Fix const-generics ICE related to binding

Author: JohnTitor

compiler/rustc_ty_utils/src/instance.rs

@@ -115,7 +115,14 @@ fn resolve_associated_item<'tcx>(
     );
 
     let trait_ref = ty::TraitRef::from_method(tcx, trait_id, rcvr_substs);
-    let vtbl = tcx.codegen_fulfill_obligation((param_env, ty::Binder::bind(trait_ref, tcx)))?;
+    let vtbl = if trait_item.kind == ty::AssocKind::Const {
+        let bound_vars = tcx
+            .mk_bound_variable_kinds(std::iter::once(ty::BoundVariableKind::Region(ty::BrAnon(0))));
+        let bind = ty::Binder::bind_with_vars(trait_ref, bound_vars);
+        tcx.codegen_fulfill_obligation((param_env, bind))?
+    } else {
+        tcx.codegen_fulfill_obligation((param_env, ty::Binder::bind(trait_ref, tcx)))?
+    };
 
     // Now that we know which impl is being used, we can dispatch to
     // the actual function:

src/test/ui/const-generics/issues/issue-83765.rs

@@ -0,0 +1,38 @@
+#![feature(const_generics, const_evaluatable_checked)]
+#![allow(incomplete_features)]
+
+trait TensorDimension {
+    const DIM: usize;
+}
+
+trait TensorSize: TensorDimension {
+    fn size(&self) -> [usize; Self::DIM];
+}
+
+trait Broadcastable: TensorSize + Sized {
+    type Element;
+    fn lazy_updim<const NEWDIM: usize>(&self, size: [usize; NEWDIM]) {}
+}
+
+struct BMap<'a, R, T: Broadcastable, F: Fn(T::Element) -> R, const DIM: usize> {
+    reference: &'a T,
+    closure: F,
+}
+
+impl<'a, R, T: Broadcastable, F: Fn(T::Element) -> R, const DIM: usize> TensorDimension
+    for BMap<'a, R, T, F, DIM>
+{
+    const DIM: usize = DIM;
+}
+impl<'a, R, T: Broadcastable, F: Fn(T::Element) -> R, const DIM: usize> TensorSize
+    for BMap<'a, R, T, F, DIM>
+{
+    fn size(&self) -> [usize; DIM] {
+        //~^ ERROR: method not compatible with trait [E0308]
+        self.reference.size()
+        //~^ ERROR: unconstrained generic constant
+        //~| ERROR: mismatched types
+    }
+}
+
+fn main() {}

src/test/ui/const-generics/issues/issue-83765.stderr

@@ -0,0 +1,29 @@
+error[E0308]: method not compatible with trait
+  --> $DIR/issue-83765.rs:30:5
+   |
+LL |     fn size(&self) -> [usize; DIM] {
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `Self::DIM`, found `DIM`
+   |
+   = note: expected type `Self::DIM`
+              found type `DIM`
+
+error: unconstrained generic constant
+  --> $DIR/issue-83765.rs:32:24
+   |
+LL |         self.reference.size()
+   |                        ^^^^
+   |
+   = help: try adding a `where` bound using this expression: `where [(); Self::DIM]:`
+
+error[E0308]: mismatched types
+  --> $DIR/issue-83765.rs:32:9
+   |
+LL |         self.reference.size()
+   |         ^^^^^^^^^^^^^^^^^^^^^ expected `DIM`, found `Self::DIM`
+   |
+   = note: expected type `DIM`
+              found type `Self::DIM`
+
+error: aborting due to 3 previous errors
+
+For more information about this error, try `rustc --explain E0308`.

src/test/ui/const-generics/issues/issue-85848.rs

@@ -0,0 +1,31 @@
+#![feature(const_generics, const_fn_trait_bound, const_evaluatable_checked)]
+#![allow(incomplete_features)]
+
+trait _Contains<T> {
+    const does_contain: bool;
+}
+
+trait Contains<T, const Satisfied: bool> {}
+
+trait Delegates<T> {}
+
+impl<T, U> Delegates<U> for T where T: Contains<U, true> {}
+
+const fn contains<A, B>() -> bool
+where
+    A: _Contains<B>,
+{
+    A::does_contain
+}
+
+impl<T, U> Contains<T, { contains::<T, U>() }> for U where T: _Contains<U> {}
+
+fn writes_to_path<C>(cap: &C) {
+    writes_to_specific_path(&cap);
+    //~^ ERROR: the trait bound `(): _Contains<&C>` is not satisfied [E0277]
+    //~| ERROR: unconstrained generic constant
+}
+
+fn writes_to_specific_path<C: Delegates<()>>(cap: &C) {}
+
+fn main() {}

src/test/ui/const-generics/issues/issue-85848.stderr

@@ -0,0 +1,44 @@
+error[E0277]: the trait bound `(): _Contains<&C>` is not satisfied
+  --> $DIR/issue-85848.rs:24:5
+   |
+LL |     writes_to_specific_path(&cap);
+   |     ^^^^^^^^^^^^^^^^^^^^^^^ the trait `_Contains<&C>` is not implemented for `()`
+...
+LL | fn writes_to_specific_path<C: Delegates<()>>(cap: &C) {}
+   |                               ------------- required by this bound in `writes_to_specific_path`
+   |
+note: required because of the requirements on the impl of `Contains<(), true>` for `&C`
+  --> $DIR/issue-85848.rs:21:12
+   |
+LL | impl<T, U> Contains<T, { contains::<T, U>() }> for U where T: _Contains<U> {}
+   |            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^     ^
+note: required because of the requirements on the impl of `Delegates<()>` for `&C`
+  --> $DIR/issue-85848.rs:12:12
+   |
+LL | impl<T, U> Delegates<U> for T where T: Contains<U, true> {}
+   |            ^^^^^^^^^^^^     ^
+
+error: unconstrained generic constant
+  --> $DIR/issue-85848.rs:24:5
+   |
+LL |     writes_to_specific_path(&cap);
+   |     ^^^^^^^^^^^^^^^^^^^^^^^
+...
+LL | fn writes_to_specific_path<C: Delegates<()>>(cap: &C) {}
+   |                               ------------- required by this bound in `writes_to_specific_path`
+   |
+   = help: try adding a `where` bound using this expression: `where [(); { contains::<T, U>() }]:`
+note: required because of the requirements on the impl of `Contains<(), true>` for `&C`
+  --> $DIR/issue-85848.rs:21:12
+   |
+LL | impl<T, U> Contains<T, { contains::<T, U>() }> for U where T: _Contains<U> {}
+   |            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^     ^
+note: required because of the requirements on the impl of `Delegates<()>` for `&C`
+  --> $DIR/issue-85848.rs:12:12
+   |
+LL | impl<T, U> Delegates<U> for T where T: Contains<U, true> {}
+   |            ^^^^^^^^^^^^     ^
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0277`.