Rollup merge of #106385 - compiler-errors:new-solver-flag, r=jackh726

Split `-Zchalk` flag into `-Ztrait-solver=(classic|chalk|next)` flag

We'll eventually need a way to select more than chalk + not-chalk.

Does this need an MCP since it's touching a `-Z` flag? Or perhaps I should preserve `-Zchalk` for the time being... maybe I could make it a warning to use that flag? cc ``@rust-lang/types``

r? types

compiler/rustc_interface/src/tests.rs

@@ -4,6 +4,7 @@ use crate::interface::parse_cfgspecs;
 use rustc_data_structures::fx::FxHashSet;
 use rustc_errors::{emitter::HumanReadableErrorType, registry, ColorConfig};
 use rustc_session::config::rustc_optgroups;
+use rustc_session::config::TraitSolver;
 use rustc_session::config::{build_configuration, build_session_options, to_crate_config};
 use rustc_session::config::{
     BranchProtection, Externs, OomStrategy, OutputType, OutputTypes, PAuthKey, PacRet,
@@ -722,7 +723,6 @@ fn test_unstable_options_tracking_hash() {
             pac_ret: Some(PacRet { leaf: true, key: PAuthKey::B })
         })
     );
-    tracked!(chalk, true);
     tracked!(codegen_backend, Some("abc".to_string()));
     tracked!(crate_attr, vec!["abc".to_string()]);
     tracked!(debug_info_for_profiling, true);
@@ -792,6 +792,7 @@ fn test_unstable_options_tracking_hash() {
     tracked!(thinlto, Some(true));
     tracked!(thir_unsafeck, true);
     tracked!(tls_model, Some(TlsModel::GeneralDynamic));
+    tracked!(trait_solver, TraitSolver::Chalk);
     tracked!(translate_remapped_path_to_local_path, false);
     tracked!(trap_unreachable, Some(false));
     tracked!(treat_err_as_bug, NonZeroUsize::new(1));

compiler/rustc_session/src/config.rs

@@ -554,6 +554,16 @@ pub enum PrintRequest {
     SplitDebuginfo,
 }
 
+#[derive(Debug, Copy, Clone, Hash, PartialEq, Eq)]
+pub enum TraitSolver {
+    /// Classic trait solver in `rustc_trait_selection::traits::select`
+    Classic,
+    /// Chalk trait solver
+    Chalk,
+    /// Experimental trait solver in `rustc_trait_selection::solve`
+    Next,
+}
+
 pub enum Input {
     /// Load source code from a file.
     File(PathBuf),
@@ -2761,7 +2771,7 @@ pub(crate) mod dep_tracking {
         BranchProtection, CFGuard, CFProtection, CrateType, DebugInfo, ErrorOutputType,
         InstrumentCoverage, LdImpl, LinkerPluginLto, LocationDetail, LtoCli, OomStrategy, OptLevel,
         OutputType, OutputTypes, Passes, SourceFileHashAlgorithm, SplitDwarfKind,
-        SwitchWithOptPath, SymbolManglingVersion, TrimmedDefPaths,
+        SwitchWithOptPath, SymbolManglingVersion, TraitSolver, TrimmedDefPaths,
     };
     use crate::lint;
     use crate::options::WasiExecModel;
@@ -2861,6 +2871,7 @@ pub(crate) mod dep_tracking {
         BranchProtection,
         OomStrategy,
         LanguageIdentifier,
+        TraitSolver,
     );
 
     impl<T1, T2> DepTrackingHash for (T1, T2)

compiler/rustc_session/src/options.rs

@@ -382,6 +382,8 @@ mod desc {
         "`all` (default), `except-unused-generics`, `except-unused-functions`, or `off`";
     pub const parse_unpretty: &str = "`string` or `string=string`";
     pub const parse_treat_err_as_bug: &str = "either no value or a number bigger than 0";
+    pub const parse_trait_solver: &str =
+        "one of the supported solver modes (`classic`, `chalk`, or `next`)";
     pub const parse_lto: &str =
         "either a boolean (`yes`, `no`, `on`, `off`, etc), `thin`, `fat`, or omitted";
     pub const parse_linker_plugin_lto: &str =
@@ -880,6 +882,18 @@ mod parse {
         }
     }
 
+    pub(crate) fn parse_trait_solver(slot: &mut TraitSolver, v: Option<&str>) -> bool {
+        match v {
+            Some("classic") => *slot = TraitSolver::Classic,
+            Some("chalk") => *slot = TraitSolver::Chalk,
+            Some("next") => *slot = TraitSolver::Next,
+            // default trait solver is subject to change..
+            Some("default") => *slot = TraitSolver::Classic,
+            _ => return false,
+        }
+        true
+    }
+
     pub(crate) fn parse_lto(slot: &mut LtoCli, v: Option<&str>) -> bool {
         if v.is_some() {
             let mut bool_arg = None;
@@ -1249,8 +1263,6 @@ options! {
         "instrument control-flow architecture protection"),
     cgu_partitioning_strategy: Option<String> = (None, parse_opt_string, [TRACKED],
         "the codegen unit partitioning strategy to use"),
-    chalk: bool = (false, parse_bool, [TRACKED],
-        "enable the experimental Chalk-based trait solving engine"),
     codegen_backend: Option<String> = (None, parse_opt_string, [TRACKED],
         "the backend to use"),
     combine_cgu: bool = (false, parse_bool, [TRACKED],
@@ -1609,6 +1621,8 @@ options! {
         "for every macro invocation, print its name and arguments (default: no)"),
     track_diagnostics: bool = (false, parse_bool, [UNTRACKED],
         "tracks where in rustc a diagnostic was emitted"),
+    trait_solver: TraitSolver = (TraitSolver::Classic, parse_trait_solver, [TRACKED],
+        "specify the trait solver mode used by rustc (default: classic)"),
     // Diagnostics are considered side-effects of a query (see `QuerySideEffects`) and are saved
     // alongside query results and changes to translation options can affect diagnostics - so
     // translation options should be tracked.

compiler/rustc_trait_selection/src/traits/engine.rs

@@ -3,6 +3,7 @@ use std::fmt::Debug;
 
 use super::TraitEngine;
 use super::{ChalkFulfillmentContext, FulfillmentContext};
+use crate::solve::FulfillmentCtxt as NextFulfillmentCtxt;
 use crate::traits::NormalizeExt;
 use rustc_data_structures::fx::FxIndexSet;
 use rustc_hir::def_id::{DefId, LocalDefId};
@@ -20,6 +21,7 @@ use rustc_middle::ty::error::TypeError;
 use rustc_middle::ty::ToPredicate;
 use rustc_middle::ty::TypeFoldable;
 use rustc_middle::ty::{self, Ty, TyCtxt};
+use rustc_session::config::TraitSolver;
 use rustc_span::Span;
 
 pub trait TraitEngineExt<'tcx> {
@@ -29,18 +31,18 @@ pub trait TraitEngineExt<'tcx> {
 
 impl<'tcx> TraitEngineExt<'tcx> for dyn TraitEngine<'tcx> {
     fn new(tcx: TyCtxt<'tcx>) -> Box<Self> {
-        if tcx.sess.opts.unstable_opts.chalk {
-            Box::new(ChalkFulfillmentContext::new())
-        } else {
-            Box::new(FulfillmentContext::new())
+        match tcx.sess.opts.unstable_opts.trait_solver {
+            TraitSolver::Classic => Box::new(FulfillmentContext::new()),
+            TraitSolver::Chalk => Box::new(ChalkFulfillmentContext::new()),
+            TraitSolver::Next => Box::new(NextFulfillmentCtxt::new()),
         }
     }
 
     fn new_in_snapshot(tcx: TyCtxt<'tcx>) -> Box<Self> {
-        if tcx.sess.opts.unstable_opts.chalk {
-            Box::new(ChalkFulfillmentContext::new_in_snapshot())
-        } else {
-            Box::new(FulfillmentContext::new_in_snapshot())
+        match tcx.sess.opts.unstable_opts.trait_solver {
+            TraitSolver::Classic => Box::new(FulfillmentContext::new_in_snapshot()),
+            TraitSolver::Chalk => Box::new(ChalkFulfillmentContext::new_in_snapshot()),
+            TraitSolver::Next => Box::new(NextFulfillmentCtxt::new()),
         }
     }
 }

compiler/rustc_trait_selection/src/traits/error_reporting/mod.rs

@@ -40,6 +40,7 @@ use rustc_middle::ty::{
     self, SubtypePredicate, ToPolyTraitRef, ToPredicate, TraitRef, Ty, TyCtxt, TypeFoldable,
     TypeVisitable,
 };
+use rustc_session::config::TraitSolver;
 use rustc_session::Limit;
 use rustc_span::def_id::LOCAL_CRATE;
 use rustc_span::symbol::sym;
@@ -1167,7 +1168,7 @@ impl<'tcx> TypeErrCtxtExt<'tcx> for TypeErrCtxt<'_, 'tcx> {
                     }
 
                     ty::PredicateKind::WellFormed(ty) => {
-                        if !self.tcx.sess.opts.unstable_opts.chalk {
+                        if self.tcx.sess.opts.unstable_opts.trait_solver != TraitSolver::Chalk {
                             // WF predicates cannot themselves make
                             // errors. They can only block due to
                             // ambiguity; otherwise, they always

compiler/rustc_trait_selection/src/traits/select/confirmation.rs

@@ -15,6 +15,7 @@ use rustc_middle::ty::{
     self, Binder, GenericArg, GenericArgKind, GenericParamDefKind, InternalSubsts, SubstsRef,
     ToPolyTraitRef, ToPredicate, TraitRef, Ty, TyCtxt,
 };
+use rustc_session::config::TraitSolver;
 use rustc_span::def_id::DefId;
 
 use crate::traits::project::{normalize_with_depth, normalize_with_depth_to};
@@ -767,8 +768,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
         debug!(?closure_def_id, ?trait_ref, ?nested, "confirm closure candidate obligations");
 
         // FIXME: Chalk
-
-        if !self.tcx().sess.opts.unstable_opts.chalk {
+        if self.tcx().sess.opts.unstable_opts.trait_solver != TraitSolver::Chalk {
             nested.push(obligation.with(
                 self.tcx(),
                 ty::Binder::dummy(ty::PredicateKind::ClosureKind(closure_def_id, substs, kind)),

compiler/rustc_ty_utils/src/ty.rs

@@ -2,6 +2,7 @@ use rustc_data_structures::fx::FxIndexSet;
 use rustc_hir as hir;
 use rustc_hir::def_id::DefId;
 use rustc_middle::ty::{self, Binder, Predicate, PredicateKind, ToPredicate, Ty, TyCtxt};
+use rustc_session::config::TraitSolver;
 use rustc_trait_selection::traits;
 
 fn sized_constraint_for_ty<'tcx>(
@@ -121,7 +122,7 @@ fn param_env(tcx: TyCtxt<'_>, def_id: DefId) -> ty::ParamEnv<'_> {
     // are any errors at that point, so outside of type inference you can be
     // sure that this will succeed without errors anyway.
 
-    if tcx.sess.opts.unstable_opts.chalk {
+    if tcx.sess.opts.unstable_opts.trait_solver == TraitSolver::Chalk {
         let environment = well_formed_types_in_env(tcx, def_id);
         predicates.extend(environment);
     }

src/test/rustdoc-ui/z-help.stdout

@@ -8,7 +8,6 @@
     -Z                       branch-protection=val -- set options for branch target identification and pointer authentication on AArch64
     -Z                           cf-protection=val -- instrument control-flow architecture protection
     -Z               cgu-partitioning-strategy=val -- the codegen unit partitioning strategy to use
-    -Z                                   chalk=val -- enable the experimental Chalk-based trait solving engine
     -Z                         codegen-backend=val -- the backend to use
     -Z                             combine-cgu=val -- combine CGUs into a single one
     -Z                              crate-attr=val -- inject the given attribute in the crate
@@ -175,6 +174,7 @@
     -Z                               tls-model=val -- choose the TLS model to use (`rustc --print tls-models` for details)
     -Z                            trace-macros=val -- for every macro invocation, print its name and arguments (default: no)
     -Z                       track-diagnostics=val -- tracks where in rustc a diagnostic was emitted
+    -Z                            trait-solver=val -- specify the trait solver mode used by rustc (default: classic)
     -Z                translate-additional-ftl=val -- additional fluent translation to preferentially use (for testing translation)
     -Z        translate-directionality-markers=val -- emit directionality isolation markers in translated diagnostics
     -Z                          translate-lang=val -- language identifier for diagnostic output

src/test/ui/chalkify/arithmetic.rs

@@ -1,5 +1,5 @@
 // check-pass
-// compile-flags: -Z chalk
+// compile-flags: -Z trait-solver=chalk
 
 fn main() {
     1 + 2;

src/test/ui/chalkify/assert.rs

@@ -1,5 +1,5 @@
 // run-pass
-// compile-flags: -Z chalk
+// compile-flags: -Z trait-solver=chalk
 
 fn main() {
     assert_eq!(1, 1);

src/test/ui/chalkify/basic.rs

@@ -1,5 +1,5 @@
 // check-pass
-// compile-flags: -Z chalk
+// compile-flags: -Z trait-solver=chalk
 
 trait Foo {}
 

src/test/ui/chalkify/bugs/async.rs

@@ -1,6 +1,6 @@
 // check-fail
 // known-bug: unknown
-// compile-flags: -Z chalk --edition=2021
+// compile-flags: -Z trait-solver=chalk --edition=2021
 
 fn main() -> () {}
 

src/test/ui/chalkify/builtin-copy-clone.rs

@@ -1,5 +1,5 @@
 // run-pass
-// compile-flags: -Z chalk
+// compile-flags: -Z trait-solver=chalk
 
 // Test that `Clone` is correctly implemented for builtin types.
 

src/test/ui/chalkify/chalk_initial_program.rs

@@ -1,4 +1,4 @@
-// compile-flags: -Z chalk
+// compile-flags: -Z trait-solver=chalk
 
 trait Foo { }
 

src/test/ui/chalkify/closure.rs

@@ -1,4 +1,4 @@
-// compile-flags: -Z chalk
+// compile-flags: -Z trait-solver=chalk
 
 fn main() -> () {
     let t = || {};

src/test/ui/chalkify/generic_impls.rs

@@ -1,4 +1,4 @@
-// compile-flags: -Z chalk
+// compile-flags: -Z trait-solver=chalk
 
 trait Foo { }
 

src/test/ui/chalkify/impl_wf.rs

@@ -1,4 +1,4 @@
-// compile-flags: -Z chalk
+// compile-flags: -Z trait-solver=chalk
 
 trait Foo: Sized { }
 

src/test/ui/chalkify/impl_wf_2.rs

@@ -1,6 +1,6 @@
 // Split out of impl_wf.rs to work around rust aborting compilation early
 
-// compile-flags: -Z chalk
+// compile-flags: -Z trait-solver=chalk
 
 trait Foo: Sized { }
 

src/test/ui/chalkify/inherent_impl.rs

@@ -1,5 +1,5 @@
 // run-pass
-// compile-flags: -Z chalk
+// compile-flags: -Z trait-solver=chalk
 
 trait Foo { }
 

src/test/ui/chalkify/inherent_impl_min.rs

@@ -1,5 +1,5 @@
 // run-pass
-// compile-flags: -Z chalk
+// compile-flags: -Z trait-solver=chalk
 
 trait Foo { }
 

src/test/ui/chalkify/lower_env1.rs

@@ -1,5 +1,5 @@
 // check-pass
-// compile-flags: -Z chalk
+// compile-flags: -Z trait-solver=chalk
 
 #![allow(dead_code)]
 

src/test/ui/chalkify/lower_env2.rs

@@ -1,5 +1,5 @@
 // check-pass
-// compile-flags: -Z chalk
+// compile-flags: -Z trait-solver=chalk
 
 #![allow(dead_code)]
 

src/test/ui/chalkify/lower_env3.rs

@@ -1,5 +1,5 @@
 // check-pass
-// compile-flags: -Z chalk
+// compile-flags: -Z trait-solver=chalk
 
 #![allow(dead_code)]
 

src/test/ui/chalkify/lower_impl.rs

@@ -1,5 +1,5 @@
 // check-pass
-// compile-flags: -Z chalk
+// compile-flags: -Z trait-solver=chalk
 
 trait Foo { }
 

src/test/ui/chalkify/lower_struct.rs

@@ -1,5 +1,5 @@
 // check-pass
-// compile-flags: -Z chalk
+// compile-flags: -Z trait-solver=chalk
 
 struct Foo<'a, T> where Box<T>: Clone {
     _x: std::marker::PhantomData<&'a T>,

src/test/ui/chalkify/lower_trait.rs

@@ -1,5 +1,5 @@
 // check-pass
-// compile-flags: -Z chalk
+// compile-flags: -Z trait-solver=chalk
 
 trait Bar { }
 

src/test/ui/chalkify/lower_trait_higher_rank.rs

@@ -1,5 +1,5 @@
 // check-pass
-// compile-flags: -Z chalk
+// compile-flags: -Z trait-solver=chalk
 
 trait Foo<F: ?Sized> where for<'a> F: Fn(&'a (u8, u16)) -> &'a u8
 {

src/test/ui/chalkify/lower_trait_where_clause.rs

@@ -1,5 +1,5 @@
 // check-pass
-// compile-flags: -Z chalk
+// compile-flags: -Z trait-solver=chalk
 
 use std::borrow::Borrow;
 

src/test/ui/chalkify/println.rs

@@ -1,5 +1,5 @@
 // check-pass
-// compile-flags: -Z chalk
+// compile-flags: -Z trait-solver=chalk
 
 fn main() {
     println!("hello");

src/test/ui/chalkify/projection.rs

@@ -1,5 +1,5 @@
 // run-pass
-// compile-flags: -Z chalk
+// compile-flags: -Z trait-solver=chalk
 
 trait Foo { }
 

src/test/ui/chalkify/recursive_where_clause_on_type.rs

@@ -1,6 +1,6 @@
 // FIXME(chalk): should fail, see comments
 // check-fail
-// compile-flags: -Z chalk
+// compile-flags: -Z trait-solver=chalk
 
 #![feature(trivial_bounds)]
 

src/test/ui/chalkify/super_trait.rs

@@ -1,5 +1,5 @@
 // run-pass
-// compile-flags: -Z chalk
+// compile-flags: -Z trait-solver=chalk
 
 trait Foo { }
 trait Bar: Foo { }

src/test/ui/chalkify/trait-objects.rs

@@ -1,5 +1,5 @@
 // check-pass
-// compile-flags: -Z chalk
+// compile-flags: -Z trait-solver=chalk
 
 use std::fmt::Display;
 

src/test/ui/chalkify/trait_implied_bound.rs

@@ -1,5 +1,5 @@
 // run-pass
-// compile-flags: -Z chalk
+// compile-flags: -Z trait-solver=chalk
 
 trait Foo { }
 trait Bar<U> where U: Foo { }

src/test/ui/chalkify/type_implied_bound.rs

@@ -1,5 +1,5 @@
 // run-pass
-// compile-flags: -Z chalk
+// compile-flags: -Z trait-solver=chalk
 
 trait Eq { }
 trait Hash: Eq { }

src/test/ui/chalkify/type_inference.rs

@@ -1,4 +1,4 @@
-// compile-flags: -Z chalk
+// compile-flags: -Z trait-solver=chalk
 
 trait Foo { }
 impl Foo for i32 { }

src/test/ui/chalkify/type_wf.rs

@@ -1,5 +1,5 @@
 // check-fail
-// compile-flags: -Z chalk
+// compile-flags: -Z trait-solver=chalk
 
 trait Foo { }
 

src/test/ui/implied-bounds/hrlt-implied-trait-bounds-guard.rs

@@ -1,5 +1,5 @@
 // A test exploiting the bug behind #25860 except with
-// implied trait bounds which currently don't exist without `-Zchalk`.
+// implied trait bounds which currently don't exist without `-Ztrait-solver=chalk`.
 use std::marker::PhantomData;
 struct Foo<'a, 'b, T>(PhantomData<(&'a (), &'b (), T)>)
 where

src/tools/compiletest/src/runtest.rs

@@ -2011,7 +2011,7 @@ impl<'test> TestCx<'test> {
                 rustc.args(&["-Zpolonius"]);
             }
             Some(CompareMode::Chalk) => {
-                rustc.args(&["-Zchalk"]);
+                rustc.args(&["-Ztrait-solver=chalk"]);
             }
             Some(CompareMode::SplitDwarf) if self.config.target.contains("windows") => {
                 rustc.args(&["-Csplit-debuginfo=unpacked", "-Zunstable-options"]);