Rollup merge of #54095 - kenta7777:kenta7777#53719, r=davidtwco

Rename all mentions of `nil` to `unit`

Fixes #53719.

Renamed keywords nil to unit.

src/librustc/traits/error_reporting.rs

@@ -661,7 +661,7 @@ pub fn report_selection_error(&self,
                         {
                             let predicate = trait_predicate.map_bound(|mut trait_pred| {
                                 trait_pred.trait_ref.substs = self.tcx.mk_substs_trait(
-                                    self.tcx.mk_nil(),
+                                    self.tcx.mk_unit(),
                                     &trait_pred.trait_ref.substs[1..],
                                 );
                                 trait_pred

src/librustc/ty/context.rs

@@ -2492,7 +2492,7 @@ pub fn mk_imm_ptr(self, ty: Ty<'tcx>) -> Ty<'tcx> {
     }
 
     pub fn mk_nil_ptr(self) -> Ty<'tcx> {
-        self.mk_imm_ptr(self.mk_nil())
+        self.mk_imm_ptr(self.mk_unit())
     }
 
     pub fn mk_array(self, ty: Ty<'tcx>, n: u64) -> Ty<'tcx> {
@@ -2511,7 +2511,7 @@ pub fn mk_tup<I: InternAs<[Ty<'tcx>], Ty<'tcx>>>(self, iter: I) -> I::Output {
         iter.intern_with(|ts| self.mk_ty(Tuple(self.intern_type_list(ts))))
     }
 
-    pub fn mk_nil(self) -> Ty<'tcx> {
+    pub fn mk_unit(self) -> Ty<'tcx> {
         self.intern_tup(&[])
     }
 

src/librustc/ty/layout.rs

@@ -132,7 +132,7 @@ fn to_ty<'a, 'tcx>(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>) -> Ty<'tcx> {
             Int(i, signed) => i.to_ty(tcx, signed),
             Float(FloatTy::F32) => tcx.types.f32,
             Float(FloatTy::F64) => tcx.types.f64,
-            Pointer => tcx.mk_mut_ptr(tcx.mk_nil()),
+            Pointer => tcx.mk_mut_ptr(tcx.mk_unit()),
         }
     }
 }
@@ -1606,7 +1606,7 @@ fn field(this: TyLayout<'tcx>, cx: C, i: usize) -> C::TyLayout {
                 // (which may have no non-DST form), and will work as long
                 // as the `Abi` or `FieldPlacement` is checked by users.
                 if i == 0 {
-                    let nil = tcx.mk_nil();
+                    let nil = tcx.mk_unit();
                     let ptr_ty = if this.ty.is_unsafe_ptr() {
                         tcx.mk_mut_ptr(nil)
                     } else {

src/librustc/ty/query/on_disk_cache.rs

@@ -1020,7 +1020,7 @@ impl<'enc, 'a, 'tcx, E> Encoder for CacheEncoder<'enc, 'a, 'tcx, E>
 {
     type Error = E::Error;
 
-    fn emit_nil(&mut self) -> Result<(), Self::Error> {
+    fn emit_unit(&mut self) -> Result<(), Self::Error> {
         Ok(())
     }
 

src/librustc/ty/sty.rs

@@ -1458,7 +1458,7 @@ pub fn free_region_binding_scope(&self, tcx: TyCtxt<'_, '_, '_>) -> DefId {
 
 /// Type utilities
 impl<'a, 'gcx, 'tcx> TyS<'tcx> {
-    pub fn is_nil(&self) -> bool {
+    pub fn is_unit(&self) -> bool {
         match self.sty {
             Tuple(ref tys) => tys.is_empty(),
             _ => false,

src/librustc/util/ppaux.rs

@@ -234,7 +234,7 @@ fn fn_sig<F: fmt::Write>(&mut self,
             }
         }
         write!(f, ")")?;
-        if !output.is_nil() {
+        if !output.is_unit() {
             print!(f, self, write(" -> "), print_display(output))?;
         }
 

src/librustc_codegen_llvm/debuginfo/type_names.rs

@@ -160,7 +160,7 @@ pub fn push_debuginfo_type_name<'a, 'tcx>(cx: &CodegenCx<'a, 'tcx>,
 
             output.push(')');
 
-            if !sig.output().is_nil() {
+            if !sig.output().is_unit() {
                 output.push_str(" -> ");
                 push_debuginfo_type_name(cx, sig.output(), true, output);
             }

src/librustc_codegen_llvm/intrinsic.rs

@@ -968,7 +968,7 @@ fn get_rust_try_fn<'ll, 'tcx>(
     let i8p = tcx.mk_mut_ptr(tcx.types.i8);
     let fn_ty = tcx.mk_fn_ptr(ty::Binder::bind(tcx.mk_fn_sig(
         iter::once(i8p),
-        tcx.mk_nil(),
+        tcx.mk_unit(),
         false,
         hir::Unsafety::Unsafe,
         Abi::Rust

src/librustc_codegen_llvm/mir/rvalue.rs

@@ -566,7 +566,7 @@ pub fn codegen_scalar_binop(
     ) -> &'ll Value {
         let is_float = input_ty.is_fp();
         let is_signed = input_ty.is_signed();
-        let is_nil = input_ty.is_nil();
+        let is_unit = input_ty.is_unit();
         match op {
             mir::BinOp::Add => if is_float {
                 bx.fadd(lhs, rhs)
@@ -604,7 +604,7 @@ pub fn codegen_scalar_binop(
             mir::BinOp::Shl => common::build_unchecked_lshift(bx, lhs, rhs),
             mir::BinOp::Shr => common::build_unchecked_rshift(bx, input_ty, lhs, rhs),
             mir::BinOp::Ne | mir::BinOp::Lt | mir::BinOp::Gt |
-            mir::BinOp::Eq | mir::BinOp::Le | mir::BinOp::Ge => if is_nil {
+            mir::BinOp::Eq | mir::BinOp::Le | mir::BinOp::Ge => if is_unit {
                 C_bool(bx.cx, match op {
                     mir::BinOp::Ne | mir::BinOp::Lt | mir::BinOp::Gt => false,
                     mir::BinOp::Eq | mir::BinOp::Le | mir::BinOp::Ge => true,

src/librustc_driver/test.rs

@@ -309,7 +309,7 @@ pub fn t_fn(&self, input_tys: &[Ty<'tcx>], output_ty: Ty<'tcx>) -> Ty<'tcx> {
     }
 
     pub fn t_nil(&self) -> Ty<'tcx> {
-        self.infcx.tcx.mk_nil()
+        self.infcx.tcx.mk_unit()
     }
 
     pub fn t_pair(&self, ty1: Ty<'tcx>, ty2: Ty<'tcx>) -> Ty<'tcx> {

src/librustc_lint/types.rs

@@ -691,7 +691,7 @@ fn check_type_for_ffi(&self,
                 }
 
                 let sig = cx.erase_late_bound_regions(&sig);
-                if !sig.output().is_nil() {
+                if !sig.output().is_unit() {
                     let r = self.check_type_for_ffi(cache, sig.output());
                     match r {
                         FfiSafe => {}
@@ -767,7 +767,7 @@ fn check_foreign_fn(&mut self, id: ast::NodeId, decl: &hir::FnDecl) {
 
         if let hir::Return(ref ret_hir) = decl.output {
             let ret_ty = sig.output();
-            if !ret_ty.is_nil() {
+            if !ret_ty.is_unit() {
                 self.check_type_for_ffi_and_report_errors(ret_hir.span, ret_ty);
             }
         }

src/librustc_metadata/encoder.rs

@@ -75,7 +75,7 @@ pub struct EncodeContext<'a, 'tcx: 'a> {
 impl<'a, 'tcx> Encoder for EncodeContext<'a, 'tcx> {
     type Error = <opaque::Encoder as Encoder>::Error;
 
-    fn emit_nil(&mut self) -> Result<(), Self::Error> {
+    fn emit_unit(&mut self) -> Result<(), Self::Error> {
         Ok(())
     }
 

src/librustc_mir/build/block.rs

@@ -167,7 +167,7 @@ fn ast_block_stmts(&mut self,
             // the case of `!`, no return value is required, as the block will never return.
             let tcx = this.hir.tcx();
             let ty = destination.ty(&this.local_decls, tcx).to_ty(tcx);
-            if ty.is_nil() {
+            if ty.is_unit() {
                 // We only want to assign an implicit `()` as the return value of the block if the
                 // block does not diverge. (Otherwise, we may try to assign a unit to a `!`-type.)
                 this.cfg.push_assign_unit(block, source_info, destination);

src/librustc_mir/hair/cx/mod.rs

@@ -118,7 +118,7 @@ pub fn bool_ty(&mut self) -> Ty<'tcx> {
     }
 
     pub fn unit_ty(&mut self) -> Ty<'tcx> {
-        self.tcx.mk_nil()
+        self.tcx.mk_unit()
     }
 
     pub fn true_literal(&mut self) -> &'tcx ty::Const<'tcx> {

src/librustc_mir/interpret/terminator.rs

@@ -436,7 +436,7 @@ fn drop_in_place(
             layout: self.layout_of(self.tcx.mk_mut_ptr(place.layout.ty))?,
         };
 
-        let ty = self.tcx.mk_nil(); // return type is ()
+        let ty = self.tcx.mk_unit(); // return type is ()
         let dest = PlaceTy::null(&self, self.layout_of(ty)?);
 
         self.eval_fn_call(

src/librustc_mir/monomorphize/item.rs

@@ -368,7 +368,7 @@ pub fn push_type_name(&self, t: Ty<'tcx>, output: &mut String) {
 
                 output.push(')');
 
-                if !sig.output().is_nil() {
+                if !sig.output().is_unit() {
                     output.push_str(" -> ");
                     self.push_type_name(sig.output(), output);
                 }

src/librustc_mir/transform/generator.rs

@@ -518,7 +518,7 @@ fn compute_layout<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
     }
 
     let upvar_len = mir.upvar_decls.len();
-    let dummy_local = LocalDecl::new_internal(tcx.mk_nil(), mir.span);
+    let dummy_local = LocalDecl::new_internal(tcx.mk_unit(), mir.span);
 
     // Gather live locals and their indices replacing values in mir.local_decls with a dummy
     // to avoid changing local indices
@@ -656,7 +656,7 @@ fn create_generator_drop_shim<'a, 'tcx>(
     // Replace the return variable
     mir.local_decls[RETURN_PLACE] = LocalDecl {
         mutability: Mutability::Mut,
-        ty: tcx.mk_nil(),
+        ty: tcx.mk_unit(),
         user_ty: None,
         name: None,
         source_info,

src/librustc_mir/util/elaborate_drops.rs

@@ -529,7 +529,7 @@ fn destructor_call_block<'a>(&mut self, (succ, unwind): (BasicBlock, Unwind))
             mutbl: hir::Mutability::MutMutable
         });
         let ref_place = self.new_temp(ref_ty);
-        let unit_temp = Place::Local(self.new_temp(tcx.mk_nil()));
+        let unit_temp = Place::Local(self.new_temp(tcx.mk_unit()));
 
         let result = BasicBlockData {
             statements: vec![self.assign(
@@ -891,7 +891,7 @@ fn unelaborated_free_block<'a>(
         unwind: Unwind
     ) -> BasicBlock {
         let tcx = self.tcx();
-        let unit_temp = Place::Local(self.new_temp(tcx.mk_nil()));
+        let unit_temp = Place::Local(self.new_temp(tcx.mk_unit()));
         let free_func = tcx.require_lang_item(lang_items::BoxFreeFnLangItem);
         let args = adt.variants[0].fields.iter().enumerate().map(|(i, f)| {
             let field = Field::new(i);

src/librustc_typeck/astconv.rs

@@ -1575,7 +1575,7 @@ pub fn ty_of_fn(&self,
 
         let output_ty = match decl.output {
             hir::Return(ref output) => self.ast_ty_to_ty(output),
-            hir::DefaultReturn(..) => tcx.mk_nil(),
+            hir::DefaultReturn(..) => tcx.mk_unit(),
         };
 
         debug!("ty_of_fn: output_ty={:?}", output_ty);

src/librustc_typeck/check/_match.rs

@@ -666,7 +666,7 @@ pub fn check_match(&self,
                 // us to give better error messages (pointing to a usually better
                 // arm for inconsistent arms or to the whole match when a `()` type
                 // is required).
-                Expectation::ExpectHasType(ety) if ety != self.tcx.mk_nil() => ety,
+                Expectation::ExpectHasType(ety) if ety != self.tcx.mk_unit() => ety,
                 _ => self.next_ty_var(TypeVariableOrigin::MiscVariable(expr.span)),
             };
             CoerceMany::with_coercion_sites(coerce_first, arms)
@@ -687,14 +687,14 @@ pub fn check_match(&self,
             // Handle the fallback arm of a desugared if-let like a missing else.
             let is_if_let_fallback = match match_src {
                 hir::MatchSource::IfLetDesugar { contains_else_clause: false } => {
-                    i == arms.len() - 1 && arm_ty.is_nil()
+                    i == arms.len() - 1 && arm_ty.is_unit()
                 }
                 _ => false
             };
 
             if is_if_let_fallback {
                 let cause = self.cause(expr.span, ObligationCauseCode::IfExpressionWithNoElse);
-                assert!(arm_ty.is_nil());
+                assert!(arm_ty.is_unit());
                 coercion.coerce_forced_unit(self, &cause, &mut |_| (), true);
             } else {
                 let cause = self.cause(expr.span, ObligationCauseCode::MatchExpressionArm {

src/librustc_typeck/check/coercion.rs

@@ -1077,7 +1077,7 @@ pub fn coerce_forced_unit<'a>(&mut self,
         self.coerce_inner(fcx,
                           cause,
                           None,
-                          fcx.tcx.mk_nil(),
+                          fcx.tcx.mk_unit(),
                           Some(augment_error),
                           label_unit_as_expected)
     }
@@ -1146,8 +1146,8 @@ fn coerce_inner<'a>(&mut self,
             // `expression_ty` will be unit).
             //
             // Another example is `break` with no argument expression.
-            assert!(expression_ty.is_nil());
-            assert!(expression_ty.is_nil(), "if let hack without unit type");
+            assert!(expression_ty.is_unit());
+            assert!(expression_ty.is_unit(), "if let hack without unit type");
             fcx.at(cause, fcx.param_env)
                .eq_exp(label_expression_as_expected, expression_ty, self.merged_ty())
                .map(|infer_ok| {

src/librustc_typeck/check/intrinsic.rs

@@ -94,7 +94,7 @@ pub fn check_intrinsic_type<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
             "load" => (1, vec![tcx.mk_imm_ptr(param(0))],
                        param(0)),
             "store" => (1, vec![tcx.mk_mut_ptr(param(0)), param(0)],
-                        tcx.mk_nil()),
+                        tcx.mk_unit()),
 
             "xchg" | "xadd" | "xsub" | "and"  | "nand" | "or" | "xor" | "max" |
             "min"  | "umax" | "umin" => {
@@ -102,7 +102,7 @@ pub fn check_intrinsic_type<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                  param(0))
             }
             "fence" | "singlethreadfence" => {
-                (0, Vec::new(), tcx.mk_nil())
+                (0, Vec::new(), tcx.mk_unit())
             }
             op => {
                 struct_span_err!(tcx.sess, it.span, E0092,
@@ -121,7 +121,7 @@ pub fn check_intrinsic_type<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
             _ => hir::Unsafety::Unsafe,
         };
         let (n_tps, inputs, output) = match &name[..] {
-            "breakpoint" => (0, Vec::new(), tcx.mk_nil()),
+            "breakpoint" => (0, Vec::new(), tcx.mk_unit()),
             "size_of" |
             "pref_align_of" | "min_align_of" => (1, Vec::new(), tcx.types.usize),
             "size_of_val" |  "min_align_of_val" => {
@@ -141,7 +141,7 @@ pub fn check_intrinsic_type<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                     tcx.mk_mut_ptr(param(0)),
                     param(0)
                   ],
-               tcx.mk_nil())
+               tcx.mk_unit())
             }
             "prefetch_read_data" | "prefetch_write_data" |
             "prefetch_read_instruction" | "prefetch_write_instruction" => {
@@ -149,10 +149,10 @@ pub fn check_intrinsic_type<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                           ty: param(0),
                           mutbl: hir::MutImmutable
                          }), tcx.types.i32],
-                    tcx.mk_nil())
+                    tcx.mk_unit())
             }
             "drop_in_place" => {
-                (1, vec![tcx.mk_mut_ptr(param(0))], tcx.mk_nil())
+                (1, vec![tcx.mk_mut_ptr(param(0))], tcx.mk_unit())
             }
             "needs_drop" => (1, Vec::new(), tcx.types.bool),
 
@@ -185,7 +185,7 @@ pub fn check_intrinsic_type<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                   }),
                   tcx.types.usize,
                ],
-               tcx.mk_nil())
+               tcx.mk_unit())
             }
             "volatile_copy_memory" | "volatile_copy_nonoverlapping_memory" => {
               (1,
@@ -200,7 +200,7 @@ pub fn check_intrinsic_type<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                   }),
                   tcx.types.usize,
                ],
-               tcx.mk_nil())
+               tcx.mk_unit())
             }
             "write_bytes" | "volatile_set_memory" => {
               (1,
@@ -212,7 +212,7 @@ pub fn check_intrinsic_type<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                   tcx.types.u8,
                   tcx.types.usize,
                ],
-               tcx.mk_nil())
+               tcx.mk_unit())
             }
             "sqrtf32" => (0, vec![ tcx.types.f32 ], tcx.types.f32),
             "sqrtf64" => (0, vec![ tcx.types.f64 ], tcx.types.f64),
@@ -280,7 +280,7 @@ pub fn check_intrinsic_type<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
             "volatile_load" | "unaligned_volatile_load" =>
                 (1, vec![ tcx.mk_imm_ptr(param(0)) ], param(0)),
             "volatile_store" | "unaligned_volatile_store" =>
-                (1, vec![ tcx.mk_mut_ptr(param(0)), param(0) ], tcx.mk_nil()),
+                (1, vec![ tcx.mk_mut_ptr(param(0)), param(0) ], tcx.mk_unit()),
 
             "ctpop" | "ctlz" | "ctlz_nonzero" | "cttz" | "cttz_nonzero" |
             "bswap" | "bitreverse" =>
@@ -300,7 +300,7 @@ pub fn check_intrinsic_type<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
             "fadd_fast" | "fsub_fast" | "fmul_fast" | "fdiv_fast" | "frem_fast" =>
                 (1, vec![param(0), param(0)], param(0)),
 
-            "assume" => (0, vec![tcx.types.bool], tcx.mk_nil()),
+            "assume" => (0, vec![tcx.types.bool], tcx.mk_unit()),
             "likely" => (0, vec![tcx.types.bool], tcx.types.bool),
             "unlikely" => (0, vec![tcx.types.bool], tcx.types.bool),
 
@@ -313,7 +313,7 @@ pub fn check_intrinsic_type<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                 let mut_u8 = tcx.mk_mut_ptr(tcx.types.u8);
                 let fn_ty = ty::Binder::bind(tcx.mk_fn_sig(
                     iter::once(mut_u8),
-                    tcx.mk_nil(),
+                    tcx.mk_unit(),
                     false,
                     hir::Unsafety::Normal,
                     Abi::Rust,
@@ -322,7 +322,7 @@ pub fn check_intrinsic_type<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
             }
 
             "nontemporal_store" => {
-                (1, vec![ tcx.mk_mut_ptr(param(0)), param(0) ], tcx.mk_nil())
+                (1, vec![ tcx.mk_mut_ptr(param(0)), param(0) ], tcx.mk_unit())
             }
 
             ref other => {
@@ -376,7 +376,7 @@ pub fn check_platform_intrinsic_type<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
             (3, vec![param(0), param(1), param(2)], param(0))
         }
         "simd_scatter" => {
-            (3, vec![param(0), param(1), param(2)], tcx.mk_nil())
+            (3, vec![param(0), param(1), param(2)], tcx.mk_unit())
         }
         "simd_insert" => (2, vec![param(0), tcx.types.u32, param(1)], param(0)),
         "simd_extract" => (2, vec![param(0), tcx.types.u32], param(1)),

src/librustc_typeck/check/mod.rs

@@ -2808,9 +2808,9 @@ fn check_argument_types(&self,
         } else {
             // is the missing argument of type `()`?
             let sugg_unit = if expected_arg_tys.len() == 1 && supplied_arg_count == 0 {
-                self.resolve_type_vars_if_possible(&expected_arg_tys[0]).is_nil()
+                self.resolve_type_vars_if_possible(&expected_arg_tys[0]).is_unit()
             } else if fn_inputs.len() == 1 && supplied_arg_count == 0 {
-                self.resolve_type_vars_if_possible(&fn_inputs[0]).is_nil()
+                self.resolve_type_vars_if_possible(&fn_inputs[0]).is_unit()
             } else {
                 false
             };
@@ -3918,7 +3918,7 @@ fn check_expr_kind(&self,
                 for input in inputs {
                     self.check_expr(input);
                 }
-                tcx.mk_nil()
+                tcx.mk_unit()
             }
             hir::ExprKind::Break(destination, ref expr_opt) => {
                 if let Ok(target_id) = destination.target_id {
@@ -3945,7 +3945,7 @@ fn check_expr_kind(&self,
                     } else {
                         // Otherwise, this is a break *without* a value. That's
                         // always legal, and is equivalent to `break ()`.
-                        e_ty = tcx.mk_nil();
+                        e_ty = tcx.mk_unit();
                         cause = self.misc(expr.span);
                     }
 
@@ -3958,7 +3958,7 @@ fn check_expr_kind(&self,
                         if let Some(ref e) = *expr_opt {
                             coerce.coerce(self, &cause, e, e_ty);
                         } else {
-                            assert!(e_ty.is_nil());
+                            assert!(e_ty.is_unit());
                             coerce.coerce_forced_unit(self, &cause, &mut |_| (), true);
                         }
                     } else {
@@ -4052,7 +4052,7 @@ fn check_expr_kind(&self,
                 if lhs_ty.references_error() || rhs_ty.references_error() {
                     tcx.types.err
                 } else {
-                    tcx.mk_nil()
+                    tcx.mk_unit()
                 }
             }
             hir::ExprKind::If(ref cond, ref then_expr, ref opt_else_expr) => {
@@ -4081,7 +4081,7 @@ fn check_expr_kind(&self,
                     self.diverges.set(Diverges::Maybe);
                 }
 
-                self.tcx.mk_nil()
+                self.tcx.mk_unit()
             }
             hir::ExprKind::Loop(ref body, _, source) => {
                 let coerce = match source {
@@ -4121,7 +4121,7 @@ fn check_expr_kind(&self,
                     // [1]
                     self.tcx.sess.delay_span_bug(body.span, "no coercion, but loop may not break");
                 }
-                ctxt.coerce.map(|c| c.complete(self)).unwrap_or(self.tcx.mk_nil())
+                ctxt.coerce.map(|c| c.complete(self)).unwrap_or(self.tcx.mk_unit())
             }
             hir::ExprKind::Match(ref discrim, ref arms, match_src) => {
                 self.check_match(expr, &discrim, arms, expected, match_src)
@@ -4352,7 +4352,7 @@ fn check_expr_kind(&self,
                                         "yield statement outside of generator literal").emit();
                     }
                 }
-                tcx.mk_nil()
+                tcx.mk_unit()
             }
         }
     }
@@ -4516,7 +4516,7 @@ pub fn check_stmt(&self, stmt: &'gcx hir::Stmt) {
             }
             hir::StmtKind::Expr(ref expr, _) => {
                 // Check with expected type of ()
-                self.check_expr_has_type_or_error(&expr, self.tcx.mk_nil());
+                self.check_expr_has_type_or_error(&expr, self.tcx.mk_unit());
             }
             hir::StmtKind::Semi(ref expr, _) => {
                 self.check_expr(&expr);
@@ -4529,7 +4529,7 @@ pub fn check_stmt(&self, stmt: &'gcx hir::Stmt) {
     }
 
     pub fn check_block_no_value(&self, blk: &'gcx hir::Block)  {
-        let unit = self.tcx.mk_nil();
+        let unit = self.tcx.mk_unit();
         let ty = self.check_block_with_expected(blk, ExpectHasType(unit));
 
         // if the block produces a `!` value, that can always be
@@ -4752,7 +4752,7 @@ fn suggest_missing_semicolon(&self,
                                  expression: &'gcx hir::Expr,
                                  expected: Ty<'tcx>,
                                  cause_span: Span) {
-        if expected.is_nil() {
+        if expected.is_unit() {
             // `BlockTailExpression` only relevant if the tail expr would be
             // useful on its own.
             match expression.node {
@@ -4795,7 +4795,7 @@ fn suggest_missing_return_type(&self,
                                    can_suggest: bool) {
         // Only suggest changing the return type for methods that
         // haven't set a return type at all (and aren't `fn main()` or an impl).
-        match (&fn_decl.output, found.is_suggestable(), can_suggest, expected.is_nil()) {
+        match (&fn_decl.output, found.is_suggestable(), can_suggest, expected.is_unit()) {
             (&hir::FunctionRetTy::DefaultReturn(span), true, true, true) => {
                 err.span_suggestion_with_applicability(
                     span,

src/librustc_typeck/check/op.rs

@@ -35,7 +35,7 @@ pub fn check_binop_assign(&self,
         let ty = if !lhs_ty.is_ty_var() && !rhs_ty.is_ty_var()
                     && is_builtin_binop(lhs_ty, rhs_ty, op) {
             self.enforce_builtin_binop_types(lhs_expr, lhs_ty, rhs_expr, rhs_ty, op);
-            self.tcx.mk_nil()
+            self.tcx.mk_unit()
         } else {
             return_ty
         };

src/librustc_typeck/lib.rs

@@ -224,7 +224,7 @@ fn check_main_fn_ty<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
                 actual.output().skip_binder()
             } else {
                 // standard () main return type
-                tcx.mk_nil()
+                tcx.mk_unit()
             };
 
             let se_ty = tcx.mk_fn_ptr(ty::Binder::bind(

src/libserialize/json.rs

@@ -490,7 +490,7 @@ pub fn new(writer: &'a mut dyn fmt::Write) -> Encoder<'a> {
 impl<'a> ::Encoder for Encoder<'a> {
     type Error = EncoderError;
 
-    fn emit_nil(&mut self) -> EncodeResult {
+    fn emit_unit(&mut self) -> EncodeResult {
         if self.is_emitting_map_key { return Err(EncoderError::BadHashmapKey); }
         write!(self.writer, "null")?;
         Ok(())
@@ -648,7 +648,7 @@ fn emit_option<F>(&mut self, f: F) -> EncodeResult where
     }
     fn emit_option_none(&mut self) -> EncodeResult {
         if self.is_emitting_map_key { return Err(EncoderError::BadHashmapKey); }
-        self.emit_nil()
+        self.emit_unit()
     }
     fn emit_option_some<F>(&mut self, f: F) -> EncodeResult where
         F: FnOnce(&mut Encoder<'a>) -> EncodeResult,
@@ -740,7 +740,7 @@ pub fn set_indent(&mut self, indent: usize) {
 impl<'a> ::Encoder for PrettyEncoder<'a> {
     type Error = EncoderError;
 
-    fn emit_nil(&mut self) -> EncodeResult {
+    fn emit_unit(&mut self) -> EncodeResult {
         if self.is_emitting_map_key { return Err(EncoderError::BadHashmapKey); }
         write!(self.writer, "null")?;
         Ok(())
@@ -923,7 +923,7 @@ fn emit_option<F>(&mut self, f: F) -> EncodeResult where
     }
     fn emit_option_none(&mut self) -> EncodeResult {
         if self.is_emitting_map_key { return Err(EncoderError::BadHashmapKey); }
-        self.emit_nil()
+        self.emit_unit()
     }
     fn emit_option_some<F>(&mut self, f: F) -> EncodeResult where
         F: FnOnce(&mut PrettyEncoder<'a>) -> EncodeResult,
@@ -1016,7 +1016,7 @@ fn encode<E: ::Encoder>(&self, e: &mut E) -> Result<(), E::Error> {
             Json::Boolean(v) => v.encode(e),
             Json::Array(ref v) => v.encode(e),
             Json::Object(ref v) => v.encode(e),
-            Json::Null => e.emit_nil(),
+            Json::Null => e.emit_unit(),
         }
     }
 }

src/libserialize/opaque.rs

@@ -55,7 +55,7 @@ impl serialize::Encoder for Encoder {
     type Error = !;
 
     #[inline]
-    fn emit_nil(&mut self) -> EncodeResult {
+    fn emit_unit(&mut self) -> EncodeResult {
         Ok(())
     }
 

src/libserialize/serialize.rs

@@ -25,7 +25,7 @@ pub trait Encoder {
     type Error;
 
     // Primitive types:
-    fn emit_nil(&mut self) -> Result<(), Self::Error>;
+    fn emit_unit(&mut self) -> Result<(), Self::Error>;
     fn emit_usize(&mut self, v: usize) -> Result<(), Self::Error>;
     fn emit_u128(&mut self, v: u128) -> Result<(), Self::Error>;
     fn emit_u64(&mut self, v: u64) -> Result<(), Self::Error>;
@@ -537,7 +537,7 @@ fn decode<D: Decoder>(d: &mut D) -> Result<char, D::Error> {
 
 impl Encodable for () {
     fn encode<S: Encoder>(&self, s: &mut S) -> Result<(), S::Error> {
-        s.emit_nil()
+        s.emit_unit()
     }
 }