Rollup merge of #66217 - RalfJung:diagnostic-items, r=Centril

invalid_value lint: use diagnostic items

This adjusts the invalid_value lint to use diagnostic items.

@Centril @oli-obk For some reason, this fails to recognize `transmute` -- somehow the diagnostic item is not found. Any idea why?

r? @Centril

Cc https://github.com/rust-lang/rust/issues/66075

src/libcore/mem/maybe_uninit.rs

@@ -256,6 +256,7 @@ pub const fn new(val: T) -> MaybeUninit<T> {
     /// [type]: union.MaybeUninit.html
     #[stable(feature = "maybe_uninit", since = "1.36.0")]
     #[inline(always)]
+    #[cfg_attr(all(not(bootstrap)), rustc_diagnostic_item = "maybe_uninit_uninit")]
     pub const fn uninit() -> MaybeUninit<T> {
         MaybeUninit { uninit: () }
     }
@@ -339,6 +340,7 @@ pub const fn uninit() -> MaybeUninit<T> {
     /// ```
     #[stable(feature = "maybe_uninit", since = "1.36.0")]
     #[inline]
+    #[cfg_attr(all(not(bootstrap)), rustc_diagnostic_item = "maybe_uninit_zeroed")]
     pub fn zeroed() -> MaybeUninit<T> {
         let mut u = MaybeUninit::<T>::uninit();
         unsafe {

src/libcore/mem/mod.rs

@@ -468,6 +468,7 @@ pub const fn needs_drop<T>() -> bool {
 #[stable(feature = "rust1", since = "1.0.0")]
 #[allow(deprecated_in_future)]
 #[allow(deprecated)]
+#[cfg_attr(all(not(bootstrap)), rustc_diagnostic_item = "mem_zeroed")]
 pub unsafe fn zeroed<T>() -> T {
     intrinsics::panic_if_uninhabited::<T>();
     intrinsics::init()
@@ -496,6 +497,7 @@ pub unsafe fn zeroed<T>() -> T {
 #[stable(feature = "rust1", since = "1.0.0")]
 #[allow(deprecated_in_future)]
 #[allow(deprecated)]
+#[cfg_attr(all(not(bootstrap)), rustc_diagnostic_item = "mem_uninitialized")]
 pub unsafe fn uninitialized<T>() -> T {
     intrinsics::panic_if_uninhabited::<T>();
     intrinsics::uninit()

src/librustc_lint/builtin.rs

@@ -1903,29 +1903,23 @@ fn is_zero(expr: &hir::Expr) -> bool {
 
         /// Determine if this expression is a "dangerous initialization".
         fn is_dangerous_init(cx: &LateContext<'_, '_>, expr: &hir::Expr) -> Option<InitKind> {
-            const ZEROED_PATH: &[Symbol] = &[sym::core, sym::mem, sym::zeroed];
-            const UININIT_PATH: &[Symbol] = &[sym::core, sym::mem, sym::uninitialized];
             // `transmute` is inside an anonymous module (the `extern` block?);
             // `Invalid` represents the empty string and matches that.
+            // FIXME(#66075): use diagnostic items.  Somehow, that does not seem to work
+            // on intrinsics right now.
             const TRANSMUTE_PATH: &[Symbol] =
                 &[sym::core, sym::intrinsics, kw::Invalid, sym::transmute];
-            const MU_ZEROED_PATH: &[Symbol] =
-                &[sym::core, sym::mem, sym::maybe_uninit, sym::MaybeUninit, sym::zeroed];
-            const MU_UNINIT_PATH: &[Symbol] =
-                &[sym::core, sym::mem, sym::maybe_uninit, sym::MaybeUninit, sym::uninit];
 
             if let hir::ExprKind::Call(ref path_expr, ref args) = expr.kind {
                 // Find calls to `mem::{uninitialized,zeroed}` methods.
                 if let hir::ExprKind::Path(ref qpath) = path_expr.kind {
                     let def_id = cx.tables.qpath_res(qpath, path_expr.hir_id).opt_def_id()?;
 
-                    if cx.match_def_path(def_id, ZEROED_PATH) {
+                    if cx.tcx.is_diagnostic_item(sym::mem_zeroed, def_id) {
                         return Some(InitKind::Zeroed);
-                    }
-                    if cx.match_def_path(def_id, UININIT_PATH) {
+                    } else if cx.tcx.is_diagnostic_item(sym::mem_uninitialized, def_id) {
                         return Some(InitKind::Uninit);
-                    }
-                    if cx.match_def_path(def_id, TRANSMUTE_PATH) {
+                    } else if cx.match_def_path(def_id, TRANSMUTE_PATH) {
                         if is_zero(&args[0]) {
                             return Some(InitKind::Zeroed);
                         }
@@ -1940,9 +1934,10 @@ fn is_dangerous_init(cx: &LateContext<'_, '_>, expr: &hir::Expr) -> Option<InitK
                     if let hir::ExprKind::Call(ref path_expr, _) = args[0].kind {
                         if let hir::ExprKind::Path(ref qpath) = path_expr.kind {
                             let def_id = cx.tables.qpath_res(qpath, path_expr.hir_id).opt_def_id()?;
-                            if cx.match_def_path(def_id, MU_ZEROED_PATH) {
+
+                            if cx.tcx.is_diagnostic_item(sym::maybe_uninit_zeroed, def_id) {
                                 return Some(InitKind::Zeroed);
-                            } else if cx.match_def_path(def_id, MU_UNINIT_PATH) {
+                            } else if cx.tcx.is_diagnostic_item(sym::maybe_uninit_uninit, def_id) {
                                 return Some(InitKind::Uninit);
                             }
                         }

src/libsyntax_pos/symbol.rs

@@ -418,9 +418,10 @@
         match_beginning_vert,
         match_default_bindings,
         may_dangle,
-        maybe_uninit,
-        MaybeUninit,
-        mem,
+        maybe_uninit_uninit,
+        maybe_uninit_zeroed,
+        mem_uninitialized,
+        mem_zeroed,
         member_constraints,
         message,
         meta,
@@ -713,8 +714,6 @@
         underscore_imports,
         underscore_lifetimes,
         uniform_paths,
-        uninit,
-        uninitialized,
         universal_impl_trait,
         unmarked_api,
         unreachable_code,
@@ -745,7 +744,6 @@
         windows,
         windows_subsystem,
         Yield,
-        zeroed,
     }
 }