Rollup merge of #112196 - compiler-errors:new-solver-resolv, r=lcnr

Resolve vars in result from `scrape_region_constraints`

Since we perform `type_op::Normalize` in the local infcx when the new solver is enabled, vars aren't necessarily resolved, which triggers this ICE:

https://github.com/rust-lang/rust/blob/f85ab544dfbbce7448993c490ad16c176339b939/compiler/rustc_infer/src/infer/nll_relate/mod.rs#L481

There are more tests that go from ICE -> pass due to this change, but I just added revisions to a few for CI.

r? `@lcnr`

Author: matthiaskrgr

compiler/rustc_trait_selection/src/traits/query/type_op/custom.rs

@@ -5,6 +5,7 @@ use crate::traits::ObligationCtxt;
 use rustc_errors::ErrorGuaranteed;
 use rustc_infer::infer::region_constraints::RegionConstraintData;
 use rustc_middle::traits::query::NoSolution;
+use rustc_middle::ty::{TyCtxt, TypeFoldable};
 use rustc_span::source_map::DUMMY_SP;
 use rustc_span::Span;
 
@@ -24,9 +25,10 @@ impl<F> CustomTypeOp<F> {
     }
 }
 
-impl<'tcx, F, R: fmt::Debug> super::TypeOp<'tcx> for CustomTypeOp<F>
+impl<'tcx, F, R> super::TypeOp<'tcx> for CustomTypeOp<F>
 where
     F: FnOnce(&ObligationCtxt<'_, 'tcx>) -> Result<R, NoSolution>,
+    R: fmt::Debug + TypeFoldable<TyCtxt<'tcx>>,
 {
     type Output = R;
     /// We can't do any custom error reporting for `CustomTypeOp`, so
@@ -57,12 +59,16 @@ impl<F> fmt::Debug for CustomTypeOp<F> {
 
 /// Executes `op` and then scrapes out all the "old style" region
 /// constraints that result, creating query-region-constraints.
-pub fn scrape_region_constraints<'tcx, Op: super::TypeOp<'tcx, Output = R>, R>(
+pub fn scrape_region_constraints<'tcx, Op, R>(
     infcx: &InferCtxt<'tcx>,
     op: impl FnOnce(&ObligationCtxt<'_, 'tcx>) -> Result<R, NoSolution>,
     name: &'static str,
     span: Span,
-) -> Result<(TypeOpOutput<'tcx, Op>, RegionConstraintData<'tcx>), ErrorGuaranteed> {
+) -> Result<(TypeOpOutput<'tcx, Op>, RegionConstraintData<'tcx>), ErrorGuaranteed>
+where
+    R: TypeFoldable<TyCtxt<'tcx>>,
+    Op: super::TypeOp<'tcx, Output = R>,
+{
     // During NLL, we expect that nobody will register region
     // obligations **except** as part of a custom type op (and, at the
     // end of each custom type op, we scrape out the region
@@ -91,6 +97,9 @@ pub fn scrape_region_constraints<'tcx, Op: super::TypeOp<'tcx, Output = R>, R>(
         }
     })?;
 
+    // Next trait solver performs operations locally, and normalize goals should resolve vars.
+    let value = infcx.resolve_vars_if_possible(value);
+
     let region_obligations = infcx.take_registered_region_obligations();
     let region_constraint_data = infcx.take_and_reset_region_constraints();
     let region_constraints = query_response::make_query_region_constraints(

tests/ui/issues/issue-13167.rs

@@ -1,5 +1,7 @@
 // check-pass
 // pretty-expanded FIXME #23616
+// revisions: current next
+//[next] compile-flags: -Ztrait-solver=next
 
 use std::slice;
 

tests/ui/issues/issue-15734.rs

@@ -1,6 +1,6 @@
 // run-pass
-// If `Index` used an associated type for its output, this test would
-// work more smoothly.
+// revisions: current next
+//[next] compile-flags: -Ztrait-solver=next
 
 use std::ops::Index;
 

tests/ui/nll/issue-53119.rs

@@ -1,4 +1,6 @@
 // check-pass
+// revisions: current next
+//[next] compile-flags: -Ztrait-solver=next
 
 use std::ops::Deref;