From 3a9bf4551374893fdc522572ee569028186e22cc Mon Sep 17 00:00:00 2001 From: Goldstein Date: Sun, 18 Aug 2024 17:11:47 +0300 Subject: [PATCH] Check that `#[may_dangle]` is properly applied It's only valid when applied to a type or lifetime parameter in `Drop` trait implementation. --- compiler/rustc_passes/messages.ftl | 3 ++ compiler/rustc_passes/src/check_attr.rs | 23 ++++++++++- compiler/rustc_passes/src/errors.rs | 7 ++++ tests/ui/attributes/may_dangle.rs | 53 +++++++++++++++++++++++++ tests/ui/attributes/may_dangle.stderr | 50 +++++++++++++++++++++++ 5 files changed, 135 insertions(+), 1 deletion(-) create mode 100644 tests/ui/attributes/may_dangle.rs create mode 100644 tests/ui/attributes/may_dangle.stderr diff --git a/compiler/rustc_passes/messages.ftl b/compiler/rustc_passes/messages.ftl index 1ea4ca375f1..7d4f351560b 100644 --- a/compiler/rustc_passes/messages.ftl +++ b/compiler/rustc_passes/messages.ftl @@ -444,6 +444,9 @@ passes_macro_export_on_decl_macro = passes_macro_use = `#[{$name}]` only has an effect on `extern crate` and modules +passes_may_dangle = + `#[may_dangle]` must be applied to a lifetime or type generic parameter in `Drop` impl + passes_maybe_string_interpolation = you might have meant to use string interpolation in this string literal passes_missing_const_err = attributes `#[rustc_const_unstable]` and `#[rustc_const_stable]` require the function or method to be `const` diff --git a/compiler/rustc_passes/src/check_attr.rs b/compiler/rustc_passes/src/check_attr.rs index a47add929eb..60c8c1e7a00 100644 --- a/compiler/rustc_passes/src/check_attr.rs +++ b/compiler/rustc_passes/src/check_attr.rs @@ -189,6 +189,7 @@ fn check_attributes( [sym::collapse_debuginfo, ..] => self.check_collapse_debuginfo(attr, span, target), [sym::must_not_suspend, ..] => self.check_must_not_suspend(attr, span, target), [sym::must_use, ..] => self.check_must_use(hir_id, attr, target), + [sym::may_dangle, ..] => self.check_may_dangle(hir_id, attr), [sym::rustc_pass_by_value, ..] => self.check_pass_by_value(attr, span, target), [sym::rustc_allow_incoherent_impl, ..] => { self.check_allow_incoherent_impl(attr, span, target) @@ -255,7 +256,6 @@ fn check_attributes( | sym::cfg_attr // need to be fixed | sym::cfi_encoding // FIXME(cfi_encoding) - | sym::may_dangle // FIXME(dropck_eyepatch) | sym::pointee // FIXME(derive_smart_pointer) | sym::omit_gdb_pretty_printer_section // FIXME(omit_gdb_pretty_printer_section) | sym::used // handled elsewhere to restrict to static items @@ -1373,6 +1373,27 @@ fn check_must_not_suspend(&self, attr: &Attribute, span: Span, target: Target) { } } + /// Checks if `#[may_dangle]` is applied to a lifetime or type generic parameter in `Drop` impl. + fn check_may_dangle(&self, hir_id: HirId, attr: &Attribute) { + if let hir::Node::GenericParam(param) = self.tcx.hir_node(hir_id) + && matches!( + param.kind, + hir::GenericParamKind::Lifetime { .. } | hir::GenericParamKind::Type { .. } + ) + && matches!(param.source, hir::GenericParamSource::Generics) + && let parent_hir_id = self.tcx.parent_hir_id(hir_id) + && let hir::Node::Item(item) = self.tcx.hir_node(parent_hir_id) + && let hir::ItemKind::Impl(impl_) = item.kind + && let Some(trait_) = impl_.of_trait + && let Some(def_id) = trait_.trait_def_id() + && self.tcx.is_lang_item(def_id, hir::LangItem::Drop) + { + return; + } + + self.dcx().emit_err(errors::InvalidMayDangle { attr_span: attr.span }); + } + /// Checks if `#[cold]` is applied to a non-function. fn check_cold(&self, hir_id: HirId, attr: &Attribute, span: Span, target: Target) { match target { diff --git a/compiler/rustc_passes/src/errors.rs b/compiler/rustc_passes/src/errors.rs index 3a043e0e3c1..ee7d097e5d3 100644 --- a/compiler/rustc_passes/src/errors.rs +++ b/compiler/rustc_passes/src/errors.rs @@ -737,6 +737,13 @@ pub struct NonExportedMacroInvalidAttrs { pub attr_span: Span, } +#[derive(Diagnostic)] +#[diag(passes_may_dangle)] +pub struct InvalidMayDangle { + #[primary_span] + pub attr_span: Span, +} + #[derive(LintDiagnostic)] #[diag(passes_unused_duplicate)] pub struct UnusedDuplicate { diff --git a/tests/ui/attributes/may_dangle.rs b/tests/ui/attributes/may_dangle.rs new file mode 100644 index 00000000000..209ba0e88ad --- /dev/null +++ b/tests/ui/attributes/may_dangle.rs @@ -0,0 +1,53 @@ +#![feature(dropck_eyepatch)] + +struct Implee1<'a, T, const N: usize>(&'a T); +struct Implee2<'a, T, const N: usize>(&'a T); +struct Implee3<'a, T, const N: usize>(&'a T); +trait NotDrop {} + +unsafe impl<#[may_dangle] 'a, T, const N: usize> NotDrop for Implee1<'a, T, N> {} +//~^ ERROR must be applied to a lifetime or type generic parameter in `Drop` impl + +unsafe impl<'a, #[may_dangle] T, const N: usize> NotDrop for Implee2<'a, T, N> {} +//~^ ERROR must be applied to a lifetime or type generic parameter in `Drop` impl + +unsafe impl<'a, T, #[may_dangle] const N: usize> Drop for Implee1<'a, T, N> { + //~^ ERROR must be applied to a lifetime or type generic parameter in `Drop` impl + fn drop(&mut self) {} +} + +// Ok, lifetime param in a `Drop` impl. +unsafe impl<#[may_dangle] 'a, T, const N: usize> Drop for Implee2<'a, T, N> { + fn drop(&mut self) {} +} + +// Ok, type param in a `Drop` impl. +unsafe impl<'a, #[may_dangle] T, const N: usize> Drop for Implee3<'a, T, N> { + fn drop(&mut self) {} +} + +// Check that this check is not textual. +mod fake { + trait Drop { + fn drop(&mut self); + } + struct Implee(T); + + unsafe impl<#[may_dangle] T> Drop for Implee { + //~^ ERROR must be applied to a lifetime or type generic parameter in `Drop` impl + fn drop(&mut self) {} + } +} + +#[may_dangle] //~ ERROR must be applied to a lifetime or type generic parameter in `Drop` impl +struct Dangling; + +#[may_dangle] //~ ERROR must be applied to a lifetime or type generic parameter in `Drop` impl +impl NotDrop for () { +} + +#[may_dangle] //~ ERROR must be applied to a lifetime or type generic parameter in `Drop` impl +fn main() { + #[may_dangle] //~ ERROR must be applied to a lifetime or type generic parameter in `Drop` impl + let () = (); +} diff --git a/tests/ui/attributes/may_dangle.stderr b/tests/ui/attributes/may_dangle.stderr new file mode 100644 index 00000000000..dc24f847f71 --- /dev/null +++ b/tests/ui/attributes/may_dangle.stderr @@ -0,0 +1,50 @@ +error: `#[may_dangle]` must be applied to a lifetime or type generic parameter in `Drop` impl + --> $DIR/may_dangle.rs:8:13 + | +LL | unsafe impl<#[may_dangle] 'a, T, const N: usize> NotDrop for Implee1<'a, T, N> {} + | ^^^^^^^^^^^^^ + +error: `#[may_dangle]` must be applied to a lifetime or type generic parameter in `Drop` impl + --> $DIR/may_dangle.rs:11:17 + | +LL | unsafe impl<'a, #[may_dangle] T, const N: usize> NotDrop for Implee2<'a, T, N> {} + | ^^^^^^^^^^^^^ + +error: `#[may_dangle]` must be applied to a lifetime or type generic parameter in `Drop` impl + --> $DIR/may_dangle.rs:14:20 + | +LL | unsafe impl<'a, T, #[may_dangle] const N: usize> Drop for Implee1<'a, T, N> { + | ^^^^^^^^^^^^^ + +error: `#[may_dangle]` must be applied to a lifetime or type generic parameter in `Drop` impl + --> $DIR/may_dangle.rs:42:1 + | +LL | #[may_dangle] + | ^^^^^^^^^^^^^ + +error: `#[may_dangle]` must be applied to a lifetime or type generic parameter in `Drop` impl + --> $DIR/may_dangle.rs:45:1 + | +LL | #[may_dangle] + | ^^^^^^^^^^^^^ + +error: `#[may_dangle]` must be applied to a lifetime or type generic parameter in `Drop` impl + --> $DIR/may_dangle.rs:49:1 + | +LL | #[may_dangle] + | ^^^^^^^^^^^^^ + +error: `#[may_dangle]` must be applied to a lifetime or type generic parameter in `Drop` impl + --> $DIR/may_dangle.rs:51:5 + | +LL | #[may_dangle] + | ^^^^^^^^^^^^^ + +error: `#[may_dangle]` must be applied to a lifetime or type generic parameter in `Drop` impl + --> $DIR/may_dangle.rs:36:17 + | +LL | unsafe impl<#[may_dangle] T> Drop for Implee { + | ^^^^^^^^^^^^^ + +error: aborting due to 8 previous errors +