[Clippy] Remove final std paths for diagnostic item

compiler/rustc_span/src/symbol.rs

@@ -309,6 +309,7 @@
         RwLockReadGuard,
         RwLockWriteGuard,
         Saturating,
+        SeekFrom,
         Send,
         SeqCst,
         Sized,

library/std/src/io/mod.rs

@@ -2058,6 +2058,7 @@ fn seek_relative(&mut self, offset: i64) -> Result<()> {
 /// It is used by the [`Seek`] trait.
 #[derive(Copy, PartialEq, Eq, Clone, Debug)]
 #[stable(feature = "rust1", since = "1.0.0")]
+#[cfg_attr(not(test), rustc_diagnostic_item = "SeekFrom")]
 pub enum SeekFrom {
     /// Sets the offset to the provided number of bytes.
     #[stable(feature = "rust1", since = "1.0.0")]

src/tools/clippy/clippy_lints/src/methods/seek_from_current.rs

@@ -8,7 +8,7 @@
 use clippy_utils::diagnostics::span_lint_and_sugg;
 use clippy_utils::source::snippet_with_applicability;
 use clippy_utils::ty::implements_trait;
-use clippy_utils::{match_def_path, paths};
+use clippy_utils::is_enum_variant_ctor;
 
 use super::SEEK_FROM_CURRENT;
 
@@ -36,8 +36,8 @@ pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>, recv: &'
 fn arg_is_seek_from_current<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) -> bool {
     if let ExprKind::Call(f, args) = expr.kind
         && let ExprKind::Path(ref path) = f.kind
-        && let Some(def_id) = cx.qpath_res(path, f.hir_id).opt_def_id()
-        && match_def_path(cx, def_id, &paths::STD_IO_SEEK_FROM_CURRENT)
+        && let Some(ctor_call_id) = cx.qpath_res(path, f.hir_id).opt_def_id()
+        && is_enum_variant_ctor(cx, sym::SeekFrom, sym!(Current), ctor_call_id)
     {
         // check if argument of `SeekFrom::Current` is `0`
         if args.len() == 1

src/tools/clippy/clippy_lints/src/methods/seek_to_start_instead_of_rewind.rs

@@ -1,6 +1,6 @@
 use clippy_utils::diagnostics::span_lint_and_then;
 use clippy_utils::ty::implements_trait;
-use clippy_utils::{is_expr_used_or_unified, match_def_path, paths};
+use clippy_utils::{is_expr_used_or_unified, is_enum_variant_ctor};
 use rustc_ast::ast::{LitIntType, LitKind};
 use rustc_data_structures::packed::Pu128;
 use rustc_errors::Applicability;
@@ -28,8 +28,8 @@ pub(super) fn check<'tcx>(
         && implements_trait(cx, ty, seek_trait_id, &[])
         && let ExprKind::Call(func, args1) = arg.kind
         && let ExprKind::Path(ref path) = func.kind
-        && let Some(def_id) = cx.qpath_res(path, func.hir_id).opt_def_id()
-        && match_def_path(cx, def_id, &paths::STD_IO_SEEKFROM_START)
+        && let Some(ctor_call_id) = cx.qpath_res(path, func.hir_id).opt_def_id()
+        && is_enum_variant_ctor(cx, sym::SeekFrom, sym!(Start), ctor_call_id)
         && args1.len() == 1
         && let ExprKind::Lit(lit) = args1[0].kind
         && let LitKind::Int(Pu128(0), LitIntType::Unsuffixed) = lit.node

src/tools/clippy/clippy_utils/src/lib.rs

@@ -263,24 +263,18 @@ pub fn is_res_lang_ctor(cx: &LateContext<'_>, res: Res, lang_item: LangItem) ->
     }
 }
 
-pub fn is_res_diagnostic_ctor(cx: &LateContext<'_>, res: Res, diag_item: Symbol) -> bool {
-    if let Res::Def(DefKind::Ctor(..), id) = res
-        && let Some(id) = cx.tcx.opt_parent(id)
-    {
-        cx.tcx.is_diagnostic_item(diag_item, id)
-    } else {
-        false
-    }
-}
 
-/// Checks if a `QPath` resolves to a constructor of a diagnostic item.
-pub fn is_diagnostic_ctor(cx: &LateContext<'_>, qpath: &QPath<'_>, diagnostic_item: Symbol) -> bool {
-    if let QPath::Resolved(_, path) = qpath {
-        if let Res::Def(DefKind::Ctor(..), ctor_id) = path.res {
-            return cx.tcx.is_diagnostic_item(diagnostic_item, cx.tcx.parent(ctor_id));
-        }
-    }
-    false
+/// Checks if `{ctor_call_id}(...)` is `{enum_item}::{variant_name}(...)`.
+pub fn is_enum_variant_ctor(cx: &LateContext<'_>, enum_item: Symbol, variant_name: Symbol, ctor_call_id: DefId) -> bool {
+    let Some(enum_def_id) = cx.tcx.get_diagnostic_item(enum_item) else {
+        return false;
+    };
+
+    let variants = cx.tcx.adt_def(enum_def_id).variants().iter();
+    variants
+        .filter(|variant| variant.name == variant_name)
+        .filter_map(|variant| variant.ctor.as_ref())
+        .any(|(_, ctor_def_id)| *ctor_def_id == ctor_call_id)
 }
 
 /// Checks if the `DefId` matches the given diagnostic item or it's constructor.

src/tools/clippy/clippy_utils/src/paths.rs

@@ -29,8 +29,7 @@
 pub const SYNTAX_CONTEXT: [&str; 3] = ["rustc_span", "hygiene", "SyntaxContext"];
 
 // Paths in `core`/`alloc`/`std`. This should be avoided and cleaned up by adding diagnostic items.
-pub const STD_IO_SEEK_FROM_CURRENT: [&str; 4] = ["std", "io", "SeekFrom", "Current"];
-pub const STD_IO_SEEKFROM_START: [&str; 4] = ["std", "io", "SeekFrom", "Start"];
+// ... none currently!
 
 // Paths in clippy itself
 pub const MSRV: [&str; 3] = ["clippy_config", "msrvs", "Msrv"];