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use super::coercion;
use super::demand;
use super::FnCtxt;
use super::structurally_resolved_type;
use lint;
use middle::infer;
use middle::ty;
use middle::ty::Ty;
use syntax::ast;
use syntax::codemap::Span;
pub struct CastCheck<'tcx> {
expr: ast::Expr,
expr_ty: Ty<'tcx>,
cast_ty: Ty<'tcx>,
span: Span,
}
impl<'tcx> CastCheck<'tcx> {
pub fn new(expr: ast::Expr, expr_ty: Ty<'tcx>, cast_ty: Ty<'tcx>, span: Span)
-> CastCheck<'tcx> {
CastCheck {
expr: expr,
expr_ty: expr_ty,
cast_ty: cast_ty,
span: span,
}
}
}
pub fn check_cast<'a, 'tcx>(fcx: &FnCtxt<'a, 'tcx>, cast: &CastCheck<'tcx>) {
fn cast_through_integer_err<'a, 'tcx>(fcx: &FnCtxt<'a, 'tcx>,
span: Span,
t_1: Ty<'tcx>,
t_e: Ty<'tcx>) {
fcx.type_error_message(span, |actual| {
format!("illegal cast; cast through an \
integer first: `{}` as `{}`",
actual,
fcx.infcx().ty_to_string(t_1))
}, t_e, None);
}
let span = cast.span;
let e = &cast.expr;
let t_e = structurally_resolved_type(fcx, span, cast.expr_ty);
let t_1 = structurally_resolved_type(fcx, span, cast.cast_ty);
if !ty::type_has_ty_infer(t_1) {
if let Ok(()) = coercion::mk_assignty(fcx, e, t_e, t_1) {
if ty::type_is_numeric(t_1) && ty::type_is_numeric(t_e) {
fcx.tcx().sess.add_lint(lint::builtin::TRIVIAL_NUMERIC_CASTS,
e.id,
span,
format!("trivial numeric cast: `{}` as `{}`. Cast can be \
replaced by coercion, this might require type \
ascription or a temporary variable",
fcx.infcx().ty_to_string(t_e),
fcx.infcx().ty_to_string(t_1)));
} else {
fcx.tcx().sess.add_lint(lint::builtin::TRIVIAL_CASTS,
e.id,
span,
format!("trivial cast: `{}` as `{}`. Cast can be \
replaced by coercion, this might require type \
ascription or a temporary variable",
fcx.infcx().ty_to_string(t_e),
fcx.infcx().ty_to_string(t_1)));
}
return;
}
}
let t_e_is_bare_fn_item = ty::type_is_bare_fn_item(t_e);
let t_e_is_scalar = ty::type_is_scalar(t_e);
let t_e_is_integral = ty::type_is_integral(t_e);
let t_e_is_float = ty::type_is_floating_point(t_e);
let t_e_is_c_enum = ty::type_is_c_like_enum(fcx.tcx(), t_e);
let t_1_is_scalar = ty::type_is_scalar(t_1);
let t_1_is_integral = ty::type_is_integral(t_1);
let t_1_is_char = ty::type_is_char(t_1);
let t_1_is_bare_fn = ty::type_is_bare_fn(t_1);
let t_1_is_float = ty::type_is_floating_point(t_1);
let t_1_is_c_enum = ty::type_is_c_like_enum(fcx.tcx(), t_1);
let t_1_is_trivial = t_1_is_scalar && !t_1_is_char && !t_1_is_bare_fn;
if t_e_is_bare_fn_item && t_1_is_bare_fn {
demand::coerce(fcx, e.span, t_1, &e);
} else if t_1_is_char {
let t_e = fcx.infcx().shallow_resolve(t_e);
if t_e.sty != ty::ty_uint(ast::TyU8) {
fcx.type_error_message(span, |actual| {
format!("only `u8` can be cast as `char`, not `{}`", actual)
}, t_e, None);
}
} else if t_1.sty == ty::ty_bool {
span_err!(fcx.tcx().sess, span, E0054,
"cannot cast as `bool`, compare with zero instead");
} else if t_e_is_float && (t_1_is_scalar || t_1_is_c_enum) &&
!(t_1_is_integral || t_1_is_float) {
cast_through_integer_err(fcx, span, t_1, t_e)
} else if t_1_is_float && (t_e_is_scalar || t_e_is_c_enum) &&
!(t_e_is_integral || t_e_is_float || t_e.sty == ty::ty_bool) {
cast_through_integer_err(fcx, span, t_1, t_e)
} else if t_e_is_c_enum && t_1_is_trivial {
if ty::type_is_unsafe_ptr(t_1) {
cast_through_integer_err(fcx, span, t_1, t_e)
}
} else if ty::type_is_region_ptr(t_e) && ty::type_is_unsafe_ptr(t_1) {
fn types_compatible<'a, 'tcx>(fcx: &FnCtxt<'a, 'tcx>, sp: Span,
t1: Ty<'tcx>, t2: Ty<'tcx>) -> bool {
match t1.sty {
ty::ty_vec(_, Some(_)) => {}
_ => return false
}
if ty::type_needs_infer(t2) {
return false
}
let el = ty::sequence_element_type(fcx.tcx(), t1);
infer::mk_eqty(fcx.infcx(),
false,
infer::Misc(sp),
el,
t2).is_ok()
}
match (&t_e.sty, &t_1.sty) {
(&ty::ty_rptr(_, ty::mt { ty: mt1, mutbl: ast::MutImmutable }),
&ty::ty_ptr(ty::mt { ty: mt2, mutbl: ast::MutImmutable }))
if types_compatible(fcx, e.span, mt1, mt2) => {
}
_ => {
demand::coerce(fcx, e.span, t_1, &e);
}
}
} else if fcx.type_is_fat_ptr(t_e, span) && !fcx.type_is_fat_ptr(t_1, span) {
fcx.type_error_message(span, |actual| {
format!("illegal cast; cast from fat pointer: `{}` as `{}`",
actual, fcx.infcx().ty_to_string(t_1))
}, t_e, None);
} else if !(t_e_is_scalar && t_1_is_trivial) {
fcx.type_error_message(span, |actual| {
format!("non-scalar cast: `{}` as `{}`",
actual,
fcx.infcx().ty_to_string(t_1))
}, t_e, None);
}
}