1 use crate::build::matches::ArmHasGuard;
2 use crate::build::ForGuard::OutsideGuard;
3 use crate::build::{BlockAnd, BlockAndExtension, BlockFrame, Builder};
6 use rustc_middle::mir::*;
7 use rustc_session::lint::builtin::UNSAFE_OP_IN_UNSAFE_FN;
8 use rustc_session::lint::Level;
11 impl<'a, 'tcx> Builder<'a, 'tcx> {
14 destination: Place<'tcx>,
16 ast_block: &'tcx hir::Block<'tcx>,
17 source_info: SourceInfo,
21 opt_destruction_scope,
27 } = self.hir.mirror(ast_block);
28 self.in_opt_scope(opt_destruction_scope.map(|de| (de, source_info)), move |this| {
29 this.in_scope((region_scope, source_info), LintLevel::Inherited, move |this| {
30 if targeted_by_break {
31 // This is a `break`-able block
32 let exit_block = this.cfg.start_new_block();
34 this.in_breakable_scope(None, exit_block, destination, |this| {
35 this.ast_block_stmts(destination, block, span, stmts, expr, safety_mode)
37 this.cfg.goto(unpack!(block_exit), source_info, exit_block);
40 this.ast_block_stmts(destination, block, span, stmts, expr, safety_mode)
48 destination: Place<'tcx>,
49 mut block: BasicBlock,
51 stmts: Vec<StmtRef<'tcx>>,
52 expr: Option<ExprRef<'tcx>>,
53 safety_mode: BlockSafety,
57 // This convoluted structure is to avoid using recursion as we walk down a list
58 // of statements. Basically, the structure we get back is something like:
60 // let x = <init> in {
62 // let y = <init> in {
69 // The let bindings are valid till the end of block so all we have to do is to pop all
70 // the let-scopes at the end.
72 // First we build all the statements in the block.
73 let mut let_scope_stack = Vec::with_capacity(8);
74 let outer_source_scope = this.source_scope;
75 let outer_push_unsafe_count = this.push_unsafe_count;
76 let outer_unpushed_unsafe = this.unpushed_unsafe;
77 this.update_source_scope_for_safety_mode(span, safety_mode);
79 let source_info = this.source_info(span);
81 let Stmt { kind, opt_destruction_scope } = this.hir.mirror(stmt);
83 StmtKind::Expr { scope, expr } => {
84 this.block_context.push(BlockFrame::Statement { ignores_expr_result: true });
86 block = this.in_opt_scope(
87 opt_destruction_scope.map(|de| (de, source_info)),
89 let si = (scope, source_info);
90 this.in_scope(si, LintLevel::Inherited, |this| {
91 let expr = this.hir.mirror(expr);
92 this.stmt_expr(block, expr, Some(scope))
98 StmtKind::Let { remainder_scope, init_scope, pattern, initializer, lint_level } => {
99 let ignores_expr_result = matches!(*pattern.kind, PatKind::Wild);
100 this.block_context.push(BlockFrame::Statement { ignores_expr_result });
102 // Enter the remainder scope, i.e., the bindings' destruction scope.
103 this.push_scope((remainder_scope, source_info));
104 let_scope_stack.push(remainder_scope);
106 // Declare the bindings, which may create a source scope.
108 remainder_scope.span(this.hir.tcx(), &this.hir.region_scope_tree);
110 let visibility_scope =
111 Some(this.new_source_scope(remainder_span, LintLevel::Inherited, None));
113 // Evaluate the initializer, if present.
114 if let Some(init) = initializer {
115 let initializer_span = init.span();
118 block = this.in_opt_scope(
119 opt_destruction_scope.map(|de| (de, source_info)),
121 let scope = (init_scope, source_info);
122 this.in_scope(scope, lint_level, |this| {
123 this.declare_bindings(
128 Some((None, initializer_span)),
130 this.expr_into_pattern(block, pattern, init)
136 let scope = (init_scope, source_info);
137 unpack!(this.in_scope(scope, lint_level, |this| {
138 this.declare_bindings(
148 debug!("ast_block_stmts: pattern={:?}", pattern);
149 this.visit_primary_bindings(
151 UserTypeProjections::none(),
152 &mut |this, _, _, _, node, span, _, _| {
153 this.storage_live_binding(block, node, span, OutsideGuard, true);
154 this.schedule_drop_for_binding(node, span, OutsideGuard);
159 // Enter the visibility scope, after evaluating the initializer.
160 if let Some(source_scope) = visibility_scope {
161 this.source_scope = source_scope;
166 let popped = this.block_context.pop();
167 assert!(popped.map_or(false, |bf| bf.is_statement()));
170 // Then, the block may have an optional trailing expression which is a “return” value
171 // of the block, which is stored into `destination`.
172 let tcx = this.hir.tcx();
173 let destination_ty = destination.ty(&this.local_decls, tcx).ty;
174 if let Some(expr) = expr {
175 let tail_result_is_ignored =
176 destination_ty.is_unit() || this.block_context.currently_ignores_tail_results();
177 let span = match expr {
178 ExprRef::Thir(expr) => expr.span,
179 ExprRef::Mirror(ref expr) => expr.span,
181 this.block_context.push(BlockFrame::TailExpr { tail_result_is_ignored, span });
183 unpack!(block = this.into(destination, block, expr));
184 let popped = this.block_context.pop();
186 assert!(popped.map_or(false, |bf| bf.is_tail_expr()));
188 // If a block has no trailing expression, then it is given an implicit return type.
189 // This return type is usually `()`, unless the block is diverging, in which case the
190 // return type is `!`. For the unit type, we need to actually return the unit, but in
191 // the case of `!`, no return value is required, as the block will never return.
192 if destination_ty.is_unit() {
193 // We only want to assign an implicit `()` as the return value of the block if the
194 // block does not diverge. (Otherwise, we may try to assign a unit to a `!`-type.)
195 this.cfg.push_assign_unit(block, source_info, destination, this.hir.tcx());
198 // Finally, we pop all the let scopes before exiting out from the scope of block
200 for scope in let_scope_stack.into_iter().rev() {
201 unpack!(block = this.pop_scope((scope, source_info), block));
203 // Restore the original source scope.
204 this.source_scope = outer_source_scope;
205 this.push_unsafe_count = outer_push_unsafe_count;
206 this.unpushed_unsafe = outer_unpushed_unsafe;
210 /// If we are changing the safety mode, create a new source scope
211 fn update_source_scope_for_safety_mode(&mut self, span: Span, safety_mode: BlockSafety) {
212 debug!("update_source_scope_for({:?}, {:?})", span, safety_mode);
213 let new_unsafety = match safety_mode {
214 BlockSafety::Safe => None,
215 BlockSafety::ExplicitUnsafe(hir_id) => {
216 assert_eq!(self.push_unsafe_count, 0);
217 match self.unpushed_unsafe {
219 // no longer treat `unsafe fn`s as `unsafe` contexts (see RFC #2585)
221 if self.hir.tcx().lint_level_at_node(UNSAFE_OP_IN_UNSAFE_FN, hir_id).0
222 != Level::Allow => {}
225 self.unpushed_unsafe = Safety::ExplicitUnsafe(hir_id);
226 Some(Safety::ExplicitUnsafe(hir_id))
228 BlockSafety::PushUnsafe => {
229 self.push_unsafe_count += 1;
230 Some(Safety::BuiltinUnsafe)
232 BlockSafety::PopUnsafe => {
233 self.push_unsafe_count = self
236 .unwrap_or_else(|| span_bug!(span, "unsafe count underflow"));
237 if self.push_unsafe_count == 0 { Some(self.unpushed_unsafe) } else { None }
241 if let Some(unsafety) = new_unsafety {
242 self.source_scope = self.new_source_scope(span, LintLevel::Inherited, Some(unsafety));