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//! A simple test for testing many permutations of allowedness of
//! impl Trait
#![feature(impl_trait_in_fn_trait_return)]
#![feature(custom_inner_attributes)]
#![rustfmt::skip]
use std::fmt::Debug;
// Allowed
fn in_parameters(_: impl Debug) { panic!() }
// Allowed
fn in_return() -> impl Debug { panic!() }
// Allowed
fn in_adt_in_parameters(_: Vec<impl Debug>) { panic!() }
// Disallowed
fn in_fn_parameter_in_parameters(_: fn(impl Debug)) { panic!() }
//~^ ERROR `impl Trait` is not allowed in `fn` pointer
// Disallowed
fn in_fn_return_in_parameters(_: fn() -> impl Debug) { panic!() }
//~^ ERROR `impl Trait` is not allowed in `fn` pointer
// Disallowed
fn in_fn_parameter_in_return() -> fn(impl Debug) { panic!() }
//~^ ERROR `impl Trait` is not allowed in `fn` pointer
// Disallowed
fn in_fn_return_in_return() -> fn() -> impl Debug { panic!() }
//~^ ERROR `impl Trait` is not allowed in `fn` pointer
// Disallowed
fn in_dyn_Fn_parameter_in_parameters(_: &dyn Fn(impl Debug)) { panic!() }
//~^ ERROR `impl Trait` is not allowed in the parameters of `Fn` trait bounds
// Disallowed
fn in_dyn_Fn_return_in_parameters(_: &dyn Fn() -> impl Debug) { panic!() }
//~^ ERROR `impl Trait` is not allowed in the return type of `Fn` trait bounds
// Disallowed
fn in_dyn_Fn_parameter_in_return() -> &'static dyn Fn(impl Debug) { panic!() }
//~^ ERROR `impl Trait` is not allowed in the parameters of `Fn` trait bounds
// Allowed (but it's still ambiguous; nothing constrains the RPIT in this body).
fn in_dyn_Fn_return_in_return() -> &'static dyn Fn() -> impl Debug { panic!() }
//~^ ERROR: type annotations needed
// Disallowed
fn in_impl_Fn_parameter_in_parameters(_: &impl Fn(impl Debug)) { panic!() }
//~^ ERROR `impl Trait` is not allowed in the parameters of `Fn` trait bounds
//~^^ ERROR nested `impl Trait` is not allowed
// Disallowed
fn in_impl_Fn_return_in_parameters(_: &impl Fn() -> impl Debug) { panic!() }
//~^ ERROR `impl Trait` is not allowed in the return type of `Fn` trait bounds
// Disallowed
fn in_impl_Fn_parameter_in_return() -> &'static impl Fn(impl Debug) { panic!() }
//~^ ERROR `impl Trait` is not allowed in the parameters of `Fn` trait bounds
//~| ERROR nested `impl Trait` is not allowed
// Allowed
fn in_impl_Fn_return_in_return() -> &'static impl Fn() -> impl Debug { panic!() }
//~^ ERROR: type annotations needed
// Disallowed
fn in_Fn_parameter_in_generics<F: Fn(impl Debug)> (_: F) { panic!() }
//~^ ERROR `impl Trait` is not allowed in the parameters of `Fn` trait bounds
// Disallowed
fn in_Fn_return_in_generics<F: Fn() -> impl Debug> (_: F) { panic!() }
//~^ ERROR `impl Trait` is not allowed in the return type of `Fn` trait bounds
// Allowed
fn in_impl_Trait_in_parameters(_: impl Iterator<Item = impl Iterator>) { panic!() }
// Allowed
fn in_impl_Trait_in_return() -> impl IntoIterator<Item = impl IntoIterator> {
vec![vec![0; 10], vec![12; 7], vec![8; 3]]
}
// Disallowed
struct InBraceStructField { x: impl Debug }
//~^ ERROR `impl Trait` is not allowed in field types
// Disallowed
struct InAdtInBraceStructField { x: Vec<impl Debug> }
//~^ ERROR `impl Trait` is not allowed in field types
// Disallowed
struct InTupleStructField(impl Debug);
//~^ ERROR `impl Trait` is not allowed in field types
// Disallowed
enum InEnum {
InBraceVariant { x: impl Debug },
//~^ ERROR `impl Trait` is not allowed in field types
InTupleVariant(impl Debug),
//~^ ERROR `impl Trait` is not allowed in field types
}
// Allowed
trait InTraitDefnParameters {
fn in_parameters(_: impl Debug);
}
// Allowed
trait InTraitDefnReturn {
fn in_return() -> impl Debug;
}
// Allowed and disallowed in trait impls
trait DummyTrait {
type Out;
fn in_trait_impl_parameter(_: impl Debug);
fn in_trait_impl_return() -> Self::Out;
}
impl DummyTrait for () {
type Out = impl Debug;
//~^ ERROR `impl Trait` in associated types is unstable
//~| ERROR unconstrained opaque type
fn in_trait_impl_parameter(_: impl Debug) { }
// Allowed
fn in_trait_impl_return() -> impl Debug { () }
//~^ ERROR `in_trait_impl_return` has an incompatible type for trait
// Allowed
}
// Allowed
struct DummyType;
impl DummyType {
fn in_inherent_impl_parameters(_: impl Debug) { }
fn in_inherent_impl_return() -> impl Debug { () }
}
// Disallowed
extern "C" {
fn in_foreign_parameters(_: impl Debug);
//~^ ERROR `impl Trait` is not allowed in `extern fn`
fn in_foreign_return() -> impl Debug;
//~^ ERROR `impl Trait` is not allowed in `extern fn`
}
// Allowed
extern "C" fn in_extern_fn_parameters(_: impl Debug) {
}
// Allowed
extern "C" fn in_extern_fn_return() -> impl Debug {
22
}
type InTypeAlias<R> = impl Debug;
//~^ ERROR `impl Trait` in type aliases is unstable
type InReturnInTypeAlias<R> = fn() -> impl Debug;
//~^ ERROR `impl Trait` is not allowed in `fn` pointer
//~| ERROR `impl Trait` in type aliases is unstable
// Disallowed in impl headers
impl PartialEq<impl Debug> for () {
//~^ ERROR `impl Trait` is not allowed in traits
}
// Disallowed in impl headers
impl PartialEq<()> for impl Debug {
//~^ ERROR `impl Trait` is not allowed in impl headers
}
// Disallowed in inherent impls
impl impl Debug {
//~^ ERROR `impl Trait` is not allowed in impl headers
}
// Disallowed in inherent impls
struct InInherentImplAdt<T> { t: T }
impl InInherentImplAdt<impl Debug> {
//~^ ERROR `impl Trait` is not allowed in impl headers
}
// Disallowed in where clauses
fn in_fn_where_clause()
where impl Debug: Debug
//~^ ERROR `impl Trait` is not allowed in bounds
{
}
// Disallowed in where clauses
fn in_adt_in_fn_where_clause()
where Vec<impl Debug>: Debug
//~^ ERROR `impl Trait` is not allowed in bounds
{
}
// Disallowed
fn in_trait_parameter_in_fn_where_clause<T>()
where T: PartialEq<impl Debug>
//~^ ERROR `impl Trait` is not allowed in bounds
{
}
// Disallowed
fn in_Fn_parameter_in_fn_where_clause<T>()
where T: Fn(impl Debug)
//~^ ERROR `impl Trait` is not allowed in the parameters of `Fn` trait bounds
{
}
// Disallowed
fn in_Fn_return_in_fn_where_clause<T>()
where T: Fn() -> impl Debug
//~^ ERROR `impl Trait` is not allowed in the return type of `Fn` trait bounds
{
}
// Disallowed
struct InStructGenericParamDefault<T = impl Debug>(T);
//~^ ERROR `impl Trait` is not allowed in generic parameter defaults
// Disallowed
enum InEnumGenericParamDefault<T = impl Debug> { Variant(T) }
//~^ ERROR `impl Trait` is not allowed in generic parameter defaults
// Disallowed
trait InTraitGenericParamDefault<T = impl Debug> {}
//~^ ERROR `impl Trait` is not allowed in generic parameter defaults
// Disallowed
type InTypeAliasGenericParamDefault<T = impl Debug> = T;
//~^ ERROR `impl Trait` is not allowed in generic parameter defaults
// Disallowed
impl <T = impl Debug> T {}
//~^ ERROR defaults for type parameters are only allowed in `struct`, `enum`, `type`, or `trait` definitions
//~| WARNING this was previously accepted by the compiler but is being phased out
//~| ERROR `impl Trait` is not allowed in generic parameter defaults
//~| ERROR no nominal type found
// Disallowed
fn in_method_generic_param_default<T = impl Debug>(_: T) {}
//~^ ERROR defaults for type parameters are only allowed in `struct`, `enum`, `type`, or `trait` definitions
//~| WARNING this was previously accepted by the compiler but is being phased out
//~| ERROR `impl Trait` is not allowed in generic parameter defaults
fn main() {
let _in_local_variable: impl Fn() = || {};
//~^ ERROR `impl Trait` is not allowed in the type of variable bindings
let _in_return_in_local_variable = || -> impl Fn() { || {} };
//~^ ERROR `impl Trait` is not allowed in closure return types
}
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