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use super::{LoweringContext, ParamMode, ParenthesizedGenericArgs, ImplTraitContext};
use crate::hir::{self, HirVec};
use crate::hir::def::Res;
use crate::hir::ptr::P;
use rustc_data_structures::thin_vec::ThinVec;
use syntax::attr;
use syntax::ptr::P as AstP;
use syntax::ast::*;
use syntax::source_map::{respan, DesugaringKind, Span, Spanned};
use syntax::symbol::{sym, Symbol};
impl LoweringContext<'_> {
fn lower_exprs(&mut self, exprs: &[AstP<Expr>]) -> HirVec<hir::Expr> {
exprs.iter().map(|x| self.lower_expr(x)).collect()
}
pub(super) fn lower_expr(&mut self, e: &Expr) -> hir::Expr {
let kind = match e.node {
ExprKind::Box(ref inner) => hir::ExprKind::Box(P(self.lower_expr(inner))),
ExprKind::Array(ref exprs) => hir::ExprKind::Array(self.lower_exprs(exprs)),
ExprKind::Repeat(ref expr, ref count) => {
let expr = P(self.lower_expr(expr));
let count = self.lower_anon_const(count);
hir::ExprKind::Repeat(expr, count)
}
ExprKind::Tup(ref elts) => hir::ExprKind::Tup(self.lower_exprs(elts)),
ExprKind::Call(ref f, ref args) => {
let f = P(self.lower_expr(f));
hir::ExprKind::Call(f, self.lower_exprs(args))
}
ExprKind::MethodCall(ref seg, ref args) => {
let hir_seg = P(self.lower_path_segment(
e.span,
seg,
ParamMode::Optional,
0,
ParenthesizedGenericArgs::Err,
ImplTraitContext::disallowed(),
None,
));
let args = self.lower_exprs(args);
hir::ExprKind::MethodCall(hir_seg, seg.ident.span, args)
}
ExprKind::Binary(binop, ref lhs, ref rhs) => {
let binop = self.lower_binop(binop);
let lhs = P(self.lower_expr(lhs));
let rhs = P(self.lower_expr(rhs));
hir::ExprKind::Binary(binop, lhs, rhs)
}
ExprKind::Unary(op, ref ohs) => {
let op = self.lower_unop(op);
let ohs = P(self.lower_expr(ohs));
hir::ExprKind::Unary(op, ohs)
}
ExprKind::Lit(ref l) => hir::ExprKind::Lit(respan(l.span, l.node.clone())),
ExprKind::Cast(ref expr, ref ty) => {
let expr = P(self.lower_expr(expr));
hir::ExprKind::Cast(expr, self.lower_ty(ty, ImplTraitContext::disallowed()))
}
ExprKind::Type(ref expr, ref ty) => {
let expr = P(self.lower_expr(expr));
hir::ExprKind::Type(expr, self.lower_ty(ty, ImplTraitContext::disallowed()))
}
ExprKind::AddrOf(m, ref ohs) => {
let m = self.lower_mutability(m);
let ohs = P(self.lower_expr(ohs));
hir::ExprKind::AddrOf(m, ohs)
}
ExprKind::Let(ref pat, ref scrutinee) => self.lower_expr_let(e.span, pat, scrutinee),
ExprKind::If(ref cond, ref then, ref else_opt) => {
self.lower_expr_if(e.span, cond, then, else_opt.as_deref())
}
ExprKind::While(ref cond, ref body, opt_label) => self.with_loop_scope(e.id, |this| {
this.lower_expr_while_in_loop_scope(e.span, cond, body, opt_label)
}),
ExprKind::Loop(ref body, opt_label) => self.with_loop_scope(e.id, |this| {
hir::ExprKind::Loop(
this.lower_block(body, false),
this.lower_label(opt_label),
hir::LoopSource::Loop,
)
}),
ExprKind::TryBlock(ref body) => self.lower_expr_try_block(body),
ExprKind::Match(ref expr, ref arms) => hir::ExprKind::Match(
P(self.lower_expr(expr)),
arms.iter().map(|x| self.lower_arm(x)).collect(),
hir::MatchSource::Normal,
),
ExprKind::Async(capture_clause, closure_node_id, ref block) => {
self.make_async_expr(capture_clause, closure_node_id, None, block.span, |this| {
this.with_new_scopes(|this| this.lower_block_expr(block))
})
}
ExprKind::Await(ref expr) => self.lower_expr_await(e.span, expr),
ExprKind::Closure(
capture_clause, asyncness, movability, ref decl, ref body, fn_decl_span
) => if let IsAsync::Async { closure_id, .. } = asyncness {
self.lower_expr_async_closure(capture_clause, closure_id, decl, body, fn_decl_span)
} else {
self.lower_expr_closure(capture_clause, movability, decl, body, fn_decl_span)
}
ExprKind::Block(ref blk, opt_label) => {
hir::ExprKind::Block(self.lower_block(blk,
opt_label.is_some()),
self.lower_label(opt_label))
}
ExprKind::Assign(ref el, ref er) => {
hir::ExprKind::Assign(P(self.lower_expr(el)), P(self.lower_expr(er)))
}
ExprKind::AssignOp(op, ref el, ref er) => hir::ExprKind::AssignOp(
self.lower_binop(op),
P(self.lower_expr(el)),
P(self.lower_expr(er)),
),
ExprKind::Field(ref el, ident) => hir::ExprKind::Field(P(self.lower_expr(el)), ident),
ExprKind::Index(ref el, ref er) => {
hir::ExprKind::Index(P(self.lower_expr(el)), P(self.lower_expr(er)))
}
ExprKind::Range(Some(ref e1), Some(ref e2), RangeLimits::Closed) => {
self.lower_expr_range_closed(e.span, e1, e2)
}
ExprKind::Range(ref e1, ref e2, lims) => {
self.lower_expr_range(e.span, e1.as_deref(), e2.as_deref(), lims)
}
ExprKind::Path(ref qself, ref path) => {
let qpath = self.lower_qpath(
e.id,
qself,
path,
ParamMode::Optional,
ImplTraitContext::disallowed(),
);
hir::ExprKind::Path(qpath)
}
ExprKind::Break(opt_label, ref opt_expr) => {
hir::ExprKind::Break(
self.lower_jump_destination(e.id, opt_label),
opt_expr.as_ref().map(|x| P(self.lower_expr(x))),
)
}
ExprKind::Continue(opt_label) => {
hir::ExprKind::Continue(self.lower_jump_destination(e.id, opt_label))
}
ExprKind::Ret(ref e) => hir::ExprKind::Ret(e.as_ref().map(|x| P(self.lower_expr(x)))),
ExprKind::InlineAsm(ref asm) => self.lower_expr_asm(asm),
ExprKind::Struct(ref path, ref fields, ref maybe_expr) => hir::ExprKind::Struct(
P(self.lower_qpath(
e.id,
&None,
path,
ParamMode::Optional,
ImplTraitContext::disallowed(),
)),
fields.iter().map(|x| self.lower_field(x)).collect(),
maybe_expr.as_ref().map(|x| P(self.lower_expr(x))),
),
ExprKind::Paren(ref ex) => {
let mut ex = self.lower_expr(ex);
// Include parens in span, but only if it is a super-span.
if e.span.contains(ex.span) {
ex.span = e.span;
}
// Merge attributes into the inner expression.
let mut attrs = e.attrs.clone();
attrs.extend::<Vec<_>>(ex.attrs.into());
ex.attrs = attrs;
return ex;
}
ExprKind::Yield(ref opt_expr) => self.lower_expr_yield(e.span, opt_expr.as_deref()),
ExprKind::Err => hir::ExprKind::Err,
// Desugar `ExprForLoop`
// from: `[opt_ident]: for <pat> in <head> <body>`
ExprKind::ForLoop(ref pat, ref head, ref body, opt_label) => {
return self.lower_expr_for(e, pat, head, body, opt_label);
}
ExprKind::Try(ref sub_expr) => self.lower_expr_try(e.span, sub_expr),
ExprKind::Mac(_) => panic!("Shouldn't exist here"),
};
hir::Expr {
hir_id: self.lower_node_id(e.id),
node: kind,
span: e.span,
attrs: e.attrs.clone(),
}
}
fn lower_unop(&mut self, u: UnOp) -> hir::UnOp {
match u {
UnOp::Deref => hir::UnDeref,
UnOp::Not => hir::UnNot,
UnOp::Neg => hir::UnNeg,
}
}
fn lower_binop(&mut self, b: BinOp) -> hir::BinOp {
Spanned {
node: match b.node {
BinOpKind::Add => hir::BinOpKind::Add,
BinOpKind::Sub => hir::BinOpKind::Sub,
BinOpKind::Mul => hir::BinOpKind::Mul,
BinOpKind::Div => hir::BinOpKind::Div,
BinOpKind::Rem => hir::BinOpKind::Rem,
BinOpKind::And => hir::BinOpKind::And,
BinOpKind::Or => hir::BinOpKind::Or,
BinOpKind::BitXor => hir::BinOpKind::BitXor,
BinOpKind::BitAnd => hir::BinOpKind::BitAnd,
BinOpKind::BitOr => hir::BinOpKind::BitOr,
BinOpKind::Shl => hir::BinOpKind::Shl,
BinOpKind::Shr => hir::BinOpKind::Shr,
BinOpKind::Eq => hir::BinOpKind::Eq,
BinOpKind::Lt => hir::BinOpKind::Lt,
BinOpKind::Le => hir::BinOpKind::Le,
BinOpKind::Ne => hir::BinOpKind::Ne,
BinOpKind::Ge => hir::BinOpKind::Ge,
BinOpKind::Gt => hir::BinOpKind::Gt,
},
span: b.span,
}
}
/// Emit an error and lower `ast::ExprKind::Let(pat, scrutinee)` into:
/// ```rust
/// match scrutinee { pats => true, _ => false }
/// ```
fn lower_expr_let(&mut self, span: Span, pat: &Pat, scrutinee: &Expr) -> hir::ExprKind {
// If we got here, the `let` expression is not allowed.
self.sess
.struct_span_err(span, "`let` expressions are not supported here")
.note("only supported directly in conditions of `if`- and `while`-expressions")
.note("as well as when nested within `&&` and parenthesis in those conditions")
.emit();
// For better recovery, we emit:
// ```
// match scrutinee { pat => true, _ => false }
// ```
// While this doesn't fully match the user's intent, it has key advantages:
// 1. We can avoid using `abort_if_errors`.
// 2. We can typeck both `pat` and `scrutinee`.
// 3. `pat` is allowed to be refutable.
// 4. The return type of the block is `bool` which seems like what the user wanted.
let scrutinee = self.lower_expr(scrutinee);
let then_arm = {
let pat = self.lower_pat_top_hack(pat);
let expr = self.expr_bool(span, true);
self.arm(pat, P(expr))
};
let else_arm = {
let pat = self.pat_wild(span);
let expr = self.expr_bool(span, false);
self.arm(hir_vec![pat], P(expr))
};
hir::ExprKind::Match(
P(scrutinee),
vec![then_arm, else_arm].into(),
hir::MatchSource::Normal,
)
}
fn lower_expr_if(
&mut self,
span: Span,
cond: &Expr,
then: &Block,
else_opt: Option<&Expr>,
) -> hir::ExprKind {
// FIXME(#53667): handle lowering of && and parens.
// `_ => else_block` where `else_block` is `{}` if there's `None`:
let else_pat = self.pat_wild(span);
let (else_expr, contains_else_clause) = match else_opt {
None => (self.expr_block_empty(span), false),
Some(els) => (self.lower_expr(els), true),
};
let else_arm = self.arm(hir_vec![else_pat], P(else_expr));
// Handle then + scrutinee:
let then_expr = self.lower_block_expr(then);
let (then_pat, scrutinee, desugar) = match cond.node {
// `<pat> => <then>`:
ExprKind::Let(ref pat, ref scrutinee) => {
let scrutinee = self.lower_expr(scrutinee);
let pat = self.lower_pat_top_hack(pat);
(pat, scrutinee, hir::MatchSource::IfLetDesugar { contains_else_clause })
}
// `true => <then>`:
_ => {
// Lower condition:
let cond = self.lower_expr(cond);
let span_block = self.mark_span_with_reason(
DesugaringKind::CondTemporary,
cond.span,
None
);
// Wrap in a construct equivalent to `{ let _t = $cond; _t }`
// to preserve drop semantics since `if cond { ... }` does not
// let temporaries live outside of `cond`.
let cond = self.expr_drop_temps(span_block, P(cond), ThinVec::new());
let pat = self.pat_bool(span, true);
(hir_vec![pat], cond, hir::MatchSource::IfDesugar { contains_else_clause })
}
};
let then_arm = self.arm(then_pat, P(then_expr));
hir::ExprKind::Match(P(scrutinee), vec![then_arm, else_arm].into(), desugar)
}
fn lower_expr_while_in_loop_scope(
&mut self,
span: Span,
cond: &Expr,
body: &Block,
opt_label: Option<Label>
) -> hir::ExprKind {
// FIXME(#53667): handle lowering of && and parens.
// Note that the block AND the condition are evaluated in the loop scope.
// This is done to allow `break` from inside the condition of the loop.
// `_ => break`:
let else_arm = {
let else_pat = self.pat_wild(span);
let else_expr = self.expr_break(span, ThinVec::new());
self.arm(hir_vec![else_pat], else_expr)
};
// Handle then + scrutinee:
let then_expr = self.lower_block_expr(body);
let (then_pat, scrutinee, desugar, source) = match cond.node {
ExprKind::Let(ref pat, ref scrutinee) => {
// to:
//
// [opt_ident]: loop {
// match <sub_expr> {
// <pat> => <body>,
// _ => break
// }
// }
let scrutinee = self.with_loop_condition_scope(|t| t.lower_expr(scrutinee));
let pat = self.lower_pat_top_hack(pat);
(pat, scrutinee, hir::MatchSource::WhileLetDesugar, hir::LoopSource::WhileLet)
}
_ => {
// We desugar: `'label: while $cond $body` into:
//
// ```
// 'label: loop {
// match drop-temps { $cond } {
// true => $body,
// _ => break,
// }
// }
// ```
// Lower condition:
let cond = self.with_loop_condition_scope(|this| this.lower_expr(cond));
let span_block = self.mark_span_with_reason(
DesugaringKind::CondTemporary,
cond.span,
None,
);
// Wrap in a construct equivalent to `{ let _t = $cond; _t }`
// to preserve drop semantics since `while cond { ... }` does not
// let temporaries live outside of `cond`.
let cond = self.expr_drop_temps(span_block, P(cond), ThinVec::new());
// `true => <then>`:
let pat = self.pat_bool(span, true);
(hir_vec![pat], cond, hir::MatchSource::WhileDesugar, hir::LoopSource::While)
}
};
let then_arm = self.arm(then_pat, P(then_expr));
// `match <scrutinee> { ... }`
let match_expr = self.expr_match(
scrutinee.span,
P(scrutinee),
hir_vec![then_arm, else_arm],
desugar,
);
// `[opt_ident]: loop { ... }`
hir::ExprKind::Loop(
P(self.block_expr(P(match_expr))),
self.lower_label(opt_label),
source
)
}
fn lower_expr_try_block(&mut self, body: &Block) -> hir::ExprKind {
self.with_catch_scope(body.id, |this| {
let unstable_span = this.mark_span_with_reason(
DesugaringKind::TryBlock,
body.span,
this.allow_try_trait.clone(),
);
let mut block = this.lower_block(body, true).into_inner();
let tail = block.expr.take().map_or_else(
|| this.expr_unit(this.sess.source_map().end_point(unstable_span)),
|x: P<hir::Expr>| x.into_inner(),
);
block.expr = Some(this.wrap_in_try_constructor(sym::from_ok, tail, unstable_span));
hir::ExprKind::Block(P(block), None)
})
}
fn wrap_in_try_constructor(
&mut self,
method: Symbol,
e: hir::Expr,
unstable_span: Span,
) -> P<hir::Expr> {
let path = &[sym::ops, sym::Try, method];
let from_err = P(self.expr_std_path(unstable_span, path, None, ThinVec::new()));
P(self.expr_call(e.span, from_err, hir_vec![e]))
}
fn lower_arm(&mut self, arm: &Arm) -> hir::Arm {
hir::Arm {
hir_id: self.next_id(),
attrs: self.lower_attrs(&arm.attrs),
pats: self.lower_pat_top_hack(&arm.pat),
guard: match arm.guard {
Some(ref x) => Some(hir::Guard::If(P(self.lower_expr(x)))),
_ => None,
},
body: P(self.lower_expr(&arm.body)),
span: arm.span,
}
}
/// HACK(or_patterns; Centril | dlrobertson): For now we don't push down top level or-patterns
/// `p | q` into `hir::PatKind::Or(...)` as post-lowering bits of the compiler are not ready
/// to deal with it. This should by fixed by pushing it down to HIR and then HAIR.
fn lower_pat_top_hack(&mut self, pat: &Pat) -> HirVec<P<hir::Pat>> {
match pat.node {
PatKind::Or(ref ps) => ps.iter().map(|x| self.lower_pat(x)).collect(),
_ => hir_vec![self.lower_pat(pat)],
}
}
pub(super) fn make_async_expr(
&mut self,
capture_clause: CaptureBy,
closure_node_id: NodeId,
ret_ty: Option<AstP<Ty>>,
span: Span,
body: impl FnOnce(&mut LoweringContext<'_>) -> hir::Expr,
) -> hir::ExprKind {
let capture_clause = self.lower_capture_clause(capture_clause);
let output = match ret_ty {
Some(ty) => FunctionRetTy::Ty(ty),
None => FunctionRetTy::Default(span),
};
let ast_decl = FnDecl {
inputs: vec![],
output,
c_variadic: false
};
let decl = self.lower_fn_decl(&ast_decl, None, /* impl trait allowed */ false, None);
let body_id = self.lower_fn_body(&ast_decl, |this| {
this.generator_kind = Some(hir::GeneratorKind::Async);
body(this)
});
// `static || -> <ret_ty> { body }`:
let generator_node = hir::ExprKind::Closure(
capture_clause,
decl,
body_id,
span,
Some(hir::GeneratorMovability::Static)
);
let generator = hir::Expr {
hir_id: self.lower_node_id(closure_node_id),
node: generator_node,
span,
attrs: ThinVec::new(),
};
// `future::from_generator`:
let unstable_span = self.mark_span_with_reason(
DesugaringKind::Async,
span,
self.allow_gen_future.clone(),
);
let gen_future = self.expr_std_path(
unstable_span,
&[sym::future, sym::from_generator],
None,
ThinVec::new()
);
// `future::from_generator(generator)`:
hir::ExprKind::Call(P(gen_future), hir_vec![generator])
}
/// Desugar `<expr>.await` into:
/// ```rust
/// match <expr> {
/// mut pinned => loop {
/// match ::std::future::poll_with_tls_context(unsafe {
/// <::std::pin::Pin>::new_unchecked(&mut pinned)
/// }) {
/// ::std::task::Poll::Ready(result) => break result,
/// ::std::task::Poll::Pending => {}
/// }
/// yield ();
/// }
/// }
/// ```
fn lower_expr_await(&mut self, await_span: Span, expr: &Expr) -> hir::ExprKind {
match self.generator_kind {
Some(hir::GeneratorKind::Async) => {},
Some(hir::GeneratorKind::Gen) |
None => {
let mut err = struct_span_err!(
self.sess,
await_span,
E0728,
"`await` is only allowed inside `async` functions and blocks"
);
err.span_label(await_span, "only allowed inside `async` functions and blocks");
if let Some(item_sp) = self.current_item {
err.span_label(item_sp, "this is not `async`");
}
err.emit();
}
}
let span = self.mark_span_with_reason(
DesugaringKind::Await,
await_span,
None,
);
let gen_future_span = self.mark_span_with_reason(
DesugaringKind::Await,
await_span,
self.allow_gen_future.clone(),
);
let pinned_ident = Ident::with_dummy_span(sym::pinned);
let (pinned_pat, pinned_pat_hid) = self.pat_ident_binding_mode(
span,
pinned_ident,
hir::BindingAnnotation::Mutable,
);
// ::std::future::poll_with_tls_context(unsafe {
// ::std::pin::Pin::new_unchecked(&mut pinned)
// })`
let poll_expr = {
let pinned = P(self.expr_ident(span, pinned_ident, pinned_pat_hid));
let ref_mut_pinned = self.expr_mut_addr_of(span, pinned);
let pin_ty_id = self.next_id();
let new_unchecked_expr_kind = self.expr_call_std_assoc_fn(
pin_ty_id,
span,
&[sym::pin, sym::Pin],
"new_unchecked",
hir_vec![ref_mut_pinned],
);
let new_unchecked = P(self.expr(span, new_unchecked_expr_kind, ThinVec::new()));
let unsafe_expr = self.expr_unsafe(new_unchecked);
P(self.expr_call_std_path(
gen_future_span,
&[sym::future, sym::poll_with_tls_context],
hir_vec![unsafe_expr],
))
};
// `::std::task::Poll::Ready(result) => break result`
let loop_node_id = self.sess.next_node_id();
let loop_hir_id = self.lower_node_id(loop_node_id);
let ready_arm = {
let x_ident = Ident::with_dummy_span(sym::result);
let (x_pat, x_pat_hid) = self.pat_ident(span, x_ident);
let x_expr = P(self.expr_ident(span, x_ident, x_pat_hid));
let ready_pat = self.pat_std_enum(
span,
&[sym::task, sym::Poll, sym::Ready],
hir_vec![x_pat],
);
let break_x = self.with_loop_scope(loop_node_id, |this| {
let expr_break = hir::ExprKind::Break(
this.lower_loop_destination(None),
Some(x_expr),
);
P(this.expr(await_span, expr_break, ThinVec::new()))
});
self.arm(hir_vec![ready_pat], break_x)
};
// `::std::task::Poll::Pending => {}`
let pending_arm = {
let pending_pat = self.pat_std_enum(
span,
&[sym::task, sym::Poll, sym::Pending],
hir_vec![],
);
let empty_block = P(self.expr_block_empty(span));
self.arm(hir_vec![pending_pat], empty_block)
};
let inner_match_stmt = {
let match_expr = self.expr_match(
span,
poll_expr,
hir_vec![ready_arm, pending_arm],
hir::MatchSource::AwaitDesugar,
);
self.stmt_expr(span, match_expr)
};
let yield_stmt = {
let unit = self.expr_unit(span);
let yield_expr = self.expr(
span,
hir::ExprKind::Yield(P(unit), hir::YieldSource::Await),
ThinVec::new(),
);
self.stmt_expr(span, yield_expr)
};
let loop_block = P(self.block_all(
span,
hir_vec![inner_match_stmt, yield_stmt],
None,
));
// loop { .. }
let loop_expr = P(hir::Expr {
hir_id: loop_hir_id,
node: hir::ExprKind::Loop(
loop_block,
None,
hir::LoopSource::Loop,
),
span,
attrs: ThinVec::new(),
});
// mut pinned => loop { ... }
let pinned_arm = self.arm(hir_vec![pinned_pat], loop_expr);
// match <expr> {
// mut pinned => loop { .. }
// }
let expr = P(self.lower_expr(expr));
hir::ExprKind::Match(expr, hir_vec![pinned_arm], hir::MatchSource::AwaitDesugar)
}
fn lower_expr_closure(
&mut self,
capture_clause: CaptureBy,
movability: Movability,
decl: &FnDecl,
body: &Expr,
fn_decl_span: Span,
) -> hir::ExprKind {
// Lower outside new scope to preserve `is_in_loop_condition`.
let fn_decl = self.lower_fn_decl(decl, None, false, None);
self.with_new_scopes(|this| {
let prev = this.current_item;
this.current_item = Some(fn_decl_span);
let mut generator_kind = None;
let body_id = this.lower_fn_body(decl, |this| {
let e = this.lower_expr(body);
generator_kind = this.generator_kind;
e
});
let generator_option = this.generator_movability_for_fn(
&decl,
fn_decl_span,
generator_kind,
movability,
);
let capture_clause = this.lower_capture_clause(capture_clause);
this.current_item = prev;
hir::ExprKind::Closure(
capture_clause,
fn_decl,
body_id,
fn_decl_span,
generator_option,
)
})
}
fn lower_capture_clause(&mut self, c: CaptureBy) -> hir::CaptureClause {
match c {
CaptureBy::Value => hir::CaptureByValue,
CaptureBy::Ref => hir::CaptureByRef,
}
}
fn generator_movability_for_fn(
&mut self,
decl: &FnDecl,
fn_decl_span: Span,
generator_kind: Option<hir::GeneratorKind>,
movability: Movability,
) -> Option<hir::GeneratorMovability> {
match generator_kind {
Some(hir::GeneratorKind::Gen) => {
if !decl.inputs.is_empty() {
span_err!(
self.sess,
fn_decl_span,
E0628,
"generators cannot have explicit parameters"
);
self.sess.abort_if_errors();
}
Some(match movability {
Movability::Movable => hir::GeneratorMovability::Movable,
Movability::Static => hir::GeneratorMovability::Static,
})
},
Some(hir::GeneratorKind::Async) => {
bug!("non-`async` closure body turned `async` during lowering");
},
None => {
if movability == Movability::Static {
span_err!(
self.sess,
fn_decl_span,
E0697,
"closures cannot be static"
);
}
None
},
}
}
fn lower_expr_async_closure(
&mut self,
capture_clause: CaptureBy,
closure_id: NodeId,
decl: &FnDecl,
body: &Expr,
fn_decl_span: Span,
) -> hir::ExprKind {
let outer_decl = FnDecl {
inputs: decl.inputs.clone(),
output: FunctionRetTy::Default(fn_decl_span),
c_variadic: false,
};
// We need to lower the declaration outside the new scope, because we
// have to conserve the state of being inside a loop condition for the
// closure argument types.
let fn_decl = self.lower_fn_decl(&outer_decl, None, false, None);
self.with_new_scopes(|this| {
// FIXME(cramertj): allow `async` non-`move` closures with arguments.
if capture_clause == CaptureBy::Ref && !decl.inputs.is_empty() {
struct_span_err!(
this.sess,
fn_decl_span,
E0708,
"`async` non-`move` closures with parameters are not currently supported",
)
.help(
"consider using `let` statements to manually capture \
variables by reference before entering an `async move` closure"
)
.emit();
}
// Transform `async |x: u8| -> X { ... }` into
// `|x: u8| future_from_generator(|| -> X { ... })`.
let body_id = this.lower_fn_body(&outer_decl, |this| {
let async_ret_ty = if let FunctionRetTy::Ty(ty) = &decl.output {
Some(ty.clone())
} else {
None
};
let async_body = this.make_async_expr(
capture_clause, closure_id, async_ret_ty, body.span,
|this| {
this.with_new_scopes(|this| this.lower_expr(body))
}
);
this.expr(fn_decl_span, async_body, ThinVec::new())
});
hir::ExprKind::Closure(
this.lower_capture_clause(capture_clause),
fn_decl,
body_id,
fn_decl_span,
None,
)
})
}
/// 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 {
let id = self.next_id();
let e1 = self.lower_expr(e1);
let e2 = self.lower_expr(e2);
self.expr_call_std_assoc_fn(
id,
span,
&[sym::ops, sym::RangeInclusive],
"new",
hir_vec![e1, e2],
)
}
fn lower_expr_range(
&mut self,
span: Span,
e1: Option<&Expr>,
e2: Option<&Expr>,
lims: RangeLimits,
) -> hir::ExprKind {
use syntax::ast::RangeLimits::*;
let path = match (e1, e2, lims) {
(None, None, HalfOpen) => sym::RangeFull,
(Some(..), None, HalfOpen) => sym::RangeFrom,
(None, Some(..), HalfOpen) => sym::RangeTo,
(Some(..), Some(..), HalfOpen) => sym::Range,
(None, Some(..), Closed) => sym::RangeToInclusive,
(Some(..), Some(..), Closed) => unreachable!(),
(_, None, Closed) => self.diagnostic()
.span_fatal(span, "inclusive range with no end")
.raise(),
};
let fields = e1.iter()
.map(|e| ("start", e))
.chain(e2.iter().map(|e| ("end", e)))
.map(|(s, e)| {
let expr = P(self.lower_expr(&e));
let ident = Ident::new(Symbol::intern(s), e.span);
self.field(ident, expr, e.span)
})
.collect::<P<[hir::Field]>>();
let is_unit = fields.is_empty();
let struct_path = [sym::ops, path];
let struct_path = self.std_path(span, &struct_path, None, is_unit);
let struct_path = hir::QPath::Resolved(None, P(struct_path));
if is_unit {
hir::ExprKind::Path(struct_path)
} else {
hir::ExprKind::Struct(P(struct_path), fields, None)
}
}
fn lower_label(&mut self, label: Option<Label>) -> Option<hir::Label> {
label.map(|label| hir::Label {
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_scopes
.last()
.cloned()
.map(|id| Ok(self.lower_node_id(id)))
.unwrap_or(Err(hir::LoopIdError::OutsideLoopScope))
.into()
}
};
hir::Destination {
label: self.lower_label(destination.map(|(_, label)| label)),
target_id,
}
}
fn lower_jump_destination(&mut self, id: NodeId, opt_label: Option<Label>) -> hir::Destination {
if self.is_in_loop_condition && opt_label.is_none() {
hir::Destination {
label: None,
target_id: Err(hir::LoopIdError::UnlabeledCfInWhileCondition).into(),
}
} else {
self.lower_loop_destination(opt_label.map(|label| (id, label)))
}
}
fn with_catch_scope<T, F>(&mut self, catch_id: NodeId, f: F) -> T
where
F: FnOnce(&mut LoweringContext<'_>) -> T,
{
let len = self.catch_scopes.len();
self.catch_scopes.push(catch_id);
let result = f(self);
assert_eq!(
len + 1,
self.catch_scopes.len(),
"catch scopes should be added and removed in stack order"
);
self.catch_scopes.pop().unwrap();
result
}
fn with_loop_scope<T, F>(&mut self, loop_id: NodeId, f: F) -> T
where
F: FnOnce(&mut LoweringContext<'_>) -> T,
{
// We're no longer in the base loop's condition; we're in another loop.
let was_in_loop_condition = self.is_in_loop_condition;
self.is_in_loop_condition = false;
let len = self.loop_scopes.len();
self.loop_scopes.push(loop_id);
let result = f(self);
assert_eq!(
len + 1,
self.loop_scopes.len(),
"loop scopes should be added and removed in stack order"
);
self.loop_scopes.pop().unwrap();
self.is_in_loop_condition = was_in_loop_condition;
result
}
fn with_loop_condition_scope<T, F>(&mut self, f: F) -> T
where
F: FnOnce(&mut LoweringContext<'_>) -> 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_asm(&mut self, asm: &InlineAsm) -> hir::ExprKind {
let hir_asm = hir::InlineAsm {
inputs: asm.inputs.iter().map(|&(ref c, _)| c.clone()).collect(),
outputs: asm.outputs
.iter()
.map(|out| hir::InlineAsmOutput {
constraint: out.constraint.clone(),
is_rw: out.is_rw,
is_indirect: out.is_indirect,
span: out.expr.span,
})
.collect(),
asm: asm.asm.clone(),
asm_str_style: asm.asm_str_style,
clobbers: asm.clobbers.clone().into(),
volatile: asm.volatile,
alignstack: asm.alignstack,
dialect: asm.dialect,
};
let outputs = asm.outputs
.iter()
.map(|out| self.lower_expr(&out.expr))
.collect();
let inputs = asm.inputs
.iter()
.map(|&(_, ref input)| self.lower_expr(input))
.collect();
hir::ExprKind::InlineAsm(P(hir_asm), outputs, inputs)
}
fn lower_field(&mut self, f: &Field) -> hir::Field {
hir::Field {
hir_id: self.next_id(),
ident: f.ident,
expr: P(self.lower_expr(&f.expr)),
span: f.span,
is_shorthand: f.is_shorthand,
}
}
fn lower_expr_yield(&mut self, span: Span, opt_expr: Option<&Expr>) -> hir::ExprKind {
match self.generator_kind {
Some(hir::GeneratorKind::Gen) => {},
Some(hir::GeneratorKind::Async) => {
span_err!(
self.sess,
span,
E0727,
"`async` generators are not yet supported",
);
self.sess.abort_if_errors();
},
None => self.generator_kind = Some(hir::GeneratorKind::Gen),
}
let expr = opt_expr
.as_ref()
.map(|x| self.lower_expr(x))
.unwrap_or_else(|| self.expr_unit(span));
hir::ExprKind::Yield(P(expr), hir::YieldSource::Yield)
}
/// Desugar `ExprForLoop` from: `[opt_ident]: for <pat> in <head> <body>` into:
/// ```rust
/// {
/// let result = match ::std::iter::IntoIterator::into_iter(<head>) {
/// mut iter => {
/// [opt_ident]: loop {
/// let mut __next;
/// match ::std::iter::Iterator::next(&mut iter) {
/// ::std::option::Option::Some(val) => __next = val,
/// ::std::option::Option::None => break
/// };
/// let <pat> = __next;
/// StmtKind::Expr(<body>);
/// }
/// }
/// };
/// result
/// }
/// ```
fn lower_expr_for(
&mut self,
e: &Expr,
pat: &Pat,
head: &Expr,
body: &Block,
opt_label: Option<Label>,
) -> hir::Expr {
// expand <head>
let mut head = self.lower_expr(head);
let head_sp = head.span;
let desugared_span = self.mark_span_with_reason(
DesugaringKind::ForLoop,
head_sp,
None,
);
head.span = desugared_span;
let iter = Ident::with_dummy_span(sym::iter);
let next_ident = Ident::with_dummy_span(sym::__next);
let (next_pat, next_pat_hid) = self.pat_ident_binding_mode(
desugared_span,
next_ident,
hir::BindingAnnotation::Mutable,
);
// `::std::option::Option::Some(val) => __next = val`
let pat_arm = {
let val_ident = Ident::with_dummy_span(sym::val);
let (val_pat, val_pat_hid) = self.pat_ident(pat.span, val_ident);
let val_expr = P(self.expr_ident(pat.span, val_ident, val_pat_hid));
let next_expr = P(self.expr_ident(pat.span, next_ident, next_pat_hid));
let assign = P(self.expr(
pat.span,
hir::ExprKind::Assign(next_expr, val_expr),
ThinVec::new(),
));
let some_pat = self.pat_some(pat.span, val_pat);
self.arm(hir_vec![some_pat], assign)
};
// `::std::option::Option::None => break`
let break_arm = {
let break_expr =
self.with_loop_scope(e.id, |this| this.expr_break(e.span, ThinVec::new()));
let pat = self.pat_none(e.span);
self.arm(hir_vec![pat], break_expr)
};
// `mut iter`
let (iter_pat, iter_pat_nid) = self.pat_ident_binding_mode(
desugared_span,
iter,
hir::BindingAnnotation::Mutable
);
// `match ::std::iter::Iterator::next(&mut iter) { ... }`
let match_expr = {
let iter = P(self.expr_ident(head_sp, iter, iter_pat_nid));
let ref_mut_iter = self.expr_mut_addr_of(head_sp, iter);
let next_path = &[sym::iter, sym::Iterator, sym::next];
let next_expr = P(self.expr_call_std_path(
head_sp,
next_path,
hir_vec![ref_mut_iter],
));
let arms = hir_vec![pat_arm, break_arm];
self.expr_match(head_sp, next_expr, arms, hir::MatchSource::ForLoopDesugar)
};
let match_stmt = self.stmt_expr(head_sp, match_expr);
let next_expr = P(self.expr_ident(head_sp, next_ident, next_pat_hid));
// `let mut __next`
let next_let = self.stmt_let_pat(
ThinVec::new(),
desugared_span,
None,
next_pat,
hir::LocalSource::ForLoopDesugar,
);
// `let <pat> = __next`
let pat = self.lower_pat(pat);
let pat_let = self.stmt_let_pat(
ThinVec::new(),
head_sp,
Some(next_expr),
pat,
hir::LocalSource::ForLoopDesugar,
);
let body_block = self.with_loop_scope(e.id, |this| this.lower_block(body, false));
let body_expr = self.expr_block(body_block, ThinVec::new());
let body_stmt = self.stmt_expr(body.span, body_expr);
let loop_block = P(self.block_all(
e.span,
hir_vec![next_let, match_stmt, pat_let, body_stmt],
None,
));
// `[opt_ident]: loop { ... }`
let loop_expr = hir::ExprKind::Loop(
loop_block,
self.lower_label(opt_label),
hir::LoopSource::ForLoop,
);
let loop_expr = P(hir::Expr {
hir_id: self.lower_node_id(e.id),
node: loop_expr,
span: e.span,
attrs: ThinVec::new(),
});
// `mut iter => { ... }`
let iter_arm = self.arm(hir_vec![iter_pat], loop_expr);
// `match ::std::iter::IntoIterator::into_iter(<head>) { ... }`
let into_iter_expr = {
let into_iter_path =
&[sym::iter, sym::IntoIterator, sym::into_iter];
P(self.expr_call_std_path(
head_sp,
into_iter_path,
hir_vec![head],
))
};
let match_expr = P(self.expr_match(
head_sp,
into_iter_expr,
hir_vec![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.
self.expr_drop_temps(head_sp, match_expr, e.attrs.clone())
}
/// Desugar `ExprKind::Try` from: `<expr>?` into:
/// ```rust
/// match Try::into_result(<expr>) {
/// Ok(val) => #[allow(unreachable_code)] val,
/// Err(err) => #[allow(unreachable_code)]
/// // If there is an enclosing `try {...}`:
/// break 'catch_target Try::from_error(From::from(err)),
/// // Otherwise:
/// return Try::from_error(From::from(err)),
/// }
/// ```
fn lower_expr_try(&mut self, span: Span, sub_expr: &Expr) -> hir::ExprKind {
let unstable_span = self.mark_span_with_reason(
DesugaringKind::QuestionMark,
span,
self.allow_try_trait.clone(),
);
let try_span = self.sess.source_map().end_point(span);
let try_span = self.mark_span_with_reason(
DesugaringKind::QuestionMark,
try_span,
self.allow_try_trait.clone(),
);
// `Try::into_result(<expr>)`
let scrutinee = {
// expand <expr>
let sub_expr = self.lower_expr(sub_expr);
let path = &[sym::ops, sym::Try, sym::into_result];
P(self.expr_call_std_path(unstable_span, path, hir_vec![sub_expr]))
};
// `#[allow(unreachable_code)]`
let attr = {
// `allow(unreachable_code)`
let allow = {
let allow_ident = Ident::new(sym::allow, span);
let uc_ident = Ident::new(sym::unreachable_code, span);
let uc_nested = attr::mk_nested_word_item(uc_ident);
attr::mk_list_item(allow_ident, vec![uc_nested])
};
attr::mk_attr_outer(allow)
};
let attrs = vec![attr];
// `Ok(val) => #[allow(unreachable_code)] val,`
let ok_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 = P(self.expr_ident_with_attrs(
span,
val_ident,
val_pat_nid,
ThinVec::from(attrs.clone()),
));
let ok_pat = self.pat_ok(span, val_pat);
self.arm(hir_vec![ok_pat], val_expr)
};
// `Err(err) => #[allow(unreachable_code)]
// return Try::from_error(From::from(err)),`
let err_arm = {
let err_ident = Ident::with_dummy_span(sym::err);
let (err_local, err_local_nid) = self.pat_ident(try_span, err_ident);
let from_expr = {
let from_path = &[sym::convert, sym::From, sym::from];
let err_expr = self.expr_ident(try_span, err_ident, err_local_nid);
self.expr_call_std_path(try_span, from_path, hir_vec![err_expr])
};
let from_err_expr =
self.wrap_in_try_constructor(sym::from_error, from_expr, unstable_span);
let thin_attrs = ThinVec::from(attrs);
let catch_scope = self.catch_scopes.last().map(|x| *x);
let ret_expr = if let Some(catch_node) = catch_scope {
let target_id = Ok(self.lower_node_id(catch_node));
P(self.expr(
try_span,
hir::ExprKind::Break(
hir::Destination {
label: None,
target_id,
},
Some(from_err_expr),
),
thin_attrs,
))
} else {
P(self.expr(try_span, hir::ExprKind::Ret(Some(from_err_expr)), thin_attrs))
};
let err_pat = self.pat_err(try_span, err_local);
self.arm(hir_vec![err_pat], ret_expr)
};
hir::ExprKind::Match(
scrutinee,
hir_vec![err_arm, ok_arm],
hir::MatchSource::TryDesugar,
)
}
// =========================================================================
// Helper methods for building HIR.
// =========================================================================
/// Constructs a `true` or `false` literal expression.
pub(super) fn expr_bool(&mut self, span: Span, val: bool) -> hir::Expr {
let lit = Spanned { span, node: LitKind::Bool(val) };
self.expr(span, hir::ExprKind::Lit(lit), ThinVec::new())
}
/// Wrap the given `expr` in a terminating scope using `hir::ExprKind::DropTemps`.
///
/// In terms of drop order, it has the same effect as wrapping `expr` in
/// `{ let _t = $expr; _t }` but should provide better compile-time performance.
///
/// The drop order can be important in e.g. `if expr { .. }`.
pub(super) fn expr_drop_temps(
&mut self,
span: Span,
expr: P<hir::Expr>,
attrs: ThinVec<Attribute>
) -> hir::Expr {
self.expr(span, hir::ExprKind::DropTemps(expr), attrs)
}
fn expr_match(
&mut self,
span: Span,
arg: P<hir::Expr>,
arms: hir::HirVec<hir::Arm>,
source: hir::MatchSource,
) -> hir::Expr {
self.expr(span, hir::ExprKind::Match(arg, arms, source), ThinVec::new())
}
fn expr_break(&mut self, span: Span, attrs: ThinVec<Attribute>) -> P<hir::Expr> {
let expr_break = hir::ExprKind::Break(self.lower_loop_destination(None), None);
P(self.expr(span, expr_break, attrs))
}
fn expr_mut_addr_of(&mut self, span: Span, e: P<hir::Expr>) -> hir::Expr {
self.expr(span, hir::ExprKind::AddrOf(hir::MutMutable, e), ThinVec::new())
}
fn expr_unit(&mut self, sp: Span) -> hir::Expr {
self.expr_tuple(sp, hir_vec![])
}
fn expr_tuple(&mut self, sp: Span, exprs: hir::HirVec<hir::Expr>) -> hir::Expr {
self.expr(sp, hir::ExprKind::Tup(exprs), ThinVec::new())
}
fn expr_call(
&mut self,
span: Span,
e: P<hir::Expr>,
args: hir::HirVec<hir::Expr>,
) -> hir::Expr {
self.expr(span, hir::ExprKind::Call(e, args), ThinVec::new())
}
// Note: associated functions must use `expr_call_std_path`.
fn expr_call_std_path(
&mut self,
span: Span,
path_components: &[Symbol],
args: hir::HirVec<hir::Expr>,
) -> hir::Expr {
let path = P(self.expr_std_path(span, path_components, None, ThinVec::new()));
self.expr_call(span, path, args)
}
// Create an expression calling an associated function of an std type.
//
// Associated functions cannot be resolved through the normal `std_path` function,
// as they are resolved differently and so cannot use `expr_call_std_path`.
//
// This function accepts the path component (`ty_path_components`) separately from
// the name of the associated function (`assoc_fn_name`) in order to facilitate
// separate resolution of the type and creation of a path referring to its associated
// function.
fn expr_call_std_assoc_fn(
&mut self,
ty_path_id: hir::HirId,
span: Span,
ty_path_components: &[Symbol],
assoc_fn_name: &str,
args: hir::HirVec<hir::Expr>,
) -> hir::ExprKind {
let ty_path = P(self.std_path(span, ty_path_components, None, false));
let ty = P(self.ty_path(ty_path_id, span, hir::QPath::Resolved(None, ty_path)));
let fn_seg = P(hir::PathSegment::from_ident(Ident::from_str(assoc_fn_name)));
let fn_path = hir::QPath::TypeRelative(ty, fn_seg);
let fn_expr = P(self.expr(span, hir::ExprKind::Path(fn_path), ThinVec::new()));
hir::ExprKind::Call(fn_expr, args)
}
fn expr_std_path(
&mut self,
span: Span,
components: &[Symbol],
params: Option<P<hir::GenericArgs>>,
attrs: ThinVec<Attribute>,
) -> hir::Expr {
let path = self.std_path(span, components, params, true);
self.expr(
span,
hir::ExprKind::Path(hir::QPath::Resolved(None, P(path))),
attrs,
)
}
pub(super) fn expr_ident(&mut self, sp: Span, ident: Ident, binding: hir::HirId) -> hir::Expr {
self.expr_ident_with_attrs(sp, ident, binding, ThinVec::new())
}
fn expr_ident_with_attrs(
&mut self,
span: Span,
ident: Ident,
binding: hir::HirId,
attrs: ThinVec<Attribute>,
) -> hir::Expr {
let expr_path = hir::ExprKind::Path(hir::QPath::Resolved(
None,
P(hir::Path {
span,
res: Res::Local(binding),
segments: hir_vec![hir::PathSegment::from_ident(ident)],
}),
));
self.expr(span, expr_path, attrs)
}
fn expr_unsafe(&mut self, expr: P<hir::Expr>) -> hir::Expr {
let hir_id = self.next_id();
let span = expr.span;
self.expr(
span,
hir::ExprKind::Block(P(hir::Block {
stmts: hir_vec![],
expr: Some(expr),
hir_id,
rules: hir::UnsafeBlock(hir::CompilerGenerated),
span,
targeted_by_break: false,
}), None),
ThinVec::new(),
)
}
fn expr_block_empty(&mut self, span: Span) -> hir::Expr {
let blk = self.block_all(span, hir_vec![], None);
self.expr_block(P(blk), ThinVec::new())
}
pub(super) fn expr_block(&mut self, b: P<hir::Block>, attrs: ThinVec<Attribute>) -> hir::Expr {
self.expr(b.span, hir::ExprKind::Block(b, None), attrs)
}
pub(super) fn expr(
&mut self,
span: Span,
node: hir::ExprKind,
attrs: ThinVec<Attribute>
) -> hir::Expr {
hir::Expr {
hir_id: self.next_id(),
node,
span,
attrs,
}
}
fn field(&mut self, ident: Ident, expr: P<hir::Expr>, span: Span) -> hir::Field {
hir::Field {
hir_id: self.next_id(),
ident,
span,
expr,
is_shorthand: false,
}
}
/// HACK(or_patterns; Centril | dlrobertson): For now we don't push down top level or-patterns
/// `p | q` into `hir::PatKind::Or(...)` as post-lowering bits of the compiler are not ready
/// to deal with it. This should by fixed by pushing it down to HIR and then HAIR.
fn arm(&mut self, pats: HirVec<P<hir::Pat>>, expr: P<hir::Expr>) -> hir::Arm {
hir::Arm {
hir_id: self.next_id(),
attrs: hir_vec![],
pats,
guard: None,
span: expr.span,
body: expr,
}
}
}
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