Auto merge of #117673 - matthewjasper:thir-unsafeck-stabilization, r=<try>

Stabilize THIR unsafeck

- Removes `-Zthir-unsafeck`, stabilizing the behaviour of `-Zthir-unsafeck=on`.
- Removes MIR unsafeck.
- Union patterns are now unsafe unless the field is matched to a wildcard pattern.

Opening for a crater run in case we need a compatibility lint.

Author: bors

compiler/rustc_interface/src/passes.rs

@@ -742,18 +742,15 @@ fn analysis(tcx: TyCtxt<'_>, (): ()) -> Result<()> {
 
     sess.time("MIR_borrow_checking", || {
         tcx.hir().par_body_owners(|def_id| {
-            // Run THIR unsafety check because it's responsible for stealing
-            // and deallocating THIR when enabled.
-            tcx.ensure().thir_check_unsafety(def_id);
+            // Run unsafety check because it's responsible for stealing and
+            // deallocating THIR.
+            tcx.ensure().check_unsafety(def_id);
             tcx.ensure().mir_borrowck(def_id)
         });
     });
 
     sess.time("MIR_effect_checking", || {
         for def_id in tcx.hir().body_owners() {
-            if !tcx.sess.opts.unstable_opts.thir_unsafeck {
-                rustc_mir_transform::check_unsafety::check_unsafety(tcx, def_id);
-            }
             tcx.ensure().has_ffi_unwind_calls(def_id);
 
             // If we need to codegen, ensure that we emit all errors from

compiler/rustc_interface/src/tests.rs

@@ -819,7 +819,6 @@ fn test_unstable_options_tracking_hash() {
     tracked!(stack_protector, StackProtector::All);
     tracked!(teach, true);
     tracked!(thinlto, Some(true));
-    tracked!(thir_unsafeck, true);
     tracked!(tiny_const_eval_limit, true);
     tracked!(tls_model, Some(TlsModel::GeneralDynamic));
     tracked!(trait_solver, TraitSolver::NextCoherence);

compiler/rustc_middle/src/arena.rs

@@ -42,7 +42,6 @@ macro_rules! arena_types {
             [] output_filenames: std::sync::Arc<rustc_session::config::OutputFilenames>,
             [] crate_for_resolver: rustc_data_structures::steal::Steal<(rustc_ast::Crate, rustc_ast::AttrVec)>,
             [] resolutions: rustc_middle::ty::ResolverGlobalCtxt,
-            [decode] unsafety_check_result: rustc_middle::mir::UnsafetyCheckResult,
             [decode] code_region: rustc_middle::mir::coverage::CodeRegion,
             [] const_allocs: rustc_middle::mir::interpret::Allocation,
             [] region_scope_tree: rustc_middle::middle::region::ScopeTree,

compiler/rustc_middle/src/mir/mod.rs

@@ -614,17 +614,6 @@ impl<'tcx> Body<'tcx> {
     }
 }
 
-#[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
-    ExplicitUnsafe(hir::HirId),
-}
-
 impl<'tcx> Index<BasicBlock> for Body<'tcx> {
     type Output = BasicBlockData<'tcx>;
 
@@ -720,7 +709,7 @@ pub struct SourceInfo {
     pub span: Span,
 
     /// The source scope, keeping track of which bindings can be
-    /// seen by debuginfo, active lint levels, `unsafe {...}`, etc.
+    /// seen by debuginfo, active lint levels, etc.
     pub scope: SourceScope,
 }
 
@@ -940,7 +929,7 @@ pub struct LocalDecl<'tcx> {
 
 /// Extra information about a some locals that's used for diagnostics and for
 /// classifying variables into local variables, statics, etc, which is needed e.g.
-/// for unsafety checking.
+/// for borrow checking.
 ///
 /// Not used for non-StaticRef temporaries, the return place, or anonymous
 /// function parameters.
@@ -1374,8 +1363,6 @@ pub struct SourceScopeData<'tcx> {
 pub struct SourceScopeLocalData {
     /// An `HirId` with lint levels equivalent to this scope's lint levels.
     pub lint_root: hir::HirId,
-    /// The unsafe block that contains this node.
-    pub safety: Safety,
 }
 
 /// A collection of projections into user types.
@@ -1631,7 +1618,7 @@ mod size_asserts {
     // tidy-alphabetical-start
     static_assert_size!(BasicBlockData<'_>, 136);
     static_assert_size!(LocalDecl<'_>, 40);
-    static_assert_size!(SourceScopeData<'_>, 72);
+    static_assert_size!(SourceScopeData<'_>, 64);
     static_assert_size!(Statement<'_>, 32);
     static_assert_size!(StatementKind<'_>, 16);
     static_assert_size!(Terminator<'_>, 104);

compiler/rustc_middle/src/query/mod.rs

@@ -867,15 +867,8 @@ rustc_queries! {
         desc { |tcx| "collecting all inherent impls for `{:?}`", key }
     }
 
-    /// The result of unsafety-checking this `LocalDefId`.
-    query unsafety_check_result(key: LocalDefId) -> &'tcx mir::UnsafetyCheckResult {
-        desc { |tcx| "unsafety-checking `{}`", tcx.def_path_str(key) }
-        cache_on_disk_if { true }
-    }
-
-    /// Unsafety-check this `LocalDefId` with THIR unsafeck. This should be
-    /// used with `-Zthir-unsafeck`.
-    query thir_check_unsafety(key: LocalDefId) {
+    /// Unsafety-check this `LocalDefId`.
+    query check_unsafety(key: LocalDefId) {
         desc { |tcx| "unsafety-checking `{}`", tcx.def_path_str(key) }
         cache_on_disk_if { true }
     }

compiler/rustc_middle/src/ty/codec.rs

@@ -431,7 +431,6 @@ impl_decodable_via_ref! {
     &'tcx ty::List<ty::PolyExistentialPredicate<'tcx>>,
     &'tcx traits::ImplSource<'tcx, ()>,
     &'tcx mir::Body<'tcx>,
-    &'tcx mir::UnsafetyCheckResult,
     &'tcx mir::BorrowCheckResult<'tcx>,
     &'tcx mir::coverage::CodeRegion,
     &'tcx ty::List<ty::BoundVariableKind>,

compiler/rustc_mir_build/src/build/block.rs

@@ -20,7 +20,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
             ref stmts,
             expr,
             targeted_by_break,
-            safety_mode,
+            safety_mode: _,
         } = self.thir[ast_block];
         let expr = expr.map(|expr| &self.thir[expr]);
         self.in_opt_scope(opt_destruction_scope.map(|de| (de, source_info)), move |this| {
@@ -33,20 +33,11 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                             span,
                             &stmts,
                             expr,
-                            safety_mode,
                             region_scope,
                         ))
                     })
                 } else {
-                    this.ast_block_stmts(
-                        destination,
-                        block,
-                        span,
-                        &stmts,
-                        expr,
-                        safety_mode,
-                        region_scope,
-                    )
+                    this.ast_block_stmts(destination, block, span, &stmts, expr, region_scope)
                 }
             })
         })
@@ -59,7 +50,6 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         span: Span,
         stmts: &[StmtId],
         expr: Option<&Expr<'tcx>>,
-        safety_mode: BlockSafety,
         region_scope: Scope,
     ) -> BlockAnd<()> {
         let this = self;
@@ -82,13 +72,11 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         // First we build all the statements in the block.
         let mut let_scope_stack = Vec::with_capacity(8);
         let outer_source_scope = this.source_scope;
-        let outer_in_scope_unsafe = this.in_scope_unsafe;
         // This scope information is kept for breaking out of the parent remainder scope in case
         // one let-else pattern matching fails.
         // By doing so, we can be sure that even temporaries that receive extended lifetime
         // assignments are dropped, too.
         let mut last_remainder_scope = region_scope;
-        this.update_source_scope_for_safety_mode(span, safety_mode);
 
         let source_info = this.source_info(span);
         for stmt in stmts {
@@ -217,7 +205,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                     let_scope_stack.push(remainder_scope);
 
                     let visibility_scope =
-                        Some(this.new_source_scope(remainder_span, LintLevel::Inherited, None));
+                        Some(this.new_source_scope(remainder_span, LintLevel::Inherited));
 
                     let init = &this.thir[*initializer];
                     let initializer_span = init.span;
@@ -292,7 +280,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                     let remainder_span = remainder_scope.span(this.tcx, this.region_scope_tree);
 
                     let visibility_scope =
-                        Some(this.new_source_scope(remainder_span, LintLevel::Inherited, None));
+                        Some(this.new_source_scope(remainder_span, LintLevel::Inherited));
 
                     // Evaluate the initializer, if present.
                     if let Some(init) = initializer {
@@ -390,22 +378,6 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
         }
         // Restore the original source scope.
         this.source_scope = outer_source_scope;
-        this.in_scope_unsafe = outer_in_scope_unsafe;
         block.unit()
     }
-
-    /// If we are entering an unsafe block, create a new source scope
-    fn update_source_scope_for_safety_mode(&mut self, span: Span, safety_mode: BlockSafety) {
-        debug!("update_source_scope_for({:?}, {:?})", span, safety_mode);
-        let new_unsafety = match safety_mode {
-            BlockSafety::Safe => return,
-            BlockSafety::BuiltinUnsafe => Safety::BuiltinUnsafe,
-            BlockSafety::ExplicitUnsafe(hir_id) => {
-                self.in_scope_unsafe = Safety::ExplicitUnsafe(hir_id);
-                Safety::ExplicitUnsafe(hir_id)
-            }
-        };
-
-        self.source_scope = self.new_source_scope(span, LintLevel::Inherited, Some(new_unsafety));
-    }
 }

compiler/rustc_mir_build/src/build/custom/mod.rs

@@ -70,10 +70,7 @@ pub(super) fn build_custom_mir<'tcx>(
         parent_scope: None,
         inlined: None,
         inlined_parent_scope: None,
-        local_data: ClearCrossCrate::Set(SourceScopeLocalData {
-            lint_root: hir_id,
-            safety: Safety::Safe,
-        }),
+        local_data: ClearCrossCrate::Set(SourceScopeLocalData { lint_root: hir_id }),
     });
     body.injection_phase = Some(parse_attribute(attr));
 

compiler/rustc_mir_build/src/build/expr/as_rvalue.rs

@@ -131,26 +131,18 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                 let value = &this.thir[value];
                 let tcx = this.tcx;
 
-                // `exchange_malloc` is unsafe but box is safe, so need a new scope.
-                let synth_scope = this.new_source_scope(
-                    expr_span,
-                    LintLevel::Inherited,
-                    Some(Safety::BuiltinUnsafe),
-                );
-                let synth_info = SourceInfo { span: expr_span, scope: synth_scope };
-
                 let size = this.temp(tcx.types.usize, expr_span);
                 this.cfg.push_assign(
                     block,
-                    synth_info,
+                    source_info,
                     size,
                     Rvalue::NullaryOp(NullOp::SizeOf, value.ty),
                 );
 
                 let align = this.temp(tcx.types.usize, expr_span);
                 this.cfg.push_assign(
                     block,
-                    synth_info,
+                    source_info,
                     align,
                     Rvalue::NullaryOp(NullOp::AlignOf, value.ty),
                 );
@@ -166,7 +158,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                 let success = this.cfg.start_new_block();
                 this.cfg.terminate(
                     block,
-                    synth_info,
+                    source_info,
                     TerminatorKind::Call {
                         func: exchange_malloc,
                         args: vec![Operand::Move(size), Operand::Move(align)],

compiler/rustc_mir_build/src/build/expr/into.rs

@@ -62,11 +62,8 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
                         LintLevel::Inherited,
                         |this| {
                             let source_info = if this.is_let(cond) {
-                                let variable_scope = this.new_source_scope(
-                                    then_expr.span,
-                                    LintLevel::Inherited,
-                                    None,
-                                );
+                                let variable_scope =
+                                    this.new_source_scope(then_expr.span, LintLevel::Inherited);
                                 this.source_scope = variable_scope;
                                 SourceInfo { span: then_expr.span, scope: variable_scope }
                             } else {

compiler/rustc_mir_build/src/build/matches/mod.rs

@@ -705,7 +705,7 @@ impl<'a, 'tcx> Builder<'a, 'tcx> {
             &mut |this, mutability, name, mode, var, span, ty, user_ty| {
                 if visibility_scope.is_none() {
                     visibility_scope =
-                        Some(this.new_source_scope(scope_span, LintLevel::Inherited, None));
+                        Some(this.new_source_scope(scope_span, LintLevel::Inherited));
                 }
                 let source_info = SourceInfo { span, scope: this.source_scope };
                 let visibility_scope = visibility_scope.unwrap();