use require_lang_item over unwrap.

src/librustc_middle/ty/adjustment.rs

@@ -2,6 +2,7 @@ use crate::ty::subst::SubstsRef;
 use crate::ty::{self, Ty, TyCtxt};
 use rustc_hir as hir;
 use rustc_hir::def_id::DefId;
+use rustc_hir::lang_items::{DerefMutTraitLangItem, DerefTraitLangItem};
 use rustc_macros::HashStable;
 
 #[derive(Clone, Copy, Debug, PartialEq, Eq, RustcEncodable, RustcDecodable, HashStable)]
@@ -117,11 +118,11 @@ pub struct OverloadedDeref<'tcx> {
 impl<'tcx> OverloadedDeref<'tcx> {
     pub fn method_call(&self, tcx: TyCtxt<'tcx>, source: Ty<'tcx>) -> (DefId, SubstsRef<'tcx>) {
         let trait_def_id = match self.mutbl {
-            hir::Mutability::Not => tcx.lang_items().deref_trait(),
-            hir::Mutability::Mut => tcx.lang_items().deref_mut_trait(),
+            hir::Mutability::Not => tcx.require_lang_item(DerefTraitLangItem, None),
+            hir::Mutability::Mut => tcx.require_lang_item(DerefMutTraitLangItem, None),
         };
         let method_def_id = tcx
-            .associated_items(trait_def_id.unwrap())
+            .associated_items(trait_def_id)
             .in_definition_order()
             .find(|m| m.kind == ty::AssocKind::Fn)
             .unwrap()

src/librustc_middle/ty/instance.rs

@@ -4,7 +4,7 @@ use crate::ty::{self, SubstsRef, Ty, TyCtxt, TypeFoldable};
 use rustc_errors::ErrorReported;
 use rustc_hir::def::Namespace;
 use rustc_hir::def_id::{CrateNum, DefId};
-use rustc_hir::lang_items::DropInPlaceFnLangItem;
+use rustc_hir::lang_items::{DropInPlaceFnLangItem, FnOnceTraitLangItem};
 use rustc_macros::HashStable;
 
 use std::fmt;
@@ -375,7 +375,7 @@ impl<'tcx> Instance<'tcx> {
         substs: ty::SubstsRef<'tcx>,
     ) -> Instance<'tcx> {
         debug!("fn_once_adapter_shim({:?}, {:?})", closure_did, substs);
-        let fn_once = tcx.lang_items().fn_once_trait().unwrap();
+        let fn_once = tcx.require_lang_item(FnOnceTraitLangItem, None);
         let call_once = tcx
             .associated_items(fn_once)
             .in_definition_order()

src/librustc_middle/ty/layout.rs

@@ -8,6 +8,7 @@ use rustc_ast::ast::{self, IntTy, UintTy};
 use rustc_attr as attr;
 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
 use rustc_hir as hir;
+use rustc_hir::lang_items::{GeneratorStateLangItem, PinTypeLangItem};
 use rustc_index::bit_set::BitSet;
 use rustc_index::vec::{Idx, IndexVec};
 use rustc_session::{DataTypeKind, FieldInfo, SizeKind, VariantInfo};
@@ -2317,13 +2318,13 @@ impl<'tcx> ty::Instance<'tcx> {
                 let env_region = ty::ReLateBound(ty::INNERMOST, ty::BrEnv);
                 let env_ty = tcx.mk_mut_ref(tcx.mk_region(env_region), ty);
 
-                let pin_did = tcx.lang_items().pin_type().unwrap();
+                let pin_did = tcx.require_lang_item(PinTypeLangItem, None);
                 let pin_adt_ref = tcx.adt_def(pin_did);
                 let pin_substs = tcx.intern_substs(&[env_ty.into()]);
                 let env_ty = tcx.mk_adt(pin_adt_ref, pin_substs);
 
                 sig.map_bound(|sig| {
-                    let state_did = tcx.lang_items().gen_state().unwrap();
+                    let state_did = tcx.require_lang_item(GeneratorStateLangItem, None);
                     let state_adt_ref = tcx.adt_def(state_did);
                     let state_substs = tcx.intern_substs(&[
                         sig.yield_ty.into(),

src/librustc_mir/borrow_check/type_check/mod.rs

@@ -10,6 +10,7 @@ use rustc_data_structures::fx::{FxHashMap, FxHashSet};
 use rustc_errors::struct_span_err;
 use rustc_hir as hir;
 use rustc_hir::def_id::{DefId, LocalDefId};
+use rustc_hir::lang_items::{CoerceUnsizedTraitLangItem, CopyTraitLangItem, SizedTraitLangItem};
 use rustc_index::vec::{Idx, IndexVec};
 use rustc_infer::infer::canonical::QueryRegionConstraints;
 use rustc_infer::infer::outlives::env::RegionBoundPairs;
@@ -502,7 +503,7 @@ impl<'a, 'b, 'tcx> TypeVerifier<'a, 'b, 'tcx> {
         if let PlaceContext::NonMutatingUse(NonMutatingUseContext::Copy) = context {
             let tcx = self.tcx();
             let trait_ref = ty::TraitRef {
-                def_id: tcx.lang_items().copy_trait().unwrap(),
+                def_id: tcx.require_lang_item(CopyTraitLangItem, Some(self.last_span)),
                 substs: tcx.mk_substs_trait(place_ty.ty, &[]),
             };
 
@@ -1468,7 +1469,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                 self.check_rvalue(body, rv, location);
                 if !self.tcx().features().unsized_locals {
                     let trait_ref = ty::TraitRef {
-                        def_id: tcx.lang_items().sized_trait().unwrap(),
+                        def_id: tcx.require_lang_item(SizedTraitLangItem, Some(self.last_span)),
                         substs: tcx.mk_substs_trait(place_ty, &[]),
                     };
                     self.prove_trait_ref(
@@ -2013,7 +2014,10 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                                     ty::Predicate::Trait(
                                         ty::Binder::bind(ty::TraitPredicate {
                                             trait_ref: ty::TraitRef::new(
-                                                self.tcx().lang_items().copy_trait().unwrap(),
+                                                self.tcx().require_lang_item(
+                                                    CopyTraitLangItem,
+                                                    Some(self.last_span),
+                                                ),
                                                 tcx.mk_substs_trait(ty, &[]),
                                             ),
                                         }),
@@ -2037,7 +2041,7 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                 }
 
                 let trait_ref = ty::TraitRef {
-                    def_id: tcx.lang_items().sized_trait().unwrap(),
+                    def_id: tcx.require_lang_item(SizedTraitLangItem, Some(self.last_span)),
                     substs: tcx.mk_substs_trait(ty, &[]),
                 };
 
@@ -2135,7 +2139,10 @@ impl<'a, 'tcx> TypeChecker<'a, 'tcx> {
                     CastKind::Pointer(PointerCast::Unsize) => {
                         let &ty = ty;
                         let trait_ref = ty::TraitRef {
-                            def_id: tcx.lang_items().coerce_unsized_trait().unwrap(),
+                            def_id: tcx.require_lang_item(
+                                CoerceUnsizedTraitLangItem,
+                                Some(self.last_span),
+                            ),
                             substs: tcx.mk_substs_trait(op.ty(body, tcx), &[ty.into()]),
                         };
 

src/librustc_mir/monomorphize/collector.rs

@@ -580,10 +580,8 @@ impl<'a, 'tcx> MirVisitor<'tcx> for MirNeighborCollector<'a, 'tcx> {
             }
             mir::Rvalue::NullaryOp(mir::NullOp::Box, _) => {
                 let tcx = self.tcx;
-                let exchange_malloc_fn_def_id = tcx
-                    .lang_items()
-                    .require(ExchangeMallocFnLangItem)
-                    .unwrap_or_else(|e| tcx.sess.fatal(&e));
+                let exchange_malloc_fn_def_id =
+                    tcx.require_lang_item(ExchangeMallocFnLangItem, None);
                 let instance = Instance::mono(tcx, exchange_malloc_fn_def_id);
                 if should_monomorphize_locally(tcx, &instance) {
                     self.output.push(create_fn_mono_item(instance));

src/librustc_mir/shim.rs

@@ -1,5 +1,6 @@
 use rustc_hir as hir;
 use rustc_hir::def_id::DefId;
+use rustc_hir::lang_items::FnMutTraitLangItem;
 use rustc_middle::mir::*;
 use rustc_middle::ty::query::Providers;
 use rustc_middle::ty::subst::{InternalSubsts, Subst};
@@ -70,7 +71,7 @@ fn make_shim<'tcx>(tcx: TyCtxt<'tcx>, instance: ty::InstanceDef<'tcx>) -> Body<'
             build_call_shim(tcx, instance, None, CallKind::Direct(def_id), None)
         }
         ty::InstanceDef::ClosureOnceShim { call_once: _ } => {
-            let fn_mut = tcx.lang_items().fn_mut_trait().unwrap();
+            let fn_mut = tcx.require_lang_item(FnMutTraitLangItem, None);
             let call_mut = tcx
                 .associated_items(fn_mut)
                 .in_definition_order()

src/librustc_mir/transform/generator.rs

@@ -61,6 +61,7 @@ use crate::util::storage;
 use rustc_data_structures::fx::FxHashMap;
 use rustc_hir as hir;
 use rustc_hir::def_id::DefId;
+use rustc_hir::lang_items::{GeneratorStateLangItem, PinTypeLangItem};
 use rustc_index::bit_set::{BitMatrix, BitSet};
 use rustc_index::vec::{Idx, IndexVec};
 use rustc_middle::mir::visit::{MutVisitor, PlaceContext};
@@ -381,7 +382,7 @@ fn make_generator_state_argument_indirect<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Bo
 fn make_generator_state_argument_pinned<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
     let ref_gen_ty = body.local_decls.raw[1].ty;
 
-    let pin_did = tcx.lang_items().pin_type().unwrap();
+    let pin_did = tcx.require_lang_item(PinTypeLangItem, Some(body.span));
     let pin_adt_ref = tcx.adt_def(pin_did);
     let substs = tcx.intern_substs(&[ref_gen_ty.into()]);
     let pin_ref_gen_ty = tcx.mk_adt(pin_adt_ref, substs);
@@ -1207,7 +1208,7 @@ impl<'tcx> MirPass<'tcx> for StateTransform {
         };
 
         // Compute GeneratorState<yield_ty, return_ty>
-        let state_did = tcx.lang_items().gen_state().unwrap();
+        let state_did = tcx.require_lang_item(GeneratorStateLangItem, None);
         let state_adt_ref = tcx.adt_def(state_did);
         let state_substs = tcx.intern_substs(&[yield_ty.into(), body.return_ty().into()]);
         let ret_ty = tcx.mk_adt(state_adt_ref, state_substs);

src/librustc_mir/util/elaborate_drops.rs

@@ -1,6 +1,6 @@
 use crate::util::patch::MirPatch;
 use rustc_hir as hir;
-use rustc_hir::lang_items;
+use rustc_hir::lang_items::{BoxFreeFnLangItem, DropTraitLangItem};
 use rustc_index::vec::Idx;
 use rustc_middle::mir::*;
 use rustc_middle::traits::Reveal;
@@ -535,7 +535,7 @@ where
     fn destructor_call_block(&mut self, (succ, unwind): (BasicBlock, Unwind)) -> BasicBlock {
         debug!("destructor_call_block({:?}, {:?})", self, succ);
         let tcx = self.tcx();
-        let drop_trait = tcx.lang_items().drop_trait().unwrap();
+        let drop_trait = tcx.require_lang_item(DropTraitLangItem, None);
         let drop_fn = tcx.associated_items(drop_trait).in_definition_order().next().unwrap();
         let ty = self.place_ty(self.place);
         let substs = tcx.mk_substs_trait(ty, &[]);
@@ -877,8 +877,7 @@ where
     ) -> BasicBlock {
         let tcx = self.tcx();
         let unit_temp = Place::from(self.new_temp(tcx.mk_unit()));
-        let free_func =
-            tcx.require_lang_item(lang_items::BoxFreeFnLangItem, Some(self.source_info.span));
+        let free_func = tcx.require_lang_item(BoxFreeFnLangItem, Some(self.source_info.span));
         let args = adt.variants[VariantIdx::new(0)]
             .fields
             .iter()

src/librustc_mir_build/hair/pattern/const_to_pat.rs

@@ -1,4 +1,5 @@
 use rustc_hir as hir;
+use rustc_hir::lang_items::EqTraitLangItem;
 use rustc_index::vec::Idx;
 use rustc_infer::infer::{InferCtxt, TyCtxtInferExt};
 use rustc_middle::mir::Field;
@@ -140,7 +141,7 @@ impl<'a, 'tcx> ConstToPat<'a, 'tcx> {
                 // code at the moment, because types like `for <'a> fn(&'a ())` do
                 // not *yet* implement `PartialEq`. So for now we leave this here.
                 let ty_is_partial_eq: bool = {
-                    let partial_eq_trait_id = self.tcx().lang_items().eq_trait().unwrap();
+                    let partial_eq_trait_id = self.tcx().require_lang_item(EqTraitLangItem, None);
                     let obligation: PredicateObligation<'_> = predicate_for_trait_def(
                         self.tcx(),
                         self.param_env,

src/librustc_trait_selection/traits/project.rs

@@ -20,6 +20,7 @@ use crate::traits::error_reporting::InferCtxtExt;
 use rustc_data_structures::stack::ensure_sufficient_stack;
 use rustc_errors::ErrorReported;
 use rustc_hir::def_id::DefId;
+use rustc_hir::lang_items::{FnOnceTraitLangItem, GeneratorTraitLangItem};
 use rustc_middle::ty::fold::{TypeFoldable, TypeFolder};
 use rustc_middle::ty::subst::{InternalSubsts, Subst};
 use rustc_middle::ty::{self, ToPolyTraitRef, ToPredicate, Ty, TyCtxt, WithConstness};
@@ -1222,7 +1223,7 @@ fn confirm_generator_candidate<'cx, 'tcx>(
 
     let tcx = selcx.tcx();
 
-    let gen_def_id = tcx.lang_items().gen_trait().unwrap();
+    let gen_def_id = tcx.require_lang_item(GeneratorTraitLangItem, None);
 
     let predicate = super::util::generator_trait_ref_and_outputs(
         tcx,
@@ -1309,7 +1310,7 @@ fn confirm_callable_candidate<'cx, 'tcx>(
     debug!("confirm_callable_candidate({:?},{:?})", obligation, fn_sig);
 
     // the `Output` associated type is declared on `FnOnce`
-    let fn_once_def_id = tcx.lang_items().fn_once_trait().unwrap();
+    let fn_once_def_id = tcx.require_lang_item(FnOnceTraitLangItem, None);
 
     let predicate = super::util::closure_trait_ref_and_return_type(
         tcx,

src/librustc_typeck/check/demand.rs

@@ -7,6 +7,7 @@ use rustc_trait_selection::traits::{self, ObligationCause};
 use rustc_ast::util::parser::PREC_POSTFIX;
 use rustc_errors::{Applicability, DiagnosticBuilder};
 use rustc_hir as hir;
+use rustc_hir::lang_items::DerefTraitLangItem;
 use rustc_hir::{is_range_literal, Node};
 use rustc_middle::ty::adjustment::AllowTwoPhase;
 use rustc_middle::ty::{self, AssocItem, Ty, TypeAndMut};
@@ -634,7 +635,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             _ if sp == expr.span && !is_macro => {
                 // Check for `Deref` implementations by constructing a predicate to
                 // prove: `<T as Deref>::Output == U`
-                let deref_trait = self.tcx.lang_items().deref_trait().unwrap();
+                let deref_trait = self.tcx.require_lang_item(DerefTraitLangItem, Some(expr.span));
                 let item_def_id = self
                     .tcx
                     .associated_items(deref_trait)