Add warn(unreachable_pub) to rustc_hir_analysis.

compiler/rustc_hir_analysis/src/variance/solve.rs

@@ -21,7 +21,7 @@ struct SolveContext<'a, 'tcx> {
     solutions: Vec<ty::Variance>,
 }
 
-pub fn solve_constraints<'tcx>(
+pub(crate) fn solve_constraints<'tcx>(
     constraints_cx: ConstraintContext<'_, 'tcx>,
 ) -> ty::CrateVariancesMap<'tcx> {
     let ConstraintContext { terms_cx, constraints, .. } = constraints_cx;