| use crate::build::{BlockAnd, BlockAndExtension, BlockFrame, Builder}; |
| use crate::build::ForGuard::OutsideGuard; |
| use crate::build::matches::ArmHasGuard; |
| use crate::hair::*; |
| use rustc::mir::*; |
| use rustc::hir; |
| use syntax_pos::Span; |
| |
| impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> { |
| pub fn ast_block(&mut self, |
| destination: &Place<'tcx>, |
| block: BasicBlock, |
| ast_block: &'tcx hir::Block, |
| source_info: SourceInfo) |
| -> BlockAnd<()> { |
| let Block { |
| region_scope, |
| opt_destruction_scope, |
| span, |
| stmts, |
| expr, |
| targeted_by_break, |
| safety_mode |
| } = |
| self.hir.mirror(ast_block); |
| self.in_opt_scope(opt_destruction_scope.map(|de|(de, source_info)), block, move |this| { |
| this.in_scope((region_scope, source_info), LintLevel::Inherited, block, move |this| { |
| if targeted_by_break { |
| // This is a `break`-able block |
| let exit_block = this.cfg.start_new_block(); |
| let block_exit = this.in_breakable_scope( |
| None, exit_block, destination.clone(), |this| { |
| this.ast_block_stmts(destination, block, span, stmts, expr, |
| safety_mode) |
| }); |
| this.cfg.terminate(unpack!(block_exit), source_info, |
| TerminatorKind::Goto { target: exit_block }); |
| exit_block.unit() |
| } else { |
| this.ast_block_stmts(destination, block, span, stmts, expr, |
| safety_mode) |
| } |
| }) |
| }) |
| } |
| |
| fn ast_block_stmts(&mut self, |
| destination: &Place<'tcx>, |
| mut block: BasicBlock, |
| span: Span, |
| stmts: Vec<StmtRef<'tcx>>, |
| expr: Option<ExprRef<'tcx>>, |
| safety_mode: BlockSafety) |
| -> BlockAnd<()> { |
| let this = self; |
| |
| // This convoluted structure is to avoid using recursion as we walk down a list |
| // of statements. Basically, the structure we get back is something like: |
| // |
| // let x = <init> in { |
| // expr1; |
| // let y = <init> in { |
| // expr2; |
| // expr3; |
| // ... |
| // } |
| // } |
| // |
| // The let bindings are valid till the end of block so all we have to do is to pop all |
| // the let-scopes at the end. |
| // |
| // 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_push_unsafe_count = this.push_unsafe_count; |
| let outer_unpushed_unsafe = this.unpushed_unsafe; |
| this.update_source_scope_for_safety_mode(span, safety_mode); |
| |
| let source_info = this.source_info(span); |
| for stmt in stmts { |
| let Stmt { kind, opt_destruction_scope, span: stmt_span } = this.hir.mirror(stmt); |
| match kind { |
| StmtKind::Expr { scope, expr } => { |
| this.block_context.push(BlockFrame::Statement { ignores_expr_result: true }); |
| unpack!(block = this.in_opt_scope( |
| opt_destruction_scope.map(|de|(de, source_info)), block, |this| { |
| let si = (scope, source_info); |
| this.in_scope(si, LintLevel::Inherited, block, |this| { |
| let expr = this.hir.mirror(expr); |
| this.stmt_expr(block, expr, Some(stmt_span)) |
| }) |
| })); |
| } |
| StmtKind::Let { |
| remainder_scope, |
| init_scope, |
| pattern, |
| initializer, |
| lint_level |
| } => { |
| let ignores_expr_result = if let PatternKind::Wild = *pattern.kind { |
| true |
| } else { |
| false |
| }; |
| this.block_context.push(BlockFrame::Statement { ignores_expr_result }); |
| |
| // Enter the remainder scope, i.e., the bindings' destruction scope. |
| this.push_scope((remainder_scope, source_info)); |
| let_scope_stack.push(remainder_scope); |
| |
| // Declare the bindings, which may create a source scope. |
| let remainder_span = remainder_scope.span(this.hir.tcx(), |
| &this.hir.region_scope_tree); |
| |
| let scope; |
| |
| // Evaluate the initializer, if present. |
| if let Some(init) = initializer { |
| let initializer_span = init.span(); |
| |
| scope = this.declare_bindings( |
| None, |
| remainder_span, |
| lint_level, |
| &pattern, |
| ArmHasGuard(false), |
| Some((None, initializer_span)), |
| ); |
| unpack!(block = this.in_opt_scope( |
| opt_destruction_scope.map(|de|(de, source_info)), block, |this| { |
| let scope = (init_scope, source_info); |
| this.in_scope(scope, lint_level, block, |this| { |
| this.expr_into_pattern(block, pattern, init) |
| }) |
| })); |
| } else { |
| scope = this.declare_bindings( |
| None, remainder_span, lint_level, &pattern, |
| ArmHasGuard(false), None); |
| |
| debug!("ast_block_stmts: pattern={:?}", pattern); |
| this.visit_bindings( |
| &pattern, |
| UserTypeProjections::none(), |
| &mut |this, _, _, _, node, span, _, _| { |
| this.storage_live_binding(block, node, span, OutsideGuard); |
| this.schedule_drop_for_binding(node, span, OutsideGuard); |
| }) |
| } |
| |
| // Enter the source scope, after evaluating the initializer. |
| if let Some(source_scope) = scope { |
| this.source_scope = source_scope; |
| } |
| } |
| } |
| |
| let popped = this.block_context.pop(); |
| assert!(popped.map_or(false, |bf|bf.is_statement())); |
| } |
| |
| // Then, the block may have an optional trailing expression which is a “return” value |
| // of the block, which is stored into `destination`. |
| let tcx = this.hir.tcx(); |
| let destination_ty = destination.ty(&this.local_decls, tcx).ty; |
| if let Some(expr) = expr { |
| let tail_result_is_ignored = destination_ty.is_unit() || |
| this.block_context.currently_ignores_tail_results(); |
| this.block_context.push(BlockFrame::TailExpr { tail_result_is_ignored }); |
| |
| unpack!(block = this.into(destination, block, expr)); |
| let popped = this.block_context.pop(); |
| |
| assert!(popped.map_or(false, |bf|bf.is_tail_expr())); |
| } else { |
| // If a block has no trailing expression, then it is given an implicit return type. |
| // This return type is usually `()`, unless the block is diverging, in which case the |
| // return type is `!`. For the unit type, we need to actually return the unit, but in |
| // the case of `!`, no return value is required, as the block will never return. |
| if destination_ty.is_unit() { |
| // We only want to assign an implicit `()` as the return value of the block if the |
| // block does not diverge. (Otherwise, we may try to assign a unit to a `!`-type.) |
| this.cfg.push_assign_unit(block, source_info, destination); |
| } |
| } |
| // Finally, we pop all the let scopes before exiting out from the scope of block |
| // itself. |
| for scope in let_scope_stack.into_iter().rev() { |
| unpack!(block = this.pop_scope((scope, source_info), block)); |
| } |
| // Restore the original source scope. |
| this.source_scope = outer_source_scope; |
| this.push_unsafe_count = outer_push_unsafe_count; |
| this.unpushed_unsafe = outer_unpushed_unsafe; |
| block.unit() |
| } |
| |
| /// If we are changing the safety mode, 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 => None, |
| BlockSafety::ExplicitUnsafe(hir_id) => { |
| assert_eq!(self.push_unsafe_count, 0); |
| match self.unpushed_unsafe { |
| Safety::Safe => {} |
| _ => return |
| } |
| self.unpushed_unsafe = Safety::ExplicitUnsafe(hir_id); |
| Some(Safety::ExplicitUnsafe(hir_id)) |
| } |
| BlockSafety::PushUnsafe => { |
| self.push_unsafe_count += 1; |
| Some(Safety::BuiltinUnsafe) |
| } |
| BlockSafety::PopUnsafe => { |
| self.push_unsafe_count = |
| self.push_unsafe_count.checked_sub(1).unwrap_or_else(|| { |
| span_bug!(span, "unsafe count underflow") |
| }); |
| if self.push_unsafe_count == 0 { |
| Some(self.unpushed_unsafe) |
| } else { |
| None |
| } |
| } |
| }; |
| |
| if let Some(unsafety) = new_unsafety { |
| self.source_scope = self.new_source_scope( |
| span, LintLevel::Inherited, Some(unsafety)); |
| } |
| } |
| } |
