2160 lines
85 KiB
Rust
2160 lines
85 KiB
Rust
use std::assert_matches::assert_matches;
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use super::errors::{
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AsyncCoroutinesNotSupported, AwaitOnlyInAsyncFnAndBlocks, BaseExpressionDoubleDot,
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ClosureCannotBeStatic, CoroutineTooManyParameters,
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FunctionalRecordUpdateDestructuringAssignment, InclusiveRangeWithNoEnd, MatchArmWithNoBody,
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NeverPatternWithBody, NeverPatternWithGuard, UnderscoreExprLhsAssign,
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};
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use super::ResolverAstLoweringExt;
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use super::{ImplTraitContext, LoweringContext, ParamMode, ParenthesizedGenericArgs};
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use crate::errors::YieldInClosure;
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use crate::{FnDeclKind, ImplTraitPosition};
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use rustc_ast::ptr::P as AstP;
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use rustc_ast::*;
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use rustc_data_structures::stack::ensure_sufficient_stack;
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use rustc_hir as hir;
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use rustc_hir::def::{DefKind, Res};
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use rustc_hir::HirId;
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use rustc_middle::span_bug;
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use rustc_session::errors::report_lit_error;
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use rustc_span::source_map::{respan, Spanned};
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use rustc_span::symbol::{kw, sym, Ident, Symbol};
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use rustc_span::DUMMY_SP;
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use rustc_span::{DesugaringKind, Span};
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use thin_vec::{thin_vec, ThinVec};
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impl<'hir> LoweringContext<'_, 'hir> {
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fn lower_exprs(&mut self, exprs: &[AstP<Expr>]) -> &'hir [hir::Expr<'hir>] {
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self.arena.alloc_from_iter(exprs.iter().map(|x| self.lower_expr_mut(x)))
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}
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pub(super) fn lower_expr(&mut self, e: &Expr) -> &'hir hir::Expr<'hir> {
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self.arena.alloc(self.lower_expr_mut(e))
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}
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pub(super) fn lower_expr_mut(&mut self, e: &Expr) -> hir::Expr<'hir> {
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ensure_sufficient_stack(|| {
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match &e.kind {
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// Parenthesis expression does not have a HirId and is handled specially.
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ExprKind::Paren(ex) => {
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let mut ex = self.lower_expr_mut(ex);
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// Include parens in span, but only if it is a super-span.
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if e.span.contains(ex.span) {
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ex.span = self.lower_span(e.span);
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}
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// Merge attributes into the inner expression.
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if !e.attrs.is_empty() {
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let old_attrs = self.attrs.get(&ex.hir_id.local_id).copied().unwrap_or(&[]);
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self.attrs.insert(
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ex.hir_id.local_id,
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&*self.arena.alloc_from_iter(
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e.attrs
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.iter()
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.map(|a| self.lower_attr(a))
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.chain(old_attrs.iter().cloned()),
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),
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);
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}
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return ex;
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}
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// Desugar `ExprForLoop`
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// from: `[opt_ident]: for await? <pat> in <iter> <body>`
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//
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// This also needs special handling because the HirId of the returned `hir::Expr` will not
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// correspond to the `e.id`, so `lower_expr_for` handles attribute lowering itself.
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ExprKind::ForLoop { pat, iter, body, label, kind } => {
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return self.lower_expr_for(e, pat, iter, body, *label, *kind);
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}
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_ => (),
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}
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let hir_id = self.lower_node_id(e.id);
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self.lower_attrs(hir_id, &e.attrs);
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let kind = match &e.kind {
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ExprKind::Array(exprs) => hir::ExprKind::Array(self.lower_exprs(exprs)),
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ExprKind::ConstBlock(c) => {
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self.has_inline_consts = true;
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hir::ExprKind::ConstBlock(self.lower_expr(c))
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}
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ExprKind::Repeat(expr, count) => {
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let expr = self.lower_expr(expr);
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let count = self.lower_array_length(count);
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hir::ExprKind::Repeat(expr, count)
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}
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ExprKind::Tup(elts) => hir::ExprKind::Tup(self.lower_exprs(elts)),
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ExprKind::Call(f, args) => {
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if let Some(legacy_args) = self.resolver.legacy_const_generic_args(f) {
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self.lower_legacy_const_generics((**f).clone(), args.clone(), &legacy_args)
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} else {
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let f = self.lower_expr(f);
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hir::ExprKind::Call(f, self.lower_exprs(args))
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}
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}
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ExprKind::MethodCall(box MethodCall { seg, receiver, args, span }) => {
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let hir_seg = self.arena.alloc(self.lower_path_segment(
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e.span,
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seg,
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ParamMode::Optional,
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ParenthesizedGenericArgs::Err,
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ImplTraitContext::Disallowed(ImplTraitPosition::Path),
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None,
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// Method calls can't have bound modifiers
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None,
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));
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let receiver = self.lower_expr(receiver);
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let args =
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self.arena.alloc_from_iter(args.iter().map(|x| self.lower_expr_mut(x)));
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hir::ExprKind::MethodCall(hir_seg, receiver, args, self.lower_span(*span))
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}
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ExprKind::Binary(binop, lhs, rhs) => {
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let binop = self.lower_binop(*binop);
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let lhs = self.lower_expr(lhs);
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let rhs = self.lower_expr(rhs);
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hir::ExprKind::Binary(binop, lhs, rhs)
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}
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ExprKind::Unary(op, ohs) => {
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let op = self.lower_unop(*op);
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let ohs = self.lower_expr(ohs);
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hir::ExprKind::Unary(op, ohs)
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}
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ExprKind::Lit(token_lit) => {
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let lit_kind = match LitKind::from_token_lit(*token_lit) {
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Ok(lit_kind) => lit_kind,
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Err(err) => {
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let guar =
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report_lit_error(&self.tcx.sess.psess, err, *token_lit, e.span);
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LitKind::Err(guar)
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}
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};
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let lit = self.arena.alloc(respan(self.lower_span(e.span), lit_kind));
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hir::ExprKind::Lit(lit)
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}
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ExprKind::IncludedBytes(bytes) => {
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let lit = self.arena.alloc(respan(
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self.lower_span(e.span),
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LitKind::ByteStr(bytes.clone(), StrStyle::Cooked),
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));
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hir::ExprKind::Lit(lit)
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}
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ExprKind::Cast(expr, ty) => {
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let expr = self.lower_expr(expr);
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let ty =
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self.lower_ty(ty, ImplTraitContext::Disallowed(ImplTraitPosition::Cast));
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hir::ExprKind::Cast(expr, ty)
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}
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ExprKind::Type(expr, ty) => {
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let expr = self.lower_expr(expr);
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let ty =
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self.lower_ty(ty, ImplTraitContext::Disallowed(ImplTraitPosition::Cast));
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hir::ExprKind::Type(expr, ty)
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}
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ExprKind::AddrOf(k, m, ohs) => {
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let ohs = self.lower_expr(ohs);
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hir::ExprKind::AddrOf(*k, *m, ohs)
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}
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ExprKind::Let(pat, scrutinee, span, recovered) => {
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hir::ExprKind::Let(self.arena.alloc(hir::LetExpr {
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span: self.lower_span(*span),
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pat: self.lower_pat(pat),
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ty: None,
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init: self.lower_expr(scrutinee),
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recovered: *recovered,
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}))
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}
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ExprKind::If(cond, then, else_opt) => {
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self.lower_expr_if(cond, then, else_opt.as_deref())
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}
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ExprKind::While(cond, body, opt_label) => self.with_loop_scope(e.id, |this| {
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let span = this.mark_span_with_reason(DesugaringKind::WhileLoop, e.span, None);
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this.lower_expr_while_in_loop_scope(span, cond, body, *opt_label)
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}),
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ExprKind::Loop(body, opt_label, span) => self.with_loop_scope(e.id, |this| {
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hir::ExprKind::Loop(
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this.lower_block(body, false),
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this.lower_label(*opt_label),
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hir::LoopSource::Loop,
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this.lower_span(*span),
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)
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}),
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ExprKind::TryBlock(body) => self.lower_expr_try_block(body),
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ExprKind::Match(expr, arms, kind) => hir::ExprKind::Match(
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self.lower_expr(expr),
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self.arena.alloc_from_iter(arms.iter().map(|x| self.lower_arm(x))),
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match kind {
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MatchKind::Prefix => hir::MatchSource::Normal,
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MatchKind::Postfix => hir::MatchSource::Postfix,
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},
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),
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ExprKind::Await(expr, await_kw_span) => self.lower_expr_await(*await_kw_span, expr),
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ExprKind::Closure(box Closure {
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binder,
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capture_clause,
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constness,
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coroutine_kind,
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movability,
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fn_decl,
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body,
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fn_decl_span,
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fn_arg_span,
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}) => match coroutine_kind {
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Some(coroutine_kind) => self.lower_expr_coroutine_closure(
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binder,
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*capture_clause,
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e.id,
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hir_id,
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*coroutine_kind,
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fn_decl,
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body,
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*fn_decl_span,
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*fn_arg_span,
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),
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None => self.lower_expr_closure(
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binder,
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*capture_clause,
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e.id,
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hir_id,
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*constness,
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*movability,
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fn_decl,
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body,
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*fn_decl_span,
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*fn_arg_span,
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),
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},
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ExprKind::Gen(capture_clause, block, genblock_kind) => {
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let desugaring_kind = match genblock_kind {
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GenBlockKind::Async => hir::CoroutineDesugaring::Async,
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GenBlockKind::Gen => hir::CoroutineDesugaring::Gen,
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GenBlockKind::AsyncGen => hir::CoroutineDesugaring::AsyncGen,
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};
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self.make_desugared_coroutine_expr(
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*capture_clause,
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e.id,
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None,
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e.span,
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desugaring_kind,
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hir::CoroutineSource::Block,
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|this| this.with_new_scopes(e.span, |this| this.lower_block_expr(block)),
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)
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}
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ExprKind::Block(blk, opt_label) => {
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let opt_label = self.lower_label(*opt_label);
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hir::ExprKind::Block(self.lower_block(blk, opt_label.is_some()), opt_label)
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}
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ExprKind::Assign(el, er, span) => self.lower_expr_assign(el, er, *span, e.span),
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ExprKind::AssignOp(op, el, er) => hir::ExprKind::AssignOp(
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self.lower_binop(*op),
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self.lower_expr(el),
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self.lower_expr(er),
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),
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ExprKind::Field(el, ident) => {
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hir::ExprKind::Field(self.lower_expr(el), self.lower_ident(*ident))
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}
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ExprKind::Index(el, er, brackets_span) => {
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hir::ExprKind::Index(self.lower_expr(el), self.lower_expr(er), *brackets_span)
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}
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ExprKind::Range(Some(e1), Some(e2), RangeLimits::Closed) => {
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self.lower_expr_range_closed(e.span, e1, e2)
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}
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ExprKind::Range(e1, e2, lims) => {
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self.lower_expr_range(e.span, e1.as_deref(), e2.as_deref(), *lims)
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}
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ExprKind::Underscore => {
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let guar = self.dcx().emit_err(UnderscoreExprLhsAssign { span: e.span });
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hir::ExprKind::Err(guar)
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}
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ExprKind::Path(qself, path) => {
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let qpath = self.lower_qpath(
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e.id,
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qself,
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path,
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ParamMode::Optional,
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ImplTraitContext::Disallowed(ImplTraitPosition::Path),
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None,
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);
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hir::ExprKind::Path(qpath)
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}
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ExprKind::Break(opt_label, opt_expr) => {
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let opt_expr = opt_expr.as_ref().map(|x| self.lower_expr(x));
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hir::ExprKind::Break(self.lower_jump_destination(e.id, *opt_label), opt_expr)
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}
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ExprKind::Continue(opt_label) => {
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hir::ExprKind::Continue(self.lower_jump_destination(e.id, *opt_label))
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}
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ExprKind::Ret(e) => {
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let e = e.as_ref().map(|x| self.lower_expr(x));
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hir::ExprKind::Ret(e)
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}
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ExprKind::Yeet(sub_expr) => self.lower_expr_yeet(e.span, sub_expr.as_deref()),
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ExprKind::Become(sub_expr) => {
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let sub_expr = self.lower_expr(sub_expr);
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hir::ExprKind::Become(sub_expr)
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}
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ExprKind::InlineAsm(asm) => {
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hir::ExprKind::InlineAsm(self.lower_inline_asm(e.span, asm))
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}
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ExprKind::FormatArgs(fmt) => self.lower_format_args(e.span, fmt),
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ExprKind::OffsetOf(container, fields) => hir::ExprKind::OffsetOf(
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self.lower_ty(
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container,
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ImplTraitContext::Disallowed(ImplTraitPosition::OffsetOf),
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),
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self.arena.alloc_from_iter(fields.iter().map(|&ident| self.lower_ident(ident))),
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),
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ExprKind::Struct(se) => {
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let rest = match &se.rest {
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StructRest::Base(e) => Some(self.lower_expr(e)),
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StructRest::Rest(sp) => {
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let guar = self.dcx().emit_err(BaseExpressionDoubleDot { span: *sp });
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Some(&*self.arena.alloc(self.expr_err(*sp, guar)))
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}
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StructRest::None => None,
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};
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hir::ExprKind::Struct(
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self.arena.alloc(self.lower_qpath(
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e.id,
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&se.qself,
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&se.path,
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ParamMode::Optional,
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ImplTraitContext::Disallowed(ImplTraitPosition::Path),
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None,
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)),
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self.arena
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.alloc_from_iter(se.fields.iter().map(|x| self.lower_expr_field(x))),
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rest,
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)
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}
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ExprKind::Yield(opt_expr) => self.lower_expr_yield(e.span, opt_expr.as_deref()),
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ExprKind::Err(guar) => hir::ExprKind::Err(*guar),
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ExprKind::Dummy => {
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span_bug!(e.span, "lowered ExprKind::Dummy")
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}
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ExprKind::Try(sub_expr) => self.lower_expr_try(e.span, sub_expr),
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ExprKind::Paren(_) | ExprKind::ForLoop { .. } => {
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unreachable!("already handled")
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}
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ExprKind::MacCall(_) => panic!("{:?} shouldn't exist here", e.span),
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};
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hir::Expr { hir_id, kind, span: self.lower_span(e.span) }
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})
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}
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fn lower_unop(&mut self, u: UnOp) -> hir::UnOp {
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match u {
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UnOp::Deref => hir::UnOp::Deref,
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UnOp::Not => hir::UnOp::Not,
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UnOp::Neg => hir::UnOp::Neg,
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}
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}
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fn lower_binop(&mut self, b: BinOp) -> BinOp {
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Spanned { node: b.node, span: self.lower_span(b.span) }
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}
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fn lower_legacy_const_generics(
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&mut self,
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mut f: Expr,
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args: ThinVec<AstP<Expr>>,
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legacy_args_idx: &[usize],
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) -> hir::ExprKind<'hir> {
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let ExprKind::Path(None, path) = &mut f.kind else {
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unreachable!();
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};
|
|
|
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// Split the arguments into const generics and normal arguments
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|
let mut real_args = vec![];
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let mut generic_args = ThinVec::new();
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for (idx, arg) in args.into_iter().enumerate() {
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if legacy_args_idx.contains(&idx) {
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let parent_def_id = self.current_hir_id_owner;
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let node_id = self.next_node_id();
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// Add a definition for the in-band const def.
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self.create_def(
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|
parent_def_id.def_id,
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|
node_id,
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|
kw::Empty,
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|
DefKind::AnonConst,
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f.span,
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);
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let anon_const = AnonConst { id: node_id, value: arg };
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generic_args.push(AngleBracketedArg::Arg(GenericArg::Const(anon_const)));
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} else {
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real_args.push(arg);
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}
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}
|
|
|
|
// Add generic args to the last element of the path.
|
|
let last_segment = path.segments.last_mut().unwrap();
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|
assert!(last_segment.args.is_none());
|
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last_segment.args = Some(AstP(GenericArgs::AngleBracketed(AngleBracketedArgs {
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span: DUMMY_SP,
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args: generic_args,
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})));
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|
|
|
// Now lower everything as normal.
|
|
let f = self.lower_expr(&f);
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hir::ExprKind::Call(f, self.lower_exprs(&real_args))
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|
}
|
|
|
|
fn lower_expr_if(
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|
&mut self,
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|
cond: &Expr,
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|
then: &Block,
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|
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 {
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|
hir::ExprKind::If(
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|
lowered_cond,
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self.arena.alloc(then_expr),
|
|
Some(self.lower_expr(rslt)),
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)
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} else {
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|
hir::ExprKind::If(lowered_cond, self.arena.alloc(then_expr), None)
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}
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|
}
|
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|
|
// 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()));
|
|
let opt_label = self.lower_label(opt_label);
|
|
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> {
|
|
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,
|
|
Some(this.allow_try_trait.clone()),
|
|
),
|
|
expr,
|
|
)
|
|
} else {
|
|
let try_span = this.mark_span_with_reason(
|
|
DesugaringKind::TryBlock,
|
|
this.tcx.sess.source_map().end_point(body.span),
|
|
Some(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));
|
|
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>>,
|
|
span: Span,
|
|
desugaring_kind: hir::CoroutineDesugaring,
|
|
coroutine_source: hir::CoroutineSource,
|
|
body: impl FnOnce(&mut Self) -> hir::Expr<'hir>,
|
|
) -> hir::ExprKind<'hir> {
|
|
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(self.allow_gen_future.clone()),
|
|
);
|
|
let resume_ty = self.make_lang_item_qpath(hir::LangItem::ResumeTy, unstable_span);
|
|
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.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: self.local_def_id(closure_node_id),
|
|
binder: hir::ClosureBinder::Default,
|
|
capture_clause,
|
|
bound_generic_params: &[],
|
|
fn_decl,
|
|
body,
|
|
fn_decl_span: self.lower_span(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(self.allow_gen_future.clone()),
|
|
);
|
|
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(self.allow_for_await.clone()),
|
|
};
|
|
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(self.allow_gen_future.clone()),
|
|
);
|
|
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_node_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 (binder_clause, generic_params) = self.lower_closure_binder(binder);
|
|
|
|
let (body_id, closure_kind) = self.with_new_scopes(fn_decl_span, 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: self.local_def_id(closure_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 (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| {
|
|
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)),
|
|
body.span,
|
|
coroutine_kind,
|
|
hir::CoroutineSource::Closure,
|
|
);
|
|
|
|
let hir_id = this.lower_node_id(coroutine_kind.closure_id());
|
|
this.maybe_forward_track_caller(body.span, closure_hir_id, 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: self.local_def_id(closure_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,
|
|
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,
|
|
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,
|
|
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,
|
|
)
|
|
}
|
|
|
|
fn lower_label(&self, opt_label: Option<Label>) -> Option<Label> {
|
|
let label = opt_label?;
|
|
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) {
|
|
Ok(self.lower_node_id(loop_id))
|
|
} else {
|
|
Err(hir::LoopIdError::UnresolvedLabel)
|
|
}
|
|
}
|
|
None => self
|
|
.loop_scope
|
|
.map(|id| Ok(self.lower_node_id(id)))
|
|
.unwrap_or(Err(hir::LoopIdError::OutsideLoopScope)),
|
|
};
|
|
let label = self.lower_label(destination.map(|(_, label)| label));
|
|
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: NodeId, 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: 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 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,
|
|
}
|
|
}
|
|
|
|
#[allow(rustc::untranslatable_diagnostic)] // FIXME: make this translatable
|
|
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,
|
|
"yield syntax is experimental",
|
|
)
|
|
.emit();
|
|
}
|
|
false
|
|
}
|
|
None => {
|
|
if !self.tcx.features().coroutines {
|
|
rustc_session::parse::feature_err(
|
|
&self.tcx.sess,
|
|
sym::coroutines,
|
|
span,
|
|
"yield syntax is experimental",
|
|
)
|
|
.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);
|
|
|
|
// `None => break`
|
|
let none_arm = {
|
|
let break_expr = self.with_loop_scope(e.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(e.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,
|
|
self.lower_label(opt_label),
|
|
hir::LoopSource::ForLoop,
|
|
self.lower_span(for_span.with_hi(head.span.hi())),
|
|
);
|
|
let loop_expr =
|
|
self.arena.alloc(hir::Expr { hir_id: self.lower_node_id(e.id), kind, span: for_span });
|
|
|
|
// `mut iter => { ... }`
|
|
let iter_arm = self.arm(iter_pat, loop_expr);
|
|
|
|
let into_iter_expr = match loop_kind {
|
|
ForLoopKind::For => {
|
|
// `::std::iter::IntoIterator::into_iter(<head>)`
|
|
self.expr_call_lang_item_fn(
|
|
head_span,
|
|
hir::LangItem::IntoIterIntoIter,
|
|
arena_vec![self; head],
|
|
)
|
|
}
|
|
// ` unsafe { Pin::new_unchecked(&mut into_async_iter(<head>)) }`
|
|
ForLoopKind::ForAwait => {
|
|
// `::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 = 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));
|
|
iter
|
|
}
|
|
};
|
|
|
|
let match_expr = self.arena.alloc(self.expr_match(
|
|
for_span,
|
|
into_iter_expr,
|
|
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(self.allow_try_trait.clone()),
|
|
);
|
|
let try_span = self.tcx.sess.source_map().end_point(span);
|
|
let try_span = self.mark_span_with_reason(
|
|
DesugaringKind::QuestionMark,
|
|
try_span,
|
|
Some(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 = attr::mk_attr_nested_word(
|
|
&self.tcx.sess.psess.attr_id_generator,
|
|
AttrStyle::Outer,
|
|
Unsafe::No,
|
|
sym::allow,
|
|
sym::unreachable_code,
|
|
self.lower_span(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_node) = self.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),
|
|
),
|
|
))
|
|
} 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(self.allow_try_trait.clone()),
|
|
);
|
|
|
|
let from_yeet_expr = self.wrap_in_try_constructor(
|
|
hir::LangItem::TryTraitFromYeet,
|
|
unstable_span,
|
|
yeeted_expr,
|
|
yeeted_span,
|
|
);
|
|
|
|
if let Some(catch_node) = self.catch_scope {
|
|
let target_id = Ok(self.lower_node_id(catch_node));
|
|
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));
|
|
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,
|
|
}
|