canonicalize consts before calling try_unify_abstract_consts query

compiler/rustc_infer/src/infer/mod.rs

@@ -670,6 +670,22 @@ pub struct CombinedSnapshot<'a, 'tcx> {
 }
 
 impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
+    /// calls `tcx.try_unify_abstract_consts` after
+    /// canonicalizing the consts.
+    pub fn try_unify_abstract_consts(
+        &self,
+        a: ty::Unevaluated<'tcx>,
+        b: ty::Unevaluated<'tcx>,
+    ) -> bool {
+        let canonical = self.canonicalize_query(
+            ((a.def, a.substs), (b.def, b.substs)),
+            &mut OriginalQueryValues::default(),
+        );
+        debug!("canonical consts: {:?}", &canonical.value);
+
+        self.tcx.try_unify_abstract_consts(canonical.value)
+    }
+
     pub fn is_in_snapshot(&self) -> bool {
         self.in_snapshot.get()
     }

compiler/rustc_trait_selection/src/traits/fulfill.rs

@@ -552,11 +552,7 @@ impl<'a, 'b, 'tcx> FulfillProcessor<'a, 'b, 'tcx> {
                         if let (ty::ConstKind::Unevaluated(a), ty::ConstKind::Unevaluated(b)) =
                             (c1.val, c2.val)
                         {
-                            if self
-                                .selcx
-                                .tcx()
-                                .try_unify_abstract_consts(((a.def, a.substs), (b.def, b.substs)))
-                            {
+                            if infcx.try_unify_abstract_consts(a, b) {
                                 return ProcessResult::Changed(vec![]);
                             }
                         }

compiler/rustc_trait_selection/src/traits/select/mod.rs

@@ -608,10 +608,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
                         if let (ty::ConstKind::Unevaluated(a), ty::ConstKind::Unevaluated(b)) =
                             (c1.val, c2.val)
                         {
-                            if self
-                                .tcx()
-                                .try_unify_abstract_consts(((a.def, a.substs), (b.def, b.substs)))
-                            {
+                            if self.infcx.try_unify_abstract_consts(a, b) {
                                 return Ok(EvaluatedToOk);
                             }
                         }

src/test/incremental/const-generics/try_unify_abstract_const_regression_tests/issue-77708-1.rs

@@ -0,0 +1,23 @@
+// revisions: cfail
+#![feature(const_generics, const_evaluatable_checked)]
+#![allow(incomplete_features, unused_braces)]
+
+trait Delegates<T> {}
+
+struct FileCap<const Op: bool> {}
+
+fn writes_to_path<C>(cap: &C)
+where
+    C: Delegates<FileCap<{ false }>>,
+{
+    writes_to_specific_path(&cap);
+    //~^ error: the trait bound
+}
+
+fn writes_to_specific_path<C>(cap: &C)
+where
+    C: Delegates<FileCap<{ false }>>,
+{
+}
+
+fn main() {}

src/test/incremental/const-generics/try_unify_abstract_const_regression_tests/issue-77708-2.rs

@@ -0,0 +1,18 @@
+// revisions: rpass
+#![feature(const_generics, const_evaluatable_checked)]
+#![allow(incomplete_features)]
+
+struct Z;
+const fn one() -> usize {
+    1
+}
+
+fn from_a_to_b<T>(source: [u8; one()]) -> T {
+    todo!()
+}
+
+fn not_main() {
+    let _: &Z = from_a_to_b([0; 1]);
+}
+
+fn main() {}

src/test/incremental/const-generics/try_unify_abstract_const_regression_tests/issue-77708-3.rs

@@ -0,0 +1,22 @@
+// revisions: rpass
+#![feature(const_generics, const_evaluatable_checked)]
+#![allow(incomplete_features)]
+
+use std::{convert::TryFrom, num::NonZeroUsize};
+
+struct A<const N: NonZeroUsize>([u8; N.get()])
+where
+    [u8; N.get()]: Sized;
+
+impl<'a, const N: NonZeroUsize> TryFrom<&'a [u8]> for A<N>
+where
+    [u8; N.get()]: Sized,
+{
+    type Error = ();
+    fn try_from(slice: &'a [u8]) -> Result<A<N>, ()> {
+        let _x = <&[u8; N.get()] as TryFrom<&[u8]>>::try_from(slice);
+        unimplemented!();
+    }
+}
+
+fn main() {}

src/test/incremental/const-generics/try_unify_abstract_const_regression_tests/issue-82034.rs

@@ -0,0 +1,34 @@
+// revisions: rpass
+#![feature(const_generics, const_evaluatable_checked)]
+#![allow(incomplete_features)]
+pub trait IsTrue {}
+pub trait IsFalse {}
+
+pub struct Assert<const CHECK: bool> {}
+
+impl IsTrue for Assert<true> {}
+impl IsFalse for Assert<false> {}
+
+pub struct SliceConstWriter<'a, const N: usize> {
+    ptr: &'a mut [u8],
+}
+impl<'a, const N: usize> SliceConstWriter<'a, { N }> {
+    pub fn from_slice(vec: &'a mut [u8]) -> Self {
+        Self { ptr: vec }
+    }
+
+    pub fn convert<const NN: usize>(mut self) -> SliceConstWriter<'a, { NN }> {
+        SliceConstWriter { ptr: self.ptr }
+    }
+}
+
+impl<'a, const N: usize> SliceConstWriter<'a, { N }>
+where
+    Assert<{ N >= 2 }>: IsTrue,
+{
+    pub fn write_u8(mut self) -> SliceConstWriter<'a, { N - 2 }> {
+        self.convert()
+    }
+}
+
+fn main() {}

src/test/incremental/const-generics/try_unify_abstract_const_regression_tests/issue-85031-1.rs

@@ -0,0 +1,23 @@
+// revisions: rpass
+#![feature(const_generics, const_evaluatable_checked)]
+#![allow(incomplete_features)]
+
+pub struct Ref<'a, const NUM: usize>(&'a i32);
+
+impl<'a, const NUM: usize> Ref<'a, NUM> {
+    pub fn foo<const A: usize>(r: Ref<'a, A>) -> Self
+    where
+        ([(); NUM - A], [(); A - NUM]): Sized,
+    {
+        Self::bar(r)
+    }
+
+    pub fn bar<const A: usize>(r: Ref<'a, A>) -> Self
+    where
+        ([(); NUM - A], [(); A - NUM]): Sized,
+    {
+        Self(r.0)
+    }
+}
+
+fn main() {}

src/test/incremental/const-generics/try_unify_abstract_const_regression_tests/issue-85031-2.rs

@@ -0,0 +1,14 @@
+// revisions: cfail
+#![allow(incomplete_features)]
+#![feature(const_generics, const_evaluatable_checked)]
+
+pub struct Ref<'a>(&'a i32);
+
+impl<'a> Ref<'a> {
+    pub fn foo<const A: usize>() -> [(); A - 0] {
+        Self::foo()
+        //~^ error: type annotations needed
+    }
+}
+
+fn main() {}

src/test/incremental/const-generics/try_unify_abstract_const_regression_tests/issue-85031-3.rs

@@ -0,0 +1,25 @@
+// revisions: rpass
+#![feature(const_generics, const_evaluatable_checked)]
+#![allow(incomplete_features)]
+
+fn test<const SIZE: usize>() {}
+
+trait SomeTrait {
+    const SIZE: usize;
+}
+
+struct A<'a, T> {
+    some_ref: &'a str,
+    _maker: core::marker::PhantomData<T>,
+}
+
+impl<'a, T: SomeTrait> A<'a, T>
+where
+    [(); T::SIZE]: ,
+{
+    fn call_test() {
+        test::<{ T::SIZE }>();
+    }
+}
+
+fn main() {}

src/test/incremental/const-generics/try_unify_abstract_const_regression_tests/issue-86953.rs

@@ -0,0 +1,16 @@
+// revisions: rpass
+#![feature(const_generics, const_evaluatable_checked)]
+#![allow(incomplete_features)]
+
+struct Foo;
+impl<'a> std::ops::Add<&'a Foo> for Foo
+where
+    [(); 0 + 0]: Sized,
+{
+    type Output = ();
+    fn add(self, _: &Foo) -> Self::Output {
+        loop {}
+    }
+}
+
+fn main() {}

src/test/incremental/const-generics/try_unify_abstract_const_regression_tests/issue-88022.rs

@@ -0,0 +1,28 @@
+// revisions: cfail
+#![feature(const_generics, const_evaluatable_checked)]
+#![allow(incomplete_features, unused_braces)]
+
+struct Buffer<T, const S: usize>
+where
+    [(); { S * 2 }]: Default,
+{
+    data: [T; { S * 2 }],
+}
+
+struct BufferIter<'a, T, const S: usize>(&'a Buffer<T, S>)
+where
+    [(); { S * 2 }]: Default;
+
+impl<'a, T, const S: usize> Iterator for BufferIter<'a, T, S> {
+    //~^ error: the trait bound
+    //~^^ error: unconstrained generic constant
+    type Item = &'a T;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        //~^ error: the trait bound
+        //~^^ error: unconstrained generic constant
+        None
+    }
+}
+
+fn main() {}