rustc: Require that vector indices are uints
This commit tightens up the restriction on types used to index slices to require exactly `uint` indices. Previously any integral type was accepted, but this leads to a few subtle problems: * 64-bit indices don't make much sense on 32-bit systems * Signed indices for slices used as negative indexing isn't implemented This was discussed at the recent work week, and also has some discussion on issue #10453. Closes #10453
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@ -2602,6 +2602,13 @@ pub fn type_is_integral(ty: t) -> bool {
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}
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}
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pub fn type_is_uint(ty: t) -> bool {
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match get(ty).sty {
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ty_infer(IntVar(_)) | ty_uint(ast::TyU) => true,
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_ => false
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}
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}
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pub fn type_is_char(ty: t) -> bool {
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match get(ty).sty {
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ty_char => true,
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@ -3151,7 +3151,7 @@ fn check_expr_with_unifier(fcx: &FnCtxt,
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lvalue_pref, |base_t, _| ty::index(base_t));
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match field_ty {
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Some(mt) => {
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require_integral(fcx, idx.span, idx_t);
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check_expr_has_type(fcx, idx, ty::mk_uint());
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fcx.write_ty(id, mt.ty);
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fcx.write_autoderef_adjustment(base.id, autoderefs);
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}
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@ -3195,6 +3195,15 @@ fn check_expr_with_unifier(fcx: &FnCtxt,
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unifier();
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}
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pub fn require_uint(fcx: &FnCtxt, sp: Span, t: ty::t) {
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if !type_is_uint(fcx, sp, t) {
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fcx.type_error_message(sp, |actual| {
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format!("mismatched types: expected `uint` type but found `{}`",
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actual)
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}, t, None);
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}
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}
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pub fn require_integral(fcx: &FnCtxt, sp: Span, t: ty::t) {
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if !type_is_integral(fcx, sp, t) {
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fcx.type_error_message(sp, |actual| {
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@ -3854,6 +3863,11 @@ pub fn type_is_integral(fcx: &FnCtxt, sp: Span, typ: ty::t) -> bool {
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return ty::type_is_integral(typ_s);
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}
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pub fn type_is_uint(fcx: &FnCtxt, sp: Span, typ: ty::t) -> bool {
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let typ_s = structurally_resolved_type(fcx, sp, typ);
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return ty::type_is_uint(typ_s);
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}
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pub fn type_is_scalar(fcx: &FnCtxt, sp: Span, typ: ty::t) -> bool {
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let typ_s = structurally_resolved_type(fcx, sp, typ);
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return ty::type_is_scalar(typ_s);
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@ -0,0 +1,25 @@
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// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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// Make sure that indexing an array is only valid with a `uint`, not any other
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// integral type.
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fn main() {
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fn bar<T>(_: T) {}
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[0][0u8]; //~ ERROR: mismatched types
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[0][0]; // should infer to be a uint
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let i = 0; // i is an IntVar
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[0][i]; // i should be locked to uint
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bar::<int>(i); // i should not be re-coerced back to an int
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//~^ ERROR: mismatched types
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}
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