Fix impl for SolverDelegate

compiler/rustc_next_trait_solver/src/infcx.rs

@@ -9,6 +9,8 @@ pub trait SolverDelegate: Sized {
     type Interner: Interner;
     fn interner(&self) -> Self::Interner;
 
+    type Span: Copy;
+
     fn solver_mode(&self) -> SolverMode;
 
     fn build_with_canonical<V>(
@@ -57,6 +59,12 @@ pub trait SolverDelegate: Sized {
         def_id: <Self::Interner as Interner>::DefId,
     ) -> <Self::Interner as Interner>::GenericArgs;
 
+    fn fresh_var_for_kind_with_span(
+        &self,
+        arg: <Self::Interner as Interner>::GenericArg,
+        span: Self::Span,
+    ) -> <Self::Interner as Interner>::GenericArg;
+
     fn instantiate_binder_with_infer<T: TypeFoldable<Self::Interner> + Copy>(
         &self,
         value: ty::Binder<Self::Interner, T>,

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

@@ -394,3 +394,35 @@ where
         state,
     )
 }
+
+// FIXME: needs to be pub to be accessed by downstream
+// `rustc_trait_selection::solve::inspect::analyse`.
+pub fn instantiate_canonical_state<Infcx, I, T: TypeFoldable<I>>(
+    infcx: &Infcx,
+    span: Infcx::Span,
+    param_env: I::ParamEnv,
+    orig_values: &mut Vec<I::GenericArg>,
+    state: inspect::CanonicalState<I, T>,
+) -> T
+where
+    Infcx: SolverDelegate<Interner = I>,
+    I: Interner,
+{
+    // In case any fresh inference variables have been created between `state`
+    // and the previous instantiation, extend `orig_values` for it.
+    assert!(orig_values.len() <= state.value.var_values.len());
+    for &arg in &state.value.var_values.var_values[orig_values.len()..state.value.var_values.len()]
+    {
+        // FIXME: This is so ugly.
+        let unconstrained = infcx.fresh_var_for_kind_with_span(arg, span);
+        orig_values.push(unconstrained);
+    }
+
+    let instantiation =
+        EvalCtxt::compute_query_response_instantiation_values(infcx, orig_values, &state);
+
+    let inspect::State { var_values, data } = infcx.instantiate_canonical(state, instantiation);
+
+    EvalCtxt::unify_query_var_values(infcx, param_env, orig_values, var_values);
+    data
+}

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

@@ -127,6 +127,17 @@ pub trait SolverDelegateEvalExt: SolverDelegate {
         goal: Goal<Self::Interner, <Self::Interner as Interner>::Predicate>,
         generate_proof_tree: GenerateProofTree,
     ) -> (Result<(bool, Certainty), NoSolution>, Option<inspect::GoalEvaluation<Self::Interner>>);
+
+    // FIXME: This is only exposed because we need to use it in `analyse.rs`
+    // which is not yet uplifted. Once that's done, we should remove this.
+    fn evaluate_root_goal_raw(
+        &self,
+        goal: Goal<Self::Interner, <Self::Interner as Interner>::Predicate>,
+        generate_proof_tree: GenerateProofTree,
+    ) -> (
+        Result<(NestedNormalizationGoals<Self::Interner>, bool, Certainty), NoSolution>,
+        Option<inspect::GoalEvaluation<Self::Interner>>,
+    );
 }
 
 impl<Infcx, I> SolverDelegateEvalExt for Infcx
@@ -148,6 +159,20 @@ where
             ecx.evaluate_goal(GoalEvaluationKind::Root, GoalSource::Misc, goal)
         })
     }
+
+    #[instrument(level = "debug", skip(self))]
+    fn evaluate_root_goal_raw(
+        &self,
+        goal: Goal<I, I::Predicate>,
+        generate_proof_tree: GenerateProofTree,
+    ) -> (
+        Result<(NestedNormalizationGoals<I>, bool, Certainty), NoSolution>,
+        Option<inspect::GoalEvaluation<I>>,
+    ) {
+        EvalCtxt::enter_root(self, generate_proof_tree, |ecx| {
+            ecx.evaluate_goal_raw(GoalEvaluationKind::Root, GoalSource::Misc, goal)
+        })
+    }
 }
 
 impl<'a, Infcx, I> EvalCtxt<'a, Infcx>

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

@@ -2,3 +2,5 @@ pub use rustc_type_ir::solve::inspect::*;
 
 mod build;
 pub(in crate::solve) use build::*;
+
+pub use crate::solve::eval_ctxt::canonical::instantiate_canonical_state;

compiler/rustc_next_trait_solver/src/solve/search_graph.rs

@@ -12,7 +12,7 @@ use crate::solve::{
 };
 
 #[derive(Copy, Clone, PartialEq, Eq, Debug)]
-pub struct Limit(usize);
+pub struct SolverLimit(usize);
 
 rustc_index::newtype_index! {
     #[orderable]
@@ -35,7 +35,7 @@ bitflags::bitflags! {
 struct StackEntry<I: Interner> {
     input: CanonicalInput<I>,
 
-    available_depth: Limit,
+    available_depth: SolverLimit,
 
     /// The maximum depth reached by this stack entry, only up-to date
     /// for the top of the stack and lazily updated for the rest.
@@ -164,19 +164,19 @@ impl<I: Interner> SearchGraph<I> {
     fn allowed_depth_for_nested(
         tcx: I,
         stack: &IndexVec<StackDepth, StackEntry<I>>,
-    ) -> Option<Limit> {
+    ) -> Option<SolverLimit> {
         if let Some(last) = stack.raw.last() {
             if last.available_depth.0 == 0 {
                 return None;
             }
 
             Some(if last.encountered_overflow {
-                Limit(last.available_depth.0 / 4)
+                SolverLimit(last.available_depth.0 / 4)
             } else {
-                Limit(last.available_depth.0 - 1)
+                SolverLimit(last.available_depth.0 - 1)
             })
         } else {
-            Some(Limit(tcx.recursion_limit()))
+            Some(SolverLimit(tcx.recursion_limit()))
         }
     }
 
@@ -414,12 +414,12 @@ impl<I: Interner> SearchGraph<I> {
         &mut self,
         tcx: I,
         input: CanonicalInput<I>,
-        available_depth: Limit,
+        available_depth: SolverLimit,
         inspect: &mut ProofTreeBuilder<Infcx>,
     ) -> Option<QueryResult<I>> {
         let CacheData { result, proof_tree, additional_depth, encountered_overflow } = self
             .global_cache(tcx)
-            // TODO: Awkward `Limit -> usize -> Limit`.
+            // FIXME: Awkward `Limit -> usize -> Limit`.
             .get(tcx, input, self.stack.iter().map(|e| e.input), available_depth.0)?;
 
         // If we're building a proof tree and the current cache entry does not