add const generics test

src/test/ui/const-generics/invariant.rs

@@ -0,0 +1,33 @@
+#![feature(generic_const_exprs)]
+#![allow(incomplete_features)]
+use std::marker::PhantomData;
+
+trait SadBee {
+ const ASSOC: usize;
+}
+// fn(&'static ())` is a supertype of `for<'a> fn(&'a ())` while
+// we allow two different impls for these types, leading
+// to different const eval results.
+impl SadBee for for<'a> fn(&'a ()) {
+ const ASSOC: usize = 0;
+}
+impl SadBee for fn(&'static ()) {
+ //~^ WARNING conflicting implementations of trait
+ //~| WARNING this was previously accepted
+ const ASSOC: usize = 100;
+}
+
+struct Foo<T: SadBee>([u8; <T as SadBee>::ASSOC], PhantomData<T>)
+where
+ [(); <T as SadBee>::ASSOC]: ;
+
+fn covariant(
+ v: &'static Foo<for<'a> fn(&'a ())>
+) -> &'static Foo<fn(&'static ())> {
+ v //~ ERROR mismatched types
+}
+
+fn main() {
+ let y = covariant(&Foo([], PhantomData));
+ println!("{:?}", y.0);
+}

src/test/ui/const-generics/invariant.stderr

@@ -0,0 +1,26 @@
+warning: conflicting implementations of trait `SadBee` for type `for<'a> fn(&'a ())`
+ --> $DIR/invariant.rs:14:1
+ |
+LL | impl SadBee for for<'a> fn(&'a ()) {
+ | ---------------------------------- first implementation here
+...
+LL | impl SadBee for fn(&'static ()) {
+ | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `for<'a> fn(&'a ())`
+ |
+ = note: `#[warn(coherence_leak_check)]` 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 #56105 <https://github.com/rust-lang/rust/issues/56105>
+ = note: this behavior recently changed as a result of a bug fix; see rust-lang/rust#56105 for details
+
+error[E0308]: mismatched types
+ --> $DIR/invariant.rs:27:5
+ |
+LL | v
+ | ^ one type is more general than the other
+ |
+ = note: expected reference `&'static Foo<fn(&'static ())>`
+ found reference `&'static Foo<for<'a> fn(&'a ())>`
+
+error: aborting due to previous error; 1 warning emitted
+
+For more information about this error, try `rustc --explain E0308`.