Turn predicate 'erased lifetimes into 'static

Author: ivarflakstad

compiler/rustc_const_eval/src/interpret/intrinsics.rs

@@ -6,11 +6,12 @@ use std::assert_matches::assert_matches;
 
 use rustc_abi::{FIRST_VARIANT, FieldIdx, HasDataLayout, Size};
 use rustc_apfloat::ieee::{Double, Half, Quad, Single};
+use rustc_hir::def_id::CRATE_DEF_ID;
 use rustc_infer::infer::TyCtxtInferExt;
 use rustc_middle::mir::interpret::{CTFE_ALLOC_SALT, read_target_uint, write_target_uint};
 use rustc_middle::mir::{self, BinOp, ConstValue, NonDivergingIntrinsic};
 use rustc_middle::ty::layout::TyAndLayout;
-use rustc_middle::ty::{Ty, TyCtxt};
+use rustc_middle::ty::{Ty, TyCtxt, TypeFoldable};
 use rustc_middle::{bug, span_bug, ty};
 use rustc_span::{Symbol, sym};
 use rustc_trait_selection::traits::{Obligation, ObligationCause, ObligationCtxt};
@@ -170,12 +171,22 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
                 let ocx = ObligationCtxt::new(&infcx);
                 ocx.register_obligations(preds.iter().map(|pred| {
                     let pred = pred.with_self_ty(tcx, tp_ty);
-                    let pred = tcx.erase_regions(pred);
+                    // Lifetimes can only be 'static because of the bound on T
+                    let pred = pred.fold_with(&mut ty::BottomUpFolder {
+                        tcx,
+                        ty_op: |ty| ty,
+                        lt_op: |lt| {
+                            if lt == tcx.lifetimes.re_erased { tcx.lifetimes.re_static } else { lt }
+                        },
+                        ct_op: |ct| ct,
+                    });
                     Obligation::new(tcx, ObligationCause::dummy(), param_env, pred)
                 }));
                 let type_impls_trait = ocx.select_all_or_error().is_empty();
+                // Since `assumed_wf_tys=[]` the choice of LocalDefId is irrelevant, so using the "default"
+                let regions_are_valid = ocx.resolve_regions(CRATE_DEF_ID, param_env, []).is_empty();
 
-                if type_impls_trait {
+                if regions_are_valid && type_impls_trait {
                     let vtable_ptr = self.get_vtable_ptr(tp_ty, preds)?;
                     // Writing a non-null pointer into an `Option<NonNull>` will automatically make it `Some`.
                     self.write_pointer(vtable_ptr, dest)?;