normalizing where-clauses is also coinductive, add tests

Author: lcnr

compiler/rustc_next_trait_solver/src/solve/eval_ctxt/mod.rs

@@ -264,7 +264,10 @@ where
 
     pub(super) fn step_kind_for_source(&self, source: GoalSource) -> PathKind {
         match (self.current_goal_kind, source) {
-            (CurrentGoalKind::CoinductiveTrait, GoalSource::ImplWhereBound) => PathKind::Coinductive,
+            (
+                CurrentGoalKind::CoinductiveTrait,
+                GoalSource::ImplWhereBound | GoalSource::NormalizeImplWhereBound,
+            ) => PathKind::Coinductive,
             _ => PathKind::Inductive,
         }
     }
@@ -670,16 +673,19 @@ where
 
     #[instrument(level = "trace", skip(self))]
     pub(super) fn add_normalizes_to_goal(&mut self, mut goal: Goal<I, ty::NormalizesTo<I>>) {
-        goal.predicate =
-            goal.predicate.fold_with(&mut ReplaceAliasWithInfer::new(self, goal.param_env));
+        goal.predicate = goal.predicate.fold_with(&mut ReplaceAliasWithInfer::new(
+            self,
+            GoalSource::Misc,
+            goal.param_env,
+        ));
         self.inspect.add_normalizes_to_goal(self.delegate, self.max_input_universe, goal);
         self.nested_goals.normalizes_to_goals.push(goal);
     }
 
     #[instrument(level = "debug", skip(self))]
     pub(super) fn add_goal(&mut self, source: GoalSource, mut goal: Goal<I, I::Predicate>) {
         goal.predicate =
-            goal.predicate.fold_with(&mut ReplaceAliasWithInfer::new(self, goal.param_env));
+            goal.predicate.fold_with(&mut ReplaceAliasWithInfer::new(self, source, goal.param_env));
         self.inspect.add_goal(self.delegate, self.max_input_universe, source, goal);
         self.nested_goals.goals.push((source, goal));
     }
@@ -1100,6 +1106,7 @@ where
 {
     ecx: &'me mut EvalCtxt<'a, D>,
     param_env: I::ParamEnv,
+    normalization_goal_source: GoalSource,
     cache: HashMap<I::Ty, I::Ty>,
 }
 
@@ -1108,8 +1115,21 @@ where
     D: SolverDelegate<Interner = I>,
     I: Interner,
 {
-    fn new(ecx: &'me mut EvalCtxt<'a, D>, param_env: I::ParamEnv) -> Self {
-        ReplaceAliasWithInfer { ecx, param_env, cache: Default::default() }
+    fn new(
+        ecx: &'me mut EvalCtxt<'a, D>,
+        for_goal_source: GoalSource,
+        param_env: I::ParamEnv,
+    ) -> Self {
+        let normalization_goal_source = match for_goal_source {
+            GoalSource::ImplWhereBound => GoalSource::NormalizeImplWhereBound,
+            _ => GoalSource::Misc,
+        };
+        ReplaceAliasWithInfer {
+            ecx,
+            param_env,
+            normalization_goal_source,
+            cache: Default::default(),
+        }
     }
 }
 
@@ -1132,7 +1152,7 @@ where
                     ty::AliasRelationDirection::Equate,
                 );
                 self.ecx.add_goal(
-                    GoalSource::Misc,
+                    self.normalization_goal_source,
                     Goal::new(self.cx(), self.param_env, normalizes_to),
                 );
                 infer_ty
@@ -1161,7 +1181,7 @@ where
                     ty::AliasRelationDirection::Equate,
                 );
                 self.ecx.add_goal(
-                    GoalSource::Misc,
+                    self.normalization_goal_source,
                     Goal::new(self.cx(), self.param_env, normalizes_to),
                 );
                 infer_ct

compiler/rustc_trait_selection/src/solve/fulfill/derive_errors.rs

@@ -438,7 +438,10 @@ impl<'tcx> ProofTreeVisitor<'tcx> for BestObligation<'tcx> {
 
             let obligation;
             match (child_mode, nested_goal.source()) {
-                (ChildMode::Trait(_) | ChildMode::Host(_), GoalSource::Misc) => {
+                (
+                    ChildMode::Trait(_) | ChildMode::Host(_),
+                    GoalSource::Misc | GoalSource::NormalizeImplWhereBound,
+                ) => {
                     continue;
                 }
                 (ChildMode::Trait(parent_trait_pred), GoalSource::ImplWhereBound) => {

compiler/rustc_type_ir/src/solve/mod.rs

@@ -68,6 +68,11 @@ pub enum GoalSource {
     /// FIXME(-Znext-solver=coinductive): Explain how and why this
     /// changes whether cycles are coinductive.
     ImplWhereBound,
+    /// When eagerly replacing aliases with impl where-bounds, we also
+    /// have to consider these normalization goals to be coinductive.
+    ///
+    /// This is necessary for tests/ui/sized/coinductive-1.rs to compile.
+    NormalizeImplWhereBound,
     /// Const conditions that need to hold for `~const` alias bounds to hold.
     ///
     /// FIXME(-Znext-solver=coinductive): Are these even coinductive?

tests/ui/const-generics/issues/issue-88119.stderr

@@ -6,30 +6,90 @@ LL | #![feature(const_trait_impl, generic_const_exprs)]
    |
    = help: remove one of these features
 
-error[E0284]: type annotations needed: cannot satisfy `the constant `name_len::<T>()` can be evaluated`
+error[E0275]: overflow evaluating the requirement `&T: ~const ConstName`
+  --> $DIR/issue-88119.rs:19:49
+   |
+LL | impl<T: ?Sized + ConstName> const ConstName for &T
+   |                                                 ^^
+
+error[E0275]: overflow evaluating the requirement `&T: ConstName`
+  --> $DIR/issue-88119.rs:19:49
+   |
+LL | impl<T: ?Sized + ConstName> const ConstName for &T
+   |                                                 ^^
+
+error[E0275]: overflow evaluating the requirement `[(); name_len::<T>()] well-formed`
   --> $DIR/issue-88119.rs:21:5
    |
 LL |     [(); name_len::<T>()]:,
-   |     ^^^^^^^^^^^^^^^^^^^^^ cannot satisfy `the constant `name_len::<T>()` can be evaluated`
+   |     ^^^^^^^^^^^^^^^^^^^^^
    |
 note: required by a bound in `<&T as ConstName>`
+  --> $DIR/issue-88119.rs:21:5
+   |
+LL |     [(); name_len::<T>()]:,
+   |     ^^^^^^^^^^^^^^^^^^^^^ required by this bound in `<&T as ConstName>`
+
+error[E0275]: overflow evaluating the requirement `[(); name_len::<T>()] well-formed`
   --> $DIR/issue-88119.rs:21:10
    |
 LL |     [(); name_len::<T>()]:,
-   |          ^^^^^^^^^^^^^^^ required by this bound in `<&T as ConstName>`
+   |          ^^^^^^^^^^^^^^^
+   |
+note: required by a bound in `<&T as ConstName>`
+  --> $DIR/issue-88119.rs:21:5
+   |
+LL |     [(); name_len::<T>()]:,
+   |     ^^^^^^^^^^^^^^^^^^^^^ required by this bound in `<&T as ConstName>`
+
+error[E0275]: overflow evaluating the requirement `&mut T: ~const ConstName`
+  --> $DIR/issue-88119.rs:26:49
+   |
+LL | impl<T: ?Sized + ConstName> const ConstName for &mut T
+   |                                                 ^^^^^^
 
-error[E0284]: type annotations needed: cannot satisfy `the constant `name_len::<T>()` can be evaluated`
+error[E0275]: overflow evaluating the requirement `&mut T: ConstName`
+  --> $DIR/issue-88119.rs:26:49
+   |
+LL | impl<T: ?Sized + ConstName> const ConstName for &mut T
+   |                                                 ^^^^^^
+
+error[E0275]: overflow evaluating the requirement `[(); name_len::<T>()] well-formed`
   --> $DIR/issue-88119.rs:28:5
    |
 LL |     [(); name_len::<T>()]:,
-   |     ^^^^^^^^^^^^^^^^^^^^^ cannot satisfy `the constant `name_len::<T>()` can be evaluated`
+   |     ^^^^^^^^^^^^^^^^^^^^^
    |
 note: required by a bound in `<&mut T as ConstName>`
+  --> $DIR/issue-88119.rs:28:5
+   |
+LL |     [(); name_len::<T>()]:,
+   |     ^^^^^^^^^^^^^^^^^^^^^ required by this bound in `<&mut T as ConstName>`
+
+error[E0275]: overflow evaluating the requirement `[(); name_len::<T>()] well-formed`
   --> $DIR/issue-88119.rs:28:10
    |
 LL |     [(); name_len::<T>()]:,
-   |          ^^^^^^^^^^^^^^^ required by this bound in `<&mut T as ConstName>`
+   |          ^^^^^^^^^^^^^^^
+   |
+note: required by a bound in `<&mut T as ConstName>`
+  --> $DIR/issue-88119.rs:28:5
+   |
+LL |     [(); name_len::<T>()]:,
+   |     ^^^^^^^^^^^^^^^^^^^^^ required by this bound in `<&mut T as ConstName>`
+
+error[E0275]: overflow evaluating the requirement `&&mut u8: ConstName`
+  --> $DIR/issue-88119.rs:33:35
+   |
+LL | pub const ICE_1: &'static [u8] = <&&mut u8 as ConstName>::NAME_BYTES;
+   |                                   ^^^^^^^^
+
+error[E0275]: overflow evaluating the requirement `&mut &u8: ConstName`
+  --> $DIR/issue-88119.rs:34:35
+   |
+LL | pub const ICE_2: &'static [u8] = <&mut &u8 as ConstName>::NAME_BYTES;
+   |                                   ^^^^^^^^
 
-error: aborting due to 3 previous errors
+error: aborting due to 11 previous errors
 
-For more information about this error, try `rustc --explain E0284`.
+For more information about this error, try `rustc --explain E0275`.

tests/ui/sized/coinductive-1.rs

@@ -1,4 +1,7 @@
 //@ check-pass
+//@ revisions: current next
+//@ ignore-compare-mode-next-solver (explicit revisions)
+//@[next] compile-flags: -Znext-solver
 struct Node<C: Trait<Self>>(C::Assoc);
 
 trait Trait<T> {

tests/ui/traits/next-solver/cycles/coinduction/item-bound-via-impl-where-clause.current.stderr

@@ -0,0 +1,23 @@
+error[E0275]: overflow evaluating the requirement `Vec<u8>: Trait<String>`
+  --> $DIR/item-bound-via-impl-where-clause.rs:31:21
+   |
+LL |     let s: String = transmute::<_, String>(vec![65_u8, 66, 67]);
+   |                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+note: required for `Vec<u8>` to implement `Trait<String>`
+  --> $DIR/item-bound-via-impl-where-clause.rs:22:12
+   |
+LL | impl<L, R> Trait<R> for L
+   |            ^^^^^^^^     ^
+LL | where
+LL |     L: Trait<R>,
+   |        -------- unsatisfied trait bound introduced here
+note: required by a bound in `transmute`
+  --> $DIR/item-bound-via-impl-where-clause.rs:29:17
+   |
+LL | fn transmute<L: Trait<R>, R>(r: L) -> <L::Proof as Trait<R>>::Proof { r }
+   |                 ^^^^^^^^ required by this bound in `transmute`
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0275`.

tests/ui/traits/next-solver/cycles/coinduction/item-bound-via-impl-where-clause.next.stderr

@@ -0,0 +1,49 @@
+error[E0275]: overflow evaluating the requirement `Vec<u8>: Trait<String>`
+  --> $DIR/item-bound-via-impl-where-clause.rs:31:33
+   |
+LL |     let s: String = transmute::<_, String>(vec![65_u8, 66, 67]);
+   |                                 ^
+   |
+note: required by a bound in `transmute`
+  --> $DIR/item-bound-via-impl-where-clause.rs:29:17
+   |
+LL | fn transmute<L: Trait<R>, R>(r: L) -> <L::Proof as Trait<R>>::Proof { r }
+   |                 ^^^^^^^^ required by this bound in `transmute`
+
+error[E0275]: overflow evaluating the requirement `<<Vec<u8> as Trait<String>>::Proof as Trait<String>>::Proof == _`
+  --> $DIR/item-bound-via-impl-where-clause.rs:31:21
+   |
+LL |     let s: String = transmute::<_, String>(vec![65_u8, 66, 67]);
+   |                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error[E0275]: overflow evaluating the requirement `<<Vec<u8> as Trait<String>>::Proof as Trait<String>>::Proof == String`
+  --> $DIR/item-bound-via-impl-where-clause.rs:31:21
+   |
+LL |     let s: String = transmute::<_, String>(vec![65_u8, 66, 67]);
+   |                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error[E0275]: overflow evaluating the requirement `<<Vec<u8> as Trait<String>>::Proof as Trait<String>>::Proof: Sized`
+  --> $DIR/item-bound-via-impl-where-clause.rs:31:21
+   |
+LL |     let s: String = transmute::<_, String>(vec![65_u8, 66, 67]);
+   |                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: the return type of a function must have a statically known size
+
+error[E0275]: overflow evaluating the requirement `<<Vec<u8> as Trait<String>>::Proof as Trait<String>>::Proof well-formed`
+  --> $DIR/item-bound-via-impl-where-clause.rs:31:21
+   |
+LL |     let s: String = transmute::<_, String>(vec![65_u8, 66, 67]);
+   |                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+error[E0275]: overflow evaluating the requirement `<<Vec<u8> as Trait<String>>::Proof as Trait<String>>::Proof == _`
+  --> $DIR/item-bound-via-impl-where-clause.rs:31:21
+   |
+LL |     let s: String = transmute::<_, String>(vec![65_u8, 66, 67]);
+   |                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |
+   = note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`
+
+error: aborting due to 6 previous errors
+
+For more information about this error, try `rustc --explain E0275`.

tests/ui/traits/next-solver/cycles/coinduction/item-bound-via-impl-where-clause.rs

@@ -0,0 +1,39 @@
+//@ revisions: current next
+//@ ignore-compare-mode-next-solver (explicit revisions)
+//@[next] compile-flags: -Znext-solver
+
+// A variation of #135246 where the cyclic bounds are part of
+// the impl instead of the impl associated item.
+
+trait Trait<R>: Sized {
+    type Proof: Trait<R, Proof = Self>;
+}
+
+// We need to use indirection here as we otherwise normalize
+// `<L::Proof as Trait<R>>::Proof` before recursing into
+// `R: Trait<R, Proof = <L::Proof as Trait<R>>::Proof>`.
+trait Indir<L: Trait<R>, R>: Trait<R, Proof = <L::Proof as Trait<R>>::Proof> {}
+impl<L, R> Indir<L, R> for R
+where
+    L: Trait<R>,
+    R: Trait<R, Proof = <L::Proof as Trait<R>>::Proof>,
+{}
+
+impl<L, R> Trait<R> for L
+where
+    L: Trait<R>,
+    R: Indir<L, R>,
+ {
+    type Proof = R;
+}
+fn transmute<L: Trait<R>, R>(r: L) -> <L::Proof as Trait<R>>::Proof { r }
+fn main() {
+    let s: String = transmute::<_, String>(vec![65_u8, 66, 67]);
+    //~^ ERROR overflow evaluating the requirement `Vec<u8>: Trait<String>`
+    //[next]~| ERROR overflow evaluating the requirement `<<Vec<u8> as Trait<String>>::Proof as Trait<String>>::Proof == _`
+    //[next]~| ERROR overflow evaluating the requirement `<<Vec<u8> as Trait<String>>::Proof as Trait<String>>::Proof == String`
+    //[next]~| ERROR overflow evaluating the requirement `<<Vec<u8> as Trait<String>>::Proof as Trait<String>>::Proof: Sized`
+    //[next]~| ERROR overflow evaluating the requirement `<<Vec<u8> as Trait<String>>::Proof as Trait<String>>::Proof well-formed`
+    //[next]~| ERROR overflow evaluating the requirement `<<Vec<u8> as Trait<String>>::Proof as Trait<String>>::Proof == _`
+    println!("{}", s); // ABC
+}

tests/ui/traits/solver-cycles/129541-recursive-enum-and-array-impl.stderr renamed to tests/ui/traits/solver-cycles/129541-recursive-enum-and-array-impl.current.stderr

@@ -0,0 +1,10 @@
+error[E0391]: cycle detected when computing layout of `<[Hello] as Normalize>::Assoc`
+   |
+   = note: ...which requires computing layout of `Hello`...
+   = note: ...which again requires computing layout of `<[Hello] as Normalize>::Assoc`, completing the cycle
+   = note: cycle used when computing layout of `Hello`
+   = note: see https://rustc-dev-guide.rust-lang.org/overview.html#queries and https://rustc-dev-guide.rust-lang.org/query.html for more information
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0391`.