_diagnostic_items` if the targets are all diagnostic items.
 pub fn match_any_def_paths(cx: &LateContext<'_>, did: DefId, paths: &[&[&str]]) -> Option<usize> {
     let search_path = cx.get_def_path(did);
     paths
@@ -1256,6 +1268,14 @@ pub fn match_any_def_paths(cx: &LateContext<'_>, did: DefId, paths: &[&[&str]])
         .position(|p| p.iter().map(|x| Symbol::intern(x)).eq(search_path.iter().copied()))
 }
 
+/// Checks if the given `DefId` matches any of provided diagnostic items. Returns the index of
+/// matching path, if any.
+pub fn match_any_diagnostic_items(cx: &LateContext<'_>, def_id: DefId, diag_items: &[Symbol]) -> Option<usize> {
+    diag_items
+        .iter()
+        .position(|item| cx.tcx.is_diagnostic_item(*item, def_id))
+}
+
 /// Checks if the given `DefId` matches the path.
 pub fn match_def_path<'tcx>(cx: &LateContext<'tcx>, did: DefId, syms: &[&str]) -> bool {
     // We should probably move to Symbols in Clippy as well rather than interning every time.
diff --git a/clippy_utils/src/paths.rs b/clippy_utils/src/paths.rs
index 3acde01b8c9..e9e371e3e3e 100644
--- a/clippy_utils/src/paths.rs
+++ b/clippy_utils/src/paths.rs
@@ -73,8 +73,6 @@ pub const IDENT_AS_STR: [&str; 4] = ["rustc_span", "symbol", "Ident", "as_str"];
 pub const INDEX: [&str; 3] = ["core", "ops", "Index"];
 pub const INDEX_MUT: [&str; 3] = ["core", "ops", "IndexMut"];
 pub const INSERT_STR: [&str; 4] = ["alloc", "string", "String", "insert_str"];
-pub const INTO: [&str; 3] = ["core", "convert", "Into"];
-pub const INTO_ITERATOR: [&str; 5] = ["core", "iter", "traits", "collect", "IntoIterator"];
 pub const IO_READ: [&str; 3] = ["std", "io", "Read"];
 pub const IO_WRITE: [&str; 3] = ["std", "io", "Write"];
 pub const IPADDR_V4: [&str; 5] = ["std", "net", "ip", "IpAddr", "V4"];
@@ -85,6 +83,7 @@ pub const KW_MODULE: [&str; 3] = ["rustc_span", "symbol", "kw"];
 #[cfg(feature = "internal-lints")]
 pub const LATE_CONTEXT: [&str; 2] = ["rustc_lint", "LateContext"];
 pub const LIBC_STRLEN: [&str; 2] = ["libc", "strlen"];
+/// Preferably use the diagnostic item `sym::LinkedList` where possible
 pub const LINKED_LIST: [&str; 4] = ["alloc", "collections", "linked_list", "LinkedList"];
 #[cfg(any(feature = "internal-lints", feature = "metadata-collector-lint"))]
 pub const LINT: [&str; 2] = ["rustc_lint_defs", "Lint"];
@@ -99,6 +98,7 @@ pub const MEM_SIZE_OF_VAL: [&str; 3] = ["core", "mem", "size_of_val"];
 pub const MUTEX_GUARD: [&str; 4] = ["std", "sync", "mutex", "MutexGuard"];
 pub const OPEN_OPTIONS: [&str; 3] = ["std", "fs", "OpenOptions"];
 pub const OPS_MODULE: [&str; 2] = ["core", "ops"];
+/// Preferably use the diagnostic item `sym::option_type` where possible
 pub const OPTION: [&str; 3] = ["core", "option", "Option"];
 pub const OPTION_NONE: [&str; 4] = ["core", "option", "Option", "None"];
 pub const OPTION_SOME: [&str; 4] = ["core", "option", "Option", "Some"];
@@ -122,8 +122,6 @@ pub const POLL_READY: [&str; 5] = ["core", "task", "poll", "Poll", "Ready"];
 pub const PTR_COPY: [&str; 3] = ["core", "intrinsics", "copy"];
 pub const PTR_COPY_NONOVERLAPPING: [&str; 3] = ["core", "intrinsics", "copy_nonoverlapping"];
 pub const PTR_EQ: [&str; 3] = ["core", "ptr", "eq"];
-pub const PTR_NULL: [&str; 3] = ["core", "ptr", "null"];
-pub const PTR_NULL_MUT: [&str; 3] = ["core", "ptr", "null_mut"];
 pub const PTR_SLICE_FROM_RAW_PARTS: [&str; 3] = ["core", "ptr", "slice_from_raw_parts"];
 pub const PTR_SLICE_FROM_RAW_PARTS_MUT: [&str; 3] = ["core", "ptr", "slice_from_raw_parts_mut"];
 pub const PTR_SWAP_NONOVERLAPPING: [&str; 3] = ["core", "ptr", "swap_nonoverlapping"];