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Merge #5971

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5971: Implement async blocks r=flodiebold a=oxalica

Fix #4018

@flodiebold already gave a generic guide in the issue. Here's some concern about implementation detail:
- Chalk doesn't support generator type yet.
- Adding generator type as a brand new type (ctor) can be complex and need to *re-introduced* builtin impls. (Like how we implement closures before native closure support of chalk, which is already removed in #5401 )
- The output type of async block should be known after type inference of the whole body.
  - We cannot directly get the type from source like return-positon-impl-trait. But we still need to provide trait bounds when chalk asking for `opaque_ty_data`.
  - During the inference, the output type of async block can be temporary unknown and participate the later inference.
    `let a = async { None }; let _: i32 = a.await.unwrap();`

So in this PR, the type of async blocks is inferred as an opaque type parameterized by the `Future::Output` type it should be, like what we do with closure type.
And it really works now.

Well, I still have some questions:
- The bounds `AsyncBlockImplType<T>: Future<Output = T>` is currently generated in `opaque_ty_data`. I'm not sure if we should put this code here.
- Type of async block is now rendered as `impl Future<Output = OutputType>`. Do we need to special display to hint that it's a async block? Note that closure type has its special format, instead of `impl Fn(..) -> ..` or function type.



Co-authored-by: oxalica <oxalicc@pm.me>
This commit is contained in:
bors[bot] 2020-09-13 17:28:22 +00:00 committed by GitHub
commit 0d03fe6ef5
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12 changed files with 314 additions and 55 deletions
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7
crates/hir/src/code_model.rs
View file

@ -1283,6 +1283,8 @@ impl Type {
/// Checks that particular type `ty` implements `std::future::Future`.
/// This function is used in `.await` syntax completion.
pub fn impls_future(&self, db: &dyn HirDatabase) -> bool {
// No special case for the type of async block, since Chalk can figure it out.
let krate = self.krate;
let std_future_trait =
@ -1600,6 +1602,11 @@ impl Type {
cb(type_.derived(ty.clone()));
}
}
TypeCtor::OpaqueType(..) => {
if let Some(bounds) = ty.impl_trait_bounds(db) {
walk_bounds(db, &type_.derived(ty.clone()), &bounds, cb);
}
}
_ => (),
}

5
crates/hir_def/src/body/lower.rs
View file

@ -239,7 +239,10 @@ impl ExprCollector<'_> {
None => self.missing_expr(),
},
// FIXME: we need to record these effects somewhere...
ast::Effect::Async(_) => self.collect_block_opt(e.block_expr()),
ast::Effect::Async(_) => {
let body = self.collect_block_opt(e.block_expr());
self.alloc_expr(Expr::Async { body }, syntax_ptr)
}
},
ast::Expr::BlockExpr(e) => self.collect_block(e),
ast::Expr::LoopExpr(e) => {

5
crates/hir_def/src/expr.rs
View file

@ -111,6 +111,9 @@ pub enum Expr {
TryBlock {
body: ExprId,
},
Async {
body: ExprId,
},
Cast {
expr: ExprId,
type_ref: TypeRef,
@ -250,7 +253,7 @@ impl Expr {
f(*expr);
}
}
Expr::TryBlock { body } | Expr::Unsafe { body } => f(*body),
Expr::TryBlock { body } | Expr::Unsafe { body } | Expr::Async { body } => f(*body),
Expr::Loop { body, .. } => f(*body),
Expr::While { condition, body, .. } => {
f(*condition);

28
crates/hir_ty/src/display.rs
View file

@ -381,19 +381,24 @@ impl HirDisplay for ApplicationTy {
}
}
TypeCtor::OpaqueType(opaque_ty_id) => {
let bounds = match opaque_ty_id {
match opaque_ty_id {
OpaqueTyId::ReturnTypeImplTrait(func, idx) => {
let datas =
f.db.return_type_impl_traits(func).expect("impl trait id without data");
let data = (*datas)
.as_ref()
.map(|rpit| rpit.impl_traits[idx as usize].bounds.clone());
data.subst(&self.parameters)
let bounds = data.subst(&self.parameters);
write!(f, "impl ")?;
write_bounds_like_dyn_trait(&bounds.value, f)?;
// FIXME: it would maybe be good to distinguish this from the alias type (when debug printing), and to show the substitution
}
};
write!(f, "impl ")?;
write_bounds_like_dyn_trait(&bounds.value, f)?;
// FIXME: it would maybe be good to distinguish this from the alias type (when debug printing), and to show the substitution
OpaqueTyId::AsyncBlockTypeImplTrait(..) => {
write!(f, "impl Future<Output = ")?;
self.parameters[0].hir_fmt(f)?;
write!(f, ">")?;
}
}
}
TypeCtor::Closure { .. } => {
let sig = self.parameters[0].callable_sig(f.db);
@ -474,18 +479,21 @@ impl HirDisplay for Ty {
write_bounds_like_dyn_trait(predicates, f)?;
}
Ty::Opaque(opaque_ty) => {
let bounds = match opaque_ty.opaque_ty_id {
match opaque_ty.opaque_ty_id {
OpaqueTyId::ReturnTypeImplTrait(func, idx) => {
let datas =
f.db.return_type_impl_traits(func).expect("impl trait id without data");
let data = (*datas)
.as_ref()
.map(|rpit| rpit.impl_traits[idx as usize].bounds.clone());
data.subst(&opaque_ty.parameters)
let bounds = data.subst(&opaque_ty.parameters);
write!(f, "impl ")?;
write_bounds_like_dyn_trait(&bounds.value, f)?;
}
OpaqueTyId::AsyncBlockTypeImplTrait(..) => {
write!(f, "{{async block}}")?;
}
};
write!(f, "impl ")?;
write_bounds_like_dyn_trait(&bounds.value, f)?;
}
Ty::Unknown => write!(f, "{{unknown}}")?,
Ty::Infer(..) => write!(f, "_")?,

11
crates/hir_ty/src/infer/expr.rs
View file

@ -17,8 +17,8 @@ use crate::{
autoderef, method_resolution, op,
traits::{FnTrait, InEnvironment},
utils::{generics, variant_data, Generics},
ApplicationTy, Binders, CallableDefId, InferTy, IntTy, Mutability, Obligation, Rawness, Substs,
TraitRef, Ty, TypeCtor,
ApplicationTy, Binders, CallableDefId, InferTy, IntTy, Mutability, Obligation, OpaqueTyId,
Rawness, Substs, TraitRef, Ty, TypeCtor,
};
use super::{
@ -146,6 +146,13 @@ impl<'a> InferenceContext<'a> {
// FIXME should be std::result::Result<{inner}, _>
Ty::Unknown
}
Expr::Async { body } => {
// Use the first type parameter as the output type of future.
// existenail type AsyncBlockImplTrait<InnerType>: Future<Output = InnerType>
let inner_ty = self.infer_expr(*body, &Expectation::none());
let opaque_ty_id = OpaqueTyId::AsyncBlockTypeImplTrait(self.owner, *body);
Ty::apply_one(TypeCtor::OpaqueType(opaque_ty_id), inner_ty)
}
Expr::Loop { body, label } => {
self.breakables.push(BreakableContext {
may_break: false,

34
crates/hir_ty/src/lib.rs
View file

@ -129,8 +129,9 @@ pub enum TypeCtor {
/// This represents a placeholder for an opaque type in situations where we
/// don't know the hidden type (i.e. currently almost always). This is
/// analogous to the `AssociatedType` type constructor. As with that one,
/// these are only produced by Chalk.
/// analogous to the `AssociatedType` type constructor.
/// It is also used as the type of async block, with one type parameter
/// representing the Future::Output type.
OpaqueType(OpaqueTyId),
/// The type of a specific closure.
@ -173,6 +174,8 @@ impl TypeCtor {
let generic_params = generics(db.upcast(), func.into());
generic_params.len()
}
// 1 param representing Future::Output type.
OpaqueTyId::AsyncBlockTypeImplTrait(..) => 1,
}
}
TypeCtor::FnPtr { num_args, is_varargs: _ } => num_args as usize + 1,
@ -205,6 +208,7 @@ impl TypeCtor {
OpaqueTyId::ReturnTypeImplTrait(func, _) => {
Some(func.lookup(db.upcast()).module(db.upcast()).krate)
}
OpaqueTyId::AsyncBlockTypeImplTrait(def, _) => Some(def.module(db.upcast()).krate),
},
}
}
@ -843,6 +847,29 @@ impl Ty {
pub fn impl_trait_bounds(&self, db: &dyn HirDatabase) -> Option<Vec<GenericPredicate>> {
match self {
Ty::Apply(ApplicationTy { ctor: TypeCtor::OpaqueType(opaque_ty_id), .. }) => {
match opaque_ty_id {
OpaqueTyId::AsyncBlockTypeImplTrait(def, _expr) => {
let krate = def.module(db.upcast()).krate;
if let Some(future_trait) = db
.lang_item(krate, "future_trait".into())
.and_then(|item| item.as_trait())
{
// This is only used by type walking.
// Parameters will be walked outside, and projection predicate is not used.
// So just provide the Future trait.
let impl_bound = GenericPredicate::Implemented(TraitRef {
trait_: future_trait,
substs: Substs::empty(),
});
Some(vec![impl_bound])
} else {
None
}
}
OpaqueTyId::ReturnTypeImplTrait(..) => None,
}
}
Ty::Opaque(opaque_ty) => {
let predicates = match opaque_ty.opaque_ty_id {
OpaqueTyId::ReturnTypeImplTrait(func, idx) => {
@ -853,6 +880,8 @@ impl Ty {
data.subst(&opaque_ty.parameters)
})
}
// It always has an parameter for Future::Output type.
OpaqueTyId::AsyncBlockTypeImplTrait(..) => unreachable!(),
};
predicates.map(|it| it.value)
@ -1065,6 +1094,7 @@ impl<T: TypeWalk> TypeWalk for Vec<T> {
#[derive(Copy, Clone, PartialEq, Eq, Debug, Hash)]
pub enum OpaqueTyId {
ReturnTypeImplTrait(hir_def::FunctionId, u16),
AsyncBlockTypeImplTrait(hir_def::DefWithBodyId, ExprId),
}
#[derive(Clone, PartialEq, Eq, Debug, Hash)]

45
crates/hir_ty/src/tests/simple.rs
View file

@ -1889,31 +1889,40 @@ fn fn_pointer_return() {
fn effects_smoke_test() {
check_infer(
r#"
fn main() {
async fn main() {
let x = unsafe { 92 };
let y = async { async { () }.await };
let z = try { () };
let t = 'a: { 92 };
}
#[prelude_import] use future::*;
mod future {
#[lang = "future_trait"]
pub trait Future { type Output; }
}
"#,
expect![[r#"
10..130 '{ ...2 }; }': ()
20..21 'x': i32
24..37 'unsafe { 92 }': i32
31..37 '{ 92 }': i32
33..35 '92': i32
47..48 'y': {unknown}
57..79 '{ asyn...wait }': {unknown}
59..77 'async ....await': {unknown}
65..71 '{ () }': ()
67..69 '()': ()
89..90 'z': {unknown}
93..103 'try { () }': {unknown}
97..103 '{ () }': ()
99..101 '()': ()
113..114 't': i32
121..127 '{ 92 }': i32
123..125 '92': i32
16..136 '{ ...2 }; }': ()
26..27 'x': i32
30..43 'unsafe { 92 }': i32
37..43 '{ 92 }': i32
39..41 '92': i32
53..54 'y': impl Future<Output = ()>
57..85 'async ...wait }': impl Future<Output = ()>
63..85 '{ asyn...wait }': ()
65..77 'async { () }': impl Future<Output = ()>
65..83 'async ....await': ()
71..77 '{ () }': ()
73..75 '()': ()
95..96 'z': {unknown}
99..109 'try { () }': {unknown}
103..109 '{ () }': ()
105..107 '()': ()
119..120 't': i32
127..133 '{ 92 }': i32
129..131 '92': i32
"#]],
)
}

40
crates/hir_ty/src/tests/traits.rs
View file

@ -85,6 +85,46 @@ mod future {
);
}
#[test]
fn infer_async_block() {
check_types(
r#"
//- /main.rs crate:main deps:core
async fn test() {
let a = async { 42 };
a;
// ^ impl Future<Output = i32>
let x = a.await;
x;
// ^ i32
let b = async {}.await;
b;
// ^ ()
let c = async {
let y = Option::None;
y
// ^ Option<u64>
};
let _: Option<u64> = c.await;
c;
// ^ impl Future<Output = Option<u64>>
}
enum Option<T> { None, Some(T) }
//- /core.rs crate:core
#[prelude_import] use future::*;
mod future {
#[lang = "future_trait"]
trait Future {
type Output;
}
}
"#,
);
}
#[test]
fn infer_try() {
check_types(

105
crates/hir_ty/src/traits/chalk.rs
View file

@ -11,6 +11,7 @@ use hir_def::{
lang_item::{lang_attr, LangItemTarget},
AssocContainerId, AssocItemId, HasModule, Lookup, TypeAliasId,
};
use hir_expand::name::name;
use super::ChalkContext;
use crate::{
@ -18,7 +19,8 @@ use crate::{
display::HirDisplay,
method_resolution::{TyFingerprint, ALL_FLOAT_FPS, ALL_INT_FPS},
utils::generics,
CallableDefId, DebruijnIndex, FnSig, GenericPredicate, Substs, Ty, TypeCtor,
BoundVar, CallableDefId, DebruijnIndex, FnSig, GenericPredicate, ProjectionPredicate,
ProjectionTy, Substs, TraitRef, Ty, TypeCtor,
};
use mapping::{
convert_where_clauses, generic_predicate_to_inline_bound, make_binders, TypeAliasAsValue,
@ -166,27 +168,88 @@ impl<'a> chalk_solve::RustIrDatabase<Interner> for ChalkContext<'a> {
fn opaque_ty_data(&self, id: chalk_ir::OpaqueTyId<Interner>) -> Arc<OpaqueTyDatum> {
let interned_id = crate::db::InternedOpaqueTyId::from(id);
let full_id = self.db.lookup_intern_impl_trait_id(interned_id);
let (func, idx) = match full_id {
crate::OpaqueTyId::ReturnTypeImplTrait(func, idx) => (func, idx),
let bound = match full_id {
crate::OpaqueTyId::ReturnTypeImplTrait(func, idx) => {
let datas = self
.db
.return_type_impl_traits(func)
.expect("impl trait id without impl traits");
let data = &datas.value.impl_traits[idx as usize];
let bound = OpaqueTyDatumBound {
bounds: make_binders(
data.bounds
.value
.iter()
.cloned()
.filter(|b| !b.is_error())
.map(|b| b.to_chalk(self.db))
.collect(),
1,
),
where_clauses: make_binders(vec![], 0),
};
let num_vars = datas.num_binders;
make_binders(bound, num_vars)
}
crate::OpaqueTyId::AsyncBlockTypeImplTrait(..) => {
if let Some((future_trait, future_output)) = self
.db
.lang_item(self.krate, "future_trait".into())
.and_then(|item| item.as_trait())
.and_then(|trait_| {
let alias =
self.db.trait_data(trait_).associated_type_by_name(&name![Output])?;
Some((trait_, alias))
})
{
// Making up `AsyncBlock<T>: Future<Output = T>`
//
// |--------------------OpaqueTyDatum-------------------|
// |-------------OpaqueTyDatumBound--------------|
// for<T> <Self> [Future<Self>, Future::Output<Self> = T]
// ^1 ^0 ^0 ^0 ^1
let impl_bound = GenericPredicate::Implemented(TraitRef {
trait_: future_trait,
// Self type as the first parameter.
substs: Substs::single(Ty::Bound(BoundVar {
debruijn: DebruijnIndex::INNERMOST,
index: 0,
})),
});
let proj_bound = GenericPredicate::Projection(ProjectionPredicate {
// The parameter of the opaque type.
ty: Ty::Bound(BoundVar { debruijn: DebruijnIndex::ONE, index: 0 }),
projection_ty: ProjectionTy {
associated_ty: future_output,
// Self type as the first parameter.
parameters: Substs::single(Ty::Bound(BoundVar::new(
DebruijnIndex::INNERMOST,
0,
))),
},
});
let bound = OpaqueTyDatumBound {
bounds: make_binders(
vec![impl_bound.to_chalk(self.db), proj_bound.to_chalk(self.db)],
1,
),
where_clauses: make_binders(vec![], 0),
};
// The opaque type has 1 parameter.
make_binders(bound, 1)
} else {
// If failed to find `Future::Output`, return empty bounds as fallback.
let bound = OpaqueTyDatumBound {
bounds: make_binders(vec![], 0),
where_clauses: make_binders(vec![], 0),
};
// The opaque type has 1 parameter.
make_binders(bound, 1)
}
}
};
let datas =
self.db.return_type_impl_traits(func).expect("impl trait id without impl traits");
let data = &datas.value.impl_traits[idx as usize];
let bound = OpaqueTyDatumBound {
bounds: make_binders(
data.bounds
.value
.iter()
.cloned()
.filter(|b| !b.is_error())
.map(|b| b.to_chalk(self.db))
.collect(),
1,
),
where_clauses: make_binders(vec![], 0),
};
let num_vars = datas.num_binders;
Arc::new(OpaqueTyDatum { opaque_ty_id: id, bound: make_binders(bound, num_vars) })
Arc::new(OpaqueTyDatum { opaque_ty_id: id, bound })
}
fn hidden_opaque_type(&self, _id: chalk_ir::OpaqueTyId<Interner>) -> chalk_ir::Ty<Interner> {

3
crates/hir_ty/src/traits/chalk/tls.rs
View file

@ -73,6 +73,9 @@ impl DebugContext<'_> {
crate::OpaqueTyId::ReturnTypeImplTrait(func, idx) => {
write!(f, "{{impl trait {} of {:?}}}", idx, func)?;
}
crate::OpaqueTyId::AsyncBlockTypeImplTrait(def, idx) => {
write!(f, "{{impl trait of async block {} of {:?}}}", idx.into_raw(), def)?;
}
},
TypeCtor::Closure { def, expr } => {
write!(f, "{{closure {:?} in ", expr.into_raw())?;

22
crates/ide/src/completion/complete_keyword.rs
View file

@ -506,6 +506,28 @@ pub mod future {
#[lang = "future_trait"]
pub trait Future {}
}
"#,
expect![[r#"
kw await expr.await
"#]],
);
check(
r#"
//- /main.rs
use std::future::*;
fn foo() {
let a = async {};
a.<|>
}
//- /std/lib.rs
pub mod future {
#[lang = "future_trait"]
pub trait Future {
type Output;
}
}
"#,
expect![[r#"
kw await expr.await

64
crates/ide/src/hover.rs
View file

@ -2646,6 +2646,70 @@ fn foo(ar<|>g: &impl Foo + Bar<S>) {}
);
}
#[test]
fn test_hover_async_block_impl_trait_has_goto_type_action() {
check_actions(
r#"
struct S;
fn foo() {
let fo<|>o = async { S };
}
#[prelude_import] use future::*;
mod future {
#[lang = "future_trait"]
pub trait Future { type Output; }
}
"#,
expect![[r#"
[
GoToType(
[
HoverGotoTypeData {
mod_path: "test::future::Future",
nav: NavigationTarget {
file_id: FileId(
1,
),
full_range: 101..163,
focus_range: Some(
140..146,
),
name: "Future",
kind: TRAIT,
container_name: None,
description: Some(
"pub trait Future",
),
docs: None,
},
},
HoverGotoTypeData {
mod_path: "test::S",
nav: NavigationTarget {
file_id: FileId(
1,
),
full_range: 0..9,
focus_range: Some(
7..8,
),
name: "S",
kind: STRUCT,
container_name: None,
description: Some(
"struct S",
),
docs: None,
},
},
],
),
]
"#]],
);
}
#[test]
fn test_hover_arg_generic_impl_trait_has_goto_type_action() {
check_actions(