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Merged
merged 1 commit into from
Apr 7, 2021
Merged

forbid impl Trait in generic param defaults #83935

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8 changes: 1 addition & 7 deletions compiler/rustc_ast_lowering/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -2259,13 +2259,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {

let kind = hir::GenericParamKind::Type {
default: default.as_ref().map(|x| {
self.lower_ty(
x,
ImplTraitContext::OtherOpaqueTy {
capturable_lifetimes: &mut FxHashSet::default(),
origin: hir::OpaqueTyOrigin::Misc,
},
)
self.lower_ty(x, ImplTraitContext::Disallowed(ImplTraitPosition::Other))
}),
synthetic: param
.attrs
Expand Down
12 changes: 12 additions & 0 deletions src/test/ui/impl-trait/issues/issue-83929-impl-trait-in-generic-default.rs
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Original file line number Diff line number Diff line change
@@ -0,0 +1,12 @@
struct Foo<T = impl Copy>(T);
//~^ ERROR `impl Trait` not allowed outside of function and inherent method return types

type Result<T, E = impl std::error::Error> = std::result::Result<T, E>;
//~^ ERROR `impl Trait` not allowed outside of function and inherent method return types

// should not cause ICE
fn x() -> Foo {
Foo(0)
}

fn main() -> Result<()> {}
15 changes: 15 additions & 0 deletions src/test/ui/impl-trait/issues/issue-83929-impl-trait-in-generic-default.stderr
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Original file line number Diff line number Diff line change
@@ -0,0 +1,15 @@
error[E0562]: `impl Trait` not allowed outside of function and inherent method return types
--> $DIR/issue-83929-impl-trait-in-generic-default.rs:1:16
|
LL | struct Foo<T = impl Copy>(T);
| ^^^^^^^^^

error[E0562]: `impl Trait` not allowed outside of function and inherent method return types
--> $DIR/issue-83929-impl-trait-in-generic-default.rs:4:20
|
LL | type Result<T, E = impl std::error::Error> = std::result::Result<T, E>;
| ^^^^^^^^^^^^^^^^^^^^^^

error: aborting due to 2 previous errors

For more information about this error, try `rustc --explain E0562`.
32 changes: 28 additions & 4 deletions src/test/ui/impl-trait/where-allowed.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -56,12 +56,10 @@ fn in_impl_Fn_return_in_parameters(_: &impl Fn() -> impl Debug) { panic!() }
fn in_impl_Fn_parameter_in_return() -> &'static impl Fn(impl Debug) { panic!() }
//~^ ERROR `impl Trait` not allowed outside of function and inherent method return types
//~| ERROR nested `impl Trait` is not allowed
//~| ERROR cannot resolve opaque type

// Disallowed
fn in_impl_Fn_return_in_return() -> &'static impl Fn() -> impl Debug { panic!() }
//~^ ERROR `impl Trait` not allowed outside of function and inherent method return types
//~| ERROR cannot resolve opaque type

// Disallowed
fn in_Fn_parameter_in_generics<F: Fn(impl Debug)> (_: F) { panic!() }
Expand Down Expand Up @@ -120,7 +118,6 @@ trait DummyTrait {
impl DummyTrait for () {
type Out = impl Debug;
//~^ ERROR `impl Trait` in type aliases is unstable
//~^^ ERROR could not find defining uses

fn in_trait_impl_parameter(_: impl Debug) { }
// Allowed
Expand Down Expand Up @@ -156,7 +153,6 @@ extern "C" fn in_extern_fn_return() -> impl Debug {

type InTypeAlias<R> = impl Debug;
//~^ ERROR `impl Trait` in type aliases is unstable
//~^^ ERROR could not find defining uses

type InReturnInTypeAlias<R> = fn() -> impl Debug;
//~^ ERROR `impl Trait` not allowed outside of function and inherent method return types
Expand Down Expand Up @@ -218,6 +214,34 @@ fn in_Fn_return_in_fn_where_clause<T>()
{
}

// Disallowed
struct InStructGenericParamDefault<T = impl Debug>(T);
//~^ ERROR `impl Trait` not allowed outside of function and inherent method return types

// Disallowed
enum InEnumGenericParamDefault<T = impl Debug> { Variant(T) }
//~^ ERROR `impl Trait` not allowed outside of function and inherent method return types

// Disallowed
trait InTraitGenericParamDefault<T = impl Debug> {}
//~^ ERROR `impl Trait` not allowed outside of function and inherent method return types

// Disallowed
type InTypeAliasGenericParamDefault<T = impl Debug> = T;
//~^ ERROR `impl Trait` not allowed outside of function and inherent method return types

// 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` not allowed outside of function and inherent method return types

// 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` not allowed outside of function and inherent method return types

fn main() {
let _in_local_variable: impl Fn() = || {};
//~^ ERROR `impl Trait` not allowed outside of function and inherent method return types
Expand Down
133 changes: 78 additions & 55 deletions src/test/ui/impl-trait/where-allowed.stderr
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Original file line number Diff line number Diff line change
Expand Up @@ -17,7 +17,7 @@ LL | fn in_impl_Fn_parameter_in_return() -> &'static impl Fn(impl Debug) { panic
| outer `impl Trait`

error[E0658]: `impl Trait` in type aliases is unstable
--> $DIR/where-allowed.rs:121:16
--> $DIR/where-allowed.rs:119:16
|
LL | type Out = impl Debug;
| ^^^^^^^^^^
Expand All @@ -26,7 +26,7 @@ LL | type Out = impl Debug;
= help: add `#![feature(min_type_alias_impl_trait)]` to the crate attributes to enable

error[E0658]: `impl Trait` in type aliases is unstable
--> $DIR/where-allowed.rs:157:23
--> $DIR/where-allowed.rs:154:23
|
LL | type InTypeAlias<R> = impl Debug;
| ^^^^^^^^^^
Expand All @@ -35,7 +35,7 @@ LL | type InTypeAlias<R> = impl Debug;
= help: add `#![feature(min_type_alias_impl_trait)]` to the crate attributes to enable

error[E0658]: `impl Trait` in type aliases is unstable
--> $DIR/where-allowed.rs:161:39
--> $DIR/where-allowed.rs:157:39
|
LL | type InReturnInTypeAlias<R> = fn() -> impl Debug;
| ^^^^^^^^^^
Expand Down Expand Up @@ -110,184 +110,207 @@ LL | fn in_impl_Fn_parameter_in_return() -> &'static impl Fn(impl Debug) { panic
| ^^^^^^^^^^

error[E0562]: `impl Trait` not allowed outside of function and inherent method return types
--> $DIR/where-allowed.rs:62:59
--> $DIR/where-allowed.rs:61:59
|
LL | fn in_impl_Fn_return_in_return() -> &'static impl Fn() -> impl Debug { panic!() }
| ^^^^^^^^^^

error[E0562]: `impl Trait` not allowed outside of function and inherent method return types
--> $DIR/where-allowed.rs:67:38
--> $DIR/where-allowed.rs:65:38
|
LL | fn in_Fn_parameter_in_generics<F: Fn(impl Debug)> (_: F) { panic!() }
| ^^^^^^^^^^

error[E0562]: `impl Trait` not allowed outside of function and inherent method return types
--> $DIR/where-allowed.rs:71:40
--> $DIR/where-allowed.rs:69:40
|
LL | fn in_Fn_return_in_generics<F: Fn() -> impl Debug> (_: F) { panic!() }
| ^^^^^^^^^^

error[E0562]: `impl Trait` not allowed outside of function and inherent method return types
--> $DIR/where-allowed.rs:84:32
--> $DIR/where-allowed.rs:82:32
|
LL | struct InBraceStructField { x: impl Debug }
| ^^^^^^^^^^

error[E0562]: `impl Trait` not allowed outside of function and inherent method return types
--> $DIR/where-allowed.rs:88:41
--> $DIR/where-allowed.rs:86:41
|
LL | struct InAdtInBraceStructField { x: Vec<impl Debug> }
| ^^^^^^^^^^

error[E0562]: `impl Trait` not allowed outside of function and inherent method return types
--> $DIR/where-allowed.rs:92:27
--> $DIR/where-allowed.rs:90:27
|
LL | struct InTupleStructField(impl Debug);
| ^^^^^^^^^^

error[E0562]: `impl Trait` not allowed outside of function and inherent method return types
--> $DIR/where-allowed.rs:97:25
--> $DIR/where-allowed.rs:95:25
|
LL | InBraceVariant { x: impl Debug },
| ^^^^^^^^^^

error[E0562]: `impl Trait` not allowed outside of function and inherent method return types
--> $DIR/where-allowed.rs:99:20
--> $DIR/where-allowed.rs:97:20
|
LL | InTupleVariant(impl Debug),
| ^^^^^^^^^^

error[E0562]: `impl Trait` not allowed outside of function and inherent method return types
--> $DIR/where-allowed.rs:110:23
--> $DIR/where-allowed.rs:108:23
|
LL | fn in_return() -> impl Debug;
| ^^^^^^^^^^

error[E0562]: `impl Trait` not allowed outside of function and inherent method return types
--> $DIR/where-allowed.rs:128:34
--> $DIR/where-allowed.rs:125:34
|
LL | fn in_trait_impl_return() -> impl Debug { () }
| ^^^^^^^^^^

error[E0562]: `impl Trait` not allowed outside of function and inherent method return types
--> $DIR/where-allowed.rs:141:33
--> $DIR/where-allowed.rs:138:33
|
LL | fn in_foreign_parameters(_: impl Debug);
| ^^^^^^^^^^

error[E0562]: `impl Trait` not allowed outside of function and inherent method return types
--> $DIR/where-allowed.rs:144:31
--> $DIR/where-allowed.rs:141:31
|
LL | fn in_foreign_return() -> impl Debug;
| ^^^^^^^^^^

error[E0562]: `impl Trait` not allowed outside of function and inherent method return types
--> $DIR/where-allowed.rs:161:39
--> $DIR/where-allowed.rs:157:39
|
LL | type InReturnInTypeAlias<R> = fn() -> impl Debug;
| ^^^^^^^^^^

error[E0562]: `impl Trait` not allowed outside of function and inherent method return types
--> $DIR/where-allowed.rs:166:16
--> $DIR/where-allowed.rs:162:16
|
LL | impl PartialEq<impl Debug> for () {
| ^^^^^^^^^^

error[E0562]: `impl Trait` not allowed outside of function and inherent method return types
--> $DIR/where-allowed.rs:171:24
--> $DIR/where-allowed.rs:167:24
|
LL | impl PartialEq<()> for impl Debug {
| ^^^^^^^^^^

error[E0562]: `impl Trait` not allowed outside of function and inherent method return types
--> $DIR/where-allowed.rs:176:6
--> $DIR/where-allowed.rs:172:6
|
LL | impl impl Debug {
| ^^^^^^^^^^

error[E0562]: `impl Trait` not allowed outside of function and inherent method return types
--> $DIR/where-allowed.rs:182:24
--> $DIR/where-allowed.rs:178:24
|
LL | impl InInherentImplAdt<impl Debug> {
| ^^^^^^^^^^

error[E0562]: `impl Trait` not allowed outside of function and inherent method return types
--> $DIR/where-allowed.rs:188:11
--> $DIR/where-allowed.rs:184:11
|
LL | where impl Debug: Debug
| ^^^^^^^^^^

error[E0562]: `impl Trait` not allowed outside of function and inherent method return types
--> $DIR/where-allowed.rs:195:15
--> $DIR/where-allowed.rs:191:15
|
LL | where Vec<impl Debug>: Debug
| ^^^^^^^^^^

error[E0562]: `impl Trait` not allowed outside of function and inherent method return types
--> $DIR/where-allowed.rs:202:24
--> $DIR/where-allowed.rs:198:24
|
LL | where T: PartialEq<impl Debug>
| ^^^^^^^^^^

error[E0562]: `impl Trait` not allowed outside of function and inherent method return types
--> $DIR/where-allowed.rs:209:17
--> $DIR/where-allowed.rs:205:17
|
LL | where T: Fn(impl Debug)
| ^^^^^^^^^^

error[E0562]: `impl Trait` not allowed outside of function and inherent method return types
--> $DIR/where-allowed.rs:216:22
--> $DIR/where-allowed.rs:212:22
|
LL | where T: Fn() -> impl Debug
| ^^^^^^^^^^

error[E0562]: `impl Trait` not allowed outside of function and inherent method return types
--> $DIR/where-allowed.rs:222:29
--> $DIR/where-allowed.rs:218:40
|
LL | struct InStructGenericParamDefault<T = impl Debug>(T);
| ^^^^^^^^^^

error[E0562]: `impl Trait` not allowed outside of function and inherent method return types
--> $DIR/where-allowed.rs:222:36
|
LL | enum InEnumGenericParamDefault<T = impl Debug> { Variant(T) }
| ^^^^^^^^^^

error[E0562]: `impl Trait` not allowed outside of function and inherent method return types
--> $DIR/where-allowed.rs:226:38
|
LL | trait InTraitGenericParamDefault<T = impl Debug> {}
| ^^^^^^^^^^

error[E0562]: `impl Trait` not allowed outside of function and inherent method return types
--> $DIR/where-allowed.rs:230:41
|
LL | type InTypeAliasGenericParamDefault<T = impl Debug> = T;
| ^^^^^^^^^^

error[E0562]: `impl Trait` not allowed outside of function and inherent method return types
--> $DIR/where-allowed.rs:234:11
|
LL | impl <T = impl Debug> T {}
| ^^^^^^^^^^

error[E0562]: `impl Trait` not allowed outside of function and inherent method return types
--> $DIR/where-allowed.rs:240:40
|
LL | fn in_method_generic_param_default<T = impl Debug>(_: T) {}
| ^^^^^^^^^^

error[E0562]: `impl Trait` not allowed outside of function and inherent method return types
--> $DIR/where-allowed.rs:246:29
|
LL | let _in_local_variable: impl Fn() = || {};
| ^^^^^^^^^
|
= help: add `#![feature(impl_trait_in_bindings)]` to the crate attributes to enable

error[E0562]: `impl Trait` not allowed outside of function and inherent method return types
--> $DIR/where-allowed.rs:224:46
--> $DIR/where-allowed.rs:248:46
|
LL | let _in_return_in_local_variable = || -> impl Fn() { || {} };
| ^^^^^^^^^

error[E0720]: cannot resolve opaque type
--> $DIR/where-allowed.rs:56:49
|
LL | fn in_impl_Fn_parameter_in_return() -> &'static impl Fn(impl Debug) { panic!() }
| ^^^^^^^^^^^^^^^^^^^ -------- this returned value is of `!` type
| |
| cannot resolve opaque type
|
= help: this error will resolve once the item's body returns a concrete type

error[E0720]: cannot resolve opaque type
--> $DIR/where-allowed.rs:62:46
error: defaults for type parameters are only allowed in `struct`, `enum`, `type`, or `trait` definitions
--> $DIR/where-allowed.rs:234:7
|
LL | fn in_impl_Fn_return_in_return() -> &'static impl Fn() -> impl Debug { panic!() }
| ^^^^^^^^^^^^^^^^^^^^^^^ -------- this returned value is of `!` type
| |
| cannot resolve opaque type
LL | impl <T = impl Debug> T {}
| ^
|
= help: this error will resolve once the item's body returns a concrete type
= note: `#[deny(invalid_type_param_default)]` on by default
= warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
= note: for more information, see issue #36887 <https://github.com/rust-lang/rust/issues/36887>

error: could not find defining uses
--> $DIR/where-allowed.rs:121:16
error: defaults for type parameters are only allowed in `struct`, `enum`, `type`, or `trait` definitions
--> $DIR/where-allowed.rs:240:36
|
LL | type Out = impl Debug;
| ^^^^^^^^^^

error: could not find defining uses
--> $DIR/where-allowed.rs:157:23
LL | fn in_method_generic_param_default<T = impl Debug>(_: T) {}
| ^
|
LL | type InTypeAlias<R> = impl Debug;
| ^^^^^^^^^^
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I think these errors disappeared because hitting the invalid_type_param_default future compat lint is making the compiler abort earlier.

= warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
= note: for more information, see issue #36887 <https://github.com/rust-lang/rust/issues/36887>

error: aborting due to 44 previous errors
error: aborting due to 48 previous errors

Some errors have detailed explanations: E0562, E0658, E0666, E0720.
Some errors have detailed explanations: E0562, E0658, E0666.
For more information about an error, try `rustc --explain E0562`.