rust-lang/rust
1
0
Fork 0
Code Issues Pull Requests Actions 1 Packages Projects Releases Wiki Activity
Files
e0bd01167e86d07c03e8ddd2bb0a25f689a2a7f5
rust/compiler/rustc_ast_lowering/src/expr.rs
Noah Lev e0bd01167e Re-enable ConstArgKind::Path lowering by default 
...and remove the `const_arg_path` feature gate as a result. It was only
a stopgap measure to fix the regression that the new lowering introduced
(which should now be fixed by this PR).
2024-09-12 13:56:01 -04:00

2194 lines
87 KiB
Rust
Raw Blame History

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_hir as hir;
use rustc_hir::def::{DefKind, Res};
use rustc_hir::HirId;
use rustc_middle::span_bug;
use rustc_session::errors::report_lit_error;
use rustc_span::source_map::{respan, Spanned};
use rustc_span::symbol::{kw, sym, Ident, Symbol};
use rustc_span::{DesugaringKind, Span, DUMMY_SP};
use thin_vec::{thin_vec, ThinVec};
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::{fluent_generated, FnDeclKind, ImplTraitPosition};
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 hir_id = self.lower_node_id(e.id);
self.lower_attrs(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(bytes.clone(), 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(e.id, |this| {
let span = this.mark_span_with_reason(DesugaringKind::WhileLoop, e.span, None);
this.lower_expr_while_in_loop_scope(span, cond, body, *opt_label)
}),
ExprKind::Loop(body, opt_label, span) => self.with_loop_scope(e.id, |this| {
hir::ExprKind::Loop(
this.lower_block(body, false),
this.lower_label(*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,
hir_id,
*coroutine_kind,
fn_decl,
body,
*fn_decl_span,
*fn_arg_span,
),
None => self.lower_expr_closure(
binder,
*capture_clause,
e.id,
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) => {
let opt_label = self.lower_label(*opt_label);
hir::ExprKind::Block(self.lower_block(blk, opt_label.is_some()), 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,
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,
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, 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() {
// 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 $cond { ... }` does not
// let temporaries live outside of `cond`.
fn lower_expr_while_in_loop_scope(
&mut self,
span: Span,
cond: &Expr,
body: &Block,
opt_label: Option<Label>,
) -> hir::ExprKind<'hir> {
let lowered_cond = self.with_loop_condition_scope(|t| t.lower_cond(cond));
let then = self.lower_block_expr(body);
let expr_break = self.expr_break(span);
let stmt_break = self.stmt_expr(span, expr_break);
let else_blk = self.block_all(span, arena_vec![self; stmt_break], None);
let else_expr = self.arena.alloc(self.expr_block(else_blk));
let if_kind = hir::ExprKind::If(lowered_cond, self.arena.alloc(then), Some(else_expr));
let if_expr = self.expr(span, if_kind);
let block = self.block_expr(self.arena.alloc(if_expr));
let span = self.lower_span(span.with_hi(cond.span.hi()));
let opt_label = self.lower_label(opt_label);
hir::ExprKind::Loop(block, opt_label, hir::LoopSource::While, span)
}
/// Desugar `try { <stmts>; <expr> }` into `{ <stmts>; ::std::ops::Try::from_output(<expr>) }`,
/// `try { <stmts>; }` into `{ <stmts>; ::std::ops::Try::from_output(()) }`
/// and save the block id to use it as a break target for desugaring of the `?` operator.
fn lower_expr_try_block(&mut self, body: &Block) -> hir::ExprKind<'hir> {
self.with_catch_scope(body.id, |this| {
let mut block = this.lower_block_noalloc(body, true);
// Final expression of the block (if present) or `()` with span at the end of block
let (try_span, tail_expr) = if let Some(expr) = block.expr.take() {
(
this.mark_span_with_reason(
DesugaringKind::TryBlock,
expr.span,
Some(this.allow_try_trait.clone()),
),
expr,
)
} else {
let try_span = this.mark_span_with_reason(
DesugaringKind::TryBlock,
this.tcx.sess.source_map().end_point(body.span),
Some(this.allow_try_trait.clone()),
);
(try_span, this.expr_unit(try_span))
};
let ok_wrapped_span =
this.mark_span_with_reason(DesugaringKind::TryBlock, tail_expr.span, None);
// `::std::ops::Try::from_output($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>>,
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(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.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(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 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,
);
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: 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,
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,
}
}
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);
// `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 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(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,
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_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,
}
Reference in New Issue View Git Blame Copy Permalink