typeck: check_expr_kind -> expr.rs

2 files changed, 708 insertions, 673 deletions

diff --git a/src/librustc_typeck/check/expr.rs b/src/librustc_typeck/check/expr.rs
new file mode 100644
index 00000000000..48c1c0b36ff
--- /dev/null
+++ b/src/librustc_typeck/check/expr.rs
@@ -0,0 +1,706 @@
+//! Type checking expressions.
+//!
+//! See `mod.rs` for more context on type checking in general.
+
+use crate::check::BreakableCtxt;
+use crate::check::cast;
+use crate::check::coercion::CoerceMany;
+use crate::check::Diverges;
+use crate::check::FnCtxt;
+use crate::check::Expectation::{self, NoExpectation, ExpectHasType, ExpectCastableToType};
+use crate::check::fatally_break_rust;
+use crate::check::report_unexpected_variant_res;
+use crate::check::Needs;
+use crate::middle::lang_items;
+use crate::util::common::ErrorReported;
+
+use errors::Applicability;
+use syntax::ast;
+use syntax::symbol::sym;
+use rustc::hir;
+use rustc::hir::{ExprKind, QPath};
+use rustc::hir::def::{CtorKind, Res, DefKind};
+use rustc::infer;
+use rustc::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
+use rustc::mir::interpret::GlobalId;
+use rustc::ty;
+use rustc::ty::adjustment::{
+    Adjust, Adjustment, AllowTwoPhase, AutoBorrow, AutoBorrowMutability,
+};
+use rustc::ty::Ty;
+use rustc::ty::TypeFoldable;
+use rustc::ty::subst::InternalSubsts;
+use rustc::traits::{self, ObligationCauseCode};
+
+impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
+    pub(super) fn check_expr_kind(
+        &self,
+        expr: &'tcx hir::Expr,
+        expected: Expectation<'tcx>,
+        needs: Needs,
+    ) -> Ty<'tcx> {
+        debug!(
+            "check_expr_kind(expr={:?}, expected={:?}, needs={:?})",
+            expr,
+            expected,
+            needs,
+        );
+
+        let tcx = self.tcx;
+        let id = expr.hir_id;
+        match expr.node {
+            ExprKind::Box(ref subexpr) => {
+                let expected_inner = expected.to_option(self).map_or(NoExpectation, |ty| {
+                    match ty.sty {
+                        ty::Adt(def, _) if def.is_box()
+                            => Expectation::rvalue_hint(self, ty.boxed_ty()),
+                        _ => NoExpectation
+                    }
+                });
+                let referent_ty = self.check_expr_with_expectation(subexpr, expected_inner);
+                tcx.mk_box(referent_ty)
+            }
+
+            ExprKind::Lit(ref lit) => {
+                self.check_lit(&lit, expected)
+            }
+            ExprKind::Binary(op, ref lhs, ref rhs) => {
+                self.check_binop(expr, op, lhs, rhs)
+            }
+            ExprKind::AssignOp(op, ref lhs, ref rhs) => {
+                self.check_binop_assign(expr, op, lhs, rhs)
+            }
+            ExprKind::Unary(unop, ref oprnd) => {
+                let expected_inner = match unop {
+                    hir::UnNot | hir::UnNeg => {
+                        expected
+                    }
+                    hir::UnDeref => {
+                        NoExpectation
+                    }
+                };
+                let needs = match unop {
+                    hir::UnDeref => needs,
+                    _ => Needs::None
+                };
+                let mut oprnd_t = self.check_expr_with_expectation_and_needs(&oprnd,
+                                                                             expected_inner,
+                                                                             needs);
+
+                if !oprnd_t.references_error() {
+                    oprnd_t = self.structurally_resolved_type(expr.span, oprnd_t);
+                    match unop {
+                        hir::UnDeref => {
+                            if let Some(mt) = oprnd_t.builtin_deref(true) {
+                                oprnd_t = mt.ty;
+                            } else if let Some(ok) = self.try_overloaded_deref(
+                                    expr.span, oprnd_t, needs) {
+                                let method = self.register_infer_ok_obligations(ok);
+                                if let ty::Ref(region, _, mutbl) = method.sig.inputs()[0].sty {
+                                    let mutbl = match mutbl {
+                                        hir::MutImmutable => AutoBorrowMutability::Immutable,
+                                        hir::MutMutable => AutoBorrowMutability::Mutable {
+                                            // (It shouldn't actually matter for unary ops whether
+                                            // we enable two-phase borrows or not, since a unary
+                                            // op has no additional operands.)
+                                            allow_two_phase_borrow: AllowTwoPhase::No,
+                                        }
+                                    };
+                                    self.apply_adjustments(oprnd, vec![Adjustment {
+                                        kind: Adjust::Borrow(AutoBorrow::Ref(region, mutbl)),
+                                        target: method.sig.inputs()[0]
+                                    }]);
+                                }
+                                oprnd_t = self.make_overloaded_place_return_type(method).ty;
+                                self.write_method_call(expr.hir_id, method);
+                            } else {
+                                let mut err = type_error_struct!(
+                                    tcx.sess,
+                                    expr.span,
+                                    oprnd_t,
+                                    E0614,
+                                    "type `{}` cannot be dereferenced",
+                                    oprnd_t,
+                                );
+                                let sp = tcx.sess.source_map().start_point(expr.span);
+                                if let Some(sp) = tcx.sess.parse_sess.ambiguous_block_expr_parse
+                                    .borrow().get(&sp)
+                                {
+                                    tcx.sess.parse_sess.expr_parentheses_needed(
+                                        &mut err,
+                                        *sp,
+                                        None,
+                                    );
+                                }
+                                err.emit();
+                                oprnd_t = tcx.types.err;
+                            }
+                        }
+                        hir::UnNot => {
+                            let result = self.check_user_unop(expr, oprnd_t, unop);
+                            // If it's builtin, we can reuse the type, this helps inference.
+                            if !(oprnd_t.is_integral() || oprnd_t.sty == ty::Bool) {
+                                oprnd_t = result;
+                            }
+                        }
+                        hir::UnNeg => {
+                            let result = self.check_user_unop(expr, oprnd_t, unop);
+                            // If it's builtin, we can reuse the type, this helps inference.
+                            if !oprnd_t.is_numeric() {
+                                oprnd_t = result;
+                            }
+                        }
+                    }
+                }
+                oprnd_t
+            }
+            ExprKind::AddrOf(mutbl, ref oprnd) => {
+                let hint = expected.only_has_type(self).map_or(NoExpectation, |ty| {
+                    match ty.sty {
+                        ty::Ref(_, ty, _) | ty::RawPtr(ty::TypeAndMut { ty, .. }) => {
+                            if oprnd.is_place_expr() {
+                                // Places may legitimately have unsized types.
+                                // For example, dereferences of a fat pointer and
+                                // the last field of a struct can be unsized.
+                                ExpectHasType(ty)
+                            } else {
+                                Expectation::rvalue_hint(self, ty)
+                            }
+                        }
+                        _ => NoExpectation
+                    }
+                });
+                let needs = Needs::maybe_mut_place(mutbl);
+                let ty = self.check_expr_with_expectation_and_needs(&oprnd, hint, needs);
+
+                let tm = ty::TypeAndMut { ty: ty, mutbl: mutbl };
+                if tm.ty.references_error() {
+                    tcx.types.err
+                } else {
+                    // Note: at this point, we cannot say what the best lifetime
+                    // is to use for resulting pointer.  We want to use the
+                    // shortest lifetime possible so as to avoid spurious borrowck
+                    // errors.  Moreover, the longest lifetime will depend on the
+                    // precise details of the value whose address is being taken
+                    // (and how long it is valid), which we don't know yet until type
+                    // inference is complete.
+                    //
+                    // Therefore, here we simply generate a region variable.  The
+                    // region inferencer will then select the ultimate value.
+                    // Finally, borrowck is charged with guaranteeing that the
+                    // value whose address was taken can actually be made to live
+                    // as long as it needs to live.
+                    let region = self.next_region_var(infer::AddrOfRegion(expr.span));
+                    tcx.mk_ref(region, tm)
+                }
+            }
+            ExprKind::Path(ref qpath) => {
+                let (res, opt_ty, segs) = self.resolve_ty_and_res_ufcs(qpath, expr.hir_id,
+                    expr.span);
+                let ty = match res {
+                    Res::Err => {
+                        self.set_tainted_by_errors();
+                        tcx.types.err
+                    }
+                    Res::Def(DefKind::Ctor(_, CtorKind::Fictive), _) => {
+                        report_unexpected_variant_res(tcx, res, expr.span, qpath);
+                        tcx.types.err
+                    }
+                    _ => self.instantiate_value_path(segs, opt_ty, res, expr.span, id).0,
+                };
+
+                if let ty::FnDef(..) = ty.sty {
+                    let fn_sig = ty.fn_sig(tcx);
+                    if !tcx.features().unsized_locals {
+                        // We want to remove some Sized bounds from std functions,
+                        // but don't want to expose the removal to stable Rust.
+                        // i.e., we don't want to allow
+                        //
+                        // ```rust
+                        // drop as fn(str);
+                        // ```
+                        //
+                        // to work in stable even if the Sized bound on `drop` is relaxed.
+                        for i in 0..fn_sig.inputs().skip_binder().len() {
+                            // We just want to check sizedness, so instead of introducing
+                            // placeholder lifetimes with probing, we just replace higher lifetimes
+                            // with fresh vars.
+                            let input = self.replace_bound_vars_with_fresh_vars(
+                                expr.span,
+                                infer::LateBoundRegionConversionTime::FnCall,
+                                &fn_sig.input(i)).0;
+                            self.require_type_is_sized_deferred(input, expr.span,
+                                                                traits::SizedArgumentType);
+                        }
+                    }
+                    // Here we want to prevent struct constructors from returning unsized types.
+                    // There were two cases this happened: fn pointer coercion in stable
+                    // and usual function call in presense of unsized_locals.
+                    // Also, as we just want to check sizedness, instead of introducing
+                    // placeholder lifetimes with probing, we just replace higher lifetimes
+                    // with fresh vars.
+                    let output = self.replace_bound_vars_with_fresh_vars(
+                        expr.span,
+                        infer::LateBoundRegionConversionTime::FnCall,
+                        &fn_sig.output()).0;
+                    self.require_type_is_sized_deferred(output, expr.span, traits::SizedReturnType);
+                }
+
+                // We always require that the type provided as the value for
+                // a type parameter outlives the moment of instantiation.
+                let substs = self.tables.borrow().node_substs(expr.hir_id);
+                self.add_wf_bounds(substs, expr);
+
+                ty
+            }
+            ExprKind::InlineAsm(_, ref outputs, ref inputs) => {
+                for expr in outputs.iter().chain(inputs.iter()) {
+                    self.check_expr(expr);
+                }
+                tcx.mk_unit()
+            }
+            ExprKind::Break(destination, ref expr_opt) => {
+                if let Ok(target_id) = destination.target_id {
+                    let (e_ty, cause);
+                    if let Some(ref e) = *expr_opt {
+                        // If this is a break with a value, we need to type-check
+                        // the expression. Get an expected type from the loop context.
+                        let opt_coerce_to = {
+                            let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
+                            enclosing_breakables.find_breakable(target_id)
+                                                .coerce
+                                                .as_ref()
+                                                .map(|coerce| coerce.expected_ty())
+                        };
+
+                        // If the loop context is not a `loop { }`, then break with
+                        // a value is illegal, and `opt_coerce_to` will be `None`.
+                        // Just set expectation to error in that case.
+                        let coerce_to = opt_coerce_to.unwrap_or(tcx.types.err);
+
+                        // Recurse without `enclosing_breakables` borrowed.
+                        e_ty = self.check_expr_with_hint(e, coerce_to);
+                        cause = self.misc(e.span);
+                    } else {
+                        // Otherwise, this is a break *without* a value. That's
+                        // always legal, and is equivalent to `break ()`.
+                        e_ty = tcx.mk_unit();
+                        cause = self.misc(expr.span);
+                    }
+
+                    // Now that we have type-checked `expr_opt`, borrow
+                    // the `enclosing_loops` field and let's coerce the
+                    // type of `expr_opt` into what is expected.
+                    let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
+                    let ctxt = enclosing_breakables.find_breakable(target_id);
+                    if let Some(ref mut coerce) = ctxt.coerce {
+                        if let Some(ref e) = *expr_opt {
+                            coerce.coerce(self, &cause, e, e_ty);
+                        } else {
+                            assert!(e_ty.is_unit());
+                            coerce.coerce_forced_unit(self, &cause, &mut |_| (), true);
+                        }
+                    } else {
+                        // If `ctxt.coerce` is `None`, we can just ignore
+                        // the type of the expresison.  This is because
+                        // either this was a break *without* a value, in
+                        // which case it is always a legal type (`()`), or
+                        // else an error would have been flagged by the
+                        // `loops` pass for using break with an expression
+                        // where you are not supposed to.
+                        assert!(expr_opt.is_none() || self.tcx.sess.err_count() > 0);
+                    }
+
+                    ctxt.may_break = true;
+
+                    // the type of a `break` is always `!`, since it diverges
+                    tcx.types.never
+                } else {
+                    // Otherwise, we failed to find the enclosing loop;
+                    // this can only happen if the `break` was not
+                    // inside a loop at all, which is caught by the
+                    // loop-checking pass.
+                    if self.tcx.sess.err_count() == 0 {
+                        self.tcx.sess.delay_span_bug(expr.span,
+                            "break was outside loop, but no error was emitted");
+                    }
+
+                    // We still need to assign a type to the inner expression to
+                    // prevent the ICE in #43162.
+                    if let Some(ref e) = *expr_opt {
+                        self.check_expr_with_hint(e, tcx.types.err);
+
+                        // ... except when we try to 'break rust;'.
+                        // ICE this expression in particular (see #43162).
+                        if let ExprKind::Path(QPath::Resolved(_, ref path)) = e.node {
+                            if path.segments.len() == 1 &&
+                               path.segments[0].ident.name == sym::rust {
+                                fatally_break_rust(self.tcx.sess);
+                            }
+                        }
+                    }
+                    // There was an error; make type-check fail.
+                    tcx.types.err
+                }
+
+            }
+            ExprKind::Continue(destination) => {
+                if destination.target_id.is_ok() {
+                    tcx.types.never
+                } else {
+                    // There was an error; make type-check fail.
+                    tcx.types.err
+                }
+            }
+            ExprKind::Ret(ref expr_opt) => {
+                if self.ret_coercion.is_none() {
+                    struct_span_err!(self.tcx.sess, expr.span, E0572,
+                                     "return statement outside of function body").emit();
+                } else if let Some(ref e) = *expr_opt {
+                    if self.ret_coercion_span.borrow().is_none() {
+                        *self.ret_coercion_span.borrow_mut() = Some(e.span);
+                    }
+                    self.check_return_expr(e);
+                } else {
+                    let mut coercion = self.ret_coercion.as_ref().unwrap().borrow_mut();
+                    if self.ret_coercion_span.borrow().is_none() {
+                        *self.ret_coercion_span.borrow_mut() = Some(expr.span);
+                    }
+                    let cause = self.cause(expr.span, ObligationCauseCode::ReturnNoExpression);
+                    if let Some((fn_decl, _)) = self.get_fn_decl(expr.hir_id) {
+                        coercion.coerce_forced_unit(
+                            self,
+                            &cause,
+                            &mut |db| {
+                                db.span_label(
+                                    fn_decl.output.span(),
+                                    format!(
+                                        "expected `{}` because of this return type",
+                                        fn_decl.output,
+                                    ),
+                                );
+                            },
+                            true,
+                        );
+                    } else {
+                        coercion.coerce_forced_unit(self, &cause, &mut |_| (), true);
+                    }
+                }
+                tcx.types.never
+            }
+            ExprKind::Assign(ref lhs, ref rhs) => {
+                self.check_assign(expr, expected, lhs, rhs)
+            }
+            ExprKind::While(ref cond, ref body, _) => {
+                let ctxt = BreakableCtxt {
+                    // cannot use break with a value from a while loop
+                    coerce: None,
+                    may_break: false,  // Will get updated if/when we find a `break`.
+                };
+
+                let (ctxt, ()) = self.with_breakable_ctxt(expr.hir_id, ctxt, || {
+                    self.check_expr_has_type_or_error(&cond, tcx.types.bool);
+                    let cond_diverging = self.diverges.get();
+                    self.check_block_no_value(&body);
+
+                    // We may never reach the body so it diverging means nothing.
+                    self.diverges.set(cond_diverging);
+                });
+
+                if ctxt.may_break {
+                    // No way to know whether it's diverging because
+                    // of a `break` or an outer `break` or `return`.
+                    self.diverges.set(Diverges::Maybe);
+                }
+
+                self.tcx.mk_unit()
+            }
+            ExprKind::Loop(ref body, _, source) => {
+                let coerce = match source {
+                    // you can only use break with a value from a normal `loop { }`
+                    hir::LoopSource::Loop => {
+                        let coerce_to = expected.coercion_target_type(self, body.span);
+                        Some(CoerceMany::new(coerce_to))
+                    }
+
+                    hir::LoopSource::WhileLet |
+                    hir::LoopSource::ForLoop => {
+                        None
+                    }
+                };
+
+                let ctxt = BreakableCtxt {
+                    coerce,
+                    may_break: false, // Will get updated if/when we find a `break`.
+                };
+
+                let (ctxt, ()) = self.with_breakable_ctxt(expr.hir_id, ctxt, || {
+                    self.check_block_no_value(&body);
+                });
+
+                if ctxt.may_break {
+                    // No way to know whether it's diverging because
+                    // of a `break` or an outer `break` or `return`.
+                    self.diverges.set(Diverges::Maybe);
+                }
+
+                // If we permit break with a value, then result type is
+                // the LUB of the breaks (possibly ! if none); else, it
+                // is nil. This makes sense because infinite loops
+                // (which would have type !) are only possible iff we
+                // permit break with a value [1].
+                if ctxt.coerce.is_none() && !ctxt.may_break {
+                    // [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_else(|| self.tcx.mk_unit())
+            }
+            ExprKind::Match(ref discrim, ref arms, match_src) => {
+                self.check_match(expr, &discrim, arms, expected, match_src)
+            }
+            ExprKind::Closure(capture, ref decl, body_id, _, gen) => {
+                self.check_expr_closure(expr, capture, &decl, body_id, gen, expected)
+            }
+            ExprKind::Block(ref body, _) => {
+                self.check_block_with_expected(&body, expected)
+            }
+            ExprKind::Call(ref callee, ref args) => {
+                self.check_call(expr, &callee, args, expected)
+            }
+            ExprKind::MethodCall(ref segment, span, ref args) => {
+                self.check_method_call(expr, segment, span, args, expected, needs)
+            }
+            ExprKind::Cast(ref e, ref t) => {
+                // Find the type of `e`. Supply hints based on the type we are casting to,
+                // if appropriate.
+                let t_cast = self.to_ty_saving_user_provided_ty(t);
+                let t_cast = self.resolve_vars_if_possible(&t_cast);
+                let t_expr = self.check_expr_with_expectation(e, ExpectCastableToType(t_cast));
+                let t_cast = self.resolve_vars_if_possible(&t_cast);
+
+                // Eagerly check for some obvious errors.
+                if t_expr.references_error() || t_cast.references_error() {
+                    tcx.types.err
+                } else {
+                    // Defer other checks until we're done type checking.
+                    let mut deferred_cast_checks = self.deferred_cast_checks.borrow_mut();
+                    match cast::CastCheck::new(self, e, t_expr, t_cast, t.span, expr.span) {
+                        Ok(cast_check) => {
+                            deferred_cast_checks.push(cast_check);
+                            t_cast
+                        }
+                        Err(ErrorReported) => {
+                            tcx.types.err
+                        }
+                    }
+                }
+            }
+            ExprKind::Type(ref e, ref t) => {
+                let ty = self.to_ty_saving_user_provided_ty(&t);
+                self.check_expr_eq_type(&e, ty);
+                ty
+            }
+            ExprKind::DropTemps(ref e) => {
+                self.check_expr_with_expectation(e, expected)
+            }
+            ExprKind::Array(ref args) => {
+                let uty = expected.to_option(self).and_then(|uty| {
+                    match uty.sty {
+                        ty::Array(ty, _) | ty::Slice(ty) => Some(ty),
+                        _ => None
+                    }
+                });
+
+                let element_ty = if !args.is_empty() {
+                    let coerce_to = uty.unwrap_or_else(|| {
+                        self.next_ty_var(TypeVariableOrigin {
+                            kind: TypeVariableOriginKind::TypeInference,
+                            span: expr.span,
+                        })
+                    });
+                    let mut coerce = CoerceMany::with_coercion_sites(coerce_to, args);
+                    assert_eq!(self.diverges.get(), Diverges::Maybe);
+                    for e in args {
+                        let e_ty = self.check_expr_with_hint(e, coerce_to);
+                        let cause = self.misc(e.span);
+                        coerce.coerce(self, &cause, e, e_ty);
+                    }
+                    coerce.complete(self)
+                } else {
+                    self.next_ty_var(TypeVariableOrigin {
+                        kind: TypeVariableOriginKind::TypeInference,
+                        span: expr.span,
+                    })
+                };
+                tcx.mk_array(element_ty, args.len() as u64)
+            }
+            ExprKind::Repeat(ref element, ref count) => {
+                let count_def_id = tcx.hir().local_def_id_from_hir_id(count.hir_id);
+                let count = if self.const_param_def_id(count).is_some() {
+                    Ok(self.to_const(count, self.tcx.type_of(count_def_id)))
+                } else {
+                    let param_env = ty::ParamEnv::empty();
+                    let substs = InternalSubsts::identity_for_item(tcx.global_tcx(), count_def_id);
+                    let instance = ty::Instance::resolve(
+                        tcx.global_tcx(),
+                        param_env,
+                        count_def_id,
+                        substs,
+                    ).unwrap();
+                    let global_id = GlobalId {
+                        instance,
+                        promoted: None
+                    };
+
+                    tcx.const_eval(param_env.and(global_id))
+                };
+
+                let uty = match expected {
+                    ExpectHasType(uty) => {
+                        match uty.sty {
+                            ty::Array(ty, _) | ty::Slice(ty) => Some(ty),
+                            _ => None
+                        }
+                    }
+                    _ => None
+                };
+
+                let (element_ty, t) = match uty {
+                    Some(uty) => {
+                        self.check_expr_coercable_to_type(&element, uty);
+                        (uty, uty)
+                    }
+                    None => {
+                        let ty = self.next_ty_var(TypeVariableOrigin {
+                            kind: TypeVariableOriginKind::MiscVariable,
+                            span: element.span,
+                        });
+                        let element_ty = self.check_expr_has_type_or_error(&element, ty);
+                        (element_ty, ty)
+                    }
+                };
+
+                if let Ok(count) = count {
+                    let zero_or_one = count.assert_usize(tcx).map_or(false, |count| count <= 1);
+                    if !zero_or_one {
+                        // For [foo, ..n] where n > 1, `foo` must have
+                        // Copy type:
+                        let lang_item = self.tcx.require_lang_item(lang_items::CopyTraitLangItem);
+                        self.require_type_meets(t, expr.span, traits::RepeatVec, lang_item);
+                    }
+                }
+
+                if element_ty.references_error() {
+                    tcx.types.err
+                } else if let Ok(count) = count {
+                    tcx.mk_ty(ty::Array(t, count))
+                } else {
+                    tcx.types.err
+                }
+            }
+            ExprKind::Tup(ref elts) => {
+                let flds = expected.only_has_type(self).and_then(|ty| {
+                    let ty = self.resolve_type_vars_with_obligations(ty);
+                    match ty.sty {
+                        ty::Tuple(ref flds) => Some(&flds[..]),
+                        _ => None
+                    }
+                });
+
+                let elt_ts_iter = elts.iter().enumerate().map(|(i, e)| {
+                    let t = match flds {
+                        Some(ref fs) if i < fs.len() => {
+                            let ety = fs[i].expect_ty();
+                            self.check_expr_coercable_to_type(&e, ety);
+                            ety
+                        }
+                        _ => {
+                            self.check_expr_with_expectation(&e, NoExpectation)
+                        }
+                    };
+                    t
+                });
+                let tuple = tcx.mk_tup(elt_ts_iter);
+                if tuple.references_error() {
+                    tcx.types.err
+                } else {
+                    self.require_type_is_sized(tuple, expr.span, traits::TupleInitializerSized);
+                    tuple
+                }
+            }
+            ExprKind::Struct(ref qpath, ref fields, ref base_expr) => {
+                self.check_expr_struct(expr, expected, qpath, fields, base_expr)
+            }
+            ExprKind::Field(ref base, field) => {
+                self.check_field(expr, needs, &base, field)
+            }
+            ExprKind::Index(ref base, ref idx) => {
+                let base_t = self.check_expr_with_needs(&base, needs);
+                let idx_t = self.check_expr(&idx);
+
+                if base_t.references_error() {
+                    base_t
+                } else if idx_t.references_error() {
+                    idx_t
+                } else {
+                    let base_t = self.structurally_resolved_type(base.span, base_t);
+                    match self.lookup_indexing(expr, base, base_t, idx_t, needs) {
+                        Some((index_ty, element_ty)) => {
+                            // two-phase not needed because index_ty is never mutable
+                            self.demand_coerce(idx, idx_t, index_ty, AllowTwoPhase::No);
+                            element_ty
+                        }
+                        None => {
+                            let mut err =
+                                type_error_struct!(tcx.sess, expr.span, base_t, E0608,
+                                                   "cannot index into a value of type `{}`",
+                                                   base_t);
+                            // Try to give some advice about indexing tuples.
+                            if let ty::Tuple(..) = base_t.sty {
+                                let mut needs_note = true;
+                                // If the index is an integer, we can show the actual
+                                // fixed expression:
+                                if let ExprKind::Lit(ref lit) = idx.node {
+                                    if let ast::LitKind::Int(i,
+                                            ast::LitIntType::Unsuffixed) = lit.node {
+                                        let snip = tcx.sess.source_map().span_to_snippet(base.span);
+                                        if let Ok(snip) = snip {
+                                            err.span_suggestion(
+                                                expr.span,
+                                                "to access tuple elements, use",
+                                                format!("{}.{}", snip, i),
+                                                Applicability::MachineApplicable,
+                                            );
+                                            needs_note = false;
+                                        }
+                                    }
+                                }
+                                if needs_note {
+                                    err.help("to access tuple elements, use tuple indexing \
+                                              syntax (e.g., `tuple.0`)");
+                                }
+                            }
+                            err.emit();
+                            self.tcx.types.err
+                        }
+                    }
+                }
+            }
+            ExprKind::Yield(ref value) => {
+                match self.yield_ty {
+                    Some(ty) => {
+                        self.check_expr_coercable_to_type(&value, ty);
+                    }
+                    None => {
+                        struct_span_err!(self.tcx.sess, expr.span, E0627,
+                                         "yield statement outside of generator literal").emit();
+                    }
+                }
+                tcx.mk_unit()
+            }
+            hir::ExprKind::Err => {
+                tcx.types.err
+            }
+        }
+    }
+}
diff --git a/src/librustc_typeck/check/mod.rs b/src/librustc_typeck/check/mod.rs
index c857eac5d3c..1cb064c23a9 100644
--- a/src/librustc_typeck/check/mod.rs
+++ b/src/librustc_typeck/check/mod.rs
@@ -74,6 +74,7 @@ pub mod writeback;
 mod regionck;
 pub mod coercion;
 pub mod demand;
+mod expr;
 pub mod method;
 mod upvar;
 mod wfcheck;
@@ -88,7 +89,7 @@ mod op;
 use crate::astconv::{AstConv, PathSeg};
 use errors::{Applicability, DiagnosticBuilder, DiagnosticId};
 use rustc::hir::{self, ExprKind, GenericArg, ItemKind, Node, PatKind, QPath};
-use rustc::hir::def::{CtorOf, CtorKind, Res, DefKind};
+use rustc::hir::def::{CtorOf, Res, DefKind};
 use rustc::hir::def_id::{CrateNum, DefId, LOCAL_CRATE};
 use rustc::hir::intravisit::{self, Visitor, NestedVisitorMap};
 use rustc::hir::itemlikevisit::ItemLikeVisitor;
@@ -3923,7 +3924,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         adt_ty
     }
 
-
     /// Invariant:
     /// If an expression has any sub-expressions that result in a type error,
     /// inspecting that expression's type with `ty.references_error()` will return
@@ -3983,677 +3983,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         ty
     }
 
-    fn check_expr_kind(
-        &self,
-        expr: &'tcx hir::Expr,
-        expected: Expectation<'tcx>,
-        needs: Needs,
-    ) -> Ty<'tcx> {
-        debug!(
-            "check_expr_kind(expr={:?}, expected={:?}, needs={:?})",
-            expr,
-            expected,
-            needs,
-        );
-
-        let tcx = self.tcx;
-        let id = expr.hir_id;
-        match expr.node {
-            ExprKind::Box(ref subexpr) => {
-                let expected_inner = expected.to_option(self).map_or(NoExpectation, |ty| {
-                    match ty.sty {
-                        ty::Adt(def, _) if def.is_box()
-                            => Expectation::rvalue_hint(self, ty.boxed_ty()),
-                        _ => NoExpectation
-                    }
-                });
-                let referent_ty = self.check_expr_with_expectation(subexpr, expected_inner);
-                tcx.mk_box(referent_ty)
-            }
-
-            ExprKind::Lit(ref lit) => {
-                self.check_lit(&lit, expected)
-            }
-            ExprKind::Binary(op, ref lhs, ref rhs) => {
-                self.check_binop(expr, op, lhs, rhs)
-            }
-            ExprKind::AssignOp(op, ref lhs, ref rhs) => {
-                self.check_binop_assign(expr, op, lhs, rhs)
-            }
-            ExprKind::Unary(unop, ref oprnd) => {
-                let expected_inner = match unop {
-                    hir::UnNot | hir::UnNeg => {
-                        expected
-                    }
-                    hir::UnDeref => {
-                        NoExpectation
-                    }
-                };
-                let needs = match unop {
-                    hir::UnDeref => needs,
-                    _ => Needs::None
-                };
-                let mut oprnd_t = self.check_expr_with_expectation_and_needs(&oprnd,
-                                                                             expected_inner,
-                                                                             needs);
-
-                if !oprnd_t.references_error() {
-                    oprnd_t = self.structurally_resolved_type(expr.span, oprnd_t);
-                    match unop {
-                        hir::UnDeref => {
-                            if let Some(mt) = oprnd_t.builtin_deref(true) {
-                                oprnd_t = mt.ty;
-                            } else if let Some(ok) = self.try_overloaded_deref(
-                                    expr.span, oprnd_t, needs) {
-                                let method = self.register_infer_ok_obligations(ok);
-                                if let ty::Ref(region, _, mutbl) = method.sig.inputs()[0].sty {
-                                    let mutbl = match mutbl {
-                                        hir::MutImmutable => AutoBorrowMutability::Immutable,
-                                        hir::MutMutable => AutoBorrowMutability::Mutable {
-                                            // (It shouldn't actually matter for unary ops whether
-                                            // we enable two-phase borrows or not, since a unary
-                                            // op has no additional operands.)
-                                            allow_two_phase_borrow: AllowTwoPhase::No,
-                                        }
-                                    };
-                                    self.apply_adjustments(oprnd, vec![Adjustment {
-                                        kind: Adjust::Borrow(AutoBorrow::Ref(region, mutbl)),
-                                        target: method.sig.inputs()[0]
-                                    }]);
-                                }
-                                oprnd_t = self.make_overloaded_place_return_type(method).ty;
-                                self.write_method_call(expr.hir_id, method);
-                            } else {
-                                let mut err = type_error_struct!(
-                                    tcx.sess,
-                                    expr.span,
-                                    oprnd_t,
-                                    E0614,
-                                    "type `{}` cannot be dereferenced",
-                                    oprnd_t,
-                                );
-                                let sp = tcx.sess.source_map().start_point(expr.span);
-                                if let Some(sp) = tcx.sess.parse_sess.ambiguous_block_expr_parse
-                                    .borrow().get(&sp)
-                                {
-                                    tcx.sess.parse_sess.expr_parentheses_needed(
-                                        &mut err,
-                                        *sp,
-                                        None,
-                                    );
-                                }
-                                err.emit();
-                                oprnd_t = tcx.types.err;
-                            }
-                        }
-                        hir::UnNot => {
-                            let result = self.check_user_unop(expr, oprnd_t, unop);
-                            // If it's builtin, we can reuse the type, this helps inference.
-                            if !(oprnd_t.is_integral() || oprnd_t.sty == ty::Bool) {
-                                oprnd_t = result;
-                            }
-                        }
-                        hir::UnNeg => {
-                            let result = self.check_user_unop(expr, oprnd_t, unop);
-                            // If it's builtin, we can reuse the type, this helps inference.
-                            if !oprnd_t.is_numeric() {
-                                oprnd_t = result;
-                            }
-                        }
-                    }
-                }
-                oprnd_t
-            }
-            ExprKind::AddrOf(mutbl, ref oprnd) => {
-                let hint = expected.only_has_type(self).map_or(NoExpectation, |ty| {
-                    match ty.sty {
-                        ty::Ref(_, ty, _) | ty::RawPtr(ty::TypeAndMut { ty, .. }) => {
-                            if oprnd.is_place_expr() {
-                                // Places may legitimately have unsized types.
-                                // For example, dereferences of a fat pointer and
-                                // the last field of a struct can be unsized.
-                                ExpectHasType(ty)
-                            } else {
-                                Expectation::rvalue_hint(self, ty)
-                            }
-                        }
-                        _ => NoExpectation
-                    }
-                });
-                let needs = Needs::maybe_mut_place(mutbl);
-                let ty = self.check_expr_with_expectation_and_needs(&oprnd, hint, needs);
-
-                let tm = ty::TypeAndMut { ty: ty, mutbl: mutbl };
-                if tm.ty.references_error() {
-                    tcx.types.err
-                } else {
-                    // Note: at this point, we cannot say what the best lifetime
-                    // is to use for resulting pointer.  We want to use the
-                    // shortest lifetime possible so as to avoid spurious borrowck
-                    // errors.  Moreover, the longest lifetime will depend on the
-                    // precise details of the value whose address is being taken
-                    // (and how long it is valid), which we don't know yet until type
-                    // inference is complete.
-                    //
-                    // Therefore, here we simply generate a region variable.  The
-                    // region inferencer will then select the ultimate value.
-                    // Finally, borrowck is charged with guaranteeing that the
-                    // value whose address was taken can actually be made to live
-                    // as long as it needs to live.
-                    let region = self.next_region_var(infer::AddrOfRegion(expr.span));
-                    tcx.mk_ref(region, tm)
-                }
-            }
-            ExprKind::Path(ref qpath) => {
-                let (res, opt_ty, segs) = self.resolve_ty_and_res_ufcs(qpath, expr.hir_id,
-                    expr.span);
-                let ty = match res {
-                    Res::Err => {
-                        self.set_tainted_by_errors();
-                        tcx.types.err
-                    }
-                    Res::Def(DefKind::Ctor(_, CtorKind::Fictive), _) => {
-                        report_unexpected_variant_res(tcx, res, expr.span, qpath);
-                        tcx.types.err
-                    }
-                    _ => self.instantiate_value_path(segs, opt_ty, res, expr.span, id).0,
-                };
-
-                if let ty::FnDef(..) = ty.sty {
-                    let fn_sig = ty.fn_sig(tcx);
-                    if !tcx.features().unsized_locals {
-                        // We want to remove some Sized bounds from std functions,
-                        // but don't want to expose the removal to stable Rust.
-                        // i.e., we don't want to allow
-                        //
-                        // ```rust
-                        // drop as fn(str);
-                        // ```
-                        //
-                        // to work in stable even if the Sized bound on `drop` is relaxed.
-                        for i in 0..fn_sig.inputs().skip_binder().len() {
-                            // We just want to check sizedness, so instead of introducing
-                            // placeholder lifetimes with probing, we just replace higher lifetimes
-                            // with fresh vars.
-                            let input = self.replace_bound_vars_with_fresh_vars(
-                                expr.span,
-                                infer::LateBoundRegionConversionTime::FnCall,
-                                &fn_sig.input(i)).0;
-                            self.require_type_is_sized_deferred(input, expr.span,
-                                                                traits::SizedArgumentType);
-                        }
-                    }
-                    // Here we want to prevent struct constructors from returning unsized types.
-                    // There were two cases this happened: fn pointer coercion in stable
-                    // and usual function call in presense of unsized_locals.
-                    // Also, as we just want to check sizedness, instead of introducing
-                    // placeholder lifetimes with probing, we just replace higher lifetimes
-                    // with fresh vars.
-                    let output = self.replace_bound_vars_with_fresh_vars(
-                        expr.span,
-                        infer::LateBoundRegionConversionTime::FnCall,
-                        &fn_sig.output()).0;
-                    self.require_type_is_sized_deferred(output, expr.span, traits::SizedReturnType);
-                }
-
-                // We always require that the type provided as the value for
-                // a type parameter outlives the moment of instantiation.
-                let substs = self.tables.borrow().node_substs(expr.hir_id);
-                self.add_wf_bounds(substs, expr);
-
-                ty
-            }
-            ExprKind::InlineAsm(_, ref outputs, ref inputs) => {
-                for expr in outputs.iter().chain(inputs.iter()) {
-                    self.check_expr(expr);
-                }
-                tcx.mk_unit()
-            }
-            ExprKind::Break(destination, ref expr_opt) => {
-                if let Ok(target_id) = destination.target_id {
-                    let (e_ty, cause);
-                    if let Some(ref e) = *expr_opt {
-                        // If this is a break with a value, we need to type-check
-                        // the expression. Get an expected type from the loop context.
-                        let opt_coerce_to = {
-                            let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
-                            enclosing_breakables.find_breakable(target_id)
-                                                .coerce
-                                                .as_ref()
-                                                .map(|coerce| coerce.expected_ty())
-                        };
-
-                        // If the loop context is not a `loop { }`, then break with
-                        // a value is illegal, and `opt_coerce_to` will be `None`.
-                        // Just set expectation to error in that case.
-                        let coerce_to = opt_coerce_to.unwrap_or(tcx.types.err);
-
-                        // Recurse without `enclosing_breakables` borrowed.
-                        e_ty = self.check_expr_with_hint(e, coerce_to);
-                        cause = self.misc(e.span);
-                    } else {
-                        // Otherwise, this is a break *without* a value. That's
-                        // always legal, and is equivalent to `break ()`.
-                        e_ty = tcx.mk_unit();
-                        cause = self.misc(expr.span);
-                    }
-
-                    // Now that we have type-checked `expr_opt`, borrow
-                    // the `enclosing_loops` field and let's coerce the
-                    // type of `expr_opt` into what is expected.
-                    let mut enclosing_breakables = self.enclosing_breakables.borrow_mut();
-                    let ctxt = enclosing_breakables.find_breakable(target_id);
-                    if let Some(ref mut coerce) = ctxt.coerce {
-                        if let Some(ref e) = *expr_opt {
-                            coerce.coerce(self, &cause, e, e_ty);
-                        } else {
-                            assert!(e_ty.is_unit());
-                            coerce.coerce_forced_unit(self, &cause, &mut |_| (), true);
-                        }
-                    } else {
-                        // If `ctxt.coerce` is `None`, we can just ignore
-                        // the type of the expresison.  This is because
-                        // either this was a break *without* a value, in
-                        // which case it is always a legal type (`()`), or
-                        // else an error would have been flagged by the
-                        // `loops` pass for using break with an expression
-                        // where you are not supposed to.
-                        assert!(expr_opt.is_none() || self.tcx.sess.err_count() > 0);
-                    }
-
-                    ctxt.may_break = true;
-
-                    // the type of a `break` is always `!`, since it diverges
-                    tcx.types.never
-                } else {
-                    // Otherwise, we failed to find the enclosing loop;
-                    // this can only happen if the `break` was not
-                    // inside a loop at all, which is caught by the
-                    // loop-checking pass.
-                    if self.tcx.sess.err_count() == 0 {
-                        self.tcx.sess.delay_span_bug(expr.span,
-                            "break was outside loop, but no error was emitted");
-                    }
-
-                    // We still need to assign a type to the inner expression to
-                    // prevent the ICE in #43162.
-                    if let Some(ref e) = *expr_opt {
-                        self.check_expr_with_hint(e, tcx.types.err);
-
-                        // ... except when we try to 'break rust;'.
-                        // ICE this expression in particular (see #43162).
-                        if let ExprKind::Path(QPath::Resolved(_, ref path)) = e.node {
-                            if path.segments.len() == 1 &&
-                               path.segments[0].ident.name == sym::rust {
-                                fatally_break_rust(self.tcx.sess);
-                            }
-                        }
-                    }
-                    // There was an error; make type-check fail.
-                    tcx.types.err
-                }
-
-            }
-            ExprKind::Continue(destination) => {
-                if destination.target_id.is_ok() {
-                    tcx.types.never
-                } else {
-                    // There was an error; make type-check fail.
-                    tcx.types.err
-                }
-            }
-            ExprKind::Ret(ref expr_opt) => {
-                if self.ret_coercion.is_none() {
-                    struct_span_err!(self.tcx.sess, expr.span, E0572,
-                                     "return statement outside of function body").emit();
-                } else if let Some(ref e) = *expr_opt {
-                    if self.ret_coercion_span.borrow().is_none() {
-                        *self.ret_coercion_span.borrow_mut() = Some(e.span);
-                    }
-                    self.check_return_expr(e);
-                } else {
-                    let mut coercion = self.ret_coercion.as_ref().unwrap().borrow_mut();
-                    if self.ret_coercion_span.borrow().is_none() {
-                        *self.ret_coercion_span.borrow_mut() = Some(expr.span);
-                    }
-                    let cause = self.cause(expr.span, ObligationCauseCode::ReturnNoExpression);
-                    if let Some((fn_decl, _)) = self.get_fn_decl(expr.hir_id) {
-                        coercion.coerce_forced_unit(
-                            self,
-                            &cause,
-                            &mut |db| {
-                                db.span_label(
-                                    fn_decl.output.span(),
-                                    format!(
-                                        "expected `{}` because of this return type",
-                                        fn_decl.output,
-                                    ),
-                                );
-                            },
-                            true,
-                        );
-                    } else {
-                        coercion.coerce_forced_unit(self, &cause, &mut |_| (), true);
-                    }
-                }
-                tcx.types.never
-            }
-            ExprKind::Assign(ref lhs, ref rhs) => {
-                self.check_assign(expr, expected, lhs, rhs)
-            }
-            ExprKind::While(ref cond, ref body, _) => {
-                let ctxt = BreakableCtxt {
-                    // cannot use break with a value from a while loop
-                    coerce: None,
-                    may_break: false,  // Will get updated if/when we find a `break`.
-                };
-
-                let (ctxt, ()) = self.with_breakable_ctxt(expr.hir_id, ctxt, || {
-                    self.check_expr_has_type_or_error(&cond, tcx.types.bool);
-                    let cond_diverging = self.diverges.get();
-                    self.check_block_no_value(&body);
-
-                    // We may never reach the body so it diverging means nothing.
-                    self.diverges.set(cond_diverging);
-                });
-
-                if ctxt.may_break {
-                    // No way to know whether it's diverging because
-                    // of a `break` or an outer `break` or `return`.
-                    self.diverges.set(Diverges::Maybe);
-                }
-
-                self.tcx.mk_unit()
-            }
-            ExprKind::Loop(ref body, _, source) => {
-                let coerce = match source {
-                    // you can only use break with a value from a normal `loop { }`
-                    hir::LoopSource::Loop => {
-                        let coerce_to = expected.coercion_target_type(self, body.span);
-                        Some(CoerceMany::new(coerce_to))
-                    }
-
-                    hir::LoopSource::WhileLet |
-                    hir::LoopSource::ForLoop => {
-                        None
-                    }
-                };
-
-                let ctxt = BreakableCtxt {
-                    coerce,
-                    may_break: false, // Will get updated if/when we find a `break`.
-                };
-
-                let (ctxt, ()) = self.with_breakable_ctxt(expr.hir_id, ctxt, || {
-                    self.check_block_no_value(&body);
-                });
-
-                if ctxt.may_break {
-                    // No way to know whether it's diverging because
-                    // of a `break` or an outer `break` or `return`.
-                    self.diverges.set(Diverges::Maybe);
-                }
-
-                // If we permit break with a value, then result type is
-                // the LUB of the breaks (possibly ! if none); else, it
-                // is nil. This makes sense because infinite loops
-                // (which would have type !) are only possible iff we
-                // permit break with a value [1].
-                if ctxt.coerce.is_none() && !ctxt.may_break {
-                    // [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_else(|| self.tcx.mk_unit())
-            }
-            ExprKind::Match(ref discrim, ref arms, match_src) => {
-                self.check_match(expr, &discrim, arms, expected, match_src)
-            }
-            ExprKind::Closure(capture, ref decl, body_id, _, gen) => {
-                self.check_expr_closure(expr, capture, &decl, body_id, gen, expected)
-            }
-            ExprKind::Block(ref body, _) => {
-                self.check_block_with_expected(&body, expected)
-            }
-            ExprKind::Call(ref callee, ref args) => {
-                self.check_call(expr, &callee, args, expected)
-            }
-            ExprKind::MethodCall(ref segment, span, ref args) => {
-                self.check_method_call(expr, segment, span, args, expected, needs)
-            }
-            ExprKind::Cast(ref e, ref t) => {
-                // Find the type of `e`. Supply hints based on the type we are casting to,
-                // if appropriate.
-                let t_cast = self.to_ty_saving_user_provided_ty(t);
-                let t_cast = self.resolve_vars_if_possible(&t_cast);
-                let t_expr = self.check_expr_with_expectation(e, ExpectCastableToType(t_cast));
-                let t_cast = self.resolve_vars_if_possible(&t_cast);
-
-                // Eagerly check for some obvious errors.
-                if t_expr.references_error() || t_cast.references_error() {
-                    tcx.types.err
-                } else {
-                    // Defer other checks until we're done type checking.
-                    let mut deferred_cast_checks = self.deferred_cast_checks.borrow_mut();
-                    match cast::CastCheck::new(self, e, t_expr, t_cast, t.span, expr.span) {
-                        Ok(cast_check) => {
-                            deferred_cast_checks.push(cast_check);
-                            t_cast
-                        }
-                        Err(ErrorReported) => {
-                            tcx.types.err
-                        }
-                    }
-                }
-            }
-            ExprKind::Type(ref e, ref t) => {
-                let ty = self.to_ty_saving_user_provided_ty(&t);
-                self.check_expr_eq_type(&e, ty);
-                ty
-            }
-            ExprKind::DropTemps(ref e) => {
-                self.check_expr_with_expectation(e, expected)
-            }
-            ExprKind::Array(ref args) => {
-                let uty = expected.to_option(self).and_then(|uty| {
-                    match uty.sty {
-                        ty::Array(ty, _) | ty::Slice(ty) => Some(ty),
-                        _ => None
-                    }
-                });
-
-                let element_ty = if !args.is_empty() {
-                    let coerce_to = uty.unwrap_or_else(|| {
-                        self.next_ty_var(TypeVariableOrigin {
-                            kind: TypeVariableOriginKind::TypeInference,
-                            span: expr.span,
-                        })
-                    });
-                    let mut coerce = CoerceMany::with_coercion_sites(coerce_to, args);
-                    assert_eq!(self.diverges.get(), Diverges::Maybe);
-                    for e in args {
-                        let e_ty = self.check_expr_with_hint(e, coerce_to);
-                        let cause = self.misc(e.span);
-                        coerce.coerce(self, &cause, e, e_ty);
-                    }
-                    coerce.complete(self)
-                } else {
-                    self.next_ty_var(TypeVariableOrigin {
-                        kind: TypeVariableOriginKind::TypeInference,
-                        span: expr.span,
-                    })
-                };
-                tcx.mk_array(element_ty, args.len() as u64)
-            }
-            ExprKind::Repeat(ref element, ref count) => {
-                let count_def_id = tcx.hir().local_def_id_from_hir_id(count.hir_id);
-                let count = if self.const_param_def_id(count).is_some() {
-                    Ok(self.to_const(count, self.tcx.type_of(count_def_id)))
-                } else {
-                    let param_env = ty::ParamEnv::empty();
-                    let substs = InternalSubsts::identity_for_item(tcx.global_tcx(), count_def_id);
-                    let instance = ty::Instance::resolve(
-                        tcx.global_tcx(),
-                        param_env,
-                        count_def_id,
-                        substs,
-                    ).unwrap();
-                    let global_id = GlobalId {
-                        instance,
-                        promoted: None
-                    };
-
-                    tcx.const_eval(param_env.and(global_id))
-                };
-
-                let uty = match expected {
-                    ExpectHasType(uty) => {
-                        match uty.sty {
-                            ty::Array(ty, _) | ty::Slice(ty) => Some(ty),
-                            _ => None
-                        }
-                    }
-                    _ => None
-                };
-
-                let (element_ty, t) = match uty {
-                    Some(uty) => {
-                        self.check_expr_coercable_to_type(&element, uty);
-                        (uty, uty)
-                    }
-                    None => {
-                        let ty = self.next_ty_var(TypeVariableOrigin {
-                            kind: TypeVariableOriginKind::MiscVariable,
-                            span: element.span,
-                        });
-                        let element_ty = self.check_expr_has_type_or_error(&element, ty);
-                        (element_ty, ty)
-                    }
-                };
-
-                if let Ok(count) = count {
-                    let zero_or_one = count.assert_usize(tcx).map_or(false, |count| count <= 1);
-                    if !zero_or_one {
-                        // For [foo, ..n] where n > 1, `foo` must have
-                        // Copy type:
-                        let lang_item = self.tcx.require_lang_item(lang_items::CopyTraitLangItem);
-                        self.require_type_meets(t, expr.span, traits::RepeatVec, lang_item);
-                    }
-                }
-
-                if element_ty.references_error() {
-                    tcx.types.err
-                } else if let Ok(count) = count {
-                    tcx.mk_ty(ty::Array(t, count))
-                } else {
-                    tcx.types.err
-                }
-            }
-            ExprKind::Tup(ref elts) => {
-                let flds = expected.only_has_type(self).and_then(|ty| {
-                    let ty = self.resolve_type_vars_with_obligations(ty);
-                    match ty.sty {
-                        ty::Tuple(ref flds) => Some(&flds[..]),
-                        _ => None
-                    }
-                });
-
-                let elt_ts_iter = elts.iter().enumerate().map(|(i, e)| {
-                    let t = match flds {
-                        Some(ref fs) if i < fs.len() => {
-                            let ety = fs[i].expect_ty();
-                            self.check_expr_coercable_to_type(&e, ety);
-                            ety
-                        }
-                        _ => {
-                            self.check_expr_with_expectation(&e, NoExpectation)
-                        }
-                    };
-                    t
-                });
-                let tuple = tcx.mk_tup(elt_ts_iter);
-                if tuple.references_error() {
-                    tcx.types.err
-                } else {
-                    self.require_type_is_sized(tuple, expr.span, traits::TupleInitializerSized);
-                    tuple
-                }
-            }
-            ExprKind::Struct(ref qpath, ref fields, ref base_expr) => {
-                self.check_expr_struct(expr, expected, qpath, fields, base_expr)
-            }
-            ExprKind::Field(ref base, field) => {
-                self.check_field(expr, needs, &base, field)
-            }
-            ExprKind::Index(ref base, ref idx) => {
-                let base_t = self.check_expr_with_needs(&base, needs);
-                let idx_t = self.check_expr(&idx);
-
-                if base_t.references_error() {
-                    base_t
-                } else if idx_t.references_error() {
-                    idx_t
-                } else {
-                    let base_t = self.structurally_resolved_type(base.span, base_t);
-                    match self.lookup_indexing(expr, base, base_t, idx_t, needs) {
-                        Some((index_ty, element_ty)) => {
-                            // two-phase not needed because index_ty is never mutable
-                            self.demand_coerce(idx, idx_t, index_ty, AllowTwoPhase::No);
-                            element_ty
-                        }
-                        None => {
-                            let mut err =
-                                type_error_struct!(tcx.sess, expr.span, base_t, E0608,
-                                                   "cannot index into a value of type `{}`",
-                                                   base_t);
-                            // Try to give some advice about indexing tuples.
-                            if let ty::Tuple(..) = base_t.sty {
-                                let mut needs_note = true;
-                                // If the index is an integer, we can show the actual
-                                // fixed expression:
-                                if let ExprKind::Lit(ref lit) = idx.node {
-                                    if let ast::LitKind::Int(i,
-                                            ast::LitIntType::Unsuffixed) = lit.node {
-                                        let snip = tcx.sess.source_map().span_to_snippet(base.span);
-                                        if let Ok(snip) = snip {
-                                            err.span_suggestion(
-                                                expr.span,
-                                                "to access tuple elements, use",
-                                                format!("{}.{}", snip, i),
-                                                Applicability::MachineApplicable,
-                                            );
-                                            needs_note = false;
-                                        }
-                                    }
-                                }
-                                if needs_note {
-                                    err.help("to access tuple elements, use tuple indexing \
-                                              syntax (e.g., `tuple.0`)");
-                                }
-                            }
-                            err.emit();
-                            self.tcx.types.err
-                        }
-                    }
-                }
-            }
-            ExprKind::Yield(ref value) => {
-                match self.yield_ty {
-                    Some(ty) => {
-                        self.check_expr_coercable_to_type(&value, ty);
-                    }
-                    None => {
-                        struct_span_err!(self.tcx.sess, expr.span, E0627,
-                                         "yield statement outside of generator literal").emit();
-                    }
-                }
-                tcx.mk_unit()
-            }
-            hir::ExprKind::Err => {
-                tcx.types.err
-            }
-        }
-    }
-
     /// Type check assignment expression `expr` of form `lhs = rhs`.
     /// The expected type is `()` and is passsed to the function for the purposes of diagnostics.
     fn check_assign(