| use std::assert_matches::assert_matches; |
| |
| use rustc_ast::ptr::P as AstP; |
| use rustc_ast::*; |
| use rustc_data_structures::stack::ensure_sufficient_stack; |
| use rustc_data_structures::sync::Lrc; |
| use rustc_hir as hir; |
| use rustc_hir::HirId; |
| use rustc_hir::def::{DefKind, Res}; |
| use rustc_middle::span_bug; |
| use rustc_session::errors::report_lit_error; |
| use rustc_span::source_map::{Spanned, respan}; |
| use rustc_span::symbol::{Ident, Symbol, kw, sym}; |
| use rustc_span::{DUMMY_SP, DesugaringKind, Span}; |
| use thin_vec::{ThinVec, thin_vec}; |
| |
| use super::errors::{ |
| AsyncCoroutinesNotSupported, AwaitOnlyInAsyncFnAndBlocks, BaseExpressionDoubleDot, |
| ClosureCannotBeStatic, CoroutineTooManyParameters, |
| FunctionalRecordUpdateDestructuringAssignment, InclusiveRangeWithNoEnd, MatchArmWithNoBody, |
| NeverPatternWithBody, NeverPatternWithGuard, UnderscoreExprLhsAssign, |
| }; |
| use super::{ |
| GenericArgsMode, ImplTraitContext, LoweringContext, ParamMode, ResolverAstLoweringExt, |
| }; |
| use crate::errors::YieldInClosure; |
| use crate::{AllowReturnTypeNotation, FnDeclKind, ImplTraitPosition, fluent_generated}; |
| |
| 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(|| { |
| match &e.kind { |
| // Parenthesis expression does not have a HirId and is handled specially. |
| ExprKind::Paren(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 = self.lower_span(e.span); |
| } |
| // Merge attributes into the inner expression. |
| if !e.attrs.is_empty() { |
| let old_attrs = self.attrs.get(&ex.hir_id.local_id).copied().unwrap_or(&[]); |
| self.attrs.insert( |
| ex.hir_id.local_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 await? <pat> in <iter> <body>` |
| // |
| // This also needs special handling because the HirId of the returned `hir::Expr` will not |
| // correspond to the `e.id`, so `lower_expr_for` handles attribute lowering itself. |
| ExprKind::ForLoop { pat, iter, body, label, kind } => { |
| return self.lower_expr_for(e, pat, iter, body, *label, *kind); |
| } |
| _ => (), |
| } |
| |
| let expr_hir_id = self.lower_node_id(e.id); |
| self.lower_attrs(expr_hir_id, &e.attrs); |
| |
| let kind = match &e.kind { |
| ExprKind::Array(exprs) => hir::ExprKind::Array(self.lower_exprs(exprs)), |
| ExprKind::ConstBlock(c) => { |
| let c = self.with_new_scopes(c.value.span, |this| { |
| let def_id = this.local_def_id(c.id); |
| hir::ConstBlock { |
| def_id, |
| hir_id: this.lower_node_id(c.id), |
| body: this.with_def_id_parent(def_id, |this| { |
| this.lower_const_body(c.value.span, Some(&c.value)) |
| }), |
| } |
| }); |
| hir::ExprKind::ConstBlock(c) |
| } |
| ExprKind::Repeat(expr, count) => { |
| let expr = self.lower_expr(expr); |
| let count = self.lower_array_length(count); |
| hir::ExprKind::Repeat(expr, count) |
| } |
| ExprKind::Tup(elts) => hir::ExprKind::Tup(self.lower_exprs(elts)), |
| ExprKind::Call(f, 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(box MethodCall { seg, receiver, args, span }) => { |
| let hir_seg = self.arena.alloc(self.lower_path_segment( |
| e.span, |
| seg, |
| ParamMode::Optional, |
| GenericArgsMode::Err, |
| ImplTraitContext::Disallowed(ImplTraitPosition::Path), |
| // Method calls can't have bound modifiers |
| None, |
| )); |
| let receiver = self.lower_expr(receiver); |
| let args = |
| self.arena.alloc_from_iter(args.iter().map(|x| self.lower_expr_mut(x))); |
| hir::ExprKind::MethodCall(hir_seg, receiver, args, self.lower_span(*span)) |
| } |
| ExprKind::Binary(binop, lhs, 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, ohs) => { |
| let op = self.lower_unop(*op); |
| let ohs = self.lower_expr(ohs); |
| hir::ExprKind::Unary(op, ohs) |
| } |
| ExprKind::Lit(token_lit) => { |
| let lit_kind = match LitKind::from_token_lit(*token_lit) { |
| Ok(lit_kind) => lit_kind, |
| Err(err) => { |
| let guar = |
| report_lit_error(&self.tcx.sess.psess, err, *token_lit, e.span); |
| LitKind::Err(guar) |
| } |
| }; |
| let lit = self.arena.alloc(respan(self.lower_span(e.span), lit_kind)); |
| hir::ExprKind::Lit(lit) |
| } |
| ExprKind::IncludedBytes(bytes) => { |
| let lit = self.arena.alloc(respan( |
| self.lower_span(e.span), |
| LitKind::ByteStr(Lrc::clone(bytes), StrStyle::Cooked), |
| )); |
| hir::ExprKind::Lit(lit) |
| } |
| ExprKind::Cast(expr, ty) => { |
| let expr = self.lower_expr(expr); |
| let ty = |
| self.lower_ty(ty, ImplTraitContext::Disallowed(ImplTraitPosition::Cast)); |
| hir::ExprKind::Cast(expr, ty) |
| } |
| ExprKind::Type(expr, ty) => { |
| let expr = self.lower_expr(expr); |
| let ty = |
| self.lower_ty(ty, ImplTraitContext::Disallowed(ImplTraitPosition::Cast)); |
| hir::ExprKind::Type(expr, ty) |
| } |
| ExprKind::AddrOf(k, m, ohs) => { |
| let ohs = self.lower_expr(ohs); |
| hir::ExprKind::AddrOf(*k, *m, ohs) |
| } |
| ExprKind::Let(pat, scrutinee, span, recovered) => { |
| hir::ExprKind::Let(self.arena.alloc(hir::LetExpr { |
| span: self.lower_span(*span), |
| pat: self.lower_pat(pat), |
| ty: None, |
| init: self.lower_expr(scrutinee), |
| recovered: *recovered, |
| })) |
| } |
| ExprKind::If(cond, then, else_opt) => { |
| self.lower_expr_if(cond, then, else_opt.as_deref()) |
| } |
| ExprKind::While(cond, body, opt_label) => { |
| self.with_loop_scope(expr_hir_id, |this| { |
| let span = |
| this.mark_span_with_reason(DesugaringKind::WhileLoop, e.span, None); |
| let opt_label = this.lower_label(*opt_label, e.id, expr_hir_id); |
| this.lower_expr_while_in_loop_scope(span, cond, body, opt_label) |
| }) |
| } |
| ExprKind::Loop(body, opt_label, span) => { |
| self.with_loop_scope(expr_hir_id, |this| { |
| let opt_label = this.lower_label(*opt_label, e.id, expr_hir_id); |
| hir::ExprKind::Loop( |
| this.lower_block(body, false), |
| opt_label, |
| hir::LoopSource::Loop, |
| this.lower_span(*span), |
| ) |
| }) |
| } |
| ExprKind::TryBlock(body) => self.lower_expr_try_block(body), |
| ExprKind::Match(expr, arms, kind) => hir::ExprKind::Match( |
| self.lower_expr(expr), |
| self.arena.alloc_from_iter(arms.iter().map(|x| self.lower_arm(x))), |
| match kind { |
| MatchKind::Prefix => hir::MatchSource::Normal, |
| MatchKind::Postfix => hir::MatchSource::Postfix, |
| }, |
| ), |
| ExprKind::Await(expr, await_kw_span) => self.lower_expr_await(*await_kw_span, expr), |
| ExprKind::Closure(box Closure { |
| binder, |
| capture_clause, |
| constness, |
| coroutine_kind, |
| movability, |
| fn_decl, |
| body, |
| fn_decl_span, |
| fn_arg_span, |
| }) => match coroutine_kind { |
| Some(coroutine_kind) => self.lower_expr_coroutine_closure( |
| binder, |
| *capture_clause, |
| e.id, |
| expr_hir_id, |
| *coroutine_kind, |
| fn_decl, |
| body, |
| *fn_decl_span, |
| *fn_arg_span, |
| ), |
| None => self.lower_expr_closure( |
| binder, |
| *capture_clause, |
| e.id, |
| expr_hir_id, |
| *constness, |
| *movability, |
| fn_decl, |
| body, |
| *fn_decl_span, |
| *fn_arg_span, |
| ), |
| }, |
| ExprKind::Gen(capture_clause, block, genblock_kind, decl_span) => { |
| let desugaring_kind = match genblock_kind { |
| GenBlockKind::Async => hir::CoroutineDesugaring::Async, |
| GenBlockKind::Gen => hir::CoroutineDesugaring::Gen, |
| GenBlockKind::AsyncGen => hir::CoroutineDesugaring::AsyncGen, |
| }; |
| self.make_desugared_coroutine_expr( |
| *capture_clause, |
| e.id, |
| None, |
| *decl_span, |
| e.span, |
| desugaring_kind, |
| hir::CoroutineSource::Block, |
| |this| this.with_new_scopes(e.span, |this| this.lower_block_expr(block)), |
| ) |
| } |
| ExprKind::Block(blk, opt_label) => { |
| // Different from loops, label of block resolves to block id rather than |
| // expr node id. |
| let block_hir_id = self.lower_node_id(blk.id); |
| let opt_label = self.lower_label(*opt_label, blk.id, block_hir_id); |
| let hir_block = self.arena.alloc(self.lower_block_noalloc( |
| block_hir_id, |
| blk, |
| opt_label.is_some(), |
| )); |
| hir::ExprKind::Block(hir_block, opt_label) |
| } |
| ExprKind::Assign(el, er, span) => self.lower_expr_assign(el, er, *span, e.span), |
| ExprKind::AssignOp(op, el, er) => hir::ExprKind::AssignOp( |
| self.lower_binop(*op), |
| self.lower_expr(el), |
| self.lower_expr(er), |
| ), |
| ExprKind::Field(el, ident) => { |
| hir::ExprKind::Field(self.lower_expr(el), self.lower_ident(*ident)) |
| } |
| ExprKind::Index(el, er, brackets_span) => { |
| hir::ExprKind::Index(self.lower_expr(el), self.lower_expr(er), *brackets_span) |
| } |
| ExprKind::Range(Some(e1), Some(e2), RangeLimits::Closed) => { |
| self.lower_expr_range_closed(e.span, e1, e2) |
| } |
| ExprKind::Range(e1, e2, lims) => { |
| self.lower_expr_range(e.span, e1.as_deref(), e2.as_deref(), *lims) |
| } |
| ExprKind::Underscore => { |
| let guar = self.dcx().emit_err(UnderscoreExprLhsAssign { span: e.span }); |
| hir::ExprKind::Err(guar) |
| } |
| ExprKind::Path(qself, path) => { |
| let qpath = self.lower_qpath( |
| e.id, |
| qself, |
| path, |
| ParamMode::Optional, |
| AllowReturnTypeNotation::No, |
| ImplTraitContext::Disallowed(ImplTraitPosition::Path), |
| None, |
| ); |
| hir::ExprKind::Path(qpath) |
| } |
| ExprKind::Break(opt_label, 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(e) => { |
| let e = e.as_ref().map(|x| self.lower_expr(x)); |
| hir::ExprKind::Ret(e) |
| } |
| ExprKind::Yeet(sub_expr) => self.lower_expr_yeet(e.span, sub_expr.as_deref()), |
| ExprKind::Become(sub_expr) => { |
| let sub_expr = self.lower_expr(sub_expr); |
| hir::ExprKind::Become(sub_expr) |
| } |
| ExprKind::InlineAsm(asm) => { |
| hir::ExprKind::InlineAsm(self.lower_inline_asm(e.span, asm)) |
| } |
| ExprKind::FormatArgs(fmt) => self.lower_format_args(e.span, fmt), |
| ExprKind::OffsetOf(container, fields) => hir::ExprKind::OffsetOf( |
| self.lower_ty( |
| container, |
| ImplTraitContext::Disallowed(ImplTraitPosition::OffsetOf), |
| ), |
| self.arena.alloc_from_iter(fields.iter().map(|&ident| self.lower_ident(ident))), |
| ), |
| ExprKind::Struct(se) => { |
| let rest = match &se.rest { |
| StructRest::Base(e) => Some(self.lower_expr(e)), |
| StructRest::Rest(sp) => { |
| let guar = self.dcx().emit_err(BaseExpressionDoubleDot { span: *sp }); |
| Some(&*self.arena.alloc(self.expr_err(*sp, guar))) |
| } |
| StructRest::None => None, |
| }; |
| hir::ExprKind::Struct( |
| self.arena.alloc(self.lower_qpath( |
| e.id, |
| &se.qself, |
| &se.path, |
| ParamMode::Optional, |
| AllowReturnTypeNotation::No, |
| ImplTraitContext::Disallowed(ImplTraitPosition::Path), |
| None, |
| )), |
| self.arena |
| .alloc_from_iter(se.fields.iter().map(|x| self.lower_expr_field(x))), |
| rest, |
| ) |
| } |
| ExprKind::Yield(opt_expr) => self.lower_expr_yield(e.span, opt_expr.as_deref()), |
| ExprKind::Err(guar) => hir::ExprKind::Err(*guar), |
| |
| ExprKind::Dummy => { |
| span_bug!(e.span, "lowered ExprKind::Dummy") |
| } |
| |
| ExprKind::Try(sub_expr) => self.lower_expr_try(e.span, sub_expr), |
| |
| ExprKind::Paren(_) | ExprKind::ForLoop { .. } => { |
| unreachable!("already handled") |
| } |
| |
| ExprKind::MacCall(_) => panic!("{:?} shouldn't exist here", e.span), |
| }; |
| |
| hir::Expr { hir_id: expr_hir_id, kind, span: self.lower_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) -> BinOp { |
| Spanned { node: b.node, span: self.lower_span(b.span) } |
| } |
| |
| fn lower_legacy_const_generics( |
| &mut self, |
| mut f: Expr, |
| args: ThinVec<AstP<Expr>>, |
| legacy_args_idx: &[usize], |
| ) -> hir::ExprKind<'hir> { |
| let ExprKind::Path(None, path) = &mut f.kind else { |
| unreachable!(); |
| }; |
| |
| // Split the arguments into const generics and normal arguments |
| let mut real_args = vec![]; |
| let mut generic_args = ThinVec::new(); |
| for (idx, arg) in args.into_iter().enumerate() { |
| if legacy_args_idx.contains(&idx) { |
| let parent_def_id = self.current_def_id_parent; |
| let node_id = self.next_node_id(); |
| |
| // HACK(min_generic_const_args): see lower_anon_const |
| if !arg.is_potential_trivial_const_arg(true) { |
| // Add a definition for the in-band const def. |
| self.create_def(parent_def_id, node_id, kw::Empty, DefKind::AnonConst, f.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 lower_expr_if( |
| &mut self, |
| cond: &Expr, |
| then: &Block, |
| else_opt: Option<&Expr>, |
| ) -> hir::ExprKind<'hir> { |
| let lowered_cond = self.lower_cond(cond); |
| let then_expr = self.lower_block_expr(then); |
| if let Some(rslt) = else_opt { |
| hir::ExprKind::If( |
| lowered_cond, |
| self.arena.alloc(then_expr), |
| Some(self.lower_expr(rslt)), |
| ) |
| } else { |
| hir::ExprKind::If(lowered_cond, self.arena.alloc(then_expr), None) |
| } |
| } |
| |
| // Lowers a condition (i.e. `cond` in `if cond` or `while cond`), wrapping it in a terminating scope |
| // so that temporaries created in the condition don't live beyond it. |
| fn lower_cond(&mut self, cond: &Expr) -> &'hir hir::Expr<'hir> { |
| fn has_let_expr(expr: &Expr) -> bool { |
| match &expr.kind { |
| ExprKind::Binary(_, lhs, rhs) => has_let_expr(lhs) || has_let_expr(rhs), |
| ExprKind::Let(..) => true, |
| _ => false, |
| } |
| } |
| |
| // We have to take special care for `let` exprs in the condition, e.g. in |
| // `if let pat = val` or `if foo && let pat = val`, as we _do_ want `val` to live beyond the |
| // condition in this case. |
| // |
| // In order to maintain the drop behavior for the non `let` parts of the condition, |
| // we still wrap them in terminating scopes, e.g. `if foo && let pat = val` essentially |
| // gets transformed into `if { let _t = foo; _t } && let pat = val` |
| match &cond.kind { |
| ExprKind::Binary(op @ Spanned { node: ast::BinOpKind::And, .. }, lhs, rhs) |
| if has_let_expr(cond) => |
| { |
| let op = self.lower_binop(*op); |
| let lhs = self.lower_cond(lhs); |
| let rhs = self.lower_cond(rhs); |
| |
| self.arena.alloc(self.expr(cond.span, hir::ExprKind::Binary(op, lhs, rhs))) |
| } |
| ExprKind::Let(..) => self.lower_expr(cond), |
| _ => { |
| let cond = self.lower_expr(cond); |
| let reason = DesugaringKind::CondTemporary; |
| let span_block = self.mark_span_with_reason(reason, cond.span, None); |
| self.expr_drop_temps(span_block, cond) |
| } |
| } |
| } |
| |
| // We desugar: `'label: while $cond $body` into: |
| // |
| // ``` |
| // 'label: loop { |
| // if { let _t = $cond; _t } { |
| // $body |
| // } |
| // else { |
| // break; |
| // } |
| // } |
| // ``` |
| // |
| // 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`. |
| fn lower_expr_while_in_loop_scope( |
| &mut self, |
| span: Span, |
| cond: &Expr, |
| body: &Block, |
| opt_label: Option<Label>, |
| ) -> hir::ExprKind<'hir> { |
| let lowered_cond = self.with_loop_condition_scope(|t| t.lower_cond(cond)); |
| let then = self.lower_block_expr(body); |
| let expr_break = self.expr_break(span); |
| let stmt_break = self.stmt_expr(span, expr_break); |
| let else_blk = self.block_all(span, arena_vec![self; stmt_break], None); |
| let else_expr = self.arena.alloc(self.expr_block(else_blk)); |
| let if_kind = hir::ExprKind::If(lowered_cond, self.arena.alloc(then), Some(else_expr)); |
| let if_expr = self.expr(span, if_kind); |
| let block = self.block_expr(self.arena.alloc(if_expr)); |
| let span = self.lower_span(span.with_hi(cond.span.hi())); |
| hir::ExprKind::Loop(block, opt_label, hir::LoopSource::While, span) |
| } |
| |
| /// 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> { |
| let body_hir_id = self.lower_node_id(body.id); |
| self.with_catch_scope(body_hir_id, |this| { |
| let mut block = this.lower_block_noalloc(body_hir_id, 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, |
| Some(Lrc::clone(&this.allow_try_trait)), |
| ), |
| expr, |
| ) |
| } else { |
| let try_span = this.mark_span_with_reason( |
| DesugaringKind::TryBlock, |
| this.tcx.sess.source_map().end_point(body.span), |
| Some(Lrc::clone(&this.allow_try_trait)), |
| ); |
| |
| (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)); |
| 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| self.lower_expr(cond)); |
| let hir_id = self.next_id(); |
| let span = self.lower_span(arm.span); |
| self.lower_attrs(hir_id, &arm.attrs); |
| let is_never_pattern = pat.is_never_pattern(); |
| let body = if let Some(body) = &arm.body |
| && !is_never_pattern |
| { |
| self.lower_expr(body) |
| } else { |
| // Either `body.is_none()` or `is_never_pattern` here. |
| if !is_never_pattern { |
| if self.tcx.features().never_patterns() { |
| // If the feature is off we already emitted the error after parsing. |
| let suggestion = span.shrink_to_hi(); |
| self.dcx().emit_err(MatchArmWithNoBody { span, suggestion }); |
| } |
| } else if let Some(body) = &arm.body { |
| self.dcx().emit_err(NeverPatternWithBody { span: body.span }); |
| } else if let Some(g) = &arm.guard { |
| self.dcx().emit_err(NeverPatternWithGuard { span: g.span }); |
| } |
| |
| // We add a fake `loop {}` arm body so that it typecks to `!`. The mir lowering of never |
| // patterns ensures this loop is not reachable. |
| let block = self.arena.alloc(hir::Block { |
| stmts: &[], |
| expr: None, |
| hir_id: self.next_id(), |
| rules: hir::BlockCheckMode::DefaultBlock, |
| span, |
| targeted_by_break: false, |
| }); |
| self.arena.alloc(hir::Expr { |
| hir_id: self.next_id(), |
| kind: hir::ExprKind::Loop(block, None, hir::LoopSource::Loop, span), |
| span, |
| }) |
| }; |
| hir::Arm { hir_id, pat, guard, body, span } |
| } |
| |
| /// Lower/desugar a coroutine construct. |
| /// |
| /// In particular, this creates the correct async resume argument and `_task_context`. |
| /// |
| /// This results in: |
| /// |
| /// ```text |
| /// static move? |<_task_context?>| -> <return_ty> { |
| /// <body> |
| /// } |
| /// ``` |
| pub(super) fn make_desugared_coroutine_expr( |
| &mut self, |
| capture_clause: CaptureBy, |
| closure_node_id: NodeId, |
| return_ty: Option<hir::FnRetTy<'hir>>, |
| fn_decl_span: Span, |
| span: Span, |
| desugaring_kind: hir::CoroutineDesugaring, |
| coroutine_source: hir::CoroutineSource, |
| body: impl FnOnce(&mut Self) -> hir::Expr<'hir>, |
| ) -> hir::ExprKind<'hir> { |
| let closure_def_id = self.local_def_id(closure_node_id); |
| let coroutine_kind = hir::CoroutineKind::Desugared(desugaring_kind, coroutine_source); |
| |
| // The `async` desugaring takes a resume argument and maintains a `task_context`, |
| // whereas a generator does not. |
| let (inputs, params, task_context): (&[_], &[_], _) = match desugaring_kind { |
| hir::CoroutineDesugaring::Async | hir::CoroutineDesugaring::AsyncGen => { |
| // Resume argument type: `ResumeTy` |
| let unstable_span = self.mark_span_with_reason( |
| DesugaringKind::Async, |
| self.lower_span(span), |
| Some(Lrc::clone(&self.allow_gen_future)), |
| ); |
| let resume_ty = |
| self.make_lang_item_qpath(hir::LangItem::ResumeTy, unstable_span, None); |
| let input_ty = hir::Ty { |
| hir_id: self.next_id(), |
| kind: hir::TyKind::Path(resume_ty), |
| span: unstable_span, |
| }; |
| let inputs = arena_vec![self; input_ty]; |
| |
| // 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::BindingMode::MUT, |
| ); |
| let param = hir::Param { |
| hir_id: self.next_id(), |
| pat, |
| ty_span: self.lower_span(span), |
| span: self.lower_span(span), |
| }; |
| let params = arena_vec![self; param]; |
| |
| (inputs, params, Some(task_context_hid)) |
| } |
| hir::CoroutineDesugaring::Gen => (&[], &[], None), |
| }; |
| |
| let output = |
| return_ty.unwrap_or_else(|| hir::FnRetTy::DefaultReturn(self.lower_span(span))); |
| |
| let fn_decl = self.arena.alloc(hir::FnDecl { |
| inputs, |
| output, |
| c_variadic: false, |
| implicit_self: hir::ImplicitSelfKind::None, |
| lifetime_elision_allowed: false, |
| }); |
| |
| let body = self.with_def_id_parent(closure_def_id, move |this| { |
| this.lower_body(move |this| { |
| this.coroutine_kind = Some(coroutine_kind); |
| |
| let old_ctx = this.task_context; |
| if task_context.is_some() { |
| this.task_context = task_context; |
| } |
| let res = body(this); |
| this.task_context = old_ctx; |
| |
| (params, res) |
| }) |
| }); |
| |
| // `static |<_task_context?>| -> <return_ty> { <body> }`: |
| hir::ExprKind::Closure(self.arena.alloc(hir::Closure { |
| def_id: closure_def_id, |
| binder: hir::ClosureBinder::Default, |
| capture_clause, |
| bound_generic_params: &[], |
| fn_decl, |
| body, |
| fn_decl_span: self.lower_span(fn_decl_span), |
| fn_arg_span: None, |
| kind: hir::ClosureKind::Coroutine(coroutine_kind), |
| constness: hir::Constness::NotConst, |
| })) |
| } |
| |
| /// Forwards a possible `#[track_caller]` annotation from `outer_hir_id` to |
| /// `inner_hir_id` in case the `async_fn_track_caller` feature is enabled. |
| pub(super) fn maybe_forward_track_caller( |
| &mut self, |
| span: Span, |
| outer_hir_id: HirId, |
| inner_hir_id: HirId, |
| ) { |
| if self.tcx.features().async_fn_track_caller() |
| && let Some(attrs) = self.attrs.get(&outer_hir_id.local_id) |
| && attrs.into_iter().any(|attr| attr.has_name(sym::track_caller)) |
| { |
| let unstable_span = self.mark_span_with_reason( |
| DesugaringKind::Async, |
| span, |
| Some(Lrc::clone(&self.allow_gen_future)), |
| ); |
| self.lower_attrs(inner_hir_id, &[Attribute { |
| kind: AttrKind::Normal(ptr::P(NormalAttr::from_ident(Ident::new( |
| sym::track_caller, |
| span, |
| )))), |
| id: self.tcx.sess.psess.attr_id_generator.mk_attr_id(), |
| style: AttrStyle::Outer, |
| span: unstable_span, |
| }]); |
| } |
| } |
| |
| /// Desugar `<expr>.await` into: |
| /// ```ignore (pseudo-rust) |
| /// match ::std::future::IntoFuture::into_future(<expr>) { |
| /// mut __awaitee => loop { |
| /// match unsafe { ::std::future::Future::poll( |
| /// <::std::pin::Pin>::new_unchecked(&mut __awaitee), |
| /// ::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_kw_span: Span, expr: &Expr) -> hir::ExprKind<'hir> { |
| let expr = self.arena.alloc(self.lower_expr_mut(expr)); |
| self.make_lowered_await(await_kw_span, expr, FutureKind::Future) |
| } |
| |
| /// Takes an expr that has already been lowered and generates a desugared await loop around it |
| fn make_lowered_await( |
| &mut self, |
| await_kw_span: Span, |
| expr: &'hir hir::Expr<'hir>, |
| await_kind: FutureKind, |
| ) -> hir::ExprKind<'hir> { |
| let full_span = expr.span.to(await_kw_span); |
| |
| let is_async_gen = match self.coroutine_kind { |
| Some(hir::CoroutineKind::Desugared(hir::CoroutineDesugaring::Async, _)) => false, |
| Some(hir::CoroutineKind::Desugared(hir::CoroutineDesugaring::AsyncGen, _)) => true, |
| Some(hir::CoroutineKind::Coroutine(_)) |
| | Some(hir::CoroutineKind::Desugared(hir::CoroutineDesugaring::Gen, _)) |
| | None => { |
| // Lower to a block `{ EXPR; <error> }` so that the awaited expr |
| // is not accidentally orphaned. |
| let stmt_id = self.next_id(); |
| let expr_err = self.expr( |
| expr.span, |
| hir::ExprKind::Err(self.dcx().emit_err(AwaitOnlyInAsyncFnAndBlocks { |
| await_kw_span, |
| item_span: self.current_item, |
| })), |
| ); |
| return hir::ExprKind::Block( |
| self.block_all( |
| expr.span, |
| arena_vec![self; hir::Stmt { |
| hir_id: stmt_id, |
| kind: hir::StmtKind::Semi(expr), |
| span: expr.span, |
| }], |
| Some(self.arena.alloc(expr_err)), |
| ), |
| None, |
| ); |
| } |
| }; |
| |
| let features = match await_kind { |
| FutureKind::Future => None, |
| FutureKind::AsyncIterator => Some(Lrc::clone(&self.allow_for_await)), |
| }; |
| let span = self.mark_span_with_reason(DesugaringKind::Await, await_kw_span, features); |
| let gen_future_span = self.mark_span_with_reason( |
| DesugaringKind::Await, |
| full_span, |
| Some(Lrc::clone(&self.allow_gen_future)), |
| ); |
| let expr_hir_id = expr.hir_id; |
| |
| // Note that the name of this binding must not be changed to something else because |
| // debuggers and debugger extensions expect it to be called `__awaitee`. They use |
| // this name to identify what is being awaited by a suspended async functions. |
| let awaitee_ident = Ident::with_dummy_span(sym::__awaitee); |
| let (awaitee_pat, awaitee_pat_hid) = |
| self.pat_ident_binding_mode(gen_future_span, awaitee_ident, hir::BindingMode::MUT); |
| |
| let task_context_ident = Ident::with_dummy_span(sym::_task_context); |
| |
| // unsafe { |
| // ::std::future::Future::poll( |
| // ::std::pin::Pin::new_unchecked(&mut __awaitee), |
| // ::std::future::get_context(task_context), |
| // ) |
| // } |
| let poll_expr = { |
| let awaitee = self.expr_ident(span, awaitee_ident, awaitee_pat_hid); |
| let ref_mut_awaitee = self.expr_mut_addr_of(span, awaitee); |
| |
| let Some(task_context_hid) = self.task_context else { |
| unreachable!("use of `await` outside of an async context."); |
| }; |
| |
| let task_context = self.expr_ident_mut(span, task_context_ident, task_context_hid); |
| |
| let new_unchecked = self.expr_call_lang_item_fn_mut( |
| span, |
| hir::LangItem::PinNewUnchecked, |
| arena_vec![self; ref_mut_awaitee], |
| ); |
| let get_context = self.expr_call_lang_item_fn_mut( |
| gen_future_span, |
| hir::LangItem::GetContext, |
| arena_vec![self; task_context], |
| ); |
| let call = match await_kind { |
| FutureKind::Future => self.expr_call_lang_item_fn( |
| span, |
| hir::LangItem::FuturePoll, |
| arena_vec![self; new_unchecked, get_context], |
| ), |
| FutureKind::AsyncIterator => self.expr_call_lang_item_fn( |
| span, |
| hir::LangItem::AsyncIteratorPollNext, |
| 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.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(gen_future_span, x_ident); |
| let x_expr = self.expr_ident(gen_future_span, x_ident, x_pat_hid); |
| let ready_field = self.single_pat_field(gen_future_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_hir_id, move |this| { |
| let expr_break = |
| hir::ExprKind::Break(this.lower_loop_destination(None), Some(x_expr)); |
| this.arena.alloc(this.expr(gen_future_span, expr_break)) |
| }); |
| 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) |
| }; |
| |
| // Depending on `async` of `async gen`: |
| // async - task_context = yield (); |
| // async gen - task_context = yield ASYNC_GEN_PENDING; |
| let yield_stmt = { |
| let yielded = if is_async_gen { |
| self.arena.alloc(self.expr_lang_item_path(span, hir::LangItem::AsyncGenPending)) |
| } else { |
| self.expr_unit(span) |
| }; |
| |
| let yield_expr = self.expr( |
| span, |
| hir::ExprKind::Yield(yielded, hir::YieldSource::Await { expr: Some(expr_hir_id) }), |
| ); |
| let yield_expr = self.arena.alloc(yield_expr); |
| |
| let Some(task_context_hid) = self.task_context else { |
| unreachable!("use of `await` outside of an async context."); |
| }; |
| |
| let lhs = self.expr_ident(span, task_context_ident, task_context_hid); |
| let assign = |
| self.expr(span, hir::ExprKind::Assign(lhs, yield_expr, self.lower_span(span))); |
| self.stmt_expr(span, assign) |
| }; |
| |
| 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, |
| self.lower_span(span), |
| ), |
| span: self.lower_span(span), |
| }); |
| |
| // mut __awaitee => loop { ... } |
| let awaitee_arm = self.arm(awaitee_pat, loop_expr); |
| |
| // `match ::std::future::IntoFuture::into_future(<expr>) { ... }` |
| let into_future_expr = match await_kind { |
| FutureKind::Future => self.expr_call_lang_item_fn( |
| span, |
| hir::LangItem::IntoFutureIntoFuture, |
| arena_vec![self; *expr], |
| ), |
| // Not needed for `for await` because we expect to have already called |
| // `IntoAsyncIterator::into_async_iter` on it. |
| FutureKind::AsyncIterator => expr, |
| }; |
| |
| // match <into_future_expr> { |
| // mut __awaitee => loop { .. } |
| // } |
| hir::ExprKind::Match( |
| into_future_expr, |
| arena_vec![self; awaitee_arm], |
| hir::MatchSource::AwaitDesugar, |
| ) |
| } |
| |
| fn lower_expr_closure( |
| &mut self, |
| binder: &ClosureBinder, |
| capture_clause: CaptureBy, |
| closure_id: NodeId, |
| closure_hir_id: hir::HirId, |
| constness: Const, |
| movability: Movability, |
| decl: &FnDecl, |
| body: &Expr, |
| fn_decl_span: Span, |
| fn_arg_span: Span, |
| ) -> hir::ExprKind<'hir> { |
| let closure_def_id = self.local_def_id(closure_id); |
| let (binder_clause, generic_params) = self.lower_closure_binder(binder); |
| |
| let (body_id, closure_kind) = self.with_new_scopes(fn_decl_span, move |this| { |
| this.with_def_id_parent(closure_def_id, move |this| { |
| let mut coroutine_kind = if this |
| .attrs |
| .get(&closure_hir_id.local_id) |
| .is_some_and(|attrs| attrs.iter().any(|attr| attr.has_name(sym::coroutine))) |
| { |
| Some(hir::CoroutineKind::Coroutine(Movability::Movable)) |
| } else { |
| None |
| }; |
| let body_id = this.lower_fn_body(decl, |this| { |
| this.coroutine_kind = coroutine_kind; |
| let e = this.lower_expr_mut(body); |
| coroutine_kind = this.coroutine_kind; |
| e |
| }); |
| let coroutine_option = |
| this.closure_movability_for_fn(decl, fn_decl_span, coroutine_kind, movability); |
| (body_id, coroutine_option) |
| }) |
| }); |
| |
| let bound_generic_params = self.lower_lifetime_binder(closure_id, generic_params); |
| // Lower outside new scope to preserve `is_in_loop_condition`. |
| let fn_decl = self.lower_fn_decl(decl, closure_id, fn_decl_span, FnDeclKind::Closure, None); |
| |
| let c = self.arena.alloc(hir::Closure { |
| def_id: closure_def_id, |
| binder: binder_clause, |
| capture_clause, |
| bound_generic_params, |
| fn_decl, |
| body: body_id, |
| fn_decl_span: self.lower_span(fn_decl_span), |
| fn_arg_span: Some(self.lower_span(fn_arg_span)), |
| kind: closure_kind, |
| constness: self.lower_constness(constness), |
| }); |
| |
| hir::ExprKind::Closure(c) |
| } |
| |
| fn closure_movability_for_fn( |
| &mut self, |
| decl: &FnDecl, |
| fn_decl_span: Span, |
| coroutine_kind: Option<hir::CoroutineKind>, |
| movability: Movability, |
| ) -> hir::ClosureKind { |
| match coroutine_kind { |
| Some(hir::CoroutineKind::Coroutine(_)) => { |
| if decl.inputs.len() > 1 { |
| self.dcx().emit_err(CoroutineTooManyParameters { fn_decl_span }); |
| } |
| hir::ClosureKind::Coroutine(hir::CoroutineKind::Coroutine(movability)) |
| } |
| Some( |
| hir::CoroutineKind::Desugared(hir::CoroutineDesugaring::Gen, _) |
| | hir::CoroutineKind::Desugared(hir::CoroutineDesugaring::Async, _) |
| | hir::CoroutineKind::Desugared(hir::CoroutineDesugaring::AsyncGen, _), |
| ) => { |
| panic!("non-`async`/`gen` closure body turned `async`/`gen` during lowering"); |
| } |
| None => { |
| if movability == Movability::Static { |
| self.dcx().emit_err(ClosureCannotBeStatic { fn_decl_span }); |
| } |
| hir::ClosureKind::Closure |
| } |
| } |
| } |
| |
| fn lower_closure_binder<'c>( |
| &mut self, |
| binder: &'c ClosureBinder, |
| ) -> (hir::ClosureBinder, &'c [GenericParam]) { |
| let (binder, params) = match binder { |
| ClosureBinder::NotPresent => (hir::ClosureBinder::Default, &[][..]), |
| ClosureBinder::For { span, generic_params } => { |
| let span = self.lower_span(*span); |
| (hir::ClosureBinder::For { span }, &**generic_params) |
| } |
| }; |
| |
| (binder, params) |
| } |
| |
| fn lower_expr_coroutine_closure( |
| &mut self, |
| binder: &ClosureBinder, |
| capture_clause: CaptureBy, |
| closure_id: NodeId, |
| closure_hir_id: HirId, |
| coroutine_kind: CoroutineKind, |
| decl: &FnDecl, |
| body: &Expr, |
| fn_decl_span: Span, |
| fn_arg_span: Span, |
| ) -> hir::ExprKind<'hir> { |
| let closure_def_id = self.local_def_id(closure_id); |
| let (binder_clause, generic_params) = self.lower_closure_binder(binder); |
| |
| assert_matches!( |
| coroutine_kind, |
| CoroutineKind::Async { .. }, |
| "only async closures are supported currently" |
| ); |
| |
| let body = self.with_new_scopes(fn_decl_span, |this| { |
| this.with_def_id_parent(closure_def_id, |this| { |
| let inner_decl = |
| FnDecl { inputs: decl.inputs.clone(), output: FnRetTy::Default(fn_decl_span) }; |
| |
| // Transform `async |x: u8| -> X { ... }` into |
| // `|x: u8| || -> X { ... }`. |
| let body_id = this.lower_body(|this| { |
| let (parameters, expr) = this.lower_coroutine_body_with_moved_arguments( |
| &inner_decl, |
| |this| this.with_new_scopes(fn_decl_span, |this| this.lower_expr_mut(body)), |
| fn_decl_span, |
| body.span, |
| coroutine_kind, |
| hir::CoroutineSource::Closure, |
| ); |
| |
| this.maybe_forward_track_caller(body.span, closure_hir_id, expr.hir_id); |
| |
| (parameters, expr) |
| }); |
| body_id |
| }) |
| }); |
| |
| let bound_generic_params = self.lower_lifetime_binder(closure_id, generic_params); |
| // 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(&decl, closure_id, fn_decl_span, FnDeclKind::Closure, None); |
| |
| let c = self.arena.alloc(hir::Closure { |
| def_id: closure_def_id, |
| binder: binder_clause, |
| capture_clause, |
| bound_generic_params, |
| fn_decl, |
| body, |
| fn_decl_span: self.lower_span(fn_decl_span), |
| fn_arg_span: Some(self.lower_span(fn_arg_span)), |
| // Lower this as a `CoroutineClosure`. That will ensure that HIR typeck |
| // knows that a `FnDecl` output type like `-> &str` actually means |
| // "coroutine that returns &str", rather than directly returning a `&str`. |
| kind: hir::ClosureKind::CoroutineClosure(hir::CoroutineDesugaring::Async), |
| constness: hir::Constness::NotConst, |
| }); |
| hir::ExprKind::Closure(c) |
| } |
| |
| /// 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 unit struct constructor. |
| ExprKind::Path(..) => lower_ctx.extract_unit_struct_path(lhs).is_none(), |
| // 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), |
| self.lower_span(eq_sign_span), |
| ); |
| } |
| |
| 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(self.lower_span(eq_sign_span)), |
| ); |
| |
| // `a = lhs1; b = lhs2;`. |
| let stmts = self.arena.alloc_from_iter(std::iter::once(destructure_let).chain(assignments)); |
| |
| // 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<AstP<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 let Some(res) = partial_res.full_res() |
| && !res.expected_in_tuple_struct_pat() |
| { |
| return None; |
| } |
| } |
| return Some((qself, path)); |
| } |
| None |
| } |
| |
| /// If the given expression is a path to a unit struct, returns that path. |
| /// It is not a complete check, but just tries to reject most paths early |
| /// if they are not unit structs. |
| /// Type checking will take care of the full validation later. |
| fn extract_unit_struct_path<'a>( |
| &mut self, |
| expr: &'a Expr, |
| ) -> Option<(&'a Option<AstP<QSelf>>, &'a Path)> { |
| if let ExprKind::Path(qself, path) = &expr.kind { |
| // Does the path resolve to something disallowed in a unit struct/variant pattern? |
| if let Some(partial_res) = self.resolver.get_partial_res(expr.id) { |
| if let Some(res) = partial_res.full_res() |
| && !res.expected_in_unit_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, |
| AllowReturnTypeNotation::No, |
| ImplTraitContext::Disallowed(ImplTraitPosition::Path), |
| None, |
| ); |
| // Destructure like a tuple struct. |
| let tuple_struct_pat = hir::PatKind::TupleStruct( |
| qpath, |
| pats, |
| hir::DotDotPos::new(rest.map(|r| r.0)), |
| ); |
| return self.pat_without_dbm(lhs.span, tuple_struct_pat); |
| } |
| } |
| // Unit structs and enum variants. |
| ExprKind::Path(..) => { |
| if let Some((qself, path)) = self.extract_unit_struct_path(lhs) { |
| let qpath = self.lower_qpath( |
| lhs.id, |
| qself, |
| path, |
| ParamMode::Optional, |
| AllowReturnTypeNotation::No, |
| ImplTraitContext::Disallowed(ImplTraitPosition::Path), |
| None, |
| ); |
| // Destructure like a unit struct. |
| let unit_struct_pat = hir::PatKind::Path(qpath); |
| return self.pat_without_dbm(lhs.span, unit_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: self.lower_ident(f.ident), |
| pat, |
| is_shorthand: f.is_shorthand, |
| span: self.lower_span(f.span), |
| } |
| })); |
| let qpath = self.lower_qpath( |
| lhs.id, |
| &se.qself, |
| &se.path, |
| ParamMode::Optional, |
| AllowReturnTypeNotation::No, |
| ImplTraitContext::Disallowed(ImplTraitPosition::Path), |
| None, |
| ); |
| let fields_omitted = match &se.rest { |
| StructRest::Base(e) => { |
| self.dcx().emit_err(FunctionalRecordUpdateDestructuringAssignment { |
| span: e.span, |
| }); |
| 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, hir::DotDotPos::new(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(&[], hir::DotDotPos::new(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, self.lower_span(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, self.lower_span(eq_sign_span)); |
| let expr = self.expr(lhs.span, assign); |
| 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, self.lower_span(span)); |
| let fn_expr = self.arena.alloc(self.expr(span, hir::ExprKind::Path(fn_path))); |
| 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!(), |
| (start, None, Closed) => { |
| self.dcx().emit_err(InclusiveRangeWithNoEnd { span }); |
| match start { |
| Some(..) => hir::LangItem::RangeFrom, |
| None => hir::LangItem::RangeFull, |
| } |
| } |
| }; |
| |
| let fields = self.arena.alloc_from_iter( |
| e1.iter().map(|e| (sym::start, e)).chain(e2.iter().map(|e| (sym::end, e))).map( |
| |(s, e)| { |
| let expr = self.lower_expr(e); |
| let ident = Ident::new(s, self.lower_span(e.span)); |
| self.expr_field(ident, expr, e.span) |
| }, |
| ), |
| ); |
| |
| hir::ExprKind::Struct( |
| self.arena.alloc(hir::QPath::LangItem(lang_item, self.lower_span(span))), |
| fields, |
| None, |
| ) |
| } |
| |
| // Record labelled expr's HirId so that we can retrieve it in `lower_jump_destination` without |
| // lowering node id again. |
| fn lower_label( |
| &mut self, |
| opt_label: Option<Label>, |
| dest_id: NodeId, |
| dest_hir_id: hir::HirId, |
| ) -> Option<Label> { |
| let label = opt_label?; |
| self.ident_and_label_to_local_id.insert(dest_id, dest_hir_id.local_id); |
| Some(Label { ident: self.lower_ident(label.ident) }) |
| } |
| |
| 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) { |
| let local_id = self.ident_and_label_to_local_id[&loop_id]; |
| let loop_hir_id = HirId { owner: self.current_hir_id_owner, local_id }; |
| Ok(loop_hir_id) |
| } else { |
| Err(hir::LoopIdError::UnresolvedLabel) |
| } |
| } |
| None => { |
| self.loop_scope.map(|id| Ok(id)).unwrap_or(Err(hir::LoopIdError::OutsideLoopScope)) |
| } |
| }; |
| let label = destination |
| .map(|(_, label)| label) |
| .map(|label| Label { ident: self.lower_ident(label.ident) }); |
| hir::Destination { 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: hir::HirId, f: impl FnOnce(&mut Self) -> T) -> T { |
| let old_scope = self.catch_scope.replace(catch_id); |
| let result = f(self); |
| self.catch_scope = old_scope; |
| result |
| } |
| |
| fn with_loop_scope<T>(&mut self, loop_id: hir::HirId, 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 old_scope = self.loop_scope.replace(loop_id); |
| let result = f(self); |
| self.loop_scope = old_scope; |
| |
| 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_field(&mut self, f: &ExprField) -> hir::ExprField<'hir> { |
| let hir_id = self.lower_node_id(f.id); |
| self.lower_attrs(hir_id, &f.attrs); |
| hir::ExprField { |
| hir_id, |
| ident: self.lower_ident(f.ident), |
| expr: self.lower_expr(&f.expr), |
| span: self.lower_span(f.span), |
| is_shorthand: f.is_shorthand, |
| } |
| } |
| |
| fn lower_expr_yield(&mut self, span: Span, opt_expr: Option<&Expr>) -> hir::ExprKind<'hir> { |
| let yielded = |
| opt_expr.as_ref().map(|x| self.lower_expr(x)).unwrap_or_else(|| self.expr_unit(span)); |
| |
| let is_async_gen = match self.coroutine_kind { |
| Some(hir::CoroutineKind::Desugared(hir::CoroutineDesugaring::Gen, _)) => false, |
| Some(hir::CoroutineKind::Desugared(hir::CoroutineDesugaring::AsyncGen, _)) => true, |
| Some(hir::CoroutineKind::Desugared(hir::CoroutineDesugaring::Async, _)) => { |
| // Lower to a block `{ EXPR; <error> }` so that the awaited expr |
| // is not accidentally orphaned. |
| let stmt_id = self.next_id(); |
| let expr_err = self.expr( |
| yielded.span, |
| hir::ExprKind::Err(self.dcx().emit_err(AsyncCoroutinesNotSupported { span })), |
| ); |
| return hir::ExprKind::Block( |
| self.block_all( |
| yielded.span, |
| arena_vec![self; hir::Stmt { |
| hir_id: stmt_id, |
| kind: hir::StmtKind::Semi(yielded), |
| span: yielded.span, |
| }], |
| Some(self.arena.alloc(expr_err)), |
| ), |
| None, |
| ); |
| } |
| Some(hir::CoroutineKind::Coroutine(_)) => { |
| if !self.tcx.features().coroutines() { |
| rustc_session::parse::feature_err( |
| &self.tcx.sess, |
| sym::coroutines, |
| span, |
| fluent_generated::ast_lowering_yield, |
| ) |
| .emit(); |
| } |
| false |
| } |
| None => { |
| if !self.tcx.features().coroutines() { |
| rustc_session::parse::feature_err( |
| &self.tcx.sess, |
| sym::coroutines, |
| span, |
| fluent_generated::ast_lowering_yield, |
| ) |
| .emit(); |
| } |
| let suggestion = self.current_item.map(|s| s.shrink_to_lo()); |
| self.dcx().emit_err(YieldInClosure { span, suggestion }); |
| self.coroutine_kind = Some(hir::CoroutineKind::Coroutine(Movability::Movable)); |
| |
| false |
| } |
| }; |
| |
| if is_async_gen { |
| // `yield $expr` is transformed into `task_context = yield async_gen_ready($expr)`. |
| // This ensures that we store our resumed `ResumeContext` correctly, and also that |
| // the apparent value of the `yield` expression is `()`. |
| let wrapped_yielded = self.expr_call_lang_item_fn( |
| span, |
| hir::LangItem::AsyncGenReady, |
| std::slice::from_ref(yielded), |
| ); |
| let yield_expr = self.arena.alloc( |
| self.expr(span, hir::ExprKind::Yield(wrapped_yielded, hir::YieldSource::Yield)), |
| ); |
| |
| let Some(task_context_hid) = self.task_context else { |
| unreachable!("use of `await` outside of an async context."); |
| }; |
| let task_context_ident = Ident::with_dummy_span(sym::_task_context); |
| let lhs = self.expr_ident(span, task_context_ident, task_context_hid); |
| |
| hir::ExprKind::Assign(lhs, yield_expr, self.lower_span(span)) |
| } else { |
| hir::ExprKind::Yield(yielded, hir::YieldSource::Yield) |
| } |
| } |
| |
| /// Desugar `ExprForLoop` from: `[opt_ident]: for <pat> in <head> <body>` into: |
| /// ```ignore (pseudo-rust) |
| /// { |
| /// let result = match IntoIterator::into_iter(<head>) { |
| /// mut iter => { |
| /// [opt_ident]: loop { |
| /// match Iterator::next(&mut iter) { |
| /// None => break, |
| /// Some(<pat>) => <body>, |
| /// }; |
| /// } |
| /// } |
| /// }; |
| /// result |
| /// } |
| /// ``` |
| fn lower_expr_for( |
| &mut self, |
| e: &Expr, |
| pat: &Pat, |
| head: &Expr, |
| body: &Block, |
| opt_label: Option<Label>, |
| loop_kind: ForLoopKind, |
| ) -> hir::Expr<'hir> { |
| let head = self.lower_expr_mut(head); |
| let pat = self.lower_pat(pat); |
| let for_span = |
| self.mark_span_with_reason(DesugaringKind::ForLoop, self.lower_span(e.span), None); |
| let head_span = self.mark_span_with_reason(DesugaringKind::ForLoop, head.span, None); |
| let pat_span = self.mark_span_with_reason(DesugaringKind::ForLoop, pat.span, None); |
| |
| let loop_hir_id = self.lower_node_id(e.id); |
| let label = self.lower_label(opt_label, e.id, loop_hir_id); |
| |
| // `None => break` |
| let none_arm = { |
| let break_expr = |
| self.with_loop_scope(loop_hir_id, |this| this.expr_break_alloc(for_span)); |
| let pat = self.pat_none(for_span); |
| self.arm(pat, break_expr) |
| }; |
| |
| // Some(<pat>) => <body>, |
| let some_arm = { |
| let some_pat = self.pat_some(pat_span, pat); |
| let body_block = |
| self.with_loop_scope(loop_hir_id, |this| this.lower_block(body, false)); |
| let body_expr = self.arena.alloc(self.expr_block(body_block)); |
| self.arm(some_pat, body_expr) |
| }; |
| |
| // `mut iter` |
| let iter = Ident::with_dummy_span(sym::iter); |
| let (iter_pat, iter_pat_nid) = |
| self.pat_ident_binding_mode(head_span, iter, hir::BindingMode::MUT); |
| |
| let match_expr = { |
| let iter = self.expr_ident(head_span, iter, iter_pat_nid); |
| let next_expr = match loop_kind { |
| ForLoopKind::For => { |
| // `Iterator::next(&mut iter)` |
| let ref_mut_iter = self.expr_mut_addr_of(head_span, iter); |
| self.expr_call_lang_item_fn( |
| head_span, |
| hir::LangItem::IteratorNext, |
| arena_vec![self; ref_mut_iter], |
| ) |
| } |
| ForLoopKind::ForAwait => { |
| // we'll generate `unsafe { Pin::new_unchecked(&mut iter) })` and then pass this |
| // to make_lowered_await with `FutureKind::AsyncIterator` which will generator |
| // calls to `poll_next`. In user code, this would probably be a call to |
| // `Pin::as_mut` but here it's easy enough to do `new_unchecked`. |
| |
| // `&mut iter` |
| let iter = self.expr_mut_addr_of(head_span, iter); |
| // `Pin::new_unchecked(...)` |
| let iter = self.arena.alloc(self.expr_call_lang_item_fn_mut( |
| head_span, |
| hir::LangItem::PinNewUnchecked, |
| arena_vec![self; iter], |
| )); |
| // `unsafe { ... }` |
| let iter = self.arena.alloc(self.expr_unsafe(iter)); |
| let kind = self.make_lowered_await(head_span, iter, FutureKind::AsyncIterator); |
| self.arena.alloc(hir::Expr { hir_id: self.next_id(), kind, span: head_span }) |
| } |
| }; |
| let arms = arena_vec![self; none_arm, some_arm]; |
| |
| // `match $next_expr { ... }` |
| self.expr_match(head_span, next_expr, arms, hir::MatchSource::ForLoopDesugar) |
| }; |
| let match_stmt = self.stmt_expr(for_span, match_expr); |
| |
| let loop_block = self.block_all(for_span, arena_vec![self; match_stmt], None); |
| |
| // `[opt_ident]: loop { ... }` |
| let kind = hir::ExprKind::Loop( |
| loop_block, |
| label, |
| hir::LoopSource::ForLoop, |
| self.lower_span(for_span.with_hi(head.span.hi())), |
| ); |
| let loop_expr = self.arena.alloc(hir::Expr { hir_id: loop_hir_id, kind, span: for_span }); |
| |
| // `mut iter => { ... }` |
| let iter_arm = self.arm(iter_pat, loop_expr); |
| |
| let match_expr = match loop_kind { |
| ForLoopKind::For => { |
| // `::std::iter::IntoIterator::into_iter(<head>)` |
| let into_iter_expr = self.expr_call_lang_item_fn( |
| head_span, |
| hir::LangItem::IntoIterIntoIter, |
| arena_vec![self; head], |
| ); |
| |
| self.arena.alloc(self.expr_match( |
| for_span, |
| into_iter_expr, |
| arena_vec![self; iter_arm], |
| hir::MatchSource::ForLoopDesugar, |
| )) |
| } |
| // `match into_async_iter(<head>) { ref mut iter => match unsafe { Pin::new_unchecked(iter) } { ... } }` |
| ForLoopKind::ForAwait => { |
| let iter_ident = iter; |
| let (async_iter_pat, async_iter_pat_id) = |
| self.pat_ident_binding_mode(head_span, iter_ident, hir::BindingMode::REF_MUT); |
| let iter = self.expr_ident_mut(head_span, iter_ident, async_iter_pat_id); |
| // `Pin::new_unchecked(...)` |
| let iter = self.arena.alloc(self.expr_call_lang_item_fn_mut( |
| head_span, |
| hir::LangItem::PinNewUnchecked, |
| arena_vec![self; iter], |
| )); |
| // `unsafe { ... }` |
| let iter = self.arena.alloc(self.expr_unsafe(iter)); |
| let inner_match_expr = self.arena.alloc(self.expr_match( |
| for_span, |
| iter, |
| arena_vec![self; iter_arm], |
| hir::MatchSource::ForLoopDesugar, |
| )); |
| |
| // `::core::async_iter::IntoAsyncIterator::into_async_iter(<head>)` |
| let iter = self.expr_call_lang_item_fn( |
| head_span, |
| hir::LangItem::IntoAsyncIterIntoIter, |
| arena_vec![self; head], |
| ); |
| let iter_arm = self.arm(async_iter_pat, inner_match_expr); |
| self.arena.alloc(self.expr_match( |
| for_span, |
| iter, |
| arena_vec![self; iter_arm], |
| hir::MatchSource::ForLoopDesugar, |
| )) |
| } |
| }; |
| |
| // 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. |
| let expr = self.expr_drop_temps_mut(for_span, match_expr); |
| self.lower_attrs(expr.hir_id, &e.attrs); |
| expr |
| } |
| |
| /// Desugar `ExprKind::Try` from: `<expr>?` into: |
| /// ```ignore (pseudo-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, |
| Some(Lrc::clone(&self.allow_try_trait)), |
| ); |
| let try_span = self.tcx.sess.source_map().end_point(span); |
| let try_span = self.mark_span_with_reason( |
| DesugaringKind::QuestionMark, |
| try_span, |
| Some(Lrc::clone(&self.allow_try_trait)), |
| ); |
| |
| // `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 = attr::mk_attr_nested_word( |
| &self.tcx.sess.psess.attr_id_generator, |
| AttrStyle::Outer, |
| Safety::Default, |
| sym::allow, |
| sym::unreachable_code, |
| try_span, |
| ); |
| let attrs: AttrVec = thin_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.expr_ident(span, val_ident, val_pat_nid); |
| self.lower_attrs(val_expr.hir_id, &attrs); |
| 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 ret_expr = if let Some(catch_id) = self.catch_scope { |
| let target_id = Ok(catch_id); |
| self.arena.alloc(self.expr( |
| try_span, |
| hir::ExprKind::Break( |
| hir::Destination { label: None, target_id }, |
| Some(from_residual_expr), |
| ), |
| )) |
| } else { |
| self.arena.alloc(self.expr(try_span, hir::ExprKind::Ret(Some(from_residual_expr)))) |
| }; |
| self.lower_attrs(ret_expr.hir_id, &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(scrutinee.hir_id), |
| ) |
| } |
| |
| /// Desugar `ExprKind::Yeet` from: `do yeet <expr>` into: |
| /// ```ignore(illustrative) |
| /// // If there is an enclosing `try {...}`: |
| /// break 'catch_target FromResidual::from_residual(Yeet(residual)); |
| /// // Otherwise: |
| /// return FromResidual::from_residual(Yeet(residual)); |
| /// ``` |
| /// But to simplify this, there's a `from_yeet` lang item function which |
| /// handles the combined `FromResidual::from_residual(Yeet(residual))`. |
| fn lower_expr_yeet(&mut self, span: Span, sub_expr: Option<&Expr>) -> hir::ExprKind<'hir> { |
| // The expression (if present) or `()` otherwise. |
| let (yeeted_span, yeeted_expr) = if let Some(sub_expr) = sub_expr { |
| (sub_expr.span, self.lower_expr(sub_expr)) |
| } else { |
| (self.mark_span_with_reason(DesugaringKind::YeetExpr, span, None), self.expr_unit(span)) |
| }; |
| |
| let unstable_span = self.mark_span_with_reason( |
| DesugaringKind::YeetExpr, |
| span, |
| Some(Lrc::clone(&self.allow_try_trait)), |
| ); |
| |
| let from_yeet_expr = self.wrap_in_try_constructor( |
| hir::LangItem::TryTraitFromYeet, |
| unstable_span, |
| yeeted_expr, |
| yeeted_span, |
| ); |
| |
| if let Some(catch_id) = self.catch_scope { |
| let target_id = Ok(catch_id); |
| hir::ExprKind::Break(hir::Destination { label: None, target_id }, Some(from_yeet_expr)) |
| } else { |
| hir::ExprKind::Ret(Some(from_yeet_expr)) |
| } |
| } |
| |
| // ========================================================================= |
| // Helper methods for building HIR. |
| // ========================================================================= |
| |
| /// 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>, |
| ) -> &'hir hir::Expr<'hir> { |
| self.arena.alloc(self.expr_drop_temps_mut(span, expr)) |
| } |
| |
| pub(super) fn expr_drop_temps_mut( |
| &mut self, |
| span: Span, |
| expr: &'hir hir::Expr<'hir>, |
| ) -> hir::Expr<'hir> { |
| self.expr(span, hir::ExprKind::DropTemps(expr)) |
| } |
| |
| pub(super) 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)) |
| } |
| |
| fn expr_break(&mut self, span: Span) -> hir::Expr<'hir> { |
| let expr_break = hir::ExprKind::Break(self.lower_loop_destination(None), None); |
| self.expr(span, expr_break) |
| } |
| |
| fn expr_break_alloc(&mut self, span: Span) -> &'hir hir::Expr<'hir> { |
| let expr_break = self.expr_break(span); |
| self.arena.alloc(expr_break) |
| } |
| |
| 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)) |
| } |
| |
| fn expr_unit(&mut self, sp: Span) -> &'hir hir::Expr<'hir> { |
| self.arena.alloc(self.expr(sp, hir::ExprKind::Tup(&[]))) |
| } |
| |
| pub(super) fn expr_usize(&mut self, sp: Span, value: usize) -> hir::Expr<'hir> { |
| let lit = self.arena.alloc(hir::Lit { |
| span: sp, |
| node: ast::LitKind::Int( |
| (value as u128).into(), |
| ast::LitIntType::Unsigned(ast::UintTy::Usize), |
| ), |
| }); |
| self.expr(sp, hir::ExprKind::Lit(lit)) |
| } |
| |
| pub(super) fn expr_u32(&mut self, sp: Span, value: u32) -> hir::Expr<'hir> { |
| let lit = self.arena.alloc(hir::Lit { |
| span: sp, |
| node: ast::LitKind::Int( |
| u128::from(value).into(), |
| ast::LitIntType::Unsigned(ast::UintTy::U32), |
| ), |
| }); |
| self.expr(sp, hir::ExprKind::Lit(lit)) |
| } |
| |
| pub(super) fn expr_char(&mut self, sp: Span, value: char) -> hir::Expr<'hir> { |
| let lit = self.arena.alloc(hir::Lit { span: sp, node: ast::LitKind::Char(value) }); |
| self.expr(sp, hir::ExprKind::Lit(lit)) |
| } |
| |
| pub(super) fn expr_str(&mut self, sp: Span, value: Symbol) -> hir::Expr<'hir> { |
| let lit = self |
| .arena |
| .alloc(hir::Lit { span: sp, node: ast::LitKind::Str(value, ast::StrStyle::Cooked) }); |
| self.expr(sp, hir::ExprKind::Lit(lit)) |
| } |
| |
| pub(super) 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)) |
| } |
| |
| pub(super) 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)); |
| 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) -> hir::Expr<'hir> { |
| self.expr(span, hir::ExprKind::Path(hir::QPath::LangItem(lang_item, self.lower_span(span)))) |
| } |
| |
| /// `<LangItem>::name` |
| pub(super) fn expr_lang_item_type_relative( |
| &mut self, |
| span: Span, |
| lang_item: hir::LangItem, |
| name: Symbol, |
| ) -> hir::Expr<'hir> { |
| let qpath = self.make_lang_item_qpath(lang_item, self.lower_span(span), None); |
| let path = hir::ExprKind::Path(hir::QPath::TypeRelative( |
| self.arena.alloc(self.ty(span, hir::TyKind::Path(qpath))), |
| self.arena.alloc(hir::PathSegment::new( |
| Ident::new(name, span), |
| self.next_id(), |
| Res::Err, |
| )), |
| )); |
| self.expr(span, path) |
| } |
| |
| pub(super) fn expr_ident( |
| &mut self, |
| sp: Span, |
| ident: Ident, |
| binding: HirId, |
| ) -> &'hir hir::Expr<'hir> { |
| self.arena.alloc(self.expr_ident_mut(sp, ident, binding)) |
| } |
| |
| pub(super) fn expr_ident_mut( |
| &mut self, |
| span: Span, |
| ident: Ident, |
| binding: HirId, |
| ) -> hir::Expr<'hir> { |
| let hir_id = self.next_id(); |
| let res = Res::Local(binding); |
| let expr_path = hir::ExprKind::Path(hir::QPath::Resolved( |
| None, |
| self.arena.alloc(hir::Path { |
| span: self.lower_span(span), |
| res, |
| segments: arena_vec![self; hir::PathSegment::new(ident, hir_id, res)], |
| }), |
| )); |
| |
| self.expr(span, expr_path) |
| } |
| |
| 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: self.lower_span(span), |
| targeted_by_break: false, |
| }), |
| None, |
| ), |
| ) |
| } |
| |
| 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); |
| self.arena.alloc(expr) |
| } |
| |
| pub(super) fn expr_block(&mut self, b: &'hir hir::Block<'hir>) -> hir::Expr<'hir> { |
| self.expr(b.span, hir::ExprKind::Block(b, None)) |
| } |
| |
| pub(super) fn expr_array_ref( |
| &mut self, |
| span: Span, |
| elements: &'hir [hir::Expr<'hir>], |
| ) -> hir::Expr<'hir> { |
| let addrof = hir::ExprKind::AddrOf( |
| hir::BorrowKind::Ref, |
| hir::Mutability::Not, |
| self.arena.alloc(self.expr(span, hir::ExprKind::Array(elements))), |
| ); |
| self.expr(span, addrof) |
| } |
| |
| pub(super) fn expr(&mut self, span: Span, kind: hir::ExprKind<'hir>) -> hir::Expr<'hir> { |
| let hir_id = self.next_id(); |
| hir::Expr { hir_id, kind, span: self.lower_span(span) } |
| } |
| |
| pub(super) 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: self.lower_span(span), |
| expr, |
| is_shorthand: false, |
| } |
| } |
| |
| pub(super) 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: self.lower_span(expr.span), |
| body: expr, |
| } |
| } |
| } |
| |
| /// Used by [`LoweringContext::make_lowered_await`] to customize the desugaring based on what kind |
| /// of future we are awaiting. |
| #[derive(Copy, Clone, Debug, PartialEq, Eq)] |
| enum FutureKind { |
| /// We are awaiting a normal future |
| Future, |
| /// We are awaiting something that's known to be an AsyncIterator (i.e. we are in the header of |
| /// a `for await` loop) |
| AsyncIterator, |
| } |
