| use super::{ImplTraitContext, LoweringContext, ParamMode, ParenthesizedGenericArgs}; |
| |
| use rustc_ast::attr; |
| use rustc_ast::ptr::P as AstP; |
| use rustc_ast::*; |
| use rustc_data_structures::stack::ensure_sufficient_stack; |
| use rustc_data_structures::thin_vec::ThinVec; |
| use rustc_errors::struct_span_err; |
| use rustc_hir as hir; |
| use rustc_hir::def::Res; |
| use rustc_hir::definitions::DefPathData; |
| use rustc_session::parse::feature_err; |
| use rustc_span::hygiene::ExpnId; |
| use rustc_span::source_map::{respan, DesugaringKind, Span, Spanned}; |
| use rustc_span::symbol::{sym, Ident, Symbol}; |
| use rustc_span::{hygiene::ForLoopLoc, DUMMY_SP}; |
| |
| impl<'hir> LoweringContext<'_, 'hir> { |
| fn lower_exprs(&mut self, exprs: &[AstP<Expr>]) -> &'hir [hir::Expr<'hir>] { |
| self.arena.alloc_from_iter(exprs.iter().map(|x| self.lower_expr_mut(x))) |
| } |
| |
| pub(super) fn lower_expr(&mut self, e: &Expr) -> &'hir hir::Expr<'hir> { |
| self.arena.alloc(self.lower_expr_mut(e)) |
| } |
| |
| pub(super) fn lower_expr_mut(&mut self, e: &Expr) -> hir::Expr<'hir> { |
| ensure_sufficient_stack(|| { |
| let kind = match e.kind { |
| ExprKind::Box(ref inner) => hir::ExprKind::Box(self.lower_expr(inner)), |
| ExprKind::Array(ref exprs) => hir::ExprKind::Array(self.lower_exprs(exprs)), |
| ExprKind::ConstBlock(ref anon_const) => { |
| let anon_const = self.lower_anon_const(anon_const); |
| hir::ExprKind::ConstBlock(anon_const) |
| } |
| ExprKind::Repeat(ref expr, ref count) => { |
| let expr = self.lower_expr(expr); |
| let count = self.lower_anon_const(count); |
| hir::ExprKind::Repeat(expr, count) |
| } |
| ExprKind::Tup(ref elts) => hir::ExprKind::Tup(self.lower_exprs(elts)), |
| ExprKind::Call(ref f, ref args) => { |
| if let Some(legacy_args) = self.resolver.legacy_const_generic_args(f) { |
| self.lower_legacy_const_generics((**f).clone(), args.clone(), &legacy_args) |
| } else { |
| let f = self.lower_expr(f); |
| hir::ExprKind::Call(f, self.lower_exprs(args)) |
| } |
| } |
| ExprKind::MethodCall(ref seg, ref args, span) => { |
| let hir_seg = self.arena.alloc(self.lower_path_segment( |
| e.span, |
| seg, |
| ParamMode::Optional, |
| 0, |
| ParenthesizedGenericArgs::Err, |
| ImplTraitContext::disallowed(), |
| None, |
| )); |
| let args = self.lower_exprs(args); |
| hir::ExprKind::MethodCall(hir_seg, seg.ident.span, args, span) |
| } |
| ExprKind::Binary(binop, ref lhs, ref rhs) => { |
| let binop = self.lower_binop(binop); |
| let lhs = self.lower_expr(lhs); |
| let rhs = self.lower_expr(rhs); |
| hir::ExprKind::Binary(binop, lhs, rhs) |
| } |
| ExprKind::Unary(op, ref ohs) => { |
| let op = self.lower_unop(op); |
| let ohs = self.lower_expr(ohs); |
| hir::ExprKind::Unary(op, ohs) |
| } |
| ExprKind::Lit(ref l) => hir::ExprKind::Lit(respan(l.span, l.kind.clone())), |
| ExprKind::Cast(ref expr, ref ty) => { |
| let expr = self.lower_expr(expr); |
| let ty = self.lower_ty(ty, ImplTraitContext::disallowed()); |
| hir::ExprKind::Cast(expr, ty) |
| } |
| ExprKind::Type(ref expr, ref ty) => { |
| let expr = self.lower_expr(expr); |
| let ty = self.lower_ty(ty, ImplTraitContext::disallowed()); |
| hir::ExprKind::Type(expr, ty) |
| } |
| ExprKind::AddrOf(k, m, ref ohs) => { |
| let ohs = self.lower_expr(ohs); |
| hir::ExprKind::AddrOf(k, m, ohs) |
| } |
| ExprKind::Let(ref pat, ref scrutinee) => { |
| self.lower_expr_let(e.span, pat, scrutinee) |
| } |
| ExprKind::If(ref cond, ref then, ref else_opt) => match cond.kind { |
| ExprKind::Let(ref pat, ref scrutinee) => { |
| self.lower_expr_if_let(e.span, pat, scrutinee, then, else_opt.as_deref()) |
| } |
| ExprKind::Paren(ref paren) => match paren.peel_parens().kind { |
| ExprKind::Let(ref pat, ref scrutinee) => { |
| // A user has written `if (let Some(x) = foo) {`, we want to avoid |
| // confusing them with mentions of nightly features. |
| // If this logic is changed, you will also likely need to touch |
| // `unused::UnusedParens::check_expr`. |
| self.if_let_expr_with_parens(cond, &paren.peel_parens()); |
| self.lower_expr_if_let( |
| e.span, |
| pat, |
| scrutinee, |
| then, |
| else_opt.as_deref(), |
| ) |
| } |
| _ => self.lower_expr_if(cond, then, else_opt.as_deref()), |
| }, |
| _ => self.lower_expr_if(cond, then, else_opt.as_deref()), |
| }, |
| ExprKind::While(ref cond, ref body, opt_label) => self |
| .with_loop_scope(e.id, |this| { |
| this.lower_expr_while_in_loop_scope(e.span, cond, body, opt_label) |
| }), |
| ExprKind::Loop(ref body, opt_label) => self.with_loop_scope(e.id, |this| { |
| hir::ExprKind::Loop( |
| this.lower_block(body, false), |
| opt_label, |
| hir::LoopSource::Loop, |
| DUMMY_SP, |
| ) |
| }), |
| ExprKind::TryBlock(ref body) => self.lower_expr_try_block(body), |
| ExprKind::Match(ref expr, ref arms) => hir::ExprKind::Match( |
| self.lower_expr(expr), |
| self.arena.alloc_from_iter(arms.iter().map(|x| self.lower_arm(x))), |
| hir::MatchSource::Normal, |
| ), |
| ExprKind::Async(capture_clause, closure_node_id, ref block) => self |
| .make_async_expr( |
| capture_clause, |
| closure_node_id, |
| None, |
| block.span, |
| hir::AsyncGeneratorKind::Block, |
| |this| this.with_new_scopes(|this| this.lower_block_expr(block)), |
| ), |
| ExprKind::Await(ref expr) => self.lower_expr_await(e.span, expr), |
| ExprKind::Closure( |
| capture_clause, |
| asyncness, |
| movability, |
| ref decl, |
| ref body, |
| fn_decl_span, |
| ) => { |
| if let Async::Yes { closure_id, .. } = asyncness { |
| self.lower_expr_async_closure( |
| capture_clause, |
| closure_id, |
| decl, |
| body, |
| fn_decl_span, |
| ) |
| } else { |
| self.lower_expr_closure( |
| capture_clause, |
| movability, |
| decl, |
| body, |
| fn_decl_span, |
| ) |
| } |
| } |
| ExprKind::Block(ref blk, opt_label) => { |
| hir::ExprKind::Block(self.lower_block(blk, opt_label.is_some()), opt_label) |
| } |
| ExprKind::Assign(ref el, ref er, span) => { |
| self.lower_expr_assign(el, er, span, e.span) |
| } |
| ExprKind::AssignOp(op, ref el, ref er) => hir::ExprKind::AssignOp( |
| self.lower_binop(op), |
| self.lower_expr(el), |
| self.lower_expr(er), |
| ), |
| ExprKind::Field(ref el, ident) => hir::ExprKind::Field(self.lower_expr(el), ident), |
| ExprKind::Index(ref el, ref er) => { |
| hir::ExprKind::Index(self.lower_expr(el), self.lower_expr(er)) |
| } |
| ExprKind::Range(Some(ref e1), Some(ref e2), RangeLimits::Closed) => { |
| self.lower_expr_range_closed(e.span, e1, e2) |
| } |
| ExprKind::Range(ref e1, ref e2, lims) => { |
| self.lower_expr_range(e.span, e1.as_deref(), e2.as_deref(), lims) |
| } |
| ExprKind::Underscore => { |
| self.sess |
| .struct_span_err( |
| e.span, |
| "in expressions, `_` can only be used on the left-hand side of an assignment", |
| ) |
| .span_label(e.span, "`_` not allowed here") |
| .emit(); |
| hir::ExprKind::Err |
| } |
| ExprKind::Path(ref qself, ref path) => { |
| let qpath = self.lower_qpath( |
| e.id, |
| qself, |
| path, |
| ParamMode::Optional, |
| ImplTraitContext::disallowed(), |
| ); |
| hir::ExprKind::Path(qpath) |
| } |
| ExprKind::Break(opt_label, ref opt_expr) => { |
| let opt_expr = opt_expr.as_ref().map(|x| self.lower_expr(x)); |
| hir::ExprKind::Break(self.lower_jump_destination(e.id, opt_label), opt_expr) |
| } |
| ExprKind::Continue(opt_label) => { |
| hir::ExprKind::Continue(self.lower_jump_destination(e.id, opt_label)) |
| } |
| ExprKind::Ret(ref e) => { |
| let e = e.as_ref().map(|x| self.lower_expr(x)); |
| hir::ExprKind::Ret(e) |
| } |
| ExprKind::InlineAsm(ref asm) => { |
| hir::ExprKind::InlineAsm(self.lower_inline_asm(e.span, asm)) |
| } |
| ExprKind::LlvmInlineAsm(ref asm) => self.lower_expr_llvm_asm(asm), |
| ExprKind::Struct(ref se) => { |
| let rest = match &se.rest { |
| StructRest::Base(e) => Some(self.lower_expr(e)), |
| StructRest::Rest(sp) => { |
| self.sess |
| .struct_span_err(*sp, "base expression required after `..`") |
| .span_label(*sp, "add a base expression here") |
| .emit(); |
| Some(&*self.arena.alloc(self.expr_err(*sp))) |
| } |
| StructRest::None => None, |
| }; |
| hir::ExprKind::Struct( |
| self.arena.alloc(self.lower_qpath( |
| e.id, |
| &se.qself, |
| &se.path, |
| ParamMode::Optional, |
| ImplTraitContext::disallowed(), |
| )), |
| self.arena |
| .alloc_from_iter(se.fields.iter().map(|x| self.lower_expr_field(x))), |
| rest, |
| ) |
| } |
| ExprKind::Yield(ref opt_expr) => self.lower_expr_yield(e.span, opt_expr.as_deref()), |
| ExprKind::Err => hir::ExprKind::Err, |
| ExprKind::Try(ref sub_expr) => self.lower_expr_try(e.span, sub_expr), |
| ExprKind::Paren(ref ex) => { |
| let mut ex = self.lower_expr_mut(ex); |
| // Include parens in span, but only if it is a super-span. |
| if e.span.contains(ex.span) { |
| ex.span = e.span; |
| } |
| // Merge attributes into the inner expression. |
| if !e.attrs.is_empty() { |
| let old_attrs = self.attrs.get(&ex.hir_id).map(|la| *la).unwrap_or(&[]); |
| self.attrs.insert( |
| ex.hir_id, |
| &*self.arena.alloc_from_iter( |
| e.attrs |
| .iter() |
| .map(|a| self.lower_attr(a)) |
| .chain(old_attrs.iter().cloned()), |
| ), |
| ); |
| } |
| return ex; |
| } |
| |
| // Desugar `ExprForLoop` |
| // from: `[opt_ident]: for <pat> in <head> <body>` |
| ExprKind::ForLoop(ref pat, ref head, ref body, opt_label) => { |
| return self.lower_expr_for(e, pat, head, body, opt_label); |
| } |
| ExprKind::MacCall(_) => panic!("{:?} shouldn't exist here", e.span), |
| }; |
| |
| let hir_id = self.lower_node_id(e.id); |
| self.lower_attrs(hir_id, &e.attrs); |
| hir::Expr { hir_id, kind, span: e.span } |
| }) |
| } |
| |
| fn lower_unop(&mut self, u: UnOp) -> hir::UnOp { |
| match u { |
| UnOp::Deref => hir::UnOp::Deref, |
| UnOp::Not => hir::UnOp::Not, |
| UnOp::Neg => hir::UnOp::Neg, |
| } |
| } |
| |
| fn lower_binop(&mut self, b: BinOp) -> hir::BinOp { |
| Spanned { |
| node: match b.node { |
| BinOpKind::Add => hir::BinOpKind::Add, |
| BinOpKind::Sub => hir::BinOpKind::Sub, |
| BinOpKind::Mul => hir::BinOpKind::Mul, |
| BinOpKind::Div => hir::BinOpKind::Div, |
| BinOpKind::Rem => hir::BinOpKind::Rem, |
| BinOpKind::And => hir::BinOpKind::And, |
| BinOpKind::Or => hir::BinOpKind::Or, |
| BinOpKind::BitXor => hir::BinOpKind::BitXor, |
| BinOpKind::BitAnd => hir::BinOpKind::BitAnd, |
| BinOpKind::BitOr => hir::BinOpKind::BitOr, |
| BinOpKind::Shl => hir::BinOpKind::Shl, |
| BinOpKind::Shr => hir::BinOpKind::Shr, |
| BinOpKind::Eq => hir::BinOpKind::Eq, |
| BinOpKind::Lt => hir::BinOpKind::Lt, |
| BinOpKind::Le => hir::BinOpKind::Le, |
| BinOpKind::Ne => hir::BinOpKind::Ne, |
| BinOpKind::Ge => hir::BinOpKind::Ge, |
| BinOpKind::Gt => hir::BinOpKind::Gt, |
| }, |
| span: b.span, |
| } |
| } |
| |
| fn lower_legacy_const_generics( |
| &mut self, |
| mut f: Expr, |
| args: Vec<AstP<Expr>>, |
| legacy_args_idx: &[usize], |
| ) -> hir::ExprKind<'hir> { |
| let path = match f.kind { |
| ExprKind::Path(None, ref mut path) => path, |
| _ => unreachable!(), |
| }; |
| |
| // Split the arguments into const generics and normal arguments |
| let mut real_args = vec![]; |
| let mut generic_args = vec![]; |
| for (idx, arg) in args.into_iter().enumerate() { |
| if legacy_args_idx.contains(&idx) { |
| let parent_def_id = self.current_hir_id_owner.0; |
| let node_id = self.resolver.next_node_id(); |
| |
| // Add a definition for the in-band const def. |
| self.resolver.create_def( |
| parent_def_id, |
| node_id, |
| DefPathData::AnonConst, |
| ExpnId::root(), |
| arg.span, |
| ); |
| |
| let anon_const = AnonConst { id: node_id, value: arg }; |
| generic_args.push(AngleBracketedArg::Arg(GenericArg::Const(anon_const))); |
| } else { |
| real_args.push(arg); |
| } |
| } |
| |
| // Add generic args to the last element of the path. |
| let last_segment = path.segments.last_mut().unwrap(); |
| assert!(last_segment.args.is_none()); |
| last_segment.args = Some(AstP(GenericArgs::AngleBracketed(AngleBracketedArgs { |
| span: DUMMY_SP, |
| args: generic_args, |
| }))); |
| |
| // Now lower everything as normal. |
| let f = self.lower_expr(&f); |
| hir::ExprKind::Call(f, self.lower_exprs(&real_args)) |
| } |
| |
| fn if_let_expr_with_parens(&mut self, cond: &Expr, paren: &Expr) { |
| let start = cond.span.until(paren.span); |
| let end = paren.span.shrink_to_hi().until(cond.span.shrink_to_hi()); |
| self.sess |
| .struct_span_err( |
| vec![start, end], |
| "invalid parentheses around `let` expression in `if let`", |
| ) |
| .multipart_suggestion( |
| "`if let` needs to be written without parentheses", |
| vec![(start, String::new()), (end, String::new())], |
| rustc_errors::Applicability::MachineApplicable, |
| ) |
| .emit(); |
| // Ideally, we'd remove the feature gating of a `let` expression since we are already |
| // complaining about it here, but `feature_gate::check_crate` has already run by now: |
| // self.sess.parse_sess.gated_spans.ungate_last(sym::let_chains, paren.span); |
| } |
| |
| /// Emit an error and lower `ast::ExprKind::Let(pat, scrutinee)` into: |
| /// ```rust |
| /// match scrutinee { pats => true, _ => false } |
| /// ``` |
| fn lower_expr_let(&mut self, span: Span, pat: &Pat, scrutinee: &Expr) -> hir::ExprKind<'hir> { |
| // If we got here, the `let` expression is not allowed. |
| |
| if self.sess.opts.unstable_features.is_nightly_build() { |
| self.sess |
| .struct_span_err(span, "`let` expressions are not supported here") |
| .note( |
| "only supported directly without parentheses in conditions of `if`- and \ |
| `while`-expressions, as well as in `let` chains within parentheses", |
| ) |
| .emit(); |
| } else { |
| self.sess |
| .struct_span_err(span, "expected expression, found statement (`let`)") |
| .note("variable declaration using `let` is a statement") |
| .emit(); |
| } |
| |
| // For better recovery, we emit: |
| // ``` |
| // match scrutinee { pat => true, _ => false } |
| // ``` |
| // While this doesn't fully match the user's intent, it has key advantages: |
| // 1. We can avoid using `abort_if_errors`. |
| // 2. We can typeck both `pat` and `scrutinee`. |
| // 3. `pat` is allowed to be refutable. |
| // 4. The return type of the block is `bool` which seems like what the user wanted. |
| let scrutinee = self.lower_expr(scrutinee); |
| let then_arm = { |
| let pat = self.lower_pat(pat); |
| let expr = self.expr_bool(span, true); |
| self.arm(pat, expr) |
| }; |
| let else_arm = { |
| let pat = self.pat_wild(span); |
| let expr = self.expr_bool(span, false); |
| self.arm(pat, expr) |
| }; |
| hir::ExprKind::Match( |
| scrutinee, |
| arena_vec![self; then_arm, else_arm], |
| hir::MatchSource::Normal, |
| ) |
| } |
| |
| fn lower_expr_if( |
| &mut self, |
| cond: &Expr, |
| then: &Block, |
| else_opt: Option<&Expr>, |
| ) -> hir::ExprKind<'hir> { |
| macro_rules! make_if { |
| ($opt:expr) => {{ |
| let cond = self.lower_expr(cond); |
| let then_expr = self.lower_block_expr(then); |
| hir::ExprKind::If(cond, self.arena.alloc(then_expr), $opt) |
| }}; |
| } |
| if let Some(rslt) = else_opt { |
| make_if!(Some(self.lower_expr(rslt))) |
| } else { |
| make_if!(None) |
| } |
| } |
| |
| fn lower_expr_if_let( |
| &mut self, |
| span: Span, |
| pat: &Pat, |
| scrutinee: &Expr, |
| then: &Block, |
| else_opt: Option<&Expr>, |
| ) -> hir::ExprKind<'hir> { |
| // FIXME(#53667): handle lowering of && and parens. |
| |
| // `_ => else_block` where `else_block` is `{}` if there's `None`: |
| let else_pat = self.pat_wild(span); |
| let (else_expr, contains_else_clause) = match else_opt { |
| None => (self.expr_block_empty(span.shrink_to_hi()), false), |
| Some(els) => (self.lower_expr(els), true), |
| }; |
| let else_arm = self.arm(else_pat, else_expr); |
| |
| // Handle then + scrutinee: |
| let scrutinee = self.lower_expr(scrutinee); |
| let then_pat = self.lower_pat(pat); |
| |
| let then_expr = self.lower_block_expr(then); |
| let then_arm = self.arm(then_pat, self.arena.alloc(then_expr)); |
| |
| let desugar = hir::MatchSource::IfLetDesugar { contains_else_clause }; |
| hir::ExprKind::Match(scrutinee, arena_vec![self; then_arm, else_arm], desugar) |
| } |
| |
| fn lower_expr_while_in_loop_scope( |
| &mut self, |
| span: Span, |
| cond: &Expr, |
| body: &Block, |
| opt_label: Option<Label>, |
| ) -> hir::ExprKind<'hir> { |
| // FIXME(#53667): handle lowering of && and parens. |
| |
| // Note that the block AND the condition are evaluated in the loop scope. |
| // This is done to allow `break` from inside the condition of the loop. |
| |
| // `_ => break`: |
| let else_arm = { |
| let else_pat = self.pat_wild(span); |
| let else_expr = self.expr_break(span, ThinVec::new()); |
| self.arm(else_pat, else_expr) |
| }; |
| |
| // Handle then + scrutinee: |
| let (then_pat, scrutinee, desugar, source) = match cond.kind { |
| ExprKind::Let(ref pat, ref scrutinee) => { |
| // to: |
| // |
| // [opt_ident]: loop { |
| // match <sub_expr> { |
| // <pat> => <body>, |
| // _ => break |
| // } |
| // } |
| let scrutinee = self.with_loop_condition_scope(|t| t.lower_expr(scrutinee)); |
| let pat = self.lower_pat(pat); |
| (pat, scrutinee, hir::MatchSource::WhileLetDesugar, hir::LoopSource::WhileLet) |
| } |
| _ => { |
| // We desugar: `'label: while $cond $body` into: |
| // |
| // ``` |
| // 'label: loop { |
| // match drop-temps { $cond } { |
| // true => $body, |
| // _ => break, |
| // } |
| // } |
| // ``` |
| |
| // Lower condition: |
| let cond = self.with_loop_condition_scope(|this| this.lower_expr(cond)); |
| let span_block = |
| self.mark_span_with_reason(DesugaringKind::CondTemporary, cond.span, None); |
| // Wrap in a construct equivalent to `{ let _t = $cond; _t }` |
| // to preserve drop semantics since `while cond { ... }` does not |
| // let temporaries live outside of `cond`. |
| let cond = self.expr_drop_temps(span_block, cond, ThinVec::new()); |
| // `true => <then>`: |
| let pat = self.pat_bool(span, true); |
| (pat, cond, hir::MatchSource::WhileDesugar, hir::LoopSource::While) |
| } |
| }; |
| let then_expr = self.lower_block_expr(body); |
| let then_arm = self.arm(then_pat, self.arena.alloc(then_expr)); |
| |
| // `match <scrutinee> { ... }` |
| let match_expr = |
| self.expr_match(span, scrutinee, arena_vec![self; then_arm, else_arm], desugar); |
| |
| // `[opt_ident]: loop { ... }` |
| hir::ExprKind::Loop( |
| self.block_expr(self.arena.alloc(match_expr)), |
| opt_label, |
| source, |
| span.with_hi(cond.span.hi()), |
| ) |
| } |
| |
| /// Desugar `try { <stmts>; <expr> }` into `{ <stmts>; ::std::ops::Try::from_output(<expr>) }`, |
| /// `try { <stmts>; }` into `{ <stmts>; ::std::ops::Try::from_output(()) }` |
| /// and save the block id to use it as a break target for desugaring of the `?` operator. |
| fn lower_expr_try_block(&mut self, body: &Block) -> hir::ExprKind<'hir> { |
| self.with_catch_scope(body.id, |this| { |
| let mut block = this.lower_block_noalloc(body, true); |
| |
| // Final expression of the block (if present) or `()` with span at the end of block |
| let (try_span, tail_expr) = if let Some(expr) = block.expr.take() { |
| ( |
| this.mark_span_with_reason( |
| DesugaringKind::TryBlock, |
| expr.span, |
| this.allow_try_trait.clone(), |
| ), |
| expr, |
| ) |
| } else { |
| let try_span = this.mark_span_with_reason( |
| DesugaringKind::TryBlock, |
| this.sess.source_map().end_point(body.span), |
| this.allow_try_trait.clone(), |
| ); |
| |
| (try_span, this.expr_unit(try_span)) |
| }; |
| |
| let ok_wrapped_span = |
| this.mark_span_with_reason(DesugaringKind::TryBlock, tail_expr.span, None); |
| |
| // `::std::ops::Try::from_output($tail_expr)` |
| block.expr = Some(this.wrap_in_try_constructor( |
| hir::LangItem::TryTraitFromOutput, |
| try_span, |
| tail_expr, |
| ok_wrapped_span, |
| )); |
| |
| hir::ExprKind::Block(this.arena.alloc(block), None) |
| }) |
| } |
| |
| fn wrap_in_try_constructor( |
| &mut self, |
| lang_item: hir::LangItem, |
| method_span: Span, |
| expr: &'hir hir::Expr<'hir>, |
| overall_span: Span, |
| ) -> &'hir hir::Expr<'hir> { |
| let constructor = |
| self.arena.alloc(self.expr_lang_item_path(method_span, lang_item, ThinVec::new())); |
| self.expr_call(overall_span, constructor, std::slice::from_ref(expr)) |
| } |
| |
| fn lower_arm(&mut self, arm: &Arm) -> hir::Arm<'hir> { |
| let pat = self.lower_pat(&arm.pat); |
| let guard = arm.guard.as_ref().map(|cond| { |
| if let ExprKind::Let(ref pat, ref scrutinee) = cond.kind { |
| hir::Guard::IfLet(self.lower_pat(pat), self.lower_expr(scrutinee)) |
| } else { |
| hir::Guard::If(self.lower_expr(cond)) |
| } |
| }); |
| let hir_id = self.next_id(); |
| self.lower_attrs(hir_id, &arm.attrs); |
| hir::Arm { hir_id, pat, guard, body: self.lower_expr(&arm.body), span: arm.span } |
| } |
| |
| /// Lower an `async` construct to a generator that is then wrapped so it implements `Future`. |
| /// |
| /// This results in: |
| /// |
| /// ```text |
| /// std::future::from_generator(static move? |_task_context| -> <ret_ty> { |
| /// <body> |
| /// }) |
| /// ``` |
| pub(super) fn make_async_expr( |
| &mut self, |
| capture_clause: CaptureBy, |
| closure_node_id: NodeId, |
| ret_ty: Option<AstP<Ty>>, |
| span: Span, |
| async_gen_kind: hir::AsyncGeneratorKind, |
| body: impl FnOnce(&mut Self) -> hir::Expr<'hir>, |
| ) -> hir::ExprKind<'hir> { |
| let output = match ret_ty { |
| Some(ty) => hir::FnRetTy::Return(self.lower_ty(&ty, ImplTraitContext::disallowed())), |
| None => hir::FnRetTy::DefaultReturn(span), |
| }; |
| |
| // Resume argument type. We let the compiler infer this to simplify the lowering. It is |
| // fully constrained by `future::from_generator`. |
| let input_ty = hir::Ty { hir_id: self.next_id(), kind: hir::TyKind::Infer, span }; |
| |
| // The closure/generator `FnDecl` takes a single (resume) argument of type `input_ty`. |
| let decl = self.arena.alloc(hir::FnDecl { |
| inputs: arena_vec![self; input_ty], |
| output, |
| c_variadic: false, |
| implicit_self: hir::ImplicitSelfKind::None, |
| }); |
| |
| // Lower the argument pattern/ident. The ident is used again in the `.await` lowering. |
| let (pat, task_context_hid) = self.pat_ident_binding_mode( |
| span, |
| Ident::with_dummy_span(sym::_task_context), |
| hir::BindingAnnotation::Mutable, |
| ); |
| let param = hir::Param { hir_id: self.next_id(), pat, ty_span: span, span }; |
| let params = arena_vec![self; param]; |
| |
| let body_id = self.lower_body(move |this| { |
| this.generator_kind = Some(hir::GeneratorKind::Async(async_gen_kind)); |
| |
| let old_ctx = this.task_context; |
| this.task_context = Some(task_context_hid); |
| let res = body(this); |
| this.task_context = old_ctx; |
| (params, res) |
| }); |
| |
| // `static |_task_context| -> <ret_ty> { body }`: |
| let generator_kind = hir::ExprKind::Closure( |
| capture_clause, |
| decl, |
| body_id, |
| span, |
| Some(hir::Movability::Static), |
| ); |
| let generator = |
| hir::Expr { hir_id: self.lower_node_id(closure_node_id), kind: generator_kind, span }; |
| |
| // `future::from_generator`: |
| let unstable_span = |
| self.mark_span_with_reason(DesugaringKind::Async, span, self.allow_gen_future.clone()); |
| let gen_future = |
| self.expr_lang_item_path(unstable_span, hir::LangItem::FromGenerator, ThinVec::new()); |
| |
| // `future::from_generator(generator)`: |
| hir::ExprKind::Call(self.arena.alloc(gen_future), arena_vec![self; generator]) |
| } |
| |
| /// Desugar `<expr>.await` into: |
| /// ```rust |
| /// match <expr> { |
| /// mut pinned => loop { |
| /// match unsafe { ::std::future::Future::poll( |
| /// <::std::pin::Pin>::new_unchecked(&mut pinned), |
| /// ::std::future::get_context(task_context), |
| /// ) } { |
| /// ::std::task::Poll::Ready(result) => break result, |
| /// ::std::task::Poll::Pending => {} |
| /// } |
| /// task_context = yield (); |
| /// } |
| /// } |
| /// ``` |
| fn lower_expr_await(&mut self, await_span: Span, expr: &Expr) -> hir::ExprKind<'hir> { |
| match self.generator_kind { |
| Some(hir::GeneratorKind::Async(_)) => {} |
| Some(hir::GeneratorKind::Gen) | None => { |
| let mut err = struct_span_err!( |
| self.sess, |
| await_span, |
| E0728, |
| "`await` is only allowed inside `async` functions and blocks" |
| ); |
| err.span_label(await_span, "only allowed inside `async` functions and blocks"); |
| if let Some(item_sp) = self.current_item { |
| err.span_label(item_sp, "this is not `async`"); |
| } |
| err.emit(); |
| } |
| } |
| let span = self.mark_span_with_reason(DesugaringKind::Await, await_span, None); |
| let gen_future_span = self.mark_span_with_reason( |
| DesugaringKind::Await, |
| await_span, |
| self.allow_gen_future.clone(), |
| ); |
| let expr = self.lower_expr(expr); |
| |
| let pinned_ident = Ident::with_dummy_span(sym::pinned); |
| let (pinned_pat, pinned_pat_hid) = |
| self.pat_ident_binding_mode(span, pinned_ident, hir::BindingAnnotation::Mutable); |
| |
| let task_context_ident = Ident::with_dummy_span(sym::_task_context); |
| |
| // unsafe { |
| // ::std::future::Future::poll( |
| // ::std::pin::Pin::new_unchecked(&mut pinned), |
| // ::std::future::get_context(task_context), |
| // ) |
| // } |
| let poll_expr = { |
| let pinned = self.expr_ident(span, pinned_ident, pinned_pat_hid); |
| let ref_mut_pinned = self.expr_mut_addr_of(span, pinned); |
| let task_context = if let Some(task_context_hid) = self.task_context { |
| self.expr_ident_mut(span, task_context_ident, task_context_hid) |
| } else { |
| // Use of `await` outside of an async context, we cannot use `task_context` here. |
| self.expr_err(span) |
| }; |
| let new_unchecked = self.expr_call_lang_item_fn_mut( |
| span, |
| hir::LangItem::PinNewUnchecked, |
| arena_vec![self; ref_mut_pinned], |
| ); |
| let get_context = self.expr_call_lang_item_fn_mut( |
| gen_future_span, |
| hir::LangItem::GetContext, |
| arena_vec![self; task_context], |
| ); |
| let call = self.expr_call_lang_item_fn( |
| span, |
| hir::LangItem::FuturePoll, |
| arena_vec![self; new_unchecked, get_context], |
| ); |
| self.arena.alloc(self.expr_unsafe(call)) |
| }; |
| |
| // `::std::task::Poll::Ready(result) => break result` |
| let loop_node_id = self.resolver.next_node_id(); |
| let loop_hir_id = self.lower_node_id(loop_node_id); |
| let ready_arm = { |
| let x_ident = Ident::with_dummy_span(sym::result); |
| let (x_pat, x_pat_hid) = self.pat_ident(span, x_ident); |
| let x_expr = self.expr_ident(span, x_ident, x_pat_hid); |
| let ready_field = self.single_pat_field(span, x_pat); |
| let ready_pat = self.pat_lang_item_variant(span, hir::LangItem::PollReady, ready_field); |
| let break_x = self.with_loop_scope(loop_node_id, move |this| { |
| let expr_break = |
| hir::ExprKind::Break(this.lower_loop_destination(None), Some(x_expr)); |
| this.arena.alloc(this.expr(await_span, expr_break, ThinVec::new())) |
| }); |
| self.arm(ready_pat, break_x) |
| }; |
| |
| // `::std::task::Poll::Pending => {}` |
| let pending_arm = { |
| let pending_pat = self.pat_lang_item_variant(span, hir::LangItem::PollPending, &[]); |
| let empty_block = self.expr_block_empty(span); |
| self.arm(pending_pat, empty_block) |
| }; |
| |
| let inner_match_stmt = { |
| let match_expr = self.expr_match( |
| span, |
| poll_expr, |
| arena_vec![self; ready_arm, pending_arm], |
| hir::MatchSource::AwaitDesugar, |
| ); |
| self.stmt_expr(span, match_expr) |
| }; |
| |
| // task_context = yield (); |
| let yield_stmt = { |
| let unit = self.expr_unit(span); |
| let yield_expr = self.expr( |
| span, |
| hir::ExprKind::Yield(unit, hir::YieldSource::Await { expr: Some(expr.hir_id) }), |
| ThinVec::new(), |
| ); |
| let yield_expr = self.arena.alloc(yield_expr); |
| |
| if let Some(task_context_hid) = self.task_context { |
| let lhs = self.expr_ident(span, task_context_ident, task_context_hid); |
| let assign = |
| self.expr(span, hir::ExprKind::Assign(lhs, yield_expr, span), AttrVec::new()); |
| self.stmt_expr(span, assign) |
| } else { |
| // Use of `await` outside of an async context. Return `yield_expr` so that we can |
| // proceed with type checking. |
| self.stmt(span, hir::StmtKind::Semi(yield_expr)) |
| } |
| }; |
| |
| let loop_block = self.block_all(span, arena_vec![self; inner_match_stmt, yield_stmt], None); |
| |
| // loop { .. } |
| let loop_expr = self.arena.alloc(hir::Expr { |
| hir_id: loop_hir_id, |
| kind: hir::ExprKind::Loop(loop_block, None, hir::LoopSource::Loop, span), |
| span, |
| }); |
| |
| // mut pinned => loop { ... } |
| let pinned_arm = self.arm(pinned_pat, loop_expr); |
| |
| // match <expr> { |
| // mut pinned => loop { .. } |
| // } |
| hir::ExprKind::Match(expr, arena_vec![self; pinned_arm], hir::MatchSource::AwaitDesugar) |
| } |
| |
| fn lower_expr_closure( |
| &mut self, |
| capture_clause: CaptureBy, |
| movability: Movability, |
| decl: &FnDecl, |
| body: &Expr, |
| fn_decl_span: Span, |
| ) -> hir::ExprKind<'hir> { |
| let (body_id, generator_option) = self.with_new_scopes(move |this| { |
| let prev = this.current_item; |
| this.current_item = Some(fn_decl_span); |
| let mut generator_kind = None; |
| let body_id = this.lower_fn_body(decl, |this| { |
| let e = this.lower_expr_mut(body); |
| generator_kind = this.generator_kind; |
| e |
| }); |
| let generator_option = |
| this.generator_movability_for_fn(&decl, fn_decl_span, generator_kind, movability); |
| this.current_item = prev; |
| (body_id, generator_option) |
| }); |
| |
| // Lower outside new scope to preserve `is_in_loop_condition`. |
| let fn_decl = self.lower_fn_decl(decl, None, false, None); |
| |
| hir::ExprKind::Closure(capture_clause, fn_decl, body_id, fn_decl_span, generator_option) |
| } |
| |
| fn generator_movability_for_fn( |
| &mut self, |
| decl: &FnDecl, |
| fn_decl_span: Span, |
| generator_kind: Option<hir::GeneratorKind>, |
| movability: Movability, |
| ) -> Option<hir::Movability> { |
| match generator_kind { |
| Some(hir::GeneratorKind::Gen) => { |
| if decl.inputs.len() > 1 { |
| struct_span_err!( |
| self.sess, |
| fn_decl_span, |
| E0628, |
| "too many parameters for a generator (expected 0 or 1 parameters)" |
| ) |
| .emit(); |
| } |
| Some(movability) |
| } |
| Some(hir::GeneratorKind::Async(_)) => { |
| panic!("non-`async` closure body turned `async` during lowering"); |
| } |
| None => { |
| if movability == Movability::Static { |
| struct_span_err!(self.sess, fn_decl_span, E0697, "closures cannot be static") |
| .emit(); |
| } |
| None |
| } |
| } |
| } |
| |
| fn lower_expr_async_closure( |
| &mut self, |
| capture_clause: CaptureBy, |
| closure_id: NodeId, |
| decl: &FnDecl, |
| body: &Expr, |
| fn_decl_span: Span, |
| ) -> hir::ExprKind<'hir> { |
| let outer_decl = |
| FnDecl { inputs: decl.inputs.clone(), output: FnRetTy::Default(fn_decl_span) }; |
| |
| let body_id = self.with_new_scopes(|this| { |
| // FIXME(cramertj): allow `async` non-`move` closures with arguments. |
| if capture_clause == CaptureBy::Ref && !decl.inputs.is_empty() { |
| struct_span_err!( |
| this.sess, |
| fn_decl_span, |
| E0708, |
| "`async` non-`move` closures with parameters are not currently supported", |
| ) |
| .help( |
| "consider using `let` statements to manually capture \ |
| variables by reference before entering an `async move` closure", |
| ) |
| .emit(); |
| } |
| |
| // Transform `async |x: u8| -> X { ... }` into |
| // `|x: u8| future_from_generator(|| -> X { ... })`. |
| let body_id = this.lower_fn_body(&outer_decl, |this| { |
| let async_ret_ty = |
| if let FnRetTy::Ty(ty) = &decl.output { Some(ty.clone()) } else { None }; |
| let async_body = this.make_async_expr( |
| capture_clause, |
| closure_id, |
| async_ret_ty, |
| body.span, |
| hir::AsyncGeneratorKind::Closure, |
| |this| this.with_new_scopes(|this| this.lower_expr_mut(body)), |
| ); |
| this.expr(fn_decl_span, async_body, ThinVec::new()) |
| }); |
| body_id |
| }); |
| |
| // We need to lower the declaration outside the new scope, because we |
| // have to conserve the state of being inside a loop condition for the |
| // closure argument types. |
| let fn_decl = self.lower_fn_decl(&outer_decl, None, false, None); |
| |
| hir::ExprKind::Closure(capture_clause, fn_decl, body_id, fn_decl_span, None) |
| } |
| |
| /// Destructure the LHS of complex assignments. |
| /// For instance, lower `(a, b) = t` to `{ let (lhs1, lhs2) = t; a = lhs1; b = lhs2; }`. |
| fn lower_expr_assign( |
| &mut self, |
| lhs: &Expr, |
| rhs: &Expr, |
| eq_sign_span: Span, |
| whole_span: Span, |
| ) -> hir::ExprKind<'hir> { |
| // Return early in case of an ordinary assignment. |
| fn is_ordinary(lower_ctx: &mut LoweringContext<'_, '_>, lhs: &Expr) -> bool { |
| match &lhs.kind { |
| ExprKind::Array(..) |
| | ExprKind::Struct(..) |
| | ExprKind::Tup(..) |
| | ExprKind::Underscore => false, |
| // Check for tuple struct constructor. |
| ExprKind::Call(callee, ..) => lower_ctx.extract_tuple_struct_path(callee).is_none(), |
| ExprKind::Paren(e) => { |
| match e.kind { |
| // We special-case `(..)` for consistency with patterns. |
| ExprKind::Range(None, None, RangeLimits::HalfOpen) => false, |
| _ => is_ordinary(lower_ctx, e), |
| } |
| } |
| _ => true, |
| } |
| } |
| if is_ordinary(self, lhs) { |
| return hir::ExprKind::Assign(self.lower_expr(lhs), self.lower_expr(rhs), eq_sign_span); |
| } |
| if !self.sess.features_untracked().destructuring_assignment { |
| feature_err( |
| &self.sess.parse_sess, |
| sym::destructuring_assignment, |
| eq_sign_span, |
| "destructuring assignments are unstable", |
| ) |
| .span_label(lhs.span, "cannot assign to this expression") |
| .emit(); |
| } |
| |
| let mut assignments = vec![]; |
| |
| // The LHS becomes a pattern: `(lhs1, lhs2)`. |
| let pat = self.destructure_assign(lhs, eq_sign_span, &mut assignments); |
| let rhs = self.lower_expr(rhs); |
| |
| // Introduce a `let` for destructuring: `let (lhs1, lhs2) = t`. |
| let destructure_let = self.stmt_let_pat( |
| None, |
| whole_span, |
| Some(rhs), |
| pat, |
| hir::LocalSource::AssignDesugar(eq_sign_span), |
| ); |
| |
| // `a = lhs1; b = lhs2;`. |
| let stmts = self |
| .arena |
| .alloc_from_iter(std::iter::once(destructure_let).chain(assignments.into_iter())); |
| |
| // Wrap everything in a block. |
| hir::ExprKind::Block(&self.block_all(whole_span, stmts, None), None) |
| } |
| |
| /// If the given expression is a path to a tuple struct, returns that path. |
| /// It is not a complete check, but just tries to reject most paths early |
| /// if they are not tuple structs. |
| /// Type checking will take care of the full validation later. |
| fn extract_tuple_struct_path<'a>( |
| &mut self, |
| expr: &'a Expr, |
| ) -> Option<(&'a Option<QSelf>, &'a Path)> { |
| if let ExprKind::Path(qself, path) = &expr.kind { |
| // Does the path resolve to something disallowed in a tuple struct/variant pattern? |
| if let Some(partial_res) = self.resolver.get_partial_res(expr.id) { |
| if partial_res.unresolved_segments() == 0 |
| && !partial_res.base_res().expected_in_tuple_struct_pat() |
| { |
| return None; |
| } |
| } |
| return Some((qself, path)); |
| } |
| None |
| } |
| |
| /// Convert the LHS of a destructuring assignment to a pattern. |
| /// Each sub-assignment is recorded in `assignments`. |
| fn destructure_assign( |
| &mut self, |
| lhs: &Expr, |
| eq_sign_span: Span, |
| assignments: &mut Vec<hir::Stmt<'hir>>, |
| ) -> &'hir hir::Pat<'hir> { |
| self.arena.alloc(self.destructure_assign_mut(lhs, eq_sign_span, assignments)) |
| } |
| |
| fn destructure_assign_mut( |
| &mut self, |
| lhs: &Expr, |
| eq_sign_span: Span, |
| assignments: &mut Vec<hir::Stmt<'hir>>, |
| ) -> hir::Pat<'hir> { |
| match &lhs.kind { |
| // Underscore pattern. |
| ExprKind::Underscore => { |
| return self.pat_without_dbm(lhs.span, hir::PatKind::Wild); |
| } |
| // Slice patterns. |
| ExprKind::Array(elements) => { |
| let (pats, rest) = |
| self.destructure_sequence(elements, "slice", eq_sign_span, assignments); |
| let slice_pat = if let Some((i, span)) = rest { |
| let (before, after) = pats.split_at(i); |
| hir::PatKind::Slice( |
| before, |
| Some(self.arena.alloc(self.pat_without_dbm(span, hir::PatKind::Wild))), |
| after, |
| ) |
| } else { |
| hir::PatKind::Slice(pats, None, &[]) |
| }; |
| return self.pat_without_dbm(lhs.span, slice_pat); |
| } |
| // Tuple structs. |
| ExprKind::Call(callee, args) => { |
| if let Some((qself, path)) = self.extract_tuple_struct_path(callee) { |
| let (pats, rest) = self.destructure_sequence( |
| args, |
| "tuple struct or variant", |
| eq_sign_span, |
| assignments, |
| ); |
| let qpath = self.lower_qpath( |
| callee.id, |
| qself, |
| path, |
| ParamMode::Optional, |
| ImplTraitContext::disallowed(), |
| ); |
| // Destructure like a tuple struct. |
| let tuple_struct_pat = |
| hir::PatKind::TupleStruct(qpath, pats, rest.map(|r| r.0)); |
| return self.pat_without_dbm(lhs.span, tuple_struct_pat); |
| } |
| } |
| // Structs. |
| ExprKind::Struct(se) => { |
| let field_pats = self.arena.alloc_from_iter(se.fields.iter().map(|f| { |
| let pat = self.destructure_assign(&f.expr, eq_sign_span, assignments); |
| hir::PatField { |
| hir_id: self.next_id(), |
| ident: f.ident, |
| pat, |
| is_shorthand: f.is_shorthand, |
| span: f.span, |
| } |
| })); |
| let qpath = self.lower_qpath( |
| lhs.id, |
| &se.qself, |
| &se.path, |
| ParamMode::Optional, |
| ImplTraitContext::disallowed(), |
| ); |
| let fields_omitted = match &se.rest { |
| StructRest::Base(e) => { |
| self.sess |
| .struct_span_err( |
| e.span, |
| "functional record updates are not allowed in destructuring \ |
| assignments", |
| ) |
| .span_suggestion( |
| e.span, |
| "consider removing the trailing pattern", |
| String::new(), |
| rustc_errors::Applicability::MachineApplicable, |
| ) |
| .emit(); |
| true |
| } |
| StructRest::Rest(_) => true, |
| StructRest::None => false, |
| }; |
| let struct_pat = hir::PatKind::Struct(qpath, field_pats, fields_omitted); |
| return self.pat_without_dbm(lhs.span, struct_pat); |
| } |
| // Tuples. |
| ExprKind::Tup(elements) => { |
| let (pats, rest) = |
| self.destructure_sequence(elements, "tuple", eq_sign_span, assignments); |
| let tuple_pat = hir::PatKind::Tuple(pats, rest.map(|r| r.0)); |
| return self.pat_without_dbm(lhs.span, tuple_pat); |
| } |
| ExprKind::Paren(e) => { |
| // We special-case `(..)` for consistency with patterns. |
| if let ExprKind::Range(None, None, RangeLimits::HalfOpen) = e.kind { |
| let tuple_pat = hir::PatKind::Tuple(&[], Some(0)); |
| return self.pat_without_dbm(lhs.span, tuple_pat); |
| } else { |
| return self.destructure_assign_mut(e, eq_sign_span, assignments); |
| } |
| } |
| _ => {} |
| } |
| // Treat all other cases as normal lvalue. |
| let ident = Ident::new(sym::lhs, lhs.span); |
| let (pat, binding) = self.pat_ident_mut(lhs.span, ident); |
| let ident = self.expr_ident(lhs.span, ident, binding); |
| let assign = hir::ExprKind::Assign(self.lower_expr(lhs), ident, eq_sign_span); |
| let expr = self.expr(lhs.span, assign, ThinVec::new()); |
| assignments.push(self.stmt_expr(lhs.span, expr)); |
| pat |
| } |
| |
| /// Destructure a sequence of expressions occurring on the LHS of an assignment. |
| /// Such a sequence occurs in a tuple (struct)/slice. |
| /// Return a sequence of corresponding patterns, and the index and the span of `..` if it |
| /// exists. |
| /// Each sub-assignment is recorded in `assignments`. |
| fn destructure_sequence( |
| &mut self, |
| elements: &[AstP<Expr>], |
| ctx: &str, |
| eq_sign_span: Span, |
| assignments: &mut Vec<hir::Stmt<'hir>>, |
| ) -> (&'hir [hir::Pat<'hir>], Option<(usize, Span)>) { |
| let mut rest = None; |
| let elements = |
| self.arena.alloc_from_iter(elements.iter().enumerate().filter_map(|(i, e)| { |
| // Check for `..` pattern. |
| if let ExprKind::Range(None, None, RangeLimits::HalfOpen) = e.kind { |
| if let Some((_, prev_span)) = rest { |
| self.ban_extra_rest_pat(e.span, prev_span, ctx); |
| } else { |
| rest = Some((i, e.span)); |
| } |
| None |
| } else { |
| Some(self.destructure_assign_mut(e, eq_sign_span, assignments)) |
| } |
| })); |
| (elements, rest) |
| } |
| |
| /// Desugar `<start>..=<end>` into `std::ops::RangeInclusive::new(<start>, <end>)`. |
| fn lower_expr_range_closed(&mut self, span: Span, e1: &Expr, e2: &Expr) -> hir::ExprKind<'hir> { |
| let e1 = self.lower_expr_mut(e1); |
| let e2 = self.lower_expr_mut(e2); |
| let fn_path = hir::QPath::LangItem(hir::LangItem::RangeInclusiveNew, span); |
| let fn_expr = |
| self.arena.alloc(self.expr(span, hir::ExprKind::Path(fn_path), ThinVec::new())); |
| hir::ExprKind::Call(fn_expr, arena_vec![self; e1, e2]) |
| } |
| |
| fn lower_expr_range( |
| &mut self, |
| span: Span, |
| e1: Option<&Expr>, |
| e2: Option<&Expr>, |
| lims: RangeLimits, |
| ) -> hir::ExprKind<'hir> { |
| use rustc_ast::RangeLimits::*; |
| |
| let lang_item = match (e1, e2, lims) { |
| (None, None, HalfOpen) => hir::LangItem::RangeFull, |
| (Some(..), None, HalfOpen) => hir::LangItem::RangeFrom, |
| (None, Some(..), HalfOpen) => hir::LangItem::RangeTo, |
| (Some(..), Some(..), HalfOpen) => hir::LangItem::Range, |
| (None, Some(..), Closed) => hir::LangItem::RangeToInclusive, |
| (Some(..), Some(..), Closed) => unreachable!(), |
| (_, None, Closed) => self.diagnostic().span_fatal(span, "inclusive range with no end"), |
| }; |
| |
| let fields = self.arena.alloc_from_iter( |
| e1.iter().map(|e| ("start", e)).chain(e2.iter().map(|e| ("end", e))).map(|(s, e)| { |
| let expr = self.lower_expr(&e); |
| let ident = Ident::new(Symbol::intern(s), e.span); |
| self.expr_field(ident, expr, e.span) |
| }), |
| ); |
| |
| hir::ExprKind::Struct(self.arena.alloc(hir::QPath::LangItem(lang_item, span)), fields, None) |
| } |
| |
| fn lower_loop_destination(&mut self, destination: Option<(NodeId, Label)>) -> hir::Destination { |
| let target_id = match destination { |
| Some((id, _)) => { |
| if let Some(loop_id) = self.resolver.get_label_res(id) { |
| Ok(self.lower_node_id(loop_id)) |
| } else { |
| Err(hir::LoopIdError::UnresolvedLabel) |
| } |
| } |
| None => self |
| .loop_scopes |
| .last() |
| .cloned() |
| .map(|id| Ok(self.lower_node_id(id))) |
| .unwrap_or(Err(hir::LoopIdError::OutsideLoopScope)), |
| }; |
| hir::Destination { label: destination.map(|(_, label)| label), target_id } |
| } |
| |
| fn lower_jump_destination(&mut self, id: NodeId, opt_label: Option<Label>) -> hir::Destination { |
| if self.is_in_loop_condition && opt_label.is_none() { |
| hir::Destination { |
| label: None, |
| target_id: Err(hir::LoopIdError::UnlabeledCfInWhileCondition), |
| } |
| } else { |
| self.lower_loop_destination(opt_label.map(|label| (id, label))) |
| } |
| } |
| |
| fn with_catch_scope<T>(&mut self, catch_id: NodeId, f: impl FnOnce(&mut Self) -> T) -> T { |
| let len = self.catch_scopes.len(); |
| self.catch_scopes.push(catch_id); |
| |
| let result = f(self); |
| assert_eq!( |
| len + 1, |
| self.catch_scopes.len(), |
| "catch scopes should be added and removed in stack order" |
| ); |
| |
| self.catch_scopes.pop().unwrap(); |
| |
| result |
| } |
| |
| fn with_loop_scope<T>(&mut self, loop_id: NodeId, f: impl FnOnce(&mut Self) -> T) -> T { |
| // We're no longer in the base loop's condition; we're in another loop. |
| let was_in_loop_condition = self.is_in_loop_condition; |
| self.is_in_loop_condition = false; |
| |
| let len = self.loop_scopes.len(); |
| self.loop_scopes.push(loop_id); |
| |
| let result = f(self); |
| assert_eq!( |
| len + 1, |
| self.loop_scopes.len(), |
| "loop scopes should be added and removed in stack order" |
| ); |
| |
| self.loop_scopes.pop().unwrap(); |
| |
| self.is_in_loop_condition = was_in_loop_condition; |
| |
| result |
| } |
| |
| fn with_loop_condition_scope<T>(&mut self, f: impl FnOnce(&mut Self) -> T) -> T { |
| let was_in_loop_condition = self.is_in_loop_condition; |
| self.is_in_loop_condition = true; |
| |
| let result = f(self); |
| |
| self.is_in_loop_condition = was_in_loop_condition; |
| |
| result |
| } |
| |
| fn lower_expr_llvm_asm(&mut self, asm: &LlvmInlineAsm) -> hir::ExprKind<'hir> { |
| let inner = hir::LlvmInlineAsmInner { |
| inputs: asm.inputs.iter().map(|&(c, _)| c).collect(), |
| outputs: asm |
| .outputs |
| .iter() |
| .map(|out| hir::LlvmInlineAsmOutput { |
| constraint: out.constraint, |
| is_rw: out.is_rw, |
| is_indirect: out.is_indirect, |
| span: out.expr.span, |
| }) |
| .collect(), |
| asm: asm.asm, |
| asm_str_style: asm.asm_str_style, |
| clobbers: asm.clobbers.clone(), |
| volatile: asm.volatile, |
| alignstack: asm.alignstack, |
| dialect: asm.dialect, |
| }; |
| let hir_asm = hir::LlvmInlineAsm { |
| inner, |
| inputs_exprs: self.arena.alloc_from_iter( |
| asm.inputs.iter().map(|&(_, ref input)| self.lower_expr_mut(input)), |
| ), |
| outputs_exprs: self |
| .arena |
| .alloc_from_iter(asm.outputs.iter().map(|out| self.lower_expr_mut(&out.expr))), |
| }; |
| hir::ExprKind::LlvmInlineAsm(self.arena.alloc(hir_asm)) |
| } |
| |
| fn lower_expr_field(&mut self, f: &ExprField) -> hir::ExprField<'hir> { |
| hir::ExprField { |
| hir_id: self.next_id(), |
| ident: f.ident, |
| expr: self.lower_expr(&f.expr), |
| span: f.span, |
| is_shorthand: f.is_shorthand, |
| } |
| } |
| |
| fn lower_expr_yield(&mut self, span: Span, opt_expr: Option<&Expr>) -> hir::ExprKind<'hir> { |
| match self.generator_kind { |
| Some(hir::GeneratorKind::Gen) => {} |
| Some(hir::GeneratorKind::Async(_)) => { |
| struct_span_err!( |
| self.sess, |
| span, |
| E0727, |
| "`async` generators are not yet supported" |
| ) |
| .emit(); |
| } |
| None => self.generator_kind = Some(hir::GeneratorKind::Gen), |
| } |
| |
| let expr = |
| opt_expr.as_ref().map(|x| self.lower_expr(x)).unwrap_or_else(|| self.expr_unit(span)); |
| |
| hir::ExprKind::Yield(expr, hir::YieldSource::Yield) |
| } |
| |
| /// Desugar `ExprForLoop` from: `[opt_ident]: for <pat> in <head> <body>` into: |
| /// ```rust |
| /// { |
| /// let result = match ::std::iter::IntoIterator::into_iter(<head>) { |
| /// mut iter => { |
| /// [opt_ident]: loop { |
| /// let mut __next; |
| /// match ::std::iter::Iterator::next(&mut iter) { |
| /// ::std::option::Option::Some(val) => __next = val, |
| /// ::std::option::Option::None => break |
| /// }; |
| /// let <pat> = __next; |
| /// StmtKind::Expr(<body>); |
| /// } |
| /// } |
| /// }; |
| /// result |
| /// } |
| /// ``` |
| fn lower_expr_for( |
| &mut self, |
| e: &Expr, |
| pat: &Pat, |
| head: &Expr, |
| body: &Block, |
| opt_label: Option<Label>, |
| ) -> hir::Expr<'hir> { |
| let orig_head_span = head.span; |
| // expand <head> |
| let mut head = self.lower_expr_mut(head); |
| let desugared_span = self.mark_span_with_reason( |
| DesugaringKind::ForLoop(ForLoopLoc::Head), |
| orig_head_span, |
| None, |
| ); |
| head.span = desugared_span; |
| |
| let iter = Ident::with_dummy_span(sym::iter); |
| |
| let next_ident = Ident::with_dummy_span(sym::__next); |
| let (next_pat, next_pat_hid) = self.pat_ident_binding_mode( |
| desugared_span, |
| next_ident, |
| hir::BindingAnnotation::Mutable, |
| ); |
| |
| // `::std::option::Option::Some(val) => __next = val` |
| let pat_arm = { |
| let val_ident = Ident::with_dummy_span(sym::val); |
| let (val_pat, val_pat_hid) = self.pat_ident(pat.span, val_ident); |
| let val_expr = self.expr_ident(pat.span, val_ident, val_pat_hid); |
| let next_expr = self.expr_ident(pat.span, next_ident, next_pat_hid); |
| let assign = self.arena.alloc(self.expr( |
| pat.span, |
| hir::ExprKind::Assign(next_expr, val_expr, pat.span), |
| ThinVec::new(), |
| )); |
| let some_pat = self.pat_some(pat.span, val_pat); |
| self.arm(some_pat, assign) |
| }; |
| |
| // `::std::option::Option::None => break` |
| let break_arm = { |
| let break_expr = |
| self.with_loop_scope(e.id, |this| this.expr_break(e.span, ThinVec::new())); |
| let pat = self.pat_none(e.span); |
| self.arm(pat, break_expr) |
| }; |
| |
| // `mut iter` |
| let (iter_pat, iter_pat_nid) = |
| self.pat_ident_binding_mode(desugared_span, iter, hir::BindingAnnotation::Mutable); |
| |
| // `match ::std::iter::Iterator::next(&mut iter) { ... }` |
| let match_expr = { |
| let iter = self.expr_ident(desugared_span, iter, iter_pat_nid); |
| let ref_mut_iter = self.expr_mut_addr_of(desugared_span, iter); |
| let next_expr = self.expr_call_lang_item_fn( |
| desugared_span, |
| hir::LangItem::IteratorNext, |
| arena_vec![self; ref_mut_iter], |
| ); |
| let arms = arena_vec![self; pat_arm, break_arm]; |
| |
| self.expr_match(desugared_span, next_expr, arms, hir::MatchSource::ForLoopDesugar) |
| }; |
| let match_stmt = self.stmt_expr(desugared_span, match_expr); |
| |
| let next_expr = self.expr_ident(desugared_span, next_ident, next_pat_hid); |
| |
| // `let mut __next` |
| let next_let = self.stmt_let_pat( |
| None, |
| desugared_span, |
| None, |
| next_pat, |
| hir::LocalSource::ForLoopDesugar, |
| ); |
| |
| // `let <pat> = __next` |
| let pat = self.lower_pat(pat); |
| let pat_let = self.stmt_let_pat( |
| None, |
| desugared_span, |
| Some(next_expr), |
| pat, |
| hir::LocalSource::ForLoopDesugar, |
| ); |
| |
| let body_block = self.with_loop_scope(e.id, |this| this.lower_block(body, false)); |
| let body_expr = self.expr_block(body_block, ThinVec::new()); |
| let body_stmt = self.stmt_expr(body.span, body_expr); |
| |
| let loop_block = self.block_all( |
| e.span, |
| arena_vec![self; next_let, match_stmt, pat_let, body_stmt], |
| None, |
| ); |
| |
| // `[opt_ident]: loop { ... }` |
| let kind = hir::ExprKind::Loop( |
| loop_block, |
| opt_label, |
| hir::LoopSource::ForLoop, |
| e.span.with_hi(orig_head_span.hi()), |
| ); |
| let loop_expr = |
| self.arena.alloc(hir::Expr { hir_id: self.lower_node_id(e.id), kind, span: e.span }); |
| |
| // `mut iter => { ... }` |
| let iter_arm = self.arm(iter_pat, loop_expr); |
| |
| let into_iter_span = self.mark_span_with_reason( |
| DesugaringKind::ForLoop(ForLoopLoc::IntoIter), |
| orig_head_span, |
| None, |
| ); |
| |
| // `match ::std::iter::IntoIterator::into_iter(<head>) { ... }` |
| let into_iter_expr = { |
| self.expr_call_lang_item_fn( |
| into_iter_span, |
| hir::LangItem::IntoIterIntoIter, |
| arena_vec![self; head], |
| ) |
| }; |
| |
| let match_expr = self.arena.alloc(self.expr_match( |
| desugared_span, |
| into_iter_expr, |
| arena_vec![self; iter_arm], |
| hir::MatchSource::ForLoopDesugar, |
| )); |
| |
| let attrs: Vec<_> = e.attrs.iter().map(|a| self.lower_attr(a)).collect(); |
| |
| // This is effectively `{ let _result = ...; _result }`. |
| // The construct was introduced in #21984 and is necessary to make sure that |
| // temporaries in the `head` expression are dropped and do not leak to the |
| // surrounding scope of the `match` since the `match` is not a terminating scope. |
| // |
| // Also, add the attributes to the outer returned expr node. |
| self.expr_drop_temps_mut(desugared_span, match_expr, attrs.into()) |
| } |
| |
| /// Desugar `ExprKind::Try` from: `<expr>?` into: |
| /// ```rust |
| /// match Try::branch(<expr>) { |
| /// ControlFlow::Continue(val) => #[allow(unreachable_code)] val,, |
| /// ControlFlow::Break(residual) => |
| /// #[allow(unreachable_code)] |
| /// // If there is an enclosing `try {...}`: |
| /// break 'catch_target Try::from_residual(residual), |
| /// // Otherwise: |
| /// return Try::from_residual(residual), |
| /// } |
| /// ``` |
| fn lower_expr_try(&mut self, span: Span, sub_expr: &Expr) -> hir::ExprKind<'hir> { |
| let unstable_span = self.mark_span_with_reason( |
| DesugaringKind::QuestionMark, |
| span, |
| self.allow_try_trait.clone(), |
| ); |
| let try_span = self.sess.source_map().end_point(span); |
| let try_span = self.mark_span_with_reason( |
| DesugaringKind::QuestionMark, |
| try_span, |
| self.allow_try_trait.clone(), |
| ); |
| |
| // `Try::branch(<expr>)` |
| let scrutinee = { |
| // expand <expr> |
| let sub_expr = self.lower_expr_mut(sub_expr); |
| |
| self.expr_call_lang_item_fn( |
| unstable_span, |
| hir::LangItem::TryTraitBranch, |
| arena_vec![self; sub_expr], |
| ) |
| }; |
| |
| // `#[allow(unreachable_code)]` |
| let attr = { |
| // `allow(unreachable_code)` |
| let allow = { |
| let allow_ident = Ident::new(sym::allow, span); |
| let uc_ident = Ident::new(sym::unreachable_code, span); |
| let uc_nested = attr::mk_nested_word_item(uc_ident); |
| attr::mk_list_item(allow_ident, vec![uc_nested]) |
| }; |
| attr::mk_attr_outer(allow) |
| }; |
| let attrs = vec![attr]; |
| |
| // `ControlFlow::Continue(val) => #[allow(unreachable_code)] val,` |
| let continue_arm = { |
| let val_ident = Ident::with_dummy_span(sym::val); |
| let (val_pat, val_pat_nid) = self.pat_ident(span, val_ident); |
| let val_expr = self.arena.alloc(self.expr_ident_with_attrs( |
| span, |
| val_ident, |
| val_pat_nid, |
| ThinVec::from(attrs.clone()), |
| )); |
| let continue_pat = self.pat_cf_continue(unstable_span, val_pat); |
| self.arm(continue_pat, val_expr) |
| }; |
| |
| // `ControlFlow::Break(residual) => |
| // #[allow(unreachable_code)] |
| // return Try::from_residual(residual),` |
| let break_arm = { |
| let residual_ident = Ident::with_dummy_span(sym::residual); |
| let (residual_local, residual_local_nid) = self.pat_ident(try_span, residual_ident); |
| let residual_expr = self.expr_ident_mut(try_span, residual_ident, residual_local_nid); |
| let from_residual_expr = self.wrap_in_try_constructor( |
| hir::LangItem::TryTraitFromResidual, |
| try_span, |
| self.arena.alloc(residual_expr), |
| unstable_span, |
| ); |
| let thin_attrs = ThinVec::from(attrs); |
| let catch_scope = self.catch_scopes.last().copied(); |
| let ret_expr = if let Some(catch_node) = catch_scope { |
| let target_id = Ok(self.lower_node_id(catch_node)); |
| self.arena.alloc(self.expr( |
| try_span, |
| hir::ExprKind::Break( |
| hir::Destination { label: None, target_id }, |
| Some(from_residual_expr), |
| ), |
| thin_attrs, |
| )) |
| } else { |
| self.arena.alloc(self.expr( |
| try_span, |
| hir::ExprKind::Ret(Some(from_residual_expr)), |
| thin_attrs, |
| )) |
| }; |
| |
| let break_pat = self.pat_cf_break(try_span, residual_local); |
| self.arm(break_pat, ret_expr) |
| }; |
| |
| hir::ExprKind::Match( |
| scrutinee, |
| arena_vec![self; break_arm, continue_arm], |
| hir::MatchSource::TryDesugar, |
| ) |
| } |
| |
| // ========================================================================= |
| // Helper methods for building HIR. |
| // ========================================================================= |
| |
| /// Constructs a `true` or `false` literal expression. |
| pub(super) fn expr_bool(&mut self, span: Span, val: bool) -> &'hir hir::Expr<'hir> { |
| let lit = Spanned { span, node: LitKind::Bool(val) }; |
| self.arena.alloc(self.expr(span, hir::ExprKind::Lit(lit), ThinVec::new())) |
| } |
| |
| /// Wrap the given `expr` in a terminating scope using `hir::ExprKind::DropTemps`. |
| /// |
| /// In terms of drop order, it has the same effect as wrapping `expr` in |
| /// `{ let _t = $expr; _t }` but should provide better compile-time performance. |
| /// |
| /// The drop order can be important in e.g. `if expr { .. }`. |
| pub(super) fn expr_drop_temps( |
| &mut self, |
| span: Span, |
| expr: &'hir hir::Expr<'hir>, |
| attrs: AttrVec, |
| ) -> &'hir hir::Expr<'hir> { |
| self.arena.alloc(self.expr_drop_temps_mut(span, expr, attrs)) |
| } |
| |
| pub(super) fn expr_drop_temps_mut( |
| &mut self, |
| span: Span, |
| expr: &'hir hir::Expr<'hir>, |
| attrs: AttrVec, |
| ) -> hir::Expr<'hir> { |
| self.expr(span, hir::ExprKind::DropTemps(expr), attrs) |
| } |
| |
| fn expr_match( |
| &mut self, |
| span: Span, |
| arg: &'hir hir::Expr<'hir>, |
| arms: &'hir [hir::Arm<'hir>], |
| source: hir::MatchSource, |
| ) -> hir::Expr<'hir> { |
| self.expr(span, hir::ExprKind::Match(arg, arms, source), ThinVec::new()) |
| } |
| |
| fn expr_break(&mut self, span: Span, attrs: AttrVec) -> &'hir hir::Expr<'hir> { |
| let expr_break = hir::ExprKind::Break(self.lower_loop_destination(None), None); |
| self.arena.alloc(self.expr(span, expr_break, attrs)) |
| } |
| |
| fn expr_mut_addr_of(&mut self, span: Span, e: &'hir hir::Expr<'hir>) -> hir::Expr<'hir> { |
| self.expr( |
| span, |
| hir::ExprKind::AddrOf(hir::BorrowKind::Ref, hir::Mutability::Mut, e), |
| ThinVec::new(), |
| ) |
| } |
| |
| fn expr_unit(&mut self, sp: Span) -> &'hir hir::Expr<'hir> { |
| self.arena.alloc(self.expr(sp, hir::ExprKind::Tup(&[]), ThinVec::new())) |
| } |
| |
| fn expr_call_mut( |
| &mut self, |
| span: Span, |
| e: &'hir hir::Expr<'hir>, |
| args: &'hir [hir::Expr<'hir>], |
| ) -> hir::Expr<'hir> { |
| self.expr(span, hir::ExprKind::Call(e, args), ThinVec::new()) |
| } |
| |
| fn expr_call( |
| &mut self, |
| span: Span, |
| e: &'hir hir::Expr<'hir>, |
| args: &'hir [hir::Expr<'hir>], |
| ) -> &'hir hir::Expr<'hir> { |
| self.arena.alloc(self.expr_call_mut(span, e, args)) |
| } |
| |
| fn expr_call_lang_item_fn_mut( |
| &mut self, |
| span: Span, |
| lang_item: hir::LangItem, |
| args: &'hir [hir::Expr<'hir>], |
| ) -> hir::Expr<'hir> { |
| let path = self.arena.alloc(self.expr_lang_item_path(span, lang_item, ThinVec::new())); |
| self.expr_call_mut(span, path, args) |
| } |
| |
| fn expr_call_lang_item_fn( |
| &mut self, |
| span: Span, |
| lang_item: hir::LangItem, |
| args: &'hir [hir::Expr<'hir>], |
| ) -> &'hir hir::Expr<'hir> { |
| self.arena.alloc(self.expr_call_lang_item_fn_mut(span, lang_item, args)) |
| } |
| |
| fn expr_lang_item_path( |
| &mut self, |
| span: Span, |
| lang_item: hir::LangItem, |
| attrs: AttrVec, |
| ) -> hir::Expr<'hir> { |
| self.expr(span, hir::ExprKind::Path(hir::QPath::LangItem(lang_item, span)), attrs) |
| } |
| |
| pub(super) fn expr_ident( |
| &mut self, |
| sp: Span, |
| ident: Ident, |
| binding: hir::HirId, |
| ) -> &'hir hir::Expr<'hir> { |
| self.arena.alloc(self.expr_ident_mut(sp, ident, binding)) |
| } |
| |
| pub(super) fn expr_ident_mut( |
| &mut self, |
| sp: Span, |
| ident: Ident, |
| binding: hir::HirId, |
| ) -> hir::Expr<'hir> { |
| self.expr_ident_with_attrs(sp, ident, binding, ThinVec::new()) |
| } |
| |
| fn expr_ident_with_attrs( |
| &mut self, |
| span: Span, |
| ident: Ident, |
| binding: hir::HirId, |
| attrs: AttrVec, |
| ) -> hir::Expr<'hir> { |
| let expr_path = hir::ExprKind::Path(hir::QPath::Resolved( |
| None, |
| self.arena.alloc(hir::Path { |
| span, |
| res: Res::Local(binding), |
| segments: arena_vec![self; hir::PathSegment::from_ident(ident)], |
| }), |
| )); |
| |
| self.expr(span, expr_path, attrs) |
| } |
| |
| fn expr_unsafe(&mut self, expr: &'hir hir::Expr<'hir>) -> hir::Expr<'hir> { |
| let hir_id = self.next_id(); |
| let span = expr.span; |
| self.expr( |
| span, |
| hir::ExprKind::Block( |
| self.arena.alloc(hir::Block { |
| stmts: &[], |
| expr: Some(expr), |
| hir_id, |
| rules: hir::BlockCheckMode::UnsafeBlock(hir::UnsafeSource::CompilerGenerated), |
| span, |
| targeted_by_break: false, |
| }), |
| None, |
| ), |
| ThinVec::new(), |
| ) |
| } |
| |
| fn expr_block_empty(&mut self, span: Span) -> &'hir hir::Expr<'hir> { |
| let blk = self.block_all(span, &[], None); |
| let expr = self.expr_block(blk, ThinVec::new()); |
| self.arena.alloc(expr) |
| } |
| |
| pub(super) fn expr_block( |
| &mut self, |
| b: &'hir hir::Block<'hir>, |
| attrs: AttrVec, |
| ) -> hir::Expr<'hir> { |
| self.expr(b.span, hir::ExprKind::Block(b, None), attrs) |
| } |
| |
| pub(super) fn expr( |
| &mut self, |
| span: Span, |
| kind: hir::ExprKind<'hir>, |
| attrs: AttrVec, |
| ) -> hir::Expr<'hir> { |
| let hir_id = self.next_id(); |
| self.lower_attrs(hir_id, &attrs); |
| hir::Expr { hir_id, kind, span } |
| } |
| |
| fn expr_field( |
| &mut self, |
| ident: Ident, |
| expr: &'hir hir::Expr<'hir>, |
| span: Span, |
| ) -> hir::ExprField<'hir> { |
| hir::ExprField { hir_id: self.next_id(), ident, span, expr, is_shorthand: false } |
| } |
| |
| fn arm(&mut self, pat: &'hir hir::Pat<'hir>, expr: &'hir hir::Expr<'hir>) -> hir::Arm<'hir> { |
| hir::Arm { hir_id: self.next_id(), pat, guard: None, span: expr.span, body: expr } |
| } |
| } |
