Show env normalization differences under two solvers

compiler/rustc_trait_selection/src/solve/normalize.rs

@@ -217,7 +217,8 @@ where
     fn try_fold_const(&mut self, ct: ty::Const<'tcx>) -> Result<ty::Const<'tcx>, Self::Error> {
         let infcx = self.at.infcx;
         debug_assert_eq!(ct, infcx.shallow_resolve_const(ct));
-        if !ct.has_aliases() {
+        // FIXME: `generic_const_exprs` causes query cycle problem. Same as the old solver.
+        if !ct.has_aliases() || infcx.tcx.features().generic_const_exprs() {
             return Ok(ct);
         }
 

compiler/rustc_trait_selection/src/traits/mod.rs

@@ -257,6 +257,7 @@ fn do_normalize_predicates<'tcx>(
     predicates: Vec<ty::Clause<'tcx>>,
 ) -> Result<Vec<ty::Clause<'tcx>>, ErrorGuaranteed> {
     let span = cause.span;
+    let original_predicates = predicates.clone();
 
     // FIXME. We should really... do something with these region
     // obligations. But this call just continues the older
@@ -283,6 +284,38 @@ fn do_normalize_predicates<'tcx>(
 
     debug!("do_normalize_predicates: normalized predicates = {:?}", predicates);
 
+    // The next solver returns nothing for values that contains type error.
+    // And type error should cause failure later. So we skip the consistency check.
+    if !tcx.next_trait_solver_globally() && !predicates.references_error() {
+        let infcx = tcx
+            .infer_ctxt()
+            .with_next_trait_solver(true)
+            .ignoring_regions()
+            .build(TypingMode::non_body_analysis());
+        for (orig_pred, pred_by_old) in original_predicates.into_iter().zip(&predicates) {
+            let inconsistent_pred_by_next =
+                match crate::solve::deeply_normalize::<_, ScrubbedTraitError<'tcx>>(
+                    infcx.at(&cause, elaborated_env),
+                    orig_pred,
+                ) {
+                    Ok(pred_by_next) => {
+                        if pred_by_next == *pred_by_old {
+                            continue;
+                        }
+                        Some(pred_by_next)
+                    }
+                    Err(_) => None,
+                };
+            tcx.dcx().span_err(
+                span,
+                format!(
+                    "inconsistency during normalizing env `{:#?}`, old={:#?}, next={:#?}",
+                    orig_pred, pred_by_old, inconsistent_pred_by_next
+                ),
+            );
+        }
+    }
+
     // We can use the `elaborated_env` here; the region code only
     // cares about declarations like `'a: 'b`.
     // FIXME: It's very weird that we ignore region obligations but apparently

tests/ui/const-generics/generic_const_exprs/cross-crate-2.rs

@@ -1,6 +1,8 @@
-//@ check-pass
 //@ aux-build: cross-crate-2.rs
 
+//~? ERROR: inconsistency during normalizing env
+//~? ERROR: inconsistency during normalizing env
+
 extern crate cross_crate_2;
 
 use cross_crate_2::Foo;

tests/ui/const-generics/generic_const_exprs/cross-crate-2.stderr

@@ -0,0 +1,18 @@
+error: inconsistency during normalizing env `Binder { value: ConstEvaluatable(UnevaluatedConst { def: DefId(20:8 ~ cross_crate_2[bdab]::{impl#0}::{constant#0}), args: [N/#0] }), bound_vars: [] }`, old=Binder { value: ConstEvaluatable(UnevaluatedConst { def: DefId(20:8 ~ cross_crate_2[bdab]::{impl#0}::{constant#0}), args: [N/#0] }), bound_vars: [] }, next=Some(
+           Binder { value: ConstEvaluatable({const error}), bound_vars: [] },
+       )
+  --> $DIR/auxiliary/cross-crate-2.rs:10:5
+   |
+LL |     pub fn new() -> Self {
+   |     ^^^^^^^^^^^^^^^^^^^^
+
+error: inconsistency during normalizing env `Binder { value: TraitPredicate(<[u8; cross_crate_2::::{impl#0}::{constant#0}] as std::marker::Sized>, polarity:Positive), bound_vars: [] }`, old=Binder { value: TraitPredicate(<[u8; cross_crate_2::::{impl#0}::{constant#0}] as std::marker::Sized>, polarity:Positive), bound_vars: [] }, next=Some(
+           Binder { value: TraitPredicate(<[u8; {const error}] as std::marker::Sized>, polarity:Positive), bound_vars: [] },
+       )
+  --> $DIR/auxiliary/cross-crate-2.rs:10:5
+   |
+LL |     pub fn new() -> Self {
+   |     ^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 2 previous errors
+

tests/ui/const-generics/generic_const_exprs/unknown-alias-defkind-anonconst-ice-116710.rs

@@ -10,5 +10,6 @@ trait Trait {}
 impl<const N: u32> Trait for A<N> {}
 
 impl<const N: u32> Trait for A<N> {}
+//~^ ERROR: conflicting implementations of trait
 
 pub fn main() {}

tests/ui/const-generics/generic_const_exprs/unknown-alias-defkind-anonconst-ice-116710.stderr

@@ -4,6 +4,16 @@ error[E0423]: expected value, found builtin type `u8`
 LL | struct A<const N: u32 = 1, const M: u32 = u8>;
    |                                           ^^ not a value
 
-error: aborting due to 1 previous error
+error[E0119]: conflicting implementations of trait `Trait` for type `A<_>`
+  --> $DIR/unknown-alias-defkind-anonconst-ice-116710.rs:12:1
+   |
+LL | impl<const N: u32> Trait for A<N> {}
+   | --------------------------------- first implementation here
+LL |
+LL | impl<const N: u32> Trait for A<N> {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `A<_>`
+
+error: aborting due to 2 previous errors
 
-For more information about this error, try `rustc --explain E0423`.
+Some errors have detailed explanations: E0119, E0423.
+For more information about an error, try `rustc --explain E0119`.

tests/ui/traits/const-traits/unsatisfied-const-trait-bound.stderr

@@ -6,94 +6,34 @@ LL | #![feature(const_trait_impl, generic_const_exprs)]
    |
    = help: remove one of these features
 
-error[E0391]: cycle detected when evaluating type-level constant
-  --> $DIR/unsatisfied-const-trait-bound.rs:28:35
+error[E0277]: the trait bound `T: const Trait` is not satisfied
+  --> $DIR/unsatisfied-const-trait-bound.rs:28:37
    |
 LL | fn accept0<T: Trait>(_: Container<{ T::make() }>) {}
-   |                                   ^^^^^^^^^^^^^
-   |
-note: ...which requires const-evaluating + checking `accept0::{constant#0}`...
-  --> $DIR/unsatisfied-const-trait-bound.rs:28:35
-   |
-LL | fn accept0<T: Trait>(_: Container<{ T::make() }>) {}
-   |                                   ^^^^^^^^^^^^^
-note: ...which requires checking if `accept0::{constant#0}` is a trivial const...
-  --> $DIR/unsatisfied-const-trait-bound.rs:28:35
-   |
-LL | fn accept0<T: Trait>(_: Container<{ T::make() }>) {}
-   |                                   ^^^^^^^^^^^^^
-note: ...which requires building MIR for `accept0::{constant#0}`...
-  --> $DIR/unsatisfied-const-trait-bound.rs:28:35
-   |
-LL | fn accept0<T: Trait>(_: Container<{ T::make() }>) {}
-   |                                   ^^^^^^^^^^^^^
-note: ...which requires building an abstract representation for `accept0::{constant#0}`...
-  --> $DIR/unsatisfied-const-trait-bound.rs:28:35
-   |
-LL | fn accept0<T: Trait>(_: Container<{ T::make() }>) {}
-   |                                   ^^^^^^^^^^^^^
-note: ...which requires building THIR for `accept0::{constant#0}`...
-  --> $DIR/unsatisfied-const-trait-bound.rs:28:35
-   |
-LL | fn accept0<T: Trait>(_: Container<{ T::make() }>) {}
-   |                                   ^^^^^^^^^^^^^
-note: ...which requires type-checking `accept0::{constant#0}`...
-  --> $DIR/unsatisfied-const-trait-bound.rs:28:35
-   |
-LL | fn accept0<T: Trait>(_: Container<{ T::make() }>) {}
-   |                                   ^^^^^^^^^^^^^
-   = note: ...which again requires evaluating type-level constant, completing the cycle
-note: cycle used when checking that `accept0` is well-formed
-  --> $DIR/unsatisfied-const-trait-bound.rs:28:35
-   |
-LL | fn accept0<T: Trait>(_: Container<{ T::make() }>) {}
-   |                                   ^^^^^^^^^^^^^
-   = 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[E0391]: cycle detected when checking if `accept1::{constant#0}` is a trivial const
-  --> $DIR/unsatisfied-const-trait-bound.rs:32:49
-   |
-LL | const fn accept1<T: [const] Trait>(_: Container<{ T::make() }>) {}
-   |                                                 ^^^^^^^^^^^^^
-   |
-note: ...which requires building MIR for `accept1::{constant#0}`...
-  --> $DIR/unsatisfied-const-trait-bound.rs:32:49
+error[E0277]: the trait bound `T: const Trait` is not satisfied
+  --> $DIR/unsatisfied-const-trait-bound.rs:32:51
    |
 LL | const fn accept1<T: [const] Trait>(_: Container<{ T::make() }>) {}
-   |                                                 ^^^^^^^^^^^^^
-note: ...which requires building an abstract representation for `accept1::{constant#0}`...
-  --> $DIR/unsatisfied-const-trait-bound.rs:32:49
-   |
-LL | const fn accept1<T: [const] Trait>(_: Container<{ T::make() }>) {}
-   |                                                 ^^^^^^^^^^^^^
-note: ...which requires building THIR for `accept1::{constant#0}`...
-  --> $DIR/unsatisfied-const-trait-bound.rs:32:49
-   |
-LL | const fn accept1<T: [const] Trait>(_: Container<{ T::make() }>) {}
-   |                                                 ^^^^^^^^^^^^^
-note: ...which requires type-checking `accept1::{constant#0}`...
-  --> $DIR/unsatisfied-const-trait-bound.rs:32:49
+   |                                                   ^
+
+error[E0277]: the trait bound `Ty: const Trait` is not satisfied
+  --> $DIR/unsatisfied-const-trait-bound.rs:21:15
    |
-LL | const fn accept1<T: [const] Trait>(_: Container<{ T::make() }>) {}
-   |                                                 ^^^^^^^^^^^^^
-note: ...which requires evaluating type-level constant...
-  --> $DIR/unsatisfied-const-trait-bound.rs:32:49
+LL |     require::<Ty>();
+   |               ^^
    |
-LL | const fn accept1<T: [const] Trait>(_: Container<{ T::make() }>) {}
-   |                                                 ^^^^^^^^^^^^^
-note: ...which requires const-evaluating + checking `accept1::{constant#0}`...
-  --> $DIR/unsatisfied-const-trait-bound.rs:32:49
+note: required by a bound in `require`
+  --> $DIR/unsatisfied-const-trait-bound.rs:8:15
    |
-LL | const fn accept1<T: [const] Trait>(_: Container<{ T::make() }>) {}
-   |                                                 ^^^^^^^^^^^^^
-   = note: ...which again requires checking if `accept1::{constant#0}` is a trivial const, completing the cycle
-note: cycle used when const-evaluating + checking `accept1::{constant#0}`
-  --> $DIR/unsatisfied-const-trait-bound.rs:32:49
+LL | fn require<T: const Trait>() {}
+   |               ^^^^^^^^^^^ required by this bound in `require`
+help: make the `impl` of trait `Trait` `const`
    |
-LL | const fn accept1<T: [const] Trait>(_: Container<{ T::make() }>) {}
-   |                                                 ^^^^^^^^^^^^^
-   = 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
+LL | impl const Trait for Ty {
+   |      +++++
 
-error: aborting due to 3 previous errors
+error: aborting due to 4 previous errors
 
-For more information about this error, try `rustc --explain E0391`.
+For more information about this error, try `rustc --explain E0277`.

tests/ui/traits/next-solver/normalize/normalize-param-env-4.current.stderr

@@ -0,0 +1,22 @@
+error: inconsistency during normalizing env `Binder { value: TraitPredicate(<<T as Trait>::Assoc as Trait>, polarity:Positive), bound_vars: [] }`, old=Binder { value: TraitPredicate(<T as Trait>, polarity:Positive), bound_vars: [] }, next=None
+  --> $DIR/normalize-param-env-4.rs:16:1
+   |
+LL | / fn foo<T>()
+LL | |
+LL | |
+LL | | where
+LL | |     <T as Trait>::Assoc: Trait,
+   | |_______________________________^
+
+error: inconsistency during normalizing env `Binder { value: TraitPredicate(<<T as Trait>::Assoc as std::marker::MetaSized>, polarity:Positive), bound_vars: [] }`, old=Binder { value: TraitPredicate(<T as std::marker::MetaSized>, polarity:Positive), bound_vars: [] }, next=None
+  --> $DIR/normalize-param-env-4.rs:16:1
+   |
+LL | / fn foo<T>()
+LL | |
+LL | |
+LL | | where
+LL | |     <T as Trait>::Assoc: Trait,
+   | |_______________________________^
+
+error: aborting due to 2 previous errors
+

tests/ui/traits/next-solver/normalize/normalize-param-env-4.next.stderr

@@ -1,5 +1,5 @@
 error[E0275]: overflow evaluating the requirement `<T as Trait>::Assoc: Trait`
-  --> $DIR/normalize-param-env-4.rs:19:26
+  --> $DIR/normalize-param-env-4.rs:20:26
    |
 LL |     <T as Trait>::Assoc: Trait,
    |                          ^^^^^

tests/ui/traits/next-solver/normalize/normalize-param-env-4.rs

@@ -2,7 +2,6 @@
 //@ ignore-compare-mode-next-solver (explicit revisions)
 //@[next] compile-flags: -Znext-solver
 //@[next] known-bug: #92505
-//@[current] check-pass
 
 trait Trait {
     type Assoc;
@@ -15,6 +14,8 @@ impl<T> Trait for T {
 fn impls_trait<T: Trait>() {}
 
 fn foo<T>()
+    //[current]~^ ERROR: inconsistency during normalizing env
+    //[current]~| ERROR: inconsistency during normalizing env
 where
     <T as Trait>::Assoc: Trait,
 {