stabilize -Znext-solver=coherence

Author: lcnr

compiler/rustc_ast_passes/src/feature_gate.rs

@@ -666,7 +666,7 @@ fn check_incompatible_features(sess: &Session, features: &Features) {
 }
 
 fn check_new_solver_banned_features(sess: &Session, features: &Features) {
-    if !sess.opts.unstable_opts.next_solver.is_some_and(|n| n.globally) {
+    if !sess.opts.unstable_opts.next_solver.globally {
         return;
     }
 

compiler/rustc_interface/src/tests.rs

@@ -810,7 +810,7 @@ fn test_unstable_options_tracking_hash() {
     tracked!(mir_opt_level, Some(4));
     tracked!(move_size_limit, Some(4096));
     tracked!(mutable_noalias, false);
-    tracked!(next_solver, Some(NextSolverConfig { coherence: true, globally: false }));
+    tracked!(next_solver, NextSolverConfig { coherence: true, globally: true });
     tracked!(no_generate_arange_section, true);
     tracked!(no_jump_tables, true);
     tracked!(no_link, true);

compiler/rustc_middle/src/ty/context.rs

@@ -3128,11 +3128,11 @@ impl<'tcx> TyCtxt<'tcx> {
     }
 
     pub fn next_trait_solver_globally(self) -> bool {
-        self.sess.opts.unstable_opts.next_solver.map_or(false, |c| c.globally)
+        self.sess.opts.unstable_opts.next_solver.globally
     }
 
     pub fn next_trait_solver_in_coherence(self) -> bool {
-        self.sess.opts.unstable_opts.next_solver.map_or(false, |c| c.coherence)
+        self.sess.opts.unstable_opts.next_solver.coherence
     }
 
     pub fn is_impl_trait_in_trait(self, def_id: DefId) -> bool {

compiler/rustc_session/src/config.rs

@@ -842,6 +842,11 @@ pub struct NextSolverConfig {
     /// This is only `true` if `coherence` is also enabled.
     pub globally: bool,
 }
+impl Default for NextSolverConfig {
+    fn default() -> Self {
+        NextSolverConfig { coherence: true, globally: false }
+    }
+}
 
 #[derive(Clone)]
 pub enum Input {

compiler/rustc_session/src/options.rs

@@ -403,7 +403,7 @@ mod desc {
     pub(crate) const parse_unpretty: &str = "`string` or `string=string`";
     pub(crate) const parse_treat_err_as_bug: &str = "either no value or a non-negative number";
     pub(crate) const parse_next_solver_config: &str =
-        "a comma separated list of solver configurations: `globally` (default), and `coherence`";
+        "either `globally` (when used without an argument), `coherence` (default) or `no`";
     pub(crate) const parse_lto: &str =
         "either a boolean (`yes`, `no`, `on`, `off`, etc), `thin`, `fat`, or omitted";
     pub(crate) const parse_linker_plugin_lto: &str =
@@ -1123,27 +1123,16 @@ mod parse {
         }
     }
 
-    pub(crate) fn parse_next_solver_config(
-        slot: &mut Option<NextSolverConfig>,
-        v: Option<&str>,
-    ) -> bool {
+    pub(crate) fn parse_next_solver_config(slot: &mut NextSolverConfig, v: Option<&str>) -> bool {
         if let Some(config) = v {
-            let mut coherence = false;
-            let mut globally = true;
-            for c in config.split(',') {
-                match c {
-                    "globally" => globally = true,
-                    "coherence" => {
-                        globally = false;
-                        coherence = true;
-                    }
-                    _ => return false,
-                }
-            }
-
-            *slot = Some(NextSolverConfig { coherence: coherence || globally, globally });
+            *slot = match config {
+                "no" => NextSolverConfig { coherence: false, globally: false },
+                "coherence" => NextSolverConfig { coherence: true, globally: false },
+                "globally" => NextSolverConfig { coherence: true, globally: true },
+                _ => return false,
+            };
         } else {
-            *slot = Some(NextSolverConfig { coherence: true, globally: true });
+            *slot = NextSolverConfig { coherence: true, globally: true };
         }
 
         true
@@ -1914,7 +1903,7 @@ options! {
         "the size at which the `large_assignments` lint starts to be emitted"),
     mutable_noalias: bool = (true, parse_bool, [TRACKED],
         "emit noalias metadata for mutable references (default: yes)"),
-    next_solver: Option<NextSolverConfig> = (None, parse_next_solver_config, [TRACKED],
+    next_solver: NextSolverConfig = (NextSolverConfig::default(), parse_next_solver_config, [TRACKED],
         "enable and configure the next generation trait solver used by rustc"),
     nll_facts: bool = (false, parse_bool, [UNTRACKED],
         "dump facts from NLL analysis into side files (default: no)"),

compiler/rustc_trait_selection/src/traits/engine.rs

@@ -36,10 +36,8 @@ where
         if infcx.next_trait_solver() {
             Box::new(NextFulfillmentCtxt::new(infcx))
         } else {
-            let new_solver_globally =
-                infcx.tcx.sess.opts.unstable_opts.next_solver.map_or(false, |c| c.globally);
             assert!(
-                !new_solver_globally,
+                !infcx.tcx.next_trait_solver_globally(),
                 "using old solver even though new solver is enabled globally"
             );
             Box::new(FulfillmentContext::new(infcx))

tests/ui/associated-types/associated-types-coherence-failure.stderr

@@ -1,20 +1,20 @@
-error[E0119]: conflicting implementations of trait `IntoCow<'_, _>` for type `Cow<'_, _>`
+error[E0119]: conflicting implementations of trait `IntoCow<'_, _>` for type `<_ as ToOwned>::Owned`
   --> $DIR/associated-types-coherence-failure.rs:21:1
    |
 LL | impl<'a, B: ?Sized> IntoCow<'a, B> for <B as ToOwned>::Owned where B: ToOwned {
    | ----------------------------------------------------------------------------- first implementation here
 ...
 LL | impl<'a, B: ?Sized> IntoCow<'a, B> for Cow<'a, B> where B: ToOwned {
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `Cow<'_, _>`
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `<_ as ToOwned>::Owned`
 
-error[E0119]: conflicting implementations of trait `IntoCow<'_, _>` for type `&_`
+error[E0119]: conflicting implementations of trait `IntoCow<'_, _>` for type `<_ as ToOwned>::Owned`
   --> $DIR/associated-types-coherence-failure.rs:28:1
    |
 LL | impl<'a, B: ?Sized> IntoCow<'a, B> for <B as ToOwned>::Owned where B: ToOwned {
    | ----------------------------------------------------------------------------- first implementation here
 ...
 LL | impl<'a, B: ?Sized> IntoCow<'a, B> for &'a B where B: ToOwned {
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `&_`
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `<_ as ToOwned>::Owned`
 
 error: aborting due to 2 previous errors
 

tests/ui/auto-traits/opaque_type_candidate_selection.rs

@@ -5,6 +5,8 @@ LL | impl<'a, T: MyPredicate<'a>> MyTrait<'a> for T {}
    | ---------------------------------------------- first implementation here
 LL | impl<'a, T> MyTrait<'a> for &'a T {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `&_`
+   |
+   = note: downstream crates may implement trait `MyPredicate<'_>` for type `&_`
 
 error: aborting due to 1 previous error
 

tests/ui/coherence/coherence-negative-outlives-lifetimes.stock.stderr

@@ -5,6 +5,8 @@ LL | impl<'a, T: MyPredicate<'a>> MyTrait<'a> for T {}
    | ---------------------------------------------- first implementation here
 LL | impl<'a, T> MyTrait<'a> for &'a T {}
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `&_`
+   |
+   = note: downstream crates may implement trait `MyPredicate<'_>` for type `&_`
 
 error: aborting due to 1 previous error
 

tests/ui/coherence/coherence-negative-outlives-lifetimes.with_negative_coherence.stderr

@@ -5,6 +5,8 @@ LL | impl<T: DerefMut> Foo for T {}
    | --------------------------- first implementation here
 LL | impl<U> Foo for &U {}
    | ^^^^^^^^^^^^^^^^^^ conflicting implementation for `&_`
+   |
+   = note: downstream crates may implement trait `std::ops::DerefMut` for type `&_`
 
 error: aborting due to 1 previous error
 

tests/ui/coherence/coherence-overlap-negate-not-use-feature-gate.stderr

@@ -12,7 +12,6 @@ LL |   impl<T> Trait for Box<T> {}
    |   ^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `Box<_>`
    |
    = note: downstream crates may implement trait `WithAssoc<'a>` for type `std::boxed::Box<_>`
-   = note: downstream crates may implement trait `WhereBound` for type `<std::boxed::Box<_> as WithAssoc<'a>>::Assoc`
 
 error: aborting due to 1 previous error
 

tests/ui/coherence/coherence-overlap-unnormalizable-projection-0.classic.stderr

@@ -12,7 +12,7 @@ LL |   impl<T> Trait for Box<T> {}
    |   ^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `Box<_>`
    |
    = note: downstream crates may implement trait `WithAssoc<'a>` for type `std::boxed::Box<_>`
-   = note: downstream crates may implement trait `WhereBound` for type `std::boxed::Box<<std::boxed::Box<_> as WithAssoc<'a>>::Assoc>`
+   = note: downstream crates may implement trait `WhereBound` for type `std::boxed::Box<_>`
 
 error: aborting due to 1 previous error
 

tests/ui/coherence/coherence-overlap-unnormalizable-projection-1.classic.stderr

@@ -5,6 +5,8 @@ LL | impl<T> Bar for T where T: Foo {}
    | ------------------------------ first implementation here
 LL | impl<T> Bar for Box<T> {}
    | ^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `Box<_>`
+   |
+   = note: downstream crates may implement trait `Foo` for type `std::boxed::Box<_>`
 
 error: aborting due to 1 previous error
 

tests/ui/coherence/negative-coherence-check-placeholder-outlives.stderr

@@ -6,6 +6,8 @@ LL | impl<T> Bar for T where T: Foo {}
 ...
 LL | impl<T> Bar for &T {}
    | ^^^^^^^^^^^^^^^^^^ conflicting implementation for `&_`
+   |
+   = note: downstream crates may implement trait `Foo` for type `&_`
 
 error: aborting due to 1 previous error
 

tests/ui/coherence/negative-coherence-considering-regions.any_lt.stderr

@@ -8,6 +8,7 @@ LL | impl<T: ?Sized> FnMarker for fn(&T) {}
    |
    = warning: the behavior may change in a future release
    = note: for more information, see issue #56105 <https://github.com/rust-lang/rust/issues/56105>
+   = note: downstream crates may implement trait `Marker` for type `&_`
    = note: this behavior recently changed as a result of a bug fix; see rust-lang/rust#56105 for details
 note: the lint level is defined here
   --> $DIR/negative-coherence-placeholder-region-constraints-on-unification.rs:4:11

tests/ui/coherence/negative-coherence-placeholder-region-constraints-on-unification.explicit.stderr

@@ -1,12 +1,13 @@
-error[E0119]: conflicting implementations of trait `MyTrait<_>` for type `(Box<(MyType,)>, _)`
+error[E0119]: conflicting implementations of trait `MyTrait<_>` for type `(Box<(MyType,)>, <_ as Iterator>::Item)`
   --> $DIR/normalize-for-errors.rs:17:1
    |
 LL | impl<T: Copy, S: Iterator> MyTrait<S> for (T, S::Item) {}
    | ------------------------------------------------------ first implementation here
 LL |
 LL | impl<S: Iterator> MyTrait<S> for (Box<<(MyType,) as Mirror>::Assoc>, S::Item) {}
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `(Box<(MyType,)>, _)`
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `(Box<(MyType,)>, <_ as Iterator>::Item)`
    |
+   = note: upstream crates may add a new impl of trait `std::clone::Clone` for type `(MyType,)` in future versions
    = note: upstream crates may add a new impl of trait `std::marker::Copy` for type `std::boxed::Box<(MyType,)>` in future versions
 
 error: aborting due to 1 previous error

tests/ui/coherence/normalize-for-errors.current.stderr

@@ -1,7 +1,3 @@
-//@ revisions: current next
-//@ ignore-compare-mode-next-solver (explicit revisions)
-//@[next] compile-flags: -Znext-solver
-
 struct MyType;
 trait MyTrait<S> {}
 
@@ -18,6 +14,6 @@ impl<S: Iterator> MyTrait<S> for (Box<<(MyType,) as Mirror>::Assoc>, S::Item) {}
 //~^ ERROR conflicting implementations of trait `MyTrait<_>` for type `(Box<(MyType,)>,
 //~| NOTE conflicting implementation for `(Box<(MyType,)>,
 //~| NOTE upstream crates may add a new impl of trait `std::marker::Copy` for type `std::boxed::Box<(MyType,)>` in future versions
-//[next]~| NOTE upstream crates may add a new impl of trait `std::clone::Clone` for type `std::boxed::Box<(MyType,)>` in future versions
+//~| NOTE upstream crates may add a new impl of trait `std::clone::Clone` for type `std::boxed::Box<(MyType,)>` in future versions
 
 fn main() {}

tests/ui/coherence/normalize-for-errors.rs

@@ -0,0 +1,15 @@
+error[E0119]: conflicting implementations of trait `MyTrait<_>` for type `(Box<(MyType,)>, <_ as Iterator>::Item)`
+  --> $DIR/normalize-for-errors.rs:13:1
+   |
+LL | impl<T: Copy, S: Iterator> MyTrait<S> for (T, S::Item) {}
+   | ------------------------------------------------------ first implementation here
+LL |
+LL | impl<S: Iterator> MyTrait<S> for (Box<<(MyType,) as Mirror>::Assoc>, S::Item) {}
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `(Box<(MyType,)>, <_ as Iterator>::Item)`
+   |
+   = note: upstream crates may add a new impl of trait `std::clone::Clone` for type `std::boxed::Box<(MyType,)>` in future versions
+   = note: upstream crates may add a new impl of trait `std::marker::Copy` for type `std::boxed::Box<(MyType,)>` in future versions
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0119`.

tests/ui/coherence/normalize-for-errors.stderr

@@ -1,12 +1,8 @@
  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), "'a")], 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, !2_0.Named(DefId(0:27 ~ associated_type[f554]::{impl#3}::'a#1), "'a")], 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), "'a")], 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, !2_0.Named(DefId(0:27 ~ associated_type[f554]::{impl#3}::'a#1), "'a")], 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), "'a")], 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, !2_0.Named(DefId(0:27 ~ associated_type[f554]::{impl#3}::'a#1), "'a")], 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), "'a")], 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, !2_0.Named(DefId(0:27 ~ associated_type[f554]::{impl#3}::'a#1), "'a")], 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 (), _)`
+error[E0119]: conflicting implementations of trait `Overlap<for<'a> fn(&'a (), ())>` for type `for<'a> fn(&'a (), ())`
   --> $DIR/associated-type.rs:31:1
    |
 LL |   impl<T> Overlap<T> for T {
@@ -16,7 +12,7 @@ LL | / impl<T> Overlap<for<'a> fn(&'a (), Assoc<'a, T>)> for T
 LL | |
 LL | | where
 LL | |     for<'a> *const T: ToUnit<'a>,
-   | |_________________________________^ conflicting implementation for `for<'a> fn(&'a (), _)`
+   | |_________________________________^ conflicting implementation for `for<'a> fn(&'a (), ())`
    |
    = note: this behavior recently changed as a result of a bug fix; see rust-lang/rust#56105 for details
 

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

@@ -0,0 +1,12 @@
+error[E0119]: conflicting implementations of trait `Trait<_>`
+  --> $DIR/opaques.rs:27:1
+   |
+LL | impl<T> Trait<T> for T {
+   | ---------------------- first implementation here
+...
+LL | impl<T> Trait<T> for defining_scope::Alias<T> {
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0119`.

tests/ui/coherence/occurs-check/opaques.current.stderr

@@ -1,5 +1,5 @@
 error[E0119]: conflicting implementations of trait `Trait<_>`
-  --> $DIR/opaques.rs:30:1
+  --> $DIR/opaques.rs:27:1
    |
 LL | impl<T> Trait<T> for T {
    | ---------------------- first implementation here
@@ -8,7 +8,7 @@ LL | impl<T> Trait<T> for defining_scope::Alias<T> {
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation
 
 error[E0282]: type annotations needed
-  --> $DIR/opaques.rs:13:23
+  --> $DIR/opaques.rs:10:23
    |
 LL |     pub fn cast<T>(x: Container<Alias<T>, T>) -> Container<T, T> {
    |                       ^^^^^^^^^^^^^^^^^^^^^^ cannot infer type

tests/ui/coherence/occurs-check/opaques.next.stderr

@@ -1,10 +1,7 @@
-//@revisions: old next
+//@revisions: current next
 //@[next] compile-flags: -Znext-solver
 
 // A regression test for #105787
-
-//@[old] known-bug: #105787
-//@[old] check-pass
 #![feature(type_alias_impl_trait)]
 mod defining_scope {
     use super::*;
@@ -28,7 +25,7 @@ impl<T> Trait<T> for T {
     type Assoc = Box<u32>;
 }
 impl<T> Trait<T> for defining_scope::Alias<T> {
-    //[next]~^ ERROR conflicting implementations of trait
+    //~^ ERROR conflicting implementations of trait
     type Assoc = usize;
 }
 

tests/ui/coherence/occurs-check/opaques.rs

@@ -9,19 +9,6 @@ help: indicate the anonymous lifetime
 LL | impl<T> ToUnit<'_> for T {}
    |               ++++
 
-error[E0277]: the trait bound `for<'a> (): ToUnit<'a>` is not satisfied
-  --> $DIR/skip-reporting-if-references-err.rs:15:29
-   |
-LL | impl Overlap for for<'a> fn(<() as ToUnit<'a>>::Unit) {}
-   |                             ^^^^^^^^^^^^^^^^^^^^^^^^ the trait `for<'a> ToUnit<'a>` is not implemented for `()`
-
-error[E0277]: the trait bound `for<'a> (): ToUnit<'a>` is not satisfied
-  --> $DIR/skip-reporting-if-references-err.rs:15:18
-   |
-LL | impl Overlap for for<'a> fn(<() as ToUnit<'a>>::Unit) {}
-   |                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `for<'a> ToUnit<'a>` is not implemented for `()`
-
-error: aborting due to 3 previous errors
+error: aborting due to 1 previous error
 
-Some errors have detailed explanations: E0277, E0726.
-For more information about an error, try `rustc --explain E0277`.
+For more information about this error, try `rustc --explain E0726`.

tests/ui/coherence/skip-reporting-if-references-err.current.stderr

@@ -1,8 +1,4 @@
 // Regression test for #121006.
-//@ revisions: current next
-//@ ignore-compare-mode-next-solver (explicit revisions)
-//@[next] compile-flags: -Znext-solver
-
 trait ToUnit<'a> {
     type Unit;
 }
@@ -13,7 +9,5 @@ impl<T> ToUnit for T {}
 trait Overlap {}
 impl<U> Overlap for fn(U) {}
 impl Overlap for for<'a> fn(<() as ToUnit<'a>>::Unit) {}
-//[current]~^ ERROR the trait bound `for<'a> (): ToUnit<'a>` is not satisfied
-//[current]~| ERROR the trait bound `for<'a> (): ToUnit<'a>` is not satisfied
 
 fn main() {}