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[wg-async-await] Drop async fn arguments in async block #59823

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merged 10 commits into from
Apr 23, 2019
Merged

[wg-async-await] Drop async fn arguments in async block #59823

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8b57be1
Add test for drop order in async functions.
davidtwco Mar 7, 2019
41c6bb1
Introduce `LocalSource` into the AST.
davidtwco Mar 12, 2019
879abb1
Add `AsyncArgument` to AST.
davidtwco Mar 12, 2019
7c6dc7a
Move `async fn` arguments into closure.
davidtwco Mar 12, 2019
6134655
Enforce consistent drop order w/ async methods.
davidtwco Mar 13, 2019
92e72df
Do not specify type in generated let bindings.
davidtwco Mar 13, 2019
9d7da82
Introduce `ArgSource` for diagnostics.
davidtwco Mar 13, 2019
44ddbc5
Correct lowering order to avoid ICE after rebase.
davidtwco Apr 20, 2019
09c707f
Display original pattern in rustdoc.
davidtwco Apr 21, 2019
119e67a
Reduce noise and document test case.
davidtwco Apr 23, 2019
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16 changes: 13 additions & 3 deletions src/librustc/hir/intravisit.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -58,10 +58,10 @@ impl<'a> FnKind<'a> {
}
}

pub fn header(&self) -> Option<FnHeader> {
pub fn header(&self) -> Option<&FnHeader> {
match *self {
FnKind::ItemFn(_, _, header, _, _) => Some(header),
FnKind::Method(_, sig, _, _) => Some(sig.header),
FnKind::ItemFn(_, _, ref header, _, _) => Some(header),
FnKind::Method(_, ref sig, _, _) => Some(&sig.header),
FnKind::Closure(_) => None,
}
}
Expand Down Expand Up @@ -262,6 +262,9 @@ pub trait Visitor<'v> : Sized {
fn visit_pat(&mut self, p: &'v Pat) {
walk_pat(self, p)
}
fn visit_argument_source(&mut self, s: &'v ArgSource) {
walk_argument_source(self, s)
}
fn visit_anon_const(&mut self, c: &'v AnonConst) {
walk_anon_const(self, c)
}
Expand Down Expand Up @@ -399,10 +402,17 @@ pub fn walk_body<'v, V: Visitor<'v>>(visitor: &mut V, body: &'v Body) {
for argument in &body.arguments {
visitor.visit_id(argument.hir_id);
visitor.visit_pat(&argument.pat);
visitor.visit_argument_source(&argument.source);
}
visitor.visit_expr(&body.value);
}

pub fn walk_argument_source<'v, V: Visitor<'v>>(visitor: &mut V, source: &'v ArgSource) {
if let ArgSource::AsyncFn(pat) = source {
visitor.visit_pat(pat);
}
}

pub fn walk_local<'v, V: Visitor<'v>>(visitor: &mut V, local: &'v Local) {
// Intentionally visiting the expr first - the initialization expr
// dominates the local's definition.
Expand Down
184 changes: 135 additions & 49 deletions src/librustc/hir/lowering.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -448,10 +448,9 @@ impl<'a> LoweringContext<'a> {
impl<'lcx, 'interner> Visitor<'lcx> for MiscCollector<'lcx, 'interner> {
fn visit_pat(&mut self, p: &'lcx Pat) {
match p.node {
// Doesn't generate a Hir node
// Doesn't generate a HIR node
PatKind::Paren(..) => {},
_ => {

if let Some(owner) = self.hir_id_owner {
self.lctx.lower_node_id_with_owner(p.id, owner);
}
Expand All @@ -461,6 +460,32 @@ impl<'a> LoweringContext<'a> {
visit::walk_pat(self, p)
}

fn visit_fn(&mut self, fk: visit::FnKind<'lcx>, fd: &'lcx FnDecl, s: Span, _: NodeId) {
if fk.header().map(|h| h.asyncness.node.is_async()).unwrap_or(false) {
// Don't visit the original pattern for async functions as it will be
// replaced.
for arg in &fd.inputs {
if let ArgSource::AsyncFn(pat) = &arg.source { self.visit_pat(pat); }
self.visit_ty(&arg.ty)
}
self.visit_fn_ret_ty(&fd.output);

match fk {
visit::FnKind::ItemFn(_, decl, _, body) => {
self.visit_fn_header(decl);
self.visit_block(body)
},
visit::FnKind::Method(_, sig, _, body) => {
self.visit_fn_header(&sig.header);
self.visit_block(body)
},
visit::FnKind::Closure(body) => self.visit_expr(body),
}
} else {
visit::walk_fn(self, fk, fd, s)
}
}

fn visit_item(&mut self, item: &'lcx Item) {
let hir_id = self.lctx.allocate_hir_id_counter(item.id).hir_id;

Expand Down Expand Up @@ -784,12 +809,10 @@ impl<'a> LoweringContext<'a> {
})
}

fn record_body(&mut self, value: hir::Expr, decl: Option<&FnDecl>) -> hir::BodyId {
fn record_body(&mut self, value: hir::Expr, arguments: HirVec<hir::Arg>) -> hir::BodyId {
let body = hir::Body {
arguments: decl.map_or(hir_vec![], |decl| {
decl.inputs.iter().map(|x| self.lower_arg(x)).collect()
}),
is_generator: self.is_generator,
arguments,
value,
};
let id = body.id();
Expand Down Expand Up @@ -1112,11 +1135,10 @@ impl<'a> LoweringContext<'a> {
capture_clause: CaptureBy,
closure_node_id: NodeId,
ret_ty: Option<&Ty>,
span: Span,
body: impl FnOnce(&mut LoweringContext<'_>) -> hir::Expr,
) -> hir::ExprKind {
let prev_is_generator = mem::replace(&mut self.is_generator, true);
let body_expr = body(self);
let span = body_expr.span;
let output = match ret_ty {
Some(ty) => FunctionRetTy::Ty(P(ty.clone())),
None => FunctionRetTy::Default(span),
Expand All @@ -1126,7 +1148,11 @@ impl<'a> LoweringContext<'a> {
output,
c_variadic: false
};
let body_id = self.record_body(body_expr, Some(&decl));
// Lower the arguments before the body otherwise the body will call `lower_def` expecting
// the argument to have been assigned an id already.
let arguments = self.lower_args(Some(&decl));
let body_expr = body(self);
let body_id = self.record_body(body_expr, arguments);
self.is_generator = prev_is_generator;

let capture_clause = self.lower_capture_clause(capture_clause);
Expand Down Expand Up @@ -1157,8 +1183,9 @@ impl<'a> LoweringContext<'a> {
F: FnOnce(&mut LoweringContext<'_>) -> hir::Expr,
{
let prev = mem::replace(&mut self.is_generator, false);
let arguments = self.lower_args(decl);
let result = f(self);
let r = self.record_body(result, decl);
let r = self.record_body(result, arguments);
self.is_generator = prev;
return r;
}
Expand Down Expand Up @@ -2224,22 +2251,41 @@ impl<'a> LoweringContext<'a> {
init: l.init.as_ref().map(|e| P(self.lower_expr(e))),
span: l.span,
attrs: l.attrs.clone(),
source: hir::LocalSource::Normal,
source: self.lower_local_source(l.source),
}, ids)
}

fn lower_local_source(&mut self, ls: LocalSource) -> hir::LocalSource {
match ls {
LocalSource::Normal => hir::LocalSource::Normal,
LocalSource::AsyncFn => hir::LocalSource::AsyncFn,
}
}

fn lower_mutability(&mut self, m: Mutability) -> hir::Mutability {
match m {
Mutability::Mutable => hir::MutMutable,
Mutability::Immutable => hir::MutImmutable,
}
}

fn lower_args(&mut self, decl: Option<&FnDecl>) -> HirVec<hir::Arg> {
decl.map_or(hir_vec![], |decl| decl.inputs.iter().map(|x| self.lower_arg(x)).collect())
}

fn lower_arg(&mut self, arg: &Arg) -> hir::Arg {
let LoweredNodeId { node_id: _, hir_id } = self.lower_node_id(arg.id);
hir::Arg {
hir_id,
pat: self.lower_pat(&arg.pat),
source: self.lower_arg_source(&arg.source),
}
}

fn lower_arg_source(&mut self, source: &ArgSource) -> hir::ArgSource {
match source {
ArgSource::Normal => hir::ArgSource::Normal,
ArgSource::AsyncFn(pat) => hir::ArgSource::AsyncFn(self.lower_pat(pat)),
}
}

Expand Down Expand Up @@ -2993,15 +3039,21 @@ impl<'a> LoweringContext<'a> {
fn lower_async_body(
&mut self,
decl: &FnDecl,
asyncness: IsAsync,
asyncness: &IsAsync,
body: &Block,
) -> hir::BodyId {
self.lower_body(Some(decl), |this| {
if let IsAsync::Async { closure_id, .. } = asyncness {
self.lower_body(Some(&decl), |this| {
if let IsAsync::Async { closure_id, ref arguments, .. } = asyncness {
let mut body = body.clone();

for a in arguments.iter().rev() {
body.stmts.insert(0, a.stmt.clone());
}

let async_expr = this.make_async_expr(
CaptureBy::Value, closure_id, None,
CaptureBy::Value, *closure_id, None, body.span,
|this| {
let body = this.lower_block(body, false);
let body = this.lower_block(&body, false);
this.expr_block(body, ThinVec::new())
});
this.expr(body.span, async_expr, ThinVec::new())
Expand Down Expand Up @@ -3060,26 +3112,42 @@ impl<'a> LoweringContext<'a> {
value
)
}
ItemKind::Fn(ref decl, header, ref generics, ref body) => {
ItemKind::Fn(ref decl, ref header, ref generics, ref body) => {
let fn_def_id = self.resolver.definitions().local_def_id(id);
self.with_new_scopes(|this| {
// Note: we don't need to change the return type from `T` to
// `impl Future<Output = T>` here because lower_body
// only cares about the input argument patterns in the function
// declaration (decl), not the return types.
let body_id = this.lower_async_body(decl, header.asyncness.node, body);
let mut lower_fn = |decl: &FnDecl| {
// Note: we don't need to change the return type from `T` to
// `impl Future<Output = T>` here because lower_body
// only cares about the input argument patterns in the function
// declaration (decl), not the return types.
let body_id = this.lower_async_body(&decl, &header.asyncness.node, body);

let (generics, fn_decl) = this.add_in_band_defs(
generics,
fn_def_id,
AnonymousLifetimeMode::PassThrough,
|this, idty| this.lower_fn_decl(
&decl,
Some((fn_def_id, idty)),
true,
header.asyncness.node.opt_return_id()
),
);

let (generics, fn_decl) = this.add_in_band_defs(
generics,
fn_def_id,
AnonymousLifetimeMode::PassThrough,
|this, idty| this.lower_fn_decl(
decl,
Some((fn_def_id, idty)),
true,
header.asyncness.node.opt_return_id()
),
);
(body_id, generics, fn_decl)
};

let (body_id, generics, fn_decl) = if let IsAsync::Async {
arguments, ..
} = &header.asyncness.node {
let mut decl = decl.clone();
// Replace the arguments of this async function with the generated
// arguments that will be moved into the closure.
decl.inputs = arguments.clone().drain(..).map(|a| a.arg).collect();
lower_fn(&decl)
} else {
lower_fn(decl)
};

hir::ItemKind::Fn(
fn_decl,
Expand Down Expand Up @@ -3558,15 +3626,33 @@ impl<'a> LoweringContext<'a> {
)
}
ImplItemKind::Method(ref sig, ref body) => {
let body_id = self.lower_async_body(&sig.decl, sig.header.asyncness.node, body);
let impl_trait_return_allow = !self.is_in_trait_impl;
let (generics, sig) = self.lower_method_sig(
&i.generics,
sig,
impl_item_def_id,
impl_trait_return_allow,
sig.header.asyncness.node.opt_return_id(),
);
let mut lower_method = |sig: &MethodSig| {
let body_id = self.lower_async_body(
&sig.decl, &sig.header.asyncness.node, body
);
let impl_trait_return_allow = !self.is_in_trait_impl;
let (generics, sig) = self.lower_method_sig(
&i.generics,
sig,
impl_item_def_id,
impl_trait_return_allow,
sig.header.asyncness.node.opt_return_id(),
);
(body_id, generics, sig)
};

let (body_id, generics, sig) = if let IsAsync::Async {
ref arguments, ..
} = sig.header.asyncness.node {
let mut sig = sig.clone();
// Replace the arguments of this async function with the generated
// arguments that will be moved into the closure.
sig.decl.inputs = arguments.clone().drain(..).map(|a| a.arg).collect();
lower_method(&sig)
} else {
lower_method(sig)
};

(generics, hir::ImplItemKind::Method(sig, body_id))
}
ImplItemKind::Type(ref ty) => (
Expand Down Expand Up @@ -3760,7 +3846,7 @@ impl<'a> LoweringContext<'a> {
impl_trait_return_allow: bool,
is_async: Option<NodeId>,
) -> (hir::Generics, hir::MethodSig) {
let header = self.lower_fn_header(sig.header);
let header = self.lower_fn_header(&sig.header);
let (generics, decl) = self.add_in_band_defs(
generics,
fn_def_id,
Expand All @@ -3782,10 +3868,10 @@ impl<'a> LoweringContext<'a> {
}
}

fn lower_fn_header(&mut self, h: FnHeader) -> hir::FnHeader {
fn lower_fn_header(&mut self, h: &FnHeader) -> hir::FnHeader {
hir::FnHeader {
unsafety: self.lower_unsafety(h.unsafety),
asyncness: self.lower_asyncness(h.asyncness.node),
asyncness: self.lower_asyncness(&h.asyncness.node),
constness: self.lower_constness(h.constness),
abi: h.abi,
}
Expand All @@ -3805,7 +3891,7 @@ impl<'a> LoweringContext<'a> {
}
}

fn lower_asyncness(&mut self, a: IsAsync) -> hir::IsAsync {
fn lower_asyncness(&mut self, a: &IsAsync) -> hir::IsAsync {
match a {
IsAsync::Async { .. } => hir::IsAsync::Async,
IsAsync::NotAsync => hir::IsAsync::NotAsync,
Expand Down Expand Up @@ -4110,15 +4196,15 @@ impl<'a> LoweringContext<'a> {
hir::MatchSource::Normal,
),
ExprKind::Async(capture_clause, closure_node_id, ref block) => {
self.make_async_expr(capture_clause, closure_node_id, None, |this| {
self.make_async_expr(capture_clause, closure_node_id, None, block.span, |this| {
this.with_new_scopes(|this| {
let block = this.lower_block(block, false);
this.expr_block(block, ThinVec::new())
})
})
}
ExprKind::Closure(
capture_clause, asyncness, movability, ref decl, ref body, fn_decl_span
capture_clause, ref asyncness, movability, ref decl, ref body, fn_decl_span
) => {
if let IsAsync::Async { closure_id, .. } = asyncness {
let outer_decl = FnDecl {
Expand Down Expand Up @@ -4156,7 +4242,7 @@ impl<'a> LoweringContext<'a> {
Some(&**ty)
} else { None };
let async_body = this.make_async_expr(
capture_clause, closure_id, async_ret_ty,
capture_clause, *closure_id, async_ret_ty, body.span,
|this| {
this.with_new_scopes(|this| this.lower_expr(body))
});
Expand Down
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