diff --git a/compiler/rustc_middle/src/mir/mod.rs b/compiler/rustc_middle/src/mir/mod.rs index 0daaec272fd..672686410f9 100644 --- a/compiler/rustc_middle/src/mir/mod.rs +++ b/compiler/rustc_middle/src/mir/mod.rs @@ -494,6 +494,8 @@ pub fn generator_kind(&self) -> Option { #[derive(Copy, Clone, PartialEq, Eq, Debug, TyEncodable, TyDecodable, HashStable)] pub enum Safety { Safe, + /// Unsafe because of compiler-generated unsafe code, like `await` desugaring + BuiltinUnsafe, /// Unsafe because of an unsafe fn FnUnsafe, /// Unsafe because of an `unsafe` block diff --git a/compiler/rustc_middle/src/thir.rs b/compiler/rustc_middle/src/thir.rs index 2f107e7b96c..6b2e542ee70 100644 --- a/compiler/rustc_middle/src/thir.rs +++ b/compiler/rustc_middle/src/thir.rs @@ -114,6 +114,7 @@ pub struct Adt<'tcx> { #[derive(Copy, Clone, Debug, HashStable)] pub enum BlockSafety { Safe, + BuiltinUnsafe, ExplicitUnsafe(hir::HirId), } diff --git a/compiler/rustc_mir/src/transform/check_unsafety.rs b/compiler/rustc_mir/src/transform/check_unsafety.rs index 324a5257f5d..103ddda1a1d 100644 --- a/compiler/rustc_mir/src/transform/check_unsafety.rs +++ b/compiler/rustc_mir/src/transform/check_unsafety.rs @@ -321,6 +321,7 @@ fn register_violations( } false } + Safety::BuiltinUnsafe => true, Safety::ExplicitUnsafe(hir_id) => { // mark unsafe block as used if there are any unsafe operations inside if !violations.is_empty() { diff --git a/compiler/rustc_mir_build/src/build/block.rs b/compiler/rustc_mir_build/src/build/block.rs index 4e1983aca94..df71379c1d8 100644 --- a/compiler/rustc_mir_build/src/build/block.rs +++ b/compiler/rustc_mir_build/src/build/block.rs @@ -214,6 +214,7 @@ fn update_source_scope_for_safety_mode(&mut self, span: Span, safety_mode: Block debug!("update_source_scope_for({:?}, {:?})", span, safety_mode); let new_unsafety = match safety_mode { BlockSafety::Safe => None, + BlockSafety::BuiltinUnsafe => Some(Safety::BuiltinUnsafe), BlockSafety::ExplicitUnsafe(hir_id) => { match self.in_scope_unsafe { Safety::Safe => {} diff --git a/compiler/rustc_mir_build/src/check_unsafety.rs b/compiler/rustc_mir_build/src/check_unsafety.rs index e4ed5dece86..4e80931ec03 100644 --- a/compiler/rustc_mir_build/src/check_unsafety.rs +++ b/compiler/rustc_mir_build/src/check_unsafety.rs @@ -29,11 +29,7 @@ struct UnsafetyVisitor<'a, 'tcx> { } impl<'tcx> UnsafetyVisitor<'_, 'tcx> { - fn in_safety_context( - &mut self, - safety_context: SafetyContext, - f: impl FnOnce(&mut Self) -> R, - ) { + fn in_safety_context(&mut self, safety_context: SafetyContext, f: impl FnOnce(&mut Self)) { if let ( SafetyContext::UnsafeBlock { span: enclosing_span, .. }, SafetyContext::UnsafeBlock { span: block_span, hir_id, .. }, @@ -63,7 +59,6 @@ fn in_safety_context( ); } self.safety_context = prev_context; - return; } } @@ -71,6 +66,7 @@ fn requires_unsafe(&mut self, span: Span, kind: UnsafeOpKind) { let (description, note) = kind.description_and_note(); let unsafe_op_in_unsafe_fn_allowed = self.unsafe_op_in_unsafe_fn_allowed(); match self.safety_context { + SafetyContext::BuiltinUnsafeBlock => {} SafetyContext::UnsafeBlock { ref mut used, .. } => { if !self.body_unsafety.is_unsafe() || !unsafe_op_in_unsafe_fn_allowed { // Mark this block as useful @@ -142,13 +138,23 @@ fn thir(&self) -> &'a Thir<'tcx> { } fn visit_block(&mut self, block: &Block) { - if let BlockSafety::ExplicitUnsafe(hir_id) = block.safety_mode { - self.in_safety_context( - SafetyContext::UnsafeBlock { span: block.span, hir_id, used: false }, - |this| visit::walk_block(this, block), - ); - } else { - visit::walk_block(self, block); + match block.safety_mode { + // compiler-generated unsafe code should not count towards the usefulness of + // an outer unsafe block + BlockSafety::BuiltinUnsafe => { + self.in_safety_context(SafetyContext::BuiltinUnsafeBlock, |this| { + visit::walk_block(this, block) + }); + } + BlockSafety::ExplicitUnsafe(hir_id) => { + self.in_safety_context( + SafetyContext::UnsafeBlock { span: block.span, hir_id, used: false }, + |this| visit::walk_block(this, block), + ); + } + BlockSafety::Safe => { + visit::walk_block(self, block); + } } } @@ -250,6 +256,7 @@ fn visit_expr(&mut self, expr: &Expr<'tcx>) { #[derive(Clone, Copy)] enum SafetyContext { Safe, + BuiltinUnsafeBlock, UnsafeFn, UnsafeBlock { span: Span, hir_id: hir::HirId, used: bool }, } diff --git a/compiler/rustc_mir_build/src/thir/cx/block.rs b/compiler/rustc_mir_build/src/thir/cx/block.rs index 4fe8cd8541a..2d9b5c1d98a 100644 --- a/compiler/rustc_mir_build/src/thir/cx/block.rs +++ b/compiler/rustc_mir_build/src/thir/cx/block.rs @@ -26,7 +26,12 @@ impl<'tcx> Cx<'tcx> { expr: block.expr.map(|expr| self.mirror_expr(expr)), safety_mode: match block.rules { hir::BlockCheckMode::DefaultBlock => BlockSafety::Safe, - hir::BlockCheckMode::UnsafeBlock(..) => BlockSafety::ExplicitUnsafe(block.hir_id), + hir::BlockCheckMode::UnsafeBlock(hir::UnsafeSource::CompilerGenerated) => { + BlockSafety::BuiltinUnsafe + } + hir::BlockCheckMode::UnsafeBlock(hir::UnsafeSource::UserProvided) => { + BlockSafety::ExplicitUnsafe(block.hir_id) + } }, } } diff --git a/src/test/ui/unsafe/unsafe-around-compiler-generated-unsafe.mir.stderr b/src/test/ui/unsafe/unsafe-around-compiler-generated-unsafe.mir.stderr index 68101326861..29bd84cd0db 100644 --- a/src/test/ui/unsafe/unsafe-around-compiler-generated-unsafe.mir.stderr +++ b/src/test/ui/unsafe/unsafe-around-compiler-generated-unsafe.mir.stderr @@ -1,11 +1,11 @@ error: unnecessary `unsafe` block - --> $DIR/unsafe-around-compiler-generated-unsafe.rs:9:5 + --> $DIR/unsafe-around-compiler-generated-unsafe.rs:9:9 | -LL | unsafe { println!("foo"); } - | ^^^^^^ unnecessary `unsafe` block +LL | unsafe { async {}.await; } + | ^^^^^^ unnecessary `unsafe` block | note: the lint level is defined here - --> $DIR/unsafe-around-compiler-generated-unsafe.rs:6:9 + --> $DIR/unsafe-around-compiler-generated-unsafe.rs:5:9 | LL | #![deny(unused_unsafe)] | ^^^^^^^^^^^^^ diff --git a/src/test/ui/unsafe/unsafe-around-compiler-generated-unsafe.rs b/src/test/ui/unsafe/unsafe-around-compiler-generated-unsafe.rs index 08801f9ef59..e9c7efb9e8b 100644 --- a/src/test/ui/unsafe/unsafe-around-compiler-generated-unsafe.rs +++ b/src/test/ui/unsafe/unsafe-around-compiler-generated-unsafe.rs @@ -1,10 +1,11 @@ -// issue #12418 - +// edition:2018 // revisions: mir thir // [thir]compile-flags: -Z thir-unsafeck #![deny(unused_unsafe)] fn main() { - unsafe { println!("foo"); } //~ ERROR unnecessary `unsafe` + let _ = async { + unsafe { async {}.await; } //~ ERROR unnecessary `unsafe` + }; } diff --git a/src/test/ui/unsafe/unsafe-around-compiler-generated-unsafe.thir.stderr b/src/test/ui/unsafe/unsafe-around-compiler-generated-unsafe.thir.stderr index 68101326861..29bd84cd0db 100644 --- a/src/test/ui/unsafe/unsafe-around-compiler-generated-unsafe.thir.stderr +++ b/src/test/ui/unsafe/unsafe-around-compiler-generated-unsafe.thir.stderr @@ -1,11 +1,11 @@ error: unnecessary `unsafe` block - --> $DIR/unsafe-around-compiler-generated-unsafe.rs:9:5 + --> $DIR/unsafe-around-compiler-generated-unsafe.rs:9:9 | -LL | unsafe { println!("foo"); } - | ^^^^^^ unnecessary `unsafe` block +LL | unsafe { async {}.await; } + | ^^^^^^ unnecessary `unsafe` block | note: the lint level is defined here - --> $DIR/unsafe-around-compiler-generated-unsafe.rs:6:9 + --> $DIR/unsafe-around-compiler-generated-unsafe.rs:5:9 | LL | #![deny(unused_unsafe)] | ^^^^^^^^^^^^^