Skip to content
Permalink
Branch: master
Find file Copy path
Find file Copy path
Fetching contributors…
Cannot retrieve contributors at this time
1658 lines (1536 sloc) 64.6 KB
//! 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::{probe, SelfSource, MethodError};
use crate::util::common::ErrorReported;
use crate::util::nodemap::FxHashMap;
use crate::astconv::AstConv as _;
use errors::{Applicability, DiagnosticBuilder, pluralise};
use syntax::ast;
use syntax::symbol::{Symbol, 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_id::DefId;
use rustc::hir::def::{CtorKind, Res, DefKind};
use rustc::hir::ptr::P;
use rustc::infer;
use rustc::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
use rustc::middle::lang_items;
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::Match(..) => {},
ExprKind::Call(ref callee, _) =>
self.warn_if_unreachable(expr.hir_id, callee.span, "call"),
ExprKind::MethodCall(_, ref span, _) =>
self.warn_if_unreachable(expr.hir_id, *span, "call"),
_ => 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(expr.span));
}
// 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().node_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.as_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.as_deref(), expr)
}
ExprKind::Assign(ref lhs, ref rhs) => {
self.check_expr_assign(expr, expected, lhs, rhs)
}
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, ref src) => {
self.check_expr_yield(value, expr, src)
}
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());
let ty = coerce.expected_ty();
coerce.coerce_forced_unit(self, &cause, &mut |err| {
let val = match ty.sty {
ty::Bool => "true",
ty::Char => "'a'",
ty::Int(_) | ty::Uint(_) => "42",
ty::Float(_) => "3.14159",
ty::Error | ty::Never => return,
_ => "value",
};
let msg = "give it a value of the expected type";
let label = destination.label
.map(|l| format!(" {}", l.ident))
.unwrap_or_else(String::new);
let sugg = format!("break{} {}", label, val);
err.span_suggestion(expr.span, msg, sugg, Applicability::HasPlaceholders);
}, false);
}
} 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.has_errors());
}
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.
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_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::While |
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_extended_method_error(segment, span, args, rcvr_t, error);
}
Err(())
}
};
// Call the generic checker.
self.check_method_argument_types(
span,
expr.span,
method,
&args[1..],
DontTupleArguments,
expected,
)
}
fn report_extended_method_error(
&self,
segment: &hir::PathSegment,
span: Span,
args: &'tcx [hir::Expr],
rcvr_t: Ty<'tcx>,
error: MethodError<'tcx>
) {
let rcvr = &args[0];
let try_alt_rcvr = |err: &mut DiagnosticBuilder<'_>, rcvr_t, lang_item| {
if let Some(new_rcvr_t) = self.tcx.mk_lang_item(rcvr_t, lang_item) {
if let Ok(pick) = self.lookup_probe(
span,
segment.ident,
new_rcvr_t,
rcvr,
probe::ProbeScope::AllTraits,
) {
err.span_label(
pick.item.ident.span,
&format!("the method is available for `{}` here", new_rcvr_t),
);
}
}
};
if let Some(mut err) = self.report_method_error(
span,
rcvr_t,
segment.ident,
SelfSource::MethodCall(rcvr),
error,
Some(args),
) {
if let ty::Adt(..) = rcvr_t.sty {
// Try alternative arbitrary self types that could fulfill this call.
// FIXME: probe for all types that *could* be arbitrary self-types, not
// just this whitelist.
try_alt_rcvr(&mut err, rcvr_t, lang_items::OwnedBoxLangItem);
try_alt_rcvr(&mut err, rcvr_t, lang_items::PinTypeLangItem);
try_alt_rcvr(&mut err, rcvr_t, lang_items::Arc);
try_alt_rcvr(&mut err, rcvr_t, lang_items::Rc);
}
err.emit();
}
}
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(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 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<P<hir::Expr>>,
) -> 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::<FxHashMap<_, _>>();
let mut seen_fields = FxHashMap::default();
let mut error_happened = false;
// Type-check each field.
for field in ast_fields {
let ident = tcx.adjust_ident(field.ident, variant.def_id);
let field_type = if let Some((i, v_field)) = remaining_fields.remove(&ident) {
seen_fields.insert(ident, field.span);
self.write_field_index(field.hir_id, i);
// We don't look at stability attributes on
// struct-like enums (yet...), but it's definitely not
// a bug to have constructed one.
if adt_kind != AdtKind::Enum {
tcx.check_stability(v_field.did, Some(expr_id), field.span);
}
self.field_ty(field.span, v_field, substs)
} else {
error_happened = true;
if let Some(prev_span) = seen_fields.get(&ident) {
let mut err = struct_span_err!(self.tcx.sess,
field.ident.span,
E0062,
"field `{}` specified more than once",
ident);
err.span_label(field.ident.span, "used more than once");
err.span_label(*prev_span, format!("first use of `{}`", ident));
err.emit();
} else {
self.report_unknown_field(adt_ty, variant, field, ast_fields, kind_name, span);
}
tcx.types.err
};
// Make sure to give a type to the field even if there's
// an error, so we can continue type-checking.
self.check_expr_coercable_to_type(&field.expr, field_type);
}
// Make sure the programmer specified correct number of fields.
if kind_name == "union" {
if ast_fields.len() != 1 {
tcx.sess.span_err(span, "union expressions should have exactly one field");
}
} else if check_completeness && !error_happened && !remaining_fields.is_empty() {
let len = remaining_fields.len();
let mut displayable_field_names = remaining_fields
.keys()
.map(|ident| ident.as_str())
.collect::<Vec<_>>();
displayable_field_names.sort();
let truncated_fields_error = if len <= 3 {
String::new()
} else {
format!(" and {} other field{}", (len - 3), if len - 3 == 1 {""} else {"s"})
};
let remaining_fields_names = displayable_field_names.iter().take(3)
.map(|n| format!("`{}`", n))
.collect::<Vec<_>>()
.join(", ");
struct_span_err!(tcx.sess, span, E0063,
"missing field{} {}{} in initializer of `{}`",
pluralise!(remaining_fields.len()),
remaining_fields_names,
truncated_fields_error,
adt_ty)
.span_label(span, format!("missing {}{}",
remaining_fields_names,
truncated_fields_error))
.emit();
}
error_happened
}
fn check_struct_fields_on_error(
&self,
fields: &'tcx [hir::Field],
base_expr: &'tcx Option<P<hir::Expr>>,
) {
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,
ty_span: Span
) {
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);
match variant.ctor_kind {
CtorKind::Fn => {
err.span_label(variant.ident.span, format!("`{adt}` defined here", adt=ty));
err.span_label(field.ident.span, "field does not exist");
err.span_label(ty_span, format!(
"`{adt}` is a tuple {kind_name}, \
use the appropriate syntax: `{adt}(/* fields */)`",
adt=ty,
kind_name=kind_name
));
}
_ => {
// prevent all specified fields from being suggested
let skip_fields = skip_fields.iter().map(|ref x| x.ident.name);
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<Symbol>)
-> Option<Symbol> {
let names = variant.fields.iter().filter_map(|field| {
// ignore already set fields and private fields from non-local crates
if skip.iter().any(|&x| x == field.ident.name) ||
(!variant.def_id.is_local() && field.vis != Visibility::Public)
{
None
} else {
Some(&field.ident.name)
}
});
find_best_match_for_name(names, field, None)
}
fn available_field_names(&self, variant: &'tcx ty::VariantDef) -> Vec<ast::Name> {
variant.fields.iter().filter(|field| {
let def_scope =
self.tcx.adjust_ident_and_get_scope(field.ident, variant.def_id, self.body_id).1;
field.vis.is_accessible_from(def_scope, self.tcx)
})
.map(|field| field.ident.name)
.collect()
}
fn name_series_display(&self, names: Vec<ast::Name>) -> String {
// dynamic limit, to never omit just one field
let limit = if names.len() == 6 { 6 } else { 5 };
let mut display = names.iter().take(limit)
.map(|n| format!("`{}`", n)).collect::<Vec<_>>().join(", ");
if names.len() > limit {
display = format!("{} ... and {} others", display, names.len() - limit);
}
display
}
// Check field access expressions
fn check_field(
&self,
expr: &'tcx hir::Expr,
needs: Needs,
base: &'tcx hir::Expr,
field: ast::Ident,
) -> Ty<'tcx> {
let expr_t = self.check_expr_with_needs(base, needs);
let expr_t = self.structurally_resolved_type(base.span,
expr_t);
let mut private_candidate = None;
let mut autoderef = self.autoderef(expr.span, expr_t);
while let Some((base_t, _)) = autoderef.next() {
match base_t.sty {
ty::Adt(base_def, substs) if !base_def.is_enum() => {
debug!("struct named {:?}", base_t);
let (ident, def_scope) =
self.tcx.adjust_ident_and_get_scope(field, base_def.did, self.body_id);
let fields = &base_def.non_enum_variant().fields;
if let Some(index) = fields.iter().position(|f| f.ident.modern() == ident) {
let field = &fields[index];
let field_ty = self.field_ty(expr.span, field, substs);
// Save the index of all fields regardless of their visibility in case
// of error recovery.
self.write_field_index(expr.hir_id, index);
if field.vis.is_accessible_from(def_scope, self.tcx) {
let adjustments = autoderef.adjust_steps(self, needs);
self.apply_adjustments(base, adjustments);
autoderef.finalize(self);
self.tcx.check_stability(field.did, Some(expr.hir_id), expr.span);
return field_ty;
}
private_candidate = Some((base_def.did, field_ty));
}
}
ty::Tuple(ref tys) => {
let fstr = field.as_str();
if let Ok(index) = fstr.parse::<usize>() {
if fstr == index.to_string() {
if let Some(field_ty) = tys.get(index) {
let adjustments = autoderef.adjust_steps(self, needs);
self.apply_adjustments(base, adjustments);
autoderef.finalize(self);
self.write_field_index(expr.hir_id, index);
return field_ty.expect_ty();
}
}
}
}
_ => {}
}
}
autoderef.unambiguous_final_ty(self);
if let Some((did, field_ty)) = private_candidate {
self.ban_private_field_access(expr, expr_t, field, did);
return field_ty;
}
if field.name == kw::Invalid {
} else if self.method_exists(field, expr_t, expr.hir_id, true) {
self.ban_take_value_of_method(expr, expr_t, field);
} else if !expr_t.is_primitive_ty() {
let mut err = self.no_such_field_err(field.span, field, expr_t);
match expr_t.sty {
ty::Adt(def, _) if !def.is_enum() => {
self.suggest_fields_on_recordish(&mut err, def, field);
}
ty::Array(_, len) => {
self.maybe_suggest_array_indexing(&mut err, expr, base, field, len);
}
ty::RawPtr(..) => {
self.suggest_first_deref_field(&mut err, expr, base, field);
}
_ => {}
}
if field.name == kw::Await {
// We know by construction that `<expr>.await` is either on Rust 2015
// or results in `ExprKind::Await`. Suggest switching the edition to 2018.
err.note("to `.await` a `Future`, switch to Rust 2018");
err.help("set `edition = \"2018\"` in `Cargo.toml`");
err.note("for more on editions, read https://doc.rust-lang.org/edition-guide");
}
err.emit();
} else {
type_error_struct!(
self.tcx().sess,
field.span,
expr_t,
E0610,
"`{}` is a primitive type and therefore doesn't have fields",
expr_t
)
.emit();
}
self.tcx().types.err
}
fn ban_private_field_access(
&self,
expr: &hir::Expr,
expr_t: Ty<'tcx>,
field: ast::Ident,
base_did: DefId,
) {
let struct_path = self.tcx().def_path_str(base_did);
let kind_name = match self.tcx().def_kind(base_did) {
Some(def_kind) => def_kind.descr(base_did),
_ => " ",
};
let mut err = struct_span_err!(
self.tcx().sess,
expr.span,
E0616,
"field `{}` of {} `{}` is private",
field,
kind_name,
struct_path
);
// Also check if an accessible method exists, which is often what is meant.
if self.method_exists(field, expr_t, expr.hir_id, false)
&& !self.expr_in_place(expr.hir_id)
{
self.suggest_method_call(
&mut err,
&format!("a method `{}` also exists, call it with parentheses", field),
field,
expr_t,
expr.hir_id,
);
}
err.emit();
}
fn ban_take_value_of_method(&self, expr: &hir::Expr, expr_t: Ty<'tcx>, field: ast::Ident) {
let mut err = type_error_struct!(
self.tcx().sess,
field.span,
expr_t,
E0615,
"attempted to take value of method `{}` on type `{}`",
field,
expr_t
);
if !self.expr_in_place(expr.hir_id) {
self.suggest_method_call(
&mut err,
"use parentheses to call the method",
field,
expr_t,
expr.hir_id
);
} else {
err.help("methods are immutable and cannot be assigned to");
}
err.emit();
}
fn suggest_fields_on_recordish(
&self,
err: &mut DiagnosticBuilder<'_>,
def: &'tcx ty::AdtDef,
field: ast::Ident,
) {
if let Some(suggested_field_name) =
Self::suggest_field_name(def.non_enum_variant(), &field.as_str(), vec![])
{
err.span_suggestion(
field.span,
"a field with a similar name exists",
suggested_field_name.to_string(),
Applicability::MaybeIncorrect,
);
} else {
err.span_label(field.span, "unknown field");
let struct_variant_def = def.non_enum_variant();
let field_names = self.available_field_names(struct_variant_def);
if !field_names.is_empty() {
err.note(&format!(
"available fields are: {}",
self.name_series_display(field_names),
));
}
}
}
fn maybe_suggest_array_indexing(
&self,
err: &mut DiagnosticBuilder<'_>,
expr: &hir::Expr,
base: &hir::Expr,
field: ast::Ident,
len: &ty::Const<'tcx>,
) {
if let (Some(len), Ok(user_index)) = (
len.try_eval_usize(self.tcx, self.param_env),
field.as_str().parse::<u64>()
) {
let base = self.tcx.sess.source_map()
.span_to_snippet(base.span)
.unwrap_or_else(|_| self.tcx.hir().hir_to_pretty_string(base.hir_id));
let help = "instead of using tuple indexing, use array indexing";
let suggestion = format!("{}[{}]", base, field);
let applicability = if len < user_index {
Applicability::MachineApplicable
} else {
Applicability::MaybeIncorrect
};
err.span_suggestion(expr.span, help, suggestion, applicability);
}
}
fn suggest_first_deref_field(
&self,
err: &mut DiagnosticBuilder<'_>,
expr: &hir::Expr,
base: &hir::Expr,
field: ast::Ident,
) {
let base = self.tcx.sess.source_map()
.span_to_snippet(base.span)
.unwrap_or_else(|_| self.tcx.hir().hir_to_pretty_string(base.hir_id));
let msg = format!("`{}` is a raw pointer; try dereferencing it", base);
let suggestion = format!("(*{}).{}", base, field);
err.span_suggestion(
expr.span,
&msg,
suggestion,
Applicability::MaybeIncorrect,
);
}
fn no_such_field_err<T: Display>(&self, span: Span, field: T, expr_t: &ty::TyS<'_>)
-> DiagnosticBuilder<'_> {
type_error_struct!(self.tcx().sess, span, expr_t, E0609,
"no field `{}` on type `{}`",
field, expr_t)
}
fn check_expr_index(
&self,
base: &'tcx hir::Expr,
idx: &'tcx hir::Expr,
needs: Needs,
expr: &'tcx hir::Expr,
) -> Ty<'tcx> {
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!(self.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 = self.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
}
}
}
}
fn check_expr_yield(
&self,
value: &'tcx hir::Expr,
expr: &'tcx hir::Expr,
src: &'tcx hir::YieldSource
) -> Ty<'tcx> {
match self.yield_ty {
Some(ty) => {
self.check_expr_coercable_to_type(&value, ty);
}
// Given that this `yield` expression was generated as a result of lowering a `.await`,
// we know that the yield type must be `()`; however, the context won't contain this
// information. Hence, we check the source of the yield expression here and check its
// value's type against `()` (this check should always hold).
None if src == &hir::YieldSource::Await => {
self.check_expr_coercable_to_type(&value, self.tcx.mk_unit());
}
_ => {
struct_span_err!(self.tcx.sess, expr.span, E0627,
"yield statement outside of generator literal").emit();
}
}
self.tcx.mk_unit()
}
}
You can’t perform that action at this time.