diff --git a/src/librustc_typeck/check/expr.rs b/src/librustc_typeck/check/expr.rs new file mode 100644 index 0000000000000..fa9e0d8a8578a --- /dev/null +++ b/src/librustc_typeck/check/expr.rs @@ -0,0 +1,1537 @@ +//! 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::check::TupleArgumentsFlag::DontTupleArguments; +use crate::check::method::SelfSource; +use crate::middle::lang_items; +use crate::util::common::ErrorReported; +use crate::util::nodemap::FxHashMap; +use crate::astconv::AstConv as _; + +use errors::{Applicability, DiagnosticBuilder}; +use syntax::ast; +use syntax::ptr::P; +use syntax::symbol::{Symbol, LocalInternedString, kw, sym}; +use syntax::source_map::Span; +use syntax::util::lev_distance::find_best_match_for_name; +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::{AdtKind, Visibility}; +use rustc::ty::Ty; +use rustc::ty::TypeFoldable; +use rustc::ty::subst::InternalSubsts; +use rustc::traits::{self, ObligationCauseCode}; + +use std::fmt::Display; + +impl<'a, 'tcx> FnCtxt<'a, 'tcx> { + fn check_expr_eq_type(&self, expr: &'tcx hir::Expr, expected: Ty<'tcx>) { + let ty = self.check_expr_with_hint(expr, expected); + self.demand_eqtype(expr.span, expected, ty); + } + + pub fn check_expr_has_type_or_error( + &self, + expr: &'tcx hir::Expr, + expected: Ty<'tcx>, + ) -> Ty<'tcx> { + self.check_expr_meets_expectation_or_error(expr, ExpectHasType(expected)) + } + + fn check_expr_meets_expectation_or_error( + &self, + expr: &'tcx hir::Expr, + expected: Expectation<'tcx>, + ) -> Ty<'tcx> { + let expected_ty = expected.to_option(&self).unwrap_or(self.tcx.types.bool); + let mut ty = self.check_expr_with_expectation(expr, expected); + + // While we don't allow *arbitrary* coercions here, we *do* allow + // coercions from ! to `expected`. + if ty.is_never() { + assert!(!self.tables.borrow().adjustments().contains_key(expr.hir_id), + "expression with never type wound up being adjusted"); + let adj_ty = self.next_diverging_ty_var( + TypeVariableOrigin { + kind: TypeVariableOriginKind::AdjustmentType, + span: expr.span, + }, + ); + self.apply_adjustments(expr, vec![Adjustment { + kind: Adjust::NeverToAny, + target: adj_ty + }]); + ty = adj_ty; + } + + if let Some(mut err) = self.demand_suptype_diag(expr.span, expected_ty, ty) { + let expr = match &expr.node { + ExprKind::DropTemps(expr) => expr, + _ => expr, + }; + // Error possibly reported in `check_assign` so avoid emitting error again. + err.emit_unless(self.is_assign_to_bool(expr, expected_ty)); + } + ty + } + + pub(super) fn check_expr_coercable_to_type( + &self, + expr: &'tcx hir::Expr, + expected: Ty<'tcx> + ) -> Ty<'tcx> { + let ty = self.check_expr_with_hint(expr, expected); + // checks don't need two phase + self.demand_coerce(expr, ty, expected, AllowTwoPhase::No) + } + + pub(super) fn check_expr_with_hint( + &self, + expr: &'tcx hir::Expr, + expected: Ty<'tcx> + ) -> Ty<'tcx> { + self.check_expr_with_expectation(expr, ExpectHasType(expected)) + } + + pub(super) fn check_expr_with_expectation( + &self, + expr: &'tcx hir::Expr, + expected: Expectation<'tcx>, + ) -> Ty<'tcx> { + self.check_expr_with_expectation_and_needs(expr, expected, Needs::None) + } + + pub(super) fn check_expr(&self, expr: &'tcx hir::Expr) -> Ty<'tcx> { + self.check_expr_with_expectation(expr, NoExpectation) + } + + pub(super) fn check_expr_with_needs(&self, expr: &'tcx hir::Expr, needs: Needs) -> Ty<'tcx> { + self.check_expr_with_expectation_and_needs(expr, NoExpectation, needs) + } + + /// 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 + /// true. Likewise, if an expression is known to diverge, inspecting its + /// type with `ty::type_is_bot` will return true (n.b.: since Rust is + /// strict, _|_ can appear in the type of an expression that does not, + /// itself, diverge: for example, fn() -> _|_.) + /// Note that inspecting a type's structure *directly* may expose the fact + /// that there are actually multiple representations for `Error`, so avoid + /// that when err needs to be handled differently. + fn check_expr_with_expectation_and_needs( + &self, + expr: &'tcx hir::Expr, + expected: Expectation<'tcx>, + needs: Needs, + ) -> Ty<'tcx> { + debug!(">> type-checking: expr={:?} expected={:?}", + expr, expected); + + // Warn for expressions after diverging siblings. + self.warn_if_unreachable(expr.hir_id, expr.span, "expression"); + + // Hide the outer diverging and has_errors flags. + let old_diverges = self.diverges.get(); + let old_has_errors = self.has_errors.get(); + self.diverges.set(Diverges::Maybe); + self.has_errors.set(false); + + let ty = self.check_expr_kind(expr, expected, needs); + + // Warn for non-block expressions with diverging children. + match expr.node { + ExprKind::Block(..) | + ExprKind::Loop(..) | ExprKind::While(..) | + ExprKind::Match(..) => {} + + _ => self.warn_if_unreachable(expr.hir_id, expr.span, "expression") + } + + // Any expression that produces a value of type `!` must have diverged + if ty.is_never() { + self.diverges.set(self.diverges.get() | Diverges::Always); + } + + // Record the type, which applies it effects. + // We need to do this after the warning above, so that + // we don't warn for the diverging expression itself. + self.write_ty(expr.hir_id, ty); + + // Combine the diverging and has_error flags. + self.diverges.set(self.diverges.get() | old_diverges); + self.has_errors.set(self.has_errors.get() | old_has_errors); + + debug!("type of {} is...", self.tcx.hir().hir_to_string(expr.hir_id)); + debug!("... {:?}, expected is {:?}", ty, expected); + + 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; + match expr.node { + ExprKind::Box(ref subexpr) => { + self.check_expr_box(subexpr, expected) + } + 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) => { + self.check_expr_unary(unop, oprnd, expected, needs, expr) + } + ExprKind::AddrOf(mutbl, ref oprnd) => { + self.check_expr_addr_of(mutbl, oprnd, expected, expr) + } + ExprKind::Path(ref qpath) => { + self.check_expr_path(qpath, expr) + } + 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) => { + self.check_expr_break(destination, expr_opt.deref(), expr) + } + 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) => { + self.check_expr_return(expr_opt.deref(), expr) + } + ExprKind::Assign(ref lhs, ref rhs) => { + self.check_expr_assign(expr, expected, lhs, rhs) + } + ExprKind::While(ref cond, ref body, _) => { + self.check_expr_while(cond, body, expr) + } + ExprKind::Loop(ref body, _, source) => { + self.check_expr_loop(body, source, expected, expr) + } + 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) => { + self.check_expr_cast(e, t, expr) + } + 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) => { + self.check_expr_array(args, expected, expr) + } + ExprKind::Repeat(ref element, ref count) => { + self.check_expr_repeat(element, count, expected, expr) + } + ExprKind::Tup(ref elts) => { + self.check_expr_tuple(elts, expected, expr) + } + 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) => { + self.check_expr_index(base, idx, needs, expr) + } + ExprKind::Yield(ref value) => { + self.check_expr_yield(value, expr) + } + hir::ExprKind::Err => { + tcx.types.err + } + } + } + + fn check_expr_box(&self, expr: &'tcx hir::Expr, expected: Expectation<'tcx>) -> Ty<'tcx> { + 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(expr, expected_inner); + self.tcx.mk_box(referent_ty) + } + + fn check_expr_unary( + &self, + unop: hir::UnOp, + oprnd: &'tcx hir::Expr, + expected: Expectation<'tcx>, + needs: Needs, + expr: &'tcx hir::Expr, + ) -> Ty<'tcx> { + let tcx = self.tcx; + 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 + } + + fn check_expr_addr_of( + &self, + mutbl: hir::Mutability, + oprnd: &'tcx hir::Expr, + expected: Expectation<'tcx>, + expr: &'tcx hir::Expr, + ) -> Ty<'tcx> { + 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() { + self.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)); + self.tcx.mk_ref(region, tm) + } + } + + fn check_expr_path(&self, qpath: &hir::QPath, expr: &'tcx hir::Expr) -> Ty<'tcx> { + let tcx = self.tcx; + 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, expr.hir_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 + } + + fn check_expr_break( + &self, + destination: hir::Destination, + expr_opt: Option<&'tcx hir::Expr>, + expr: &'tcx hir::Expr, + ) -> Ty<'tcx> { + let tcx = self.tcx; + 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 + } + } + + fn check_expr_return( + &self, + expr_opt: Option<&'tcx hir::Expr>, + expr: &'tcx hir::Expr + ) -> Ty<'tcx> { + 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); + } + } + self.tcx.types.never + } + + pub(super) fn check_return_expr(&self, return_expr: &'tcx hir::Expr) { + let ret_coercion = + self.ret_coercion + .as_ref() + .unwrap_or_else(|| span_bug!(return_expr.span, + "check_return_expr called outside fn body")); + + let ret_ty = ret_coercion.borrow().expected_ty(); + let return_expr_ty = self.check_expr_with_hint(return_expr, ret_ty.clone()); + ret_coercion.borrow_mut() + .coerce(self, + &self.cause(return_expr.span, + ObligationCauseCode::ReturnType(return_expr.hir_id)), + return_expr, + return_expr_ty); + } + + /// 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_expr_assign( + &self, + expr: &'tcx hir::Expr, + expected: Expectation<'tcx>, + lhs: &'tcx hir::Expr, + rhs: &'tcx hir::Expr, + ) -> Ty<'tcx> { + let lhs_ty = self.check_expr_with_needs(&lhs, Needs::MutPlace); + let rhs_ty = self.check_expr_coercable_to_type(&rhs, lhs_ty); + + let expected_ty = expected.coercion_target_type(self, expr.span); + if expected_ty == self.tcx.types.bool { + // The expected type is `bool` but this will result in `()` so we can reasonably + // say that the user intended to write `lhs == rhs` instead of `lhs = rhs`. + // The likely cause of this is `if foo = bar { .. }`. + let actual_ty = self.tcx.mk_unit(); + let mut err = self.demand_suptype_diag(expr.span, expected_ty, actual_ty).unwrap(); + let msg = "try comparing for equality"; + let left = self.tcx.sess.source_map().span_to_snippet(lhs.span); + let right = self.tcx.sess.source_map().span_to_snippet(rhs.span); + if let (Ok(left), Ok(right)) = (left, right) { + let help = format!("{} == {}", left, right); + err.span_suggestion(expr.span, msg, help, Applicability::MaybeIncorrect); + } else { + err.help(msg); + } + err.emit(); + } else if !lhs.is_place_expr() { + struct_span_err!(self.tcx.sess, expr.span, E0070, + "invalid left-hand side expression") + .span_label(expr.span, "left-hand of expression not valid") + .emit(); + } + + self.require_type_is_sized(lhs_ty, lhs.span, traits::AssignmentLhsSized); + + if lhs_ty.references_error() || rhs_ty.references_error() { + self.tcx.types.err + } else { + self.tcx.mk_unit() + } + } + + fn check_expr_while( + &self, + cond: &'tcx hir::Expr, + body: &'tcx hir::Block, + expr: &'tcx hir::Expr + ) -> Ty<'tcx> { + 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, self.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() + } + + fn check_expr_loop( + &self, + body: &'tcx hir::Block, + source: hir::LoopSource, + expected: Expectation<'tcx>, + expr: &'tcx hir::Expr, + ) -> Ty<'tcx> { + 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()) + } + + /// Checks a method call. + fn check_method_call( + &self, + expr: &'tcx hir::Expr, + segment: &hir::PathSegment, + span: Span, + args: &'tcx [hir::Expr], + expected: Expectation<'tcx>, + needs: Needs, + ) -> Ty<'tcx> { + let rcvr = &args[0]; + let rcvr_t = self.check_expr_with_needs(&rcvr, needs); + // no need to check for bot/err -- callee does that + let rcvr_t = self.structurally_resolved_type(args[0].span, rcvr_t); + + let method = match self.lookup_method(rcvr_t, + segment, + span, + expr, + rcvr) { + Ok(method) => { + self.write_method_call(expr.hir_id, method); + Ok(method) + } + Err(error) => { + if segment.ident.name != kw::Invalid { + self.report_method_error(span, + rcvr_t, + segment.ident, + SelfSource::MethodCall(rcvr), + error, + Some(args)); + } + Err(()) + } + }; + + // Call the generic checker. + self.check_method_argument_types(span, + expr.span, + method, + &args[1..], + DontTupleArguments, + expected) + } + + fn check_expr_cast( + &self, + e: &'tcx hir::Expr, + t: &'tcx hir::Ty, + expr: &'tcx hir::Expr, + ) -> Ty<'tcx> { + // 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() { + self.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) => { + self.tcx.types.err + } + } + } + } + + fn check_expr_array( + &self, + args: &'tcx [hir::Expr], + expected: Expectation<'tcx>, + expr: &'tcx hir::Expr + ) -> Ty<'tcx> { + 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, + }) + }; + self.tcx.mk_array(element_ty, args.len() as u64) + } + + fn check_expr_repeat( + &self, + element: &'tcx hir::Expr, + count: &'tcx hir::AnonConst, + expected: Expectation<'tcx>, + expr: &'tcx hir::Expr, + ) -> Ty<'tcx> { + let tcx = self.tcx; + 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, 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 = 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 + } + } + + fn check_expr_tuple( + &self, + elts: &'tcx [hir::Expr], + expected: Expectation<'tcx>, + expr: &'tcx hir::Expr, + ) -> Ty<'tcx> { + 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 = self.tcx.mk_tup(elt_ts_iter); + if tuple.references_error() { + self.tcx.types.err + } else { + self.require_type_is_sized(tuple, expr.span, traits::TupleInitializerSized); + tuple + } + } + + fn check_expr_struct( + &self, + expr: &hir::Expr, + expected: Expectation<'tcx>, + qpath: &QPath, + fields: &'tcx [hir::Field], + base_expr: &'tcx Option
>,
+ ) -> Ty<'tcx> {
+ // Find the relevant variant
+ let (variant, adt_ty) =
+ if let Some(variant_ty) = self.check_struct_path(qpath, expr.hir_id) {
+ variant_ty
+ } else {
+ self.check_struct_fields_on_error(fields, base_expr);
+ return self.tcx.types.err;
+ };
+
+ let path_span = match *qpath {
+ QPath::Resolved(_, ref path) => path.span,
+ QPath::TypeRelative(ref qself, _) => qself.span
+ };
+
+ // Prohibit struct expressions when non-exhaustive flag is set.
+ let adt = adt_ty.ty_adt_def().expect("`check_struct_path` returned non-ADT type");
+ if !adt.did.is_local() && variant.is_field_list_non_exhaustive() {
+ span_err!(self.tcx.sess, expr.span, E0639,
+ "cannot create non-exhaustive {} using struct expression",
+ adt.variant_descr());
+ }
+
+ let error_happened = self.check_expr_struct_fields(adt_ty, expected, expr.hir_id, path_span,
+ variant, fields, base_expr.is_none());
+ if let &Some(ref base_expr) = base_expr {
+ // If check_expr_struct_fields hit an error, do not attempt to populate
+ // the fields with the base_expr. This could cause us to hit errors later
+ // when certain fields are assumed to exist that in fact do not.
+ if !error_happened {
+ self.check_expr_has_type_or_error(base_expr, adt_ty);
+ match adt_ty.sty {
+ ty::Adt(adt, substs) if adt.is_struct() => {
+ let fru_field_types = adt.non_enum_variant().fields.iter().map(|f| {
+ self.normalize_associated_types_in(expr.span, &f.ty(self.tcx, substs))
+ }).collect();
+
+ self.tables
+ .borrow_mut()
+ .fru_field_types_mut()
+ .insert(expr.hir_id, fru_field_types);
+ }
+ _ => {
+ span_err!(self.tcx.sess, base_expr.span, E0436,
+ "functional record update syntax requires a struct");
+ }
+ }
+ }
+ }
+ self.require_type_is_sized(adt_ty, expr.span, traits::StructInitializerSized);
+ adt_ty
+ }
+
+ fn check_expr_struct_fields(
+ &self,
+ adt_ty: Ty<'tcx>,
+ expected: Expectation<'tcx>,
+ expr_id: hir::HirId,
+ span: Span,
+ variant: &'tcx ty::VariantDef,
+ ast_fields: &'tcx [hir::Field],
+ check_completeness: bool,
+ ) -> bool {
+ let tcx = self.tcx;
+
+ let adt_ty_hint =
+ self.expected_inputs_for_expected_output(span, expected, adt_ty, &[adt_ty])
+ .get(0).cloned().unwrap_or(adt_ty);
+ // re-link the regions that EIfEO can erase.
+ self.demand_eqtype(span, adt_ty_hint, adt_ty);
+
+ let (substs, adt_kind, kind_name) = match &adt_ty.sty {
+ &ty::Adt(adt, substs) => {
+ (substs, adt.adt_kind(), adt.variant_descr())
+ }
+ _ => span_bug!(span, "non-ADT passed to check_expr_struct_fields")
+ };
+
+ let mut remaining_fields = variant.fields.iter().enumerate().map(|(i, field)|
+ (field.ident.modern(), (i, field))
+ ).collect:: >,
+ ) {
+ for field in fields {
+ self.check_expr(&field.expr);
+ }
+ if let Some(ref base) = *base_expr {
+ self.check_expr(&base);
+ }
+ }
+
+ fn report_unknown_field(
+ &self,
+ ty: Ty<'tcx>,
+ variant: &'tcx ty::VariantDef,
+ field: &hir::Field,
+ skip_fields: &[hir::Field],
+ kind_name: &str,
+ ) {
+ if variant.recovered {
+ return;
+ }
+ let mut err = self.type_error_struct_with_diag(
+ field.ident.span,
+ |actual| match ty.sty {
+ ty::Adt(adt, ..) if adt.is_enum() => {
+ struct_span_err!(self.tcx.sess, field.ident.span, E0559,
+ "{} `{}::{}` has no field named `{}`",
+ kind_name, actual, variant.ident, field.ident)
+ }
+ _ => {
+ struct_span_err!(self.tcx.sess, field.ident.span, E0560,
+ "{} `{}` has no field named `{}`",
+ kind_name, actual, field.ident)
+ }
+ },
+ ty);
+ // prevent all specified fields from being suggested
+ let skip_fields = skip_fields.iter().map(|ref x| x.ident.as_str());
+ if let Some(field_name) = Self::suggest_field_name(variant,
+ &field.ident.as_str(),
+ skip_fields.collect()) {
+ err.span_suggestion(
+ field.ident.span,
+ "a field with a similar name exists",
+ field_name.to_string(),
+ Applicability::MaybeIncorrect,
+ );
+ } else {
+ match ty.sty {
+ ty::Adt(adt, ..) => {
+ if adt.is_enum() {
+ err.span_label(field.ident.span,
+ format!("`{}::{}` does not have this field",
+ ty, variant.ident));
+ } else {
+ err.span_label(field.ident.span,
+ format!("`{}` does not have this field", ty));
+ }
+ let available_field_names = self.available_field_names(variant);
+ if !available_field_names.is_empty() {
+ err.note(&format!("available fields are: {}",
+ self.name_series_display(available_field_names)));
+ }
+ }
+ _ => bug!("non-ADT passed to report_unknown_field")
+ }
+ };
+ err.emit();
+ }
+
+ // Return an hint about the closest match in field names
+ fn suggest_field_name(variant: &'tcx ty::VariantDef,
+ field: &str,
+ skip: Vec >,
- ) {
- for field in fields {
- self.check_expr(&field.expr);
- }
- if let Some(ref base) = *base_expr {
- self.check_expr(&base);
- }
- }
-
pub fn check_struct_path(&self,
qpath: &QPath,
hir_id: hir::HirId)
@@ -3863,842 +3322,6 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
}
}
- fn check_expr_struct(
- &self,
- expr: &hir::Expr,
- expected: Expectation<'tcx>,
- qpath: &QPath,
- fields: &'tcx [hir::Field],
- base_expr: &'tcx Option >,
- ) -> Ty<'tcx> {
- // Find the relevant variant
- let (variant, adt_ty) =
- if let Some(variant_ty) = self.check_struct_path(qpath, expr.hir_id) {
- variant_ty
- } else {
- self.check_struct_fields_on_error(fields, base_expr);
- return self.tcx.types.err;
- };
-
- let path_span = match *qpath {
- QPath::Resolved(_, ref path) => path.span,
- QPath::TypeRelative(ref qself, _) => qself.span
- };
-
- // Prohibit struct expressions when non-exhaustive flag is set.
- let adt = adt_ty.ty_adt_def().expect("`check_struct_path` returned non-ADT type");
- if !adt.did.is_local() && variant.is_field_list_non_exhaustive() {
- span_err!(self.tcx.sess, expr.span, E0639,
- "cannot create non-exhaustive {} using struct expression",
- adt.variant_descr());
- }
-
- let error_happened = self.check_expr_struct_fields(adt_ty, expected, expr.hir_id, path_span,
- variant, fields, base_expr.is_none());
- if let &Some(ref base_expr) = base_expr {
- // If check_expr_struct_fields hit an error, do not attempt to populate
- // the fields with the base_expr. This could cause us to hit errors later
- // when certain fields are assumed to exist that in fact do not.
- if !error_happened {
- self.check_expr_has_type_or_error(base_expr, adt_ty);
- match adt_ty.sty {
- ty::Adt(adt, substs) if adt.is_struct() => {
- let fru_field_types = adt.non_enum_variant().fields.iter().map(|f| {
- self.normalize_associated_types_in(expr.span, &f.ty(self.tcx, substs))
- }).collect();
-
- self.tables
- .borrow_mut()
- .fru_field_types_mut()
- .insert(expr.hir_id, fru_field_types);
- }
- _ => {
- span_err!(self.tcx.sess, base_expr.span, E0436,
- "functional record update syntax requires a struct");
- }
- }
- }
- }
- self.require_type_is_sized(adt_ty, expr.span, traits::StructInitializerSized);
- 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
- /// true. Likewise, if an expression is known to diverge, inspecting its
- /// type with `ty::type_is_bot` will return true (n.b.: since Rust is
- /// strict, _|_ can appear in the type of an expression that does not,
- /// itself, diverge: for example, fn() -> _|_.)
- /// Note that inspecting a type's structure *directly* may expose the fact
- /// that there are actually multiple representations for `Error`, so avoid
- /// that when err needs to be handled differently.
- fn check_expr_with_expectation_and_needs(
- &self,
- expr: &'tcx hir::Expr,
- expected: Expectation<'tcx>,
- needs: Needs,
- ) -> Ty<'tcx> {
- debug!(">> type-checking: expr={:?} expected={:?}",
- expr, expected);
-
- // Warn for expressions after diverging siblings.
- self.warn_if_unreachable(expr.hir_id, expr.span, "expression");
-
- // Hide the outer diverging and has_errors flags.
- let old_diverges = self.diverges.get();
- let old_has_errors = self.has_errors.get();
- self.diverges.set(Diverges::Maybe);
- self.has_errors.set(false);
-
- let ty = self.check_expr_kind(expr, expected, needs);
-
- // Warn for non-block expressions with diverging children.
- match expr.node {
- ExprKind::Block(..) |
- ExprKind::Loop(..) | ExprKind::While(..) |
- ExprKind::Match(..) => {}
-
- _ => self.warn_if_unreachable(expr.hir_id, expr.span, "expression")
- }
-
- // Any expression that produces a value of type `!` must have diverged
- if ty.is_never() {
- self.diverges.set(self.diverges.get() | Diverges::Always);
- }
-
- // Record the type, which applies it effects.
- // We need to do this after the warning above, so that
- // we don't warn for the diverging expression itself.
- self.write_ty(expr.hir_id, ty);
-
- // Combine the diverging and has_error flags.
- self.diverges.set(self.diverges.get() | old_diverges);
- self.has_errors.set(self.has_errors.get() | old_has_errors);
-
- debug!("type of {} is...", self.tcx.hir().hir_to_string(expr.hir_id));
- debug!("... {:?}, expected is {:?}", ty, expected);
-
- 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(
- &self,
- expr: &'tcx hir::Expr,
- expected: Expectation<'tcx>,
- lhs: &'tcx hir::Expr,
- rhs: &'tcx hir::Expr,
- ) -> Ty<'tcx> {
- let lhs_ty = self.check_expr_with_needs(&lhs, Needs::MutPlace);
- let rhs_ty = self.check_expr_coercable_to_type(&rhs, lhs_ty);
-
- let expected_ty = expected.coercion_target_type(self, expr.span);
- if expected_ty == self.tcx.types.bool {
- // The expected type is `bool` but this will result in `()` so we can reasonably
- // say that the user intended to write `lhs == rhs` instead of `lhs = rhs`.
- // The likely cause of this is `if foo = bar { .. }`.
- let actual_ty = self.tcx.mk_unit();
- let mut err = self.demand_suptype_diag(expr.span, expected_ty, actual_ty).unwrap();
- let msg = "try comparing for equality";
- let left = self.tcx.sess.source_map().span_to_snippet(lhs.span);
- let right = self.tcx.sess.source_map().span_to_snippet(rhs.span);
- if let (Ok(left), Ok(right)) = (left, right) {
- let help = format!("{} == {}", left, right);
- err.span_suggestion(expr.span, msg, help, Applicability::MaybeIncorrect);
- } else {
- err.help(msg);
- }
- err.emit();
- } else if !lhs.is_place_expr() {
- struct_span_err!(self.tcx.sess, expr.span, E0070,
- "invalid left-hand side expression")
- .span_label(expr.span, "left-hand of expression not valid")
- .emit();
- }
-
- self.require_type_is_sized(lhs_ty, lhs.span, traits::AssignmentLhsSized);
-
- if lhs_ty.references_error() || rhs_ty.references_error() {
- self.tcx.types.err
- } else {
- self.tcx.mk_unit()
- }
- }
-
// Finish resolving a path in a struct expression or pattern `S::A { .. }` if necessary.
// The newly resolved definition is written into `type_dependent_defs`.
fn finish_resolving_struct_path(&self,
diff --git a/src/librustc_typeck/lib.rs b/src/librustc_typeck/lib.rs
index 79674e4baeba0..cc6f7a07d9621 100644
--- a/src/librustc_typeck/lib.rs
+++ b/src/librustc_typeck/lib.rs
@@ -68,6 +68,7 @@ This API is completely unstable and subject to change.
#![feature(rustc_diagnostic_macros)]
#![feature(slice_patterns)]
#![feature(never_type)]
+#![feature(inner_deref)]
#![recursion_limit="256"]