warn against 'specialization' feature

Author: RalfJung

src/librustc_feature/active.rs

@@ -596,4 +596,5 @@ pub const INCOMPLETE_FEATURES: &[Symbol] = &[
     sym::raw_dylib,
     sym::const_trait_impl,
     sym::const_trait_bound_opt_out,
+    sym::specialization,
 ];

src/test/ui/associated-types/defaults-specialization.rs

@@ -1,6 +1,7 @@
 //! Tests the interaction of associated type defaults and specialization.
 
 #![feature(associated_type_defaults, specialization)]
+//~^ WARN the feature `specialization` is incomplete
 
 trait Tr {
     type Ty = u8;

src/test/ui/associated-types/defaults-specialization.stderr

@@ -1,5 +1,14 @@
+warning: the feature `specialization` is incomplete and may be unsafe to use and/or cause compiler crashes
+  --> $DIR/defaults-specialization.rs:3:38
+   |
+LL | #![feature(associated_type_defaults, specialization)]
+   |                                      ^^^^^^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
+   = note: see issue #31844 <https://github.com/rust-lang/rust/issues/31844> for more information
+
 error[E0053]: method `make` has an incompatible type for trait
-  --> $DIR/defaults-specialization.rs:18:18
+  --> $DIR/defaults-specialization.rs:19:18
    |
 LL |     fn make() -> Self::Ty {
    |                  -------- type in trait
@@ -11,7 +20,7 @@ LL |     fn make() -> u8 { 0 }
               found fn pointer `fn() -> u8`
 
 error[E0053]: method `make` has an incompatible type for trait
-  --> $DIR/defaults-specialization.rs:34:18
+  --> $DIR/defaults-specialization.rs:35:18
    |
 LL |     fn make() -> Self::Ty {
    |                  -------- type in trait
@@ -26,7 +35,7 @@ LL |     fn make() -> bool { true }
               found fn pointer `fn() -> bool`
 
 error[E0308]: mismatched types
-  --> $DIR/defaults-specialization.rs:9:9
+  --> $DIR/defaults-specialization.rs:10:9
    |
 LL |     type Ty = u8;
    |     ------------- associated type defaults can't be assumed inside the trait defining them
@@ -40,7 +49,7 @@ LL |         0u8
                          found type `u8`
 
 error[E0308]: mismatched types
-  --> $DIR/defaults-specialization.rs:25:29
+  --> $DIR/defaults-specialization.rs:26:29
    |
 LL |     fn make() -> Self::Ty { 0u8 }
    |                  --------   ^^^ expected associated type, found `u8`
@@ -53,7 +62,7 @@ LL |     fn make() -> Self::Ty { 0u8 }
    = note: for more information, visit https://doc.rust-lang.org/book/ch19-03-advanced-traits.html
 
 error[E0308]: mismatched types
-  --> $DIR/defaults-specialization.rs:43:29
+  --> $DIR/defaults-specialization.rs:44:29
    |
 LL |     default type Ty = bool;
    |     ----------------------- expected this associated type
@@ -67,7 +76,7 @@ LL |     fn make() -> Self::Ty { true }
                          found type `bool`
 
 error[E0308]: mismatched types
-  --> $DIR/defaults-specialization.rs:86:32
+  --> $DIR/defaults-specialization.rs:87:32
    |
 LL |     let _: <B<()> as Tr>::Ty = 0u8;
    |            -----------------   ^^^ expected associated type, found `u8`
@@ -77,13 +86,13 @@ LL |     let _: <B<()> as Tr>::Ty = 0u8;
    = note: expected associated type `<B<()> as Tr>::Ty`
                          found type `u8`
 help: a method is available that returns `<B<()> as Tr>::Ty`
-  --> $DIR/defaults-specialization.rs:8:5
+  --> $DIR/defaults-specialization.rs:9:5
    |
 LL |     fn make() -> Self::Ty {
    |     ^^^^^^^^^^^^^^^^^^^^^ consider calling `Tr::make`
 
 error[E0308]: mismatched types
-  --> $DIR/defaults-specialization.rs:87:32
+  --> $DIR/defaults-specialization.rs:88:32
    |
 LL |     let _: <B<()> as Tr>::Ty = true;
    |            -----------------   ^^^^ expected associated type, found `bool`
@@ -93,13 +102,13 @@ LL |     let _: <B<()> as Tr>::Ty = true;
    = note: expected associated type `<B<()> as Tr>::Ty`
                          found type `bool`
 help: a method is available that returns `<B<()> as Tr>::Ty`
-  --> $DIR/defaults-specialization.rs:8:5
+  --> $DIR/defaults-specialization.rs:9:5
    |
 LL |     fn make() -> Self::Ty {
    |     ^^^^^^^^^^^^^^^^^^^^^ consider calling `Tr::make`
 
 error[E0308]: mismatched types
-  --> $DIR/defaults-specialization.rs:88:33
+  --> $DIR/defaults-specialization.rs:89:33
    |
 LL |     let _: <B2<()> as Tr>::Ty = 0u8;
    |            ------------------   ^^^ expected associated type, found `u8`
@@ -109,13 +118,13 @@ LL |     let _: <B2<()> as Tr>::Ty = 0u8;
    = note: expected associated type `<B2<()> as Tr>::Ty`
                          found type `u8`
 help: a method is available that returns `<B2<()> as Tr>::Ty`
-  --> $DIR/defaults-specialization.rs:8:5
+  --> $DIR/defaults-specialization.rs:9:5
    |
 LL |     fn make() -> Self::Ty {
    |     ^^^^^^^^^^^^^^^^^^^^^ consider calling `Tr::make`
 
 error[E0308]: mismatched types
-  --> $DIR/defaults-specialization.rs:89:33
+  --> $DIR/defaults-specialization.rs:90:33
    |
 LL |     let _: <B2<()> as Tr>::Ty = true;
    |            ------------------   ^^^^ expected associated type, found `bool`
@@ -125,12 +134,12 @@ LL |     let _: <B2<()> as Tr>::Ty = true;
    = note: expected associated type `<B2<()> as Tr>::Ty`
                          found type `bool`
 help: a method is available that returns `<B2<()> as Tr>::Ty`
-  --> $DIR/defaults-specialization.rs:8:5
+  --> $DIR/defaults-specialization.rs:9:5
    |
 LL |     fn make() -> Self::Ty {
    |     ^^^^^^^^^^^^^^^^^^^^^ consider calling `Tr::make`
 
-error: aborting due to 9 previous errors
+error: aborting due to 9 previous errors; 1 warning emitted
 
 Some errors have detailed explanations: E0053, E0308.
 For more information about an error, try `rustc --explain E0053`.

src/test/ui/consts/trait_specialization.rs

@@ -5,7 +5,7 @@
 // Tests that specialization does not cause optimizations running on polymorphic MIR to resolve
 // to a `default` implementation.
 
-#![feature(specialization)]
+#![feature(specialization)] //~ WARN the feature `specialization` is incomplete
 
 trait Marker {}
 

src/test/ui/consts/trait_specialization.stderr

@@ -0,0 +1,11 @@
+warning: the feature `specialization` is incomplete and may not be safe to use and/or cause compiler crashes
+  --> $DIR/trait_specialization.rs:8:12
+   |
+LL | #![feature(specialization)]
+   |            ^^^^^^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
+   = note: see issue #31844 <https://github.com/rust-lang/rust/issues/31844> for more information
+
+warning: 1 warning emitted
+

src/test/ui/impl-trait/equality-rpass.rs

@@ -1,6 +1,6 @@
 // run-pass
 
-#![feature(specialization)]
+#![feature(specialization)] //~ WARN the feature `specialization` is incomplete
 
 trait Foo: std::fmt::Debug + Eq {}
 

src/test/ui/impl-trait/equality-rpass.stderr

@@ -0,0 +1,11 @@
+warning: the feature `specialization` is incomplete and may not be safe to use and/or cause compiler crashes
+  --> $DIR/equality-rpass.rs:3:12
+   |
+LL | #![feature(specialization)]
+   |            ^^^^^^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
+   = note: see issue #31844 <https://github.com/rust-lang/rust/issues/31844> for more information
+
+warning: 1 warning emitted
+

src/test/ui/impl-trait/equality.rs

@@ -1,4 +1,4 @@
-#![feature(specialization)]
+#![feature(specialization)] //~ WARN the feature `specialization` is incomplete
 
 trait Foo: Copy + ToString {}
 

src/test/ui/impl-trait/equality.stderr

@@ -1,3 +1,12 @@
+warning: the feature `specialization` is incomplete and may not be safe to use and/or cause compiler crashes
+  --> $DIR/equality.rs:1:12
+   |
+LL | #![feature(specialization)]
+   |            ^^^^^^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
+   = note: see issue #31844 <https://github.com/rust-lang/rust/issues/31844> for more information
+
 error[E0308]: mismatched types
   --> $DIR/equality.rs:15:5
    |
@@ -24,7 +33,7 @@ LL |         n + sum_to(n - 1)
    |
    = help: the trait `std::ops::Add<impl Foo>` is not implemented for `u32`
 
-error: aborting due to 2 previous errors
+error: aborting due to 2 previous errors; 1 warning emitted
 
 Some errors have detailed explanations: E0277, E0308.
 For more information about an error, try `rustc --explain E0277`.

src/test/ui/impl-trait/equality2.rs

@@ -1,4 +1,4 @@
-#![feature(specialization)]
+#![feature(specialization)] //~ WARN the feature `specialization` is incomplete
 
 trait Foo: Copy + ToString {}
 

src/test/ui/impl-trait/equality2.stderr

@@ -1,3 +1,12 @@
+warning: the feature `specialization` is incomplete and may not be safe to use and/or cause compiler crashes
+  --> $DIR/equality2.rs:1:12
+   |
+LL | #![feature(specialization)]
+   |            ^^^^^^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
+   = note: see issue #31844 <https://github.com/rust-lang/rust/issues/31844> for more information
+
 error[E0308]: mismatched types
   --> $DIR/equality2.rs:25:18
    |
@@ -58,6 +67,6 @@ LL |          x.0);
    = note: expected opaque type `impl Foo` (`i32`)
               found opaque type `impl Foo` (`u32`)
 
-error: aborting due to 4 previous errors
+error: aborting due to 4 previous errors; 1 warning emitted
 
 For more information about this error, try `rustc --explain E0308`.

src/test/ui/overlap-doesnt-conflict-with-specialization.rs

@@ -1,7 +1,7 @@
 // run-pass
 
 #![feature(marker_trait_attr)]
-#![feature(specialization)]
+#![feature(specialization)] //~ WARN the feature `specialization` is incomplete
 
 #[marker]
 trait MyMarker {}

src/test/ui/overlap-doesnt-conflict-with-specialization.stderr

@@ -0,0 +1,11 @@
+warning: the feature `specialization` is incomplete and may be unsafe to use and/or cause compiler crashes
+  --> $DIR/overlap-doesnt-conflict-with-specialization.rs:4:12
+   |
+LL | #![feature(specialization)]
+   |            ^^^^^^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
+   = note: see issue #31844 <https://github.com/rust-lang/rust/issues/31844> for more information
+
+warning: 1 warning emitted
+

src/test/ui/parser/trait-item-with-defaultness-fail-semantic.rs

@@ -1,4 +1,4 @@
-#![feature(specialization)]
+#![feature(specialization)] //~ WARN the feature `specialization` is incomplete
 
 fn main() {}
 

src/test/ui/parser/trait-item-with-defaultness-fail-semantic.stderr

@@ -46,5 +46,14 @@ LL |     default fn f2() {}
    |     |
    |     `default` because of this
 
-error: aborting due to 6 previous errors
+warning: the feature `specialization` is incomplete and may not be safe to use and/or cause compiler crashes
+  --> $DIR/trait-item-with-defaultness-fail-semantic.rs:1:12
+   |
+LL | #![feature(specialization)]
+   |            ^^^^^^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
+   = note: see issue #31844 <https://github.com/rust-lang/rust/issues/31844> for more information
+
+error: aborting due to 6 previous errors; 1 warning emitted
 

src/test/ui/specialization/assoc-ty-graph-cycle.rs

@@ -2,7 +2,7 @@
 
 // Make sure we don't crash with a cycle error during coherence.
 
-#![feature(specialization)]
+#![feature(specialization)] //~ WARN the feature `specialization` is incomplete
 
 trait Trait<T> {
     type Assoc;

src/test/ui/specialization/assoc-ty-graph-cycle.stderr

@@ -0,0 +1,11 @@
+warning: the feature `specialization` is incomplete and may be unsafe to use and/or cause compiler crashes
+  --> $DIR/assoc-ty-graph-cycle.rs:5:12
+   |
+LL | #![feature(specialization)]
+   |            ^^^^^^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
+   = note: see issue #31844 <https://github.com/rust-lang/rust/issues/31844> for more information
+
+warning: 1 warning emitted
+

src/test/ui/specialization/cross-crate-defaults.rs

@@ -2,7 +2,7 @@
 
 // aux-build:cross_crates_defaults.rs
 
-#![feature(specialization)]
+#![feature(specialization)] //~ WARN the feature `specialization` is incomplete
 
 extern crate cross_crates_defaults;
 

src/test/ui/specialization/cross-crate-defaults.stderr

@@ -0,0 +1,11 @@
+warning: the feature `specialization` is incomplete and may be unsafe to use and/or cause compiler crashes
+  --> $DIR/cross-crate-defaults.rs:5:12
+   |
+LL | #![feature(specialization)]
+   |            ^^^^^^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
+   = note: see issue #31844 <https://github.com/rust-lang/rust/issues/31844> for more information
+
+warning: 1 warning emitted
+

src/test/ui/specialization/defaultimpl/allowed-cross-crate.rs

@@ -5,7 +5,7 @@
 
 // aux-build:go_trait.rs
 
-#![feature(specialization)]
+#![feature(specialization)] //~ WARN the feature `specialization` is incomplete
 
 extern crate go_trait;
 

src/test/ui/specialization/defaultimpl/allowed-cross-crate.stderr

@@ -0,0 +1,11 @@
+warning: the feature `specialization` is incomplete and may be unsafe to use and/or cause compiler crashes
+  --> $DIR/allowed-cross-crate.rs:8:12
+   |
+LL | #![feature(specialization)]
+   |            ^^^^^^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
+   = note: see issue #31844 <https://github.com/rust-lang/rust/issues/31844> for more information
+
+warning: 1 warning emitted
+

src/test/ui/specialization/defaultimpl/out-of-order.rs

@@ -2,7 +2,7 @@
 
 // Test that you can list the more specific impl before the more general one.
 
-#![feature(specialization)]
+#![feature(specialization)] //~ WARN the feature `specialization` is incomplete
 
 trait Foo {
     type Out;

src/test/ui/specialization/defaultimpl/out-of-order.stderr

@@ -0,0 +1,11 @@
+warning: the feature `specialization` is incomplete and may be unsafe to use and/or cause compiler crashes
+  --> $DIR/out-of-order.rs:5:12
+   |
+LL | #![feature(specialization)]
+   |            ^^^^^^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
+   = note: see issue #31844 <https://github.com/rust-lang/rust/issues/31844> for more information
+
+warning: 1 warning emitted
+

src/test/ui/specialization/defaultimpl/overlap-projection.rs

@@ -4,7 +4,7 @@
 // projections involve specialization, so long as the associated type is
 // provided by the most specialized impl.
 
-#![feature(specialization)]
+#![feature(specialization)] //~ WARN the feature `specialization` is incomplete
 
 trait Assoc {
     type Output;

src/test/ui/specialization/defaultimpl/overlap-projection.stderr

@@ -0,0 +1,11 @@
+warning: the feature `specialization` is incomplete and may be unsafe to use and/or cause compiler crashes
+  --> $DIR/overlap-projection.rs:7:12
+   |
+LL | #![feature(specialization)]
+   |            ^^^^^^^^^^^^^^
+   |
+   = note: `#[warn(incomplete_features)]` on by default
+   = note: see issue #31844 <https://github.com/rust-lang/rust/issues/31844> for more information
+
+warning: 1 warning emitted
+

src/test/ui/specialization/defaultimpl/projection.rs

@@ -1,7 +1,7 @@
 // run-pass
 #![allow(dead_code)]
 
-#![feature(specialization)]
+#![feature(specialization)] //~ WARN the feature `specialization` is incomplete
 
 // Make sure we *can* project non-defaulted associated types
 // cf compile-fail/specialization-default-projection.rs