Properly generalize unevaluated consts

compiler/rustc_infer/src/infer/unify_key.rs

@@ -110,6 +110,13 @@ impl<'tcx> ConstVariableValue<'tcx> {
             ConstVariableValue::Known { value } => Some(value),
         }
     }
+
+    pub(crate) fn is_unknown(&self) -> bool {
+        match *self {
+            ConstVariableValue::Unknown { .. } => true,
+            ConstVariableValue::Known { .. } => false,
+        }
+    }
 }
 
 #[derive(PartialEq, Copy, Clone, Debug)]

compiler/rustc_middle/src/ty/consts.rs

@@ -323,6 +323,13 @@ impl<'tcx> Const<'tcx> {
         matches!(self.kind(), ty::ConstKind::Infer(_))
     }
 
+    pub fn ct_vid(self) -> Option<ty::ConstVid> {
+        match self.kind() {
+            ConstKind::Infer(ty::InferConst::Var(vid)) => Some(vid),
+            _ => None,
+        }
+    }
+
     /// Iterator that walks `self` and any types reachable from
     /// `self`, in depth-first order. Note that just walks the types
     /// that appear in `self`, it does not descend into the fields of

tests/ui/coherence/occurs-check/associated-type.next.stderr

@@ -1,5 +1,5 @@
- WARN rustc_infer::infer::relate::generalize may incompletely handle alias type: AliasTy { args: [*const ?1t, '^0.Named(DefId(0:27 ~ associated_type[f554]::{impl#3}::'a#1))], def_id: DefId(0:5 ~ associated_type[f554]::ToUnit::Unit), .. }
- WARN rustc_infer::infer::relate::generalize may incompletely handle alias type: AliasTy { args: [*const ?1t, '^0.Named(DefId(0:27 ~ associated_type[f554]::{impl#3}::'a#1))], def_id: DefId(0:5 ~ associated_type[f554]::ToUnit::Unit), .. }
+ WARN rustc_infer::infer::relate::generalize may incompletely handle alias type: AliasTerm { args: [*const ?1t, '^0.Named(DefId(0:27 ~ associated_type[f554]::{impl#3}::'a#1))], def_id: DefId(0:5 ~ associated_type[f554]::ToUnit::Unit), .. }
+ WARN rustc_infer::infer::relate::generalize may incompletely handle alias type: AliasTerm { args: [*const ?1t, '^0.Named(DefId(0:27 ~ associated_type[f554]::{impl#3}::'a#1))], def_id: DefId(0:5 ~ associated_type[f554]::ToUnit::Unit), .. }
 error[E0119]: conflicting implementations of trait `Overlap<for<'a> fn(&'a (), ())>` for type `for<'a> fn(&'a (), ())`
   --> $DIR/associated-type.rs:32:1
    |

tests/ui/coherence/occurs-check/associated-type.old.stderr

@@ -1,5 +1,5 @@
- WARN rustc_infer::infer::relate::generalize may incompletely handle alias type: AliasTy { args: [*const ?1t, '^0.Named(DefId(0:27 ~ associated_type[f554]::{impl#3}::'a#1))], def_id: DefId(0:5 ~ associated_type[f554]::ToUnit::Unit), .. }
- WARN rustc_infer::infer::relate::generalize may incompletely handle alias type: AliasTy { args: [*const ?1t, '^0.Named(DefId(0:27 ~ associated_type[f554]::{impl#3}::'a#1))], def_id: DefId(0:5 ~ associated_type[f554]::ToUnit::Unit), .. }
+ WARN rustc_infer::infer::relate::generalize may incompletely handle alias type: AliasTerm { args: [*const ?1t, '^0.Named(DefId(0:27 ~ associated_type[f554]::{impl#3}::'a#1))], def_id: DefId(0:5 ~ associated_type[f554]::ToUnit::Unit), .. }
+ WARN rustc_infer::infer::relate::generalize may incompletely handle alias type: AliasTerm { args: [*const ?1t, '^0.Named(DefId(0:27 ~ associated_type[f554]::{impl#3}::'a#1))], def_id: DefId(0:5 ~ associated_type[f554]::ToUnit::Unit), .. }
 error[E0119]: conflicting implementations of trait `Overlap<for<'a> fn(&'a (), ())>` for type `for<'a> fn(&'a (), ())`
   --> $DIR/associated-type.rs:32:1
    |

tests/ui/const-generics/mgca/free-type-alias-recursive.rs

@@ -0,0 +1,13 @@
+//! Regression test for <https://github.com/rust-lang/rust/issues/153831>
+//@ check-fail
+//@compile-flags: -Znext-solver=globally --emit=obj
+#![feature(min_generic_const_args)]
+#![expect(incomplete_features)]
+
+type const A: () = A;
+//~^ ERROR type mismatch resolving `A normalizes-to _`
+//~| ERROR the constant `A` is not of type `()`
+
+fn main() {
+    A;
+}

tests/ui/const-generics/mgca/free-type-alias-recursive.stderr

@@ -0,0 +1,15 @@
+error[E0271]: type mismatch resolving `A normalizes-to _`
+  --> $DIR/free-type-alias-recursive.rs:7:1
+   |
+LL | type const A: () = A;
+   | ^^^^^^^^^^^^^^^^ types differ
+
+error: the constant `A` is not of type `()`
+  --> $DIR/free-type-alias-recursive.rs:7:1
+   |
+LL | type const A: () = A;
+   | ^^^^^^^^^^^^^^^^ expected `()`, found a different `()`
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0271`.

tests/ui/const-generics/ogca/coherence-ambiguous.rs

@@ -1,5 +1,4 @@
-// FIXME(ogca): this should ERROR not pass!!
-//@ check-pass
+//@ check-fail
 
 #![feature(generic_const_items, min_generic_const_args, opaque_generic_const_args)]
 #![expect(incomplete_features)]
@@ -12,8 +11,8 @@ trait Trait {}
 
 impl Trait for [(); FOO::<1>] {}
 impl Trait for [(); BAR::<1>] {}
-// FIXME(ogca): this should ERROR!
+//~^ ERROR conflicting implementations of trait `Trait` for type `[(); FOO::<1>]`
 impl Trait for [(); BAR::<2>] {}
-// FIXME(ogca): this should ERROR!
+//~^ ERROR conflicting implementations of trait `Trait` for type `[(); FOO::<1>]`
 
 fn main() {}

tests/ui/const-generics/ogca/coherence-ambiguous.stderr

@@ -0,0 +1,20 @@
+error[E0119]: conflicting implementations of trait `Trait` for type `[(); FOO::<1>]`
+  --> $DIR/coherence-ambiguous.rs:13:1
+   |
+LL | impl Trait for [(); FOO::<1>] {}
+   | ----------------------------- first implementation here
+LL | impl Trait for [(); BAR::<1>] {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `[(); FOO::<1>]`
+
+error[E0119]: conflicting implementations of trait `Trait` for type `[(); FOO::<1>]`
+  --> $DIR/coherence-ambiguous.rs:15:1
+   |
+LL | impl Trait for [(); FOO::<1>] {}
+   | ----------------------------- first implementation here
+...
+LL | impl Trait for [(); BAR::<2>] {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `[(); FOO::<1>]`
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0119`.

tests/ui/higher-ranked/structually-relate-aliases.stderr

@@ -1,4 +1,4 @@
- WARN rustc_infer::infer::relate::generalize may incompletely handle alias type: AliasTy { args: [?1t, '^0.Named(DefId(0:15 ~ structually_relate_aliases[de75]::{impl#1}::'a))], def_id: DefId(0:5 ~ structually_relate_aliases[de75]::ToUnit::Unit), .. }
+ WARN rustc_infer::infer::relate::generalize may incompletely handle alias type: AliasTerm { args: [?1t, '^0.Named(DefId(0:15 ~ structually_relate_aliases[de75]::{impl#1}::'a))], def_id: DefId(0:5 ~ structually_relate_aliases[de75]::ToUnit::Unit), .. }
 error[E0277]: the trait bound `for<'a> T: ToUnit<'a>` is not satisfied
   --> $DIR/structually-relate-aliases.rs:13:36
    |

tests/ui/traits/next-solver/issue-118950-root-region.stderr

@@ -16,7 +16,7 @@ help: this trait has no implementations, consider adding one
 LL | trait ToUnit<'a> {
    | ^^^^^^^^^^^^^^^^
 
- WARN rustc_infer::infer::relate::generalize may incompletely handle alias type: AliasTy { args: ['^0.Named(DefId(0:15 ~ issue_118950_root_region[d54f]::{impl#1}::'a)), ?1t], def_id: DefId(0:8 ~ issue_118950_root_region[d54f]::Assoc), .. }
+ WARN rustc_infer::infer::relate::generalize may incompletely handle alias type: AliasTerm { args: ['^0.Named(DefId(0:15 ~ issue_118950_root_region[d54f]::{impl#1}::'a)), ?1t], def_id: DefId(0:8 ~ issue_118950_root_region[d54f]::Assoc), .. }
 error: aborting due to 2 previous errors
 
 Some errors have detailed explanations: E0277, E0425.