src/libsyntax/attr.rs

   1 // Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 // Functions dealing with attributes and meta items
  12
  13 // BitSet
  14 #![allow(deprecated)]
  15
  16 pub use self::StabilityLevel::*;
  17 pub use self::ReprAttr::*;
  18 pub use self::IntType::*;
  19
  20 use ast;
  21 use ast::{AttrId, Attribute, Attribute_, MetaItem, MetaWord, MetaNameValue, MetaList};
  22 use codemap::{Span, Spanned, spanned, dummy_spanned};
  23 use codemap::BytePos;
  24 use diagnostic::SpanHandler;
  25 use parse::lexer::comments::{doc_comment_style, strip_doc_comment_decoration};
  26 use parse::token::{InternedString, intern_and_get_ident};
  27 use parse::token;
  28 use ptr::P;
  29
  30 use std::cell::{RefCell, Cell};
  31 use std::collections::BitSet;
  32 use std::collections::HashSet;
  33 use std::fmt;
  34
  35 thread_local! { static USED_ATTRS: RefCell<BitSet> = RefCell::new(BitSet::new()) }
  36
  37 pub fn mark_used(attr: &Attribute) {
  38     let AttrId(id) = attr.node.id;
  39     USED_ATTRS.with(|slot| slot.borrow_mut().insert(id));
  40 }
  41
  42 pub fn is_used(attr: &Attribute) -> bool {
  43     let AttrId(id) = attr.node.id;
  44     USED_ATTRS.with(|slot| slot.borrow().contains(&id))
  45 }
  46
  47 pub trait AttrMetaMethods {
  48     fn check_name(&self, name: &str) -> bool {
  49         name == &self.name()[..]
  50     }
  51
  52     /// Retrieve the name of the meta item, e.g. `foo` in `#[foo]`,
  53     /// `#[foo="bar"]` and `#[foo(bar)]`
  54     fn name(&self) -> InternedString;
  55
  56     /// Gets the string value if self is a MetaNameValue variant
  57     /// containing a string, otherwise None.
  58     fn value_str(&self) -> Option<InternedString>;
  59     /// Gets a list of inner meta items from a list MetaItem type.
  60     fn meta_item_list<'a>(&'a self) -> Option<&'a [P<MetaItem>]>;
  61
  62     fn span(&self) -> Span;
  63 }
  64
  65 impl AttrMetaMethods for Attribute {
  66     fn check_name(&self, name: &str) -> bool {
  67         let matches = name == &self.name()[..];
  68         if matches {
  69             mark_used(self);
  70         }
  71         matches
  72     }
  73     fn name(&self) -> InternedString { self.meta().name() }
  74     fn value_str(&self) -> Option<InternedString> {
  75         self.meta().value_str()
  76     }
  77     fn meta_item_list<'a>(&'a self) -> Option<&'a [P<MetaItem>]> {
  78         self.node.value.meta_item_list()
  79     }
  80     fn span(&self) -> Span { self.meta().span }
  81 }
  82
  83 impl AttrMetaMethods for MetaItem {
  84     fn name(&self) -> InternedString {
  85         match self.node {
  86             MetaWord(ref n) => (*n).clone(),
  87             MetaNameValue(ref n, _) => (*n).clone(),
  88             MetaList(ref n, _) => (*n).clone(),
  89         }
  90     }
  91
  92     fn value_str(&self) -> Option<InternedString> {
  93         match self.node {
  94             MetaNameValue(_, ref v) => {
  95                 match v.node {
  96                     ast::LitStr(ref s, _) => Some((*s).clone()),
  97                     _ => None,
  98                 }
  99             },
 100             _ => None
 101         }
 102     }
 103
 104     fn meta_item_list<'a>(&'a self) -> Option<&'a [P<MetaItem>]> {
 105         match self.node {
 106             MetaList(_, ref l) => Some(&l[..]),
 107             _ => None
 108         }
 109     }
 110     fn span(&self) -> Span { self.span }
 111 }
 112
 113 // Annoying, but required to get test_cfg to work
 114 impl AttrMetaMethods for P<MetaItem> {
 115     fn name(&self) -> InternedString { (**self).name() }
 116     fn value_str(&self) -> Option<InternedString> { (**self).value_str() }
 117     fn meta_item_list<'a>(&'a self) -> Option<&'a [P<MetaItem>]> {
 118         (**self).meta_item_list()
 119     }
 120     fn span(&self) -> Span { (**self).span() }
 121 }
 122
 123
 124 pub trait AttributeMethods {
 125     fn meta<'a>(&'a self) -> &'a MetaItem;
 126     fn with_desugared_doc<T, F>(&self, f: F) -> T where
 127         F: FnOnce(&Attribute) -> T;
 128 }
 129
 130 impl AttributeMethods for Attribute {
 131     /// Extract the MetaItem from inside this Attribute.
 132     fn meta<'a>(&'a self) -> &'a MetaItem {
 133         &*self.node.value
 134     }
 135
 136     /// Convert self to a normal #[doc="foo"] comment, if it is a
 137     /// comment like `///` or `/** */`. (Returns self unchanged for
 138     /// non-sugared doc attributes.)
 139     fn with_desugared_doc<T, F>(&self, f: F) -> T where
 140         F: FnOnce(&Attribute) -> T,
 141     {
 142         if self.node.is_sugared_doc {
 143             let comment = self.value_str().unwrap();
 144             let meta = mk_name_value_item_str(
 145                 InternedString::new("doc"),
 146                 token::intern_and_get_ident(&strip_doc_comment_decoration(
 147                         &comment)));
 148             if self.node.style == ast::AttrOuter {
 149                 f(&mk_attr_outer(self.node.id, meta))
 150             } else {
 151                 f(&mk_attr_inner(self.node.id, meta))
 152             }
 153         } else {
 154             f(self)
 155         }
 156     }
 157 }
 158
 159 /* Constructors */
 160
 161 pub fn mk_name_value_item_str(name: InternedString, value: InternedString)
 162                               -> P<MetaItem> {
 163     let value_lit = dummy_spanned(ast::LitStr(value, ast::CookedStr));
 164     mk_name_value_item(name, value_lit)
 165 }
 166
 167 pub fn mk_name_value_item(name: InternedString, value: ast::Lit)
 168                           -> P<MetaItem> {
 169     P(dummy_spanned(MetaNameValue(name, value)))
 170 }
 171
 172 pub fn mk_list_item(name: InternedString, items: Vec<P<MetaItem>>) -> P<MetaItem> {
 173     P(dummy_spanned(MetaList(name, items)))
 174 }
 175
 176 pub fn mk_word_item(name: InternedString) -> P<MetaItem> {
 177     P(dummy_spanned(MetaWord(name)))
 178 }
 179
 180 thread_local! { static NEXT_ATTR_ID: Cell<usize> = Cell::new(0) }
 181
 182 pub fn mk_attr_id() -> AttrId {
 183     let id = NEXT_ATTR_ID.with(|slot| {
 184         let r = slot.get();
 185         slot.set(r + 1);
 186         r
 187     });
 188     AttrId(id)
 189 }
 190
 191 /// Returns an inner attribute with the given value.
 192 pub fn mk_attr_inner(id: AttrId, item: P<MetaItem>) -> Attribute {
 193     dummy_spanned(Attribute_ {
 194         id: id,
 195         style: ast::AttrInner,
 196         value: item,
 197         is_sugared_doc: false,
 198     })
 199 }
 200
 201 /// Returns an outer attribute with the given value.
 202 pub fn mk_attr_outer(id: AttrId, item: P<MetaItem>) -> Attribute {
 203     dummy_spanned(Attribute_ {
 204         id: id,
 205         style: ast::AttrOuter,
 206         value: item,
 207         is_sugared_doc: false,
 208     })
 209 }
 210
 211 pub fn mk_sugared_doc_attr(id: AttrId, text: InternedString, lo: BytePos,
 212                            hi: BytePos)
 213                            -> Attribute {
 214     let style = doc_comment_style(&text);
 215     let lit = spanned(lo, hi, ast::LitStr(text, ast::CookedStr));
 216     let attr = Attribute_ {
 217         id: id,
 218         style: style,
 219         value: P(spanned(lo, hi, MetaNameValue(InternedString::new("doc"),
 220                                                lit))),
 221         is_sugared_doc: true
 222     };
 223     spanned(lo, hi, attr)
 224 }
 225
 226 /* Searching */
 227 /// Check if `needle` occurs in `haystack` by a structural
 228 /// comparison. This is slightly subtle, and relies on ignoring the
 229 /// span included in the `==` comparison a plain MetaItem.
 230 pub fn contains(haystack: &[P<MetaItem>], needle: &MetaItem) -> bool {
 231     debug!("attr::contains (name={})", needle.name());
 232     haystack.iter().any(|item| {
 233         debug!("  testing: {}", item.name());
 234         item.node == needle.node
 235     })
 236 }
 237
 238 pub fn contains_name<AM: AttrMetaMethods>(metas: &[AM], name: &str) -> bool {
 239     debug!("attr::contains_name (name={})", name);
 240     metas.iter().any(|item| {
 241         debug!("  testing: {}", item.name());
 242         item.check_name(name)
 243     })
 244 }
 245
 246 pub fn first_attr_value_str_by_name(attrs: &[Attribute], name: &str)
 247                                  -> Option<InternedString> {
 248     attrs.iter()
 249         .find(|at| at.check_name(name))
 250         .and_then(|at| at.value_str())
 251 }
 252
 253 pub fn last_meta_item_value_str_by_name(items: &[P<MetaItem>], name: &str)
 254                                      -> Option<InternedString> {
 255     items.iter()
 256          .rev()
 257          .find(|mi| mi.check_name(name))
 258          .and_then(|i| i.value_str())
 259 }
 260
 261 /* Higher-level applications */
 262
 263 pub fn sort_meta_items(items: Vec<P<MetaItem>>) -> Vec<P<MetaItem>> {
 264     // This is sort of stupid here, but we need to sort by
 265     // human-readable strings.
 266     let mut v = items.into_iter()
 267         .map(|mi| (mi.name(), mi))
 268         .collect::<Vec<(InternedString, P<MetaItem>)>>();
 269
 270     v.sort_by(|&(ref a, _), &(ref b, _)| a.cmp(b));
 271
 272     // There doesn't seem to be a more optimal way to do this
 273     v.into_iter().map(|(_, m)| m.map(|Spanned {node, span}| {
 274         Spanned {
 275             node: match node {
 276                 MetaList(n, mis) => MetaList(n, sort_meta_items(mis)),
 277                 _ => node
 278             },
 279             span: span
 280         }
 281     })).collect()
 282 }
 283
 284 pub fn find_crate_name(attrs: &[Attribute]) -> Option<InternedString> {
 285     first_attr_value_str_by_name(attrs, "crate_name")
 286 }
 287
 288 /// Find the value of #[export_name=*] attribute and check its validity.
 289 pub fn find_export_name_attr(diag: &SpanHandler, attrs: &[Attribute]) -> Option<InternedString> {
 290     attrs.iter().fold(None, |ia,attr| {
 291         if attr.check_name("export_name") {
 292             if let s@Some(_) = attr.value_str() {
 293                 s
 294             } else {
 295                 diag.span_err(attr.span, "export_name attribute has invalid format");
 296                 diag.handler.help("use #[export_name=\"*\"]");
 297                 None
 298             }
 299         } else {
 300             ia
 301         }
 302     })
 303 }
 304
 305 #[derive(Copy, Clone, PartialEq)]
 306 pub enum InlineAttr {
 307     None,
 308     Hint,
 309     Always,
 310     Never,
 311 }
 312
 313 /// Determine what `#[inline]` attribute is present in `attrs`, if any.
 314 pub fn find_inline_attr(diagnostic: Option<&SpanHandler>, attrs: &[Attribute]) -> InlineAttr {
 315     // FIXME (#2809)---validate the usage of #[inline] and #[inline]
 316     attrs.iter().fold(InlineAttr::None, |ia,attr| {
 317         match attr.node.value.node {
 318             MetaWord(ref n) if *n == "inline" => {
 319                 mark_used(attr);
 320                 InlineAttr::Hint
 321             }
 322             MetaList(ref n, ref items) if *n == "inline" => {
 323                 mark_used(attr);
 324                 if items.len() != 1 {
 325                     diagnostic.map(|d|{ d.span_err(attr.span, "expected one argument"); });
 326                     InlineAttr::None
 327                 } else if contains_name(&items[..], "always") {
 328                     InlineAttr::Always
 329                 } else if contains_name(&items[..], "never") {
 330                     InlineAttr::Never
 331                 } else {
 332                     diagnostic.map(|d|{ d.span_err((*items[0]).span, "invalid argument"); });
 333                     InlineAttr::None
 334                 }
 335             }
 336             _ => ia
 337         }
 338     })
 339 }
 340
 341 /// True if `#[inline]` or `#[inline(always)]` is present in `attrs`.
 342 pub fn requests_inline(attrs: &[Attribute]) -> bool {
 343     match find_inline_attr(None, attrs) {
 344         InlineAttr::Hint | InlineAttr::Always => true,
 345         InlineAttr::None | InlineAttr::Never => false,
 346     }
 347 }
 348
 349 /// Tests if a cfg-pattern matches the cfg set
 350 pub fn cfg_matches(diagnostic: &SpanHandler, cfgs: &[P<MetaItem>], cfg: &ast::MetaItem) -> bool {
 351     match cfg.node {
 352         ast::MetaList(ref pred, ref mis) if &pred[..] == "any" =>
 353             mis.iter().any(|mi| cfg_matches(diagnostic, cfgs, &**mi)),
 354         ast::MetaList(ref pred, ref mis) if &pred[..] == "all" =>
 355             mis.iter().all(|mi| cfg_matches(diagnostic, cfgs, &**mi)),
 356         ast::MetaList(ref pred, ref mis) if &pred[..] == "not" => {
 357             if mis.len() != 1 {
 358                 diagnostic.span_err(cfg.span, "expected 1 cfg-pattern");
 359                 return false;
 360             }
 361             !cfg_matches(diagnostic, cfgs, &*mis[0])
 362         }
 363         ast::MetaList(ref pred, _) => {
 364             diagnostic.span_err(cfg.span, &format!("invalid predicate `{}`", pred));
 365             false
 366         },
 367         ast::MetaWord(_) | ast::MetaNameValue(..) => contains(cfgs, cfg),
 368     }
 369 }
 370
 371 /// Represents the #[deprecated] and friends attributes.
 372 #[derive(RustcEncodable, RustcDecodable, Clone, Debug, PartialEq, Eq, Hash)]
 373 pub struct Stability {
 374     pub level: StabilityLevel,
 375     pub feature: InternedString,
 376     pub since: Option<InternedString>,
 377     pub deprecated_since: Option<InternedString>,
 378     // The reason for the current stability level. If deprecated, the
 379     // reason for deprecation.
 380     pub reason: Option<InternedString>,
 381     // The relevant rust-lang issue
 382     pub issue: Option<u32>
 383 }
 384
 385 /// The available stability levels.
 386 #[derive(RustcEncodable, RustcDecodable, PartialEq, PartialOrd, Clone, Debug, Copy, Eq, Hash)]
 387 pub enum StabilityLevel {
 388     Unstable,
 389     Stable,
 390 }
 391
 392 impl fmt::Display for StabilityLevel {
 393     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
 394         fmt::Debug::fmt(self, f)
 395     }
 396 }
 397
 398 fn find_stability_generic<'a,
 399                               AM: AttrMetaMethods,
 400                               I: Iterator<Item=&'a AM>>
 401                              (diagnostic: &SpanHandler, attrs: I, item_sp: Span)
 402                              -> (Option<Stability>, Vec<&'a AM>) {
 403
 404     let mut stab: Option<Stability> = None;
 405     let mut deprecated: Option<(Option<InternedString>, Option<InternedString>)> = None;
 406     let mut used_attrs: Vec<&'a AM> = vec![];
 407
 408     'outer: for attr in attrs {
 409         let tag = attr.name();
 410         let tag = &tag[..];
 411         if tag != "deprecated" && tag != "unstable" && tag != "stable" {
 412             continue // not a stability level
 413         }
 414
 415         used_attrs.push(attr);
 416
 417         let (feature, since, reason, issue) = match attr.meta_item_list() {
 418             Some(metas) => {
 419                 let mut feature = None;
 420                 let mut since = None;
 421                 let mut reason = None;
 422                 let mut issue = None;
 423                 for meta in metas {
 424                     match &*meta.name() {
 425                         "feature" => {
 426                             match meta.value_str() {
 427                                 Some(v) => feature = Some(v),
 428                                 None => {
 429                                     diagnostic.span_err(meta.span, "incorrect meta item");
 430                                     continue 'outer;
 431                                 }
 432                             }
 433                         }
 434                         "since" => {
 435                             match meta.value_str() {
 436                                 Some(v) => since = Some(v),
 437                                 None => {
 438                                     diagnostic.span_err(meta.span, "incorrect meta item");
 439                                     continue 'outer;
 440                                 }
 441                             }
 442                         }
 443                         "reason" => {
 444                             match meta.value_str() {
 445                                 Some(v) => reason = Some(v),
 446                                 None => {
 447                                     diagnostic.span_err(meta.span, "incorrect meta item");
 448                                     continue 'outer;
 449                                 }
 450                             }
 451                         }
 452                         "issue" => {
 453                             match meta.value_str().and_then(|s| s.parse().ok()) {
 454                                 Some(v) => issue = Some(v),
 455                                 None => {
 456                                     diagnostic.span_err(meta.span, "incorrect meta item");
 457                                     continue 'outer;
 458                                 }
 459                             }
 460                         }
 461                         _ => {}
 462                     }
 463                 }
 464                 (feature, since, reason, issue)
 465             }
 466             None => {
 467                 diagnostic.span_err(attr.span(), "incorrect stability attribute type");
 468                 continue
 469             }
 470         };
 471
 472         // Deprecated tags don't require feature names
 473         if feature == None && tag != "deprecated" {
 474             diagnostic.span_err(attr.span(), "missing 'feature'");
 475         }
 476
 477         // Unstable tags don't require a version
 478         if since == None && tag != "unstable" {
 479             diagnostic.span_err(attr.span(), "missing 'since'");
 480         }
 481
 482         if tag == "unstable" || tag == "stable" {
 483             if stab.is_some() {
 484                 diagnostic.span_err(item_sp, "multiple stability levels");
 485             }
 486
 487             let level = match tag {
 488                 "unstable" => Unstable,
 489                 "stable" => Stable,
 490                 _ => unreachable!()
 491             };
 492
 493             stab = Some(Stability {
 494                 level: level,
 495                 feature: feature.unwrap_or(intern_and_get_ident("bogus")),
 496                 since: since,
 497                 deprecated_since: None,
 498                 reason: reason,
 499                 issue: issue,
 500             });
 501         } else { // "deprecated"
 502             if deprecated.is_some() {
 503                 diagnostic.span_err(item_sp, "multiple deprecated attributes");
 504             }
 505
 506             deprecated = Some((since, reason));
 507         }
 508     }
 509
 510     // Merge the deprecation info into the stability info
 511     if deprecated.is_some() {
 512         match stab {
 513             Some(ref mut s) => {
 514                 let (since, reason) = deprecated.unwrap();
 515                 s.deprecated_since = since;
 516                 s.reason = reason;
 517             }
 518             None => {
 519                 diagnostic.span_err(item_sp, "deprecated attribute must be paired with \
 520                                               either stable or unstable attribute");
 521             }
 522         }
 523     } else if stab.as_ref().map_or(false, |s| s.level == Unstable && s.issue.is_none()) {
 524         // non-deprecated unstable items need to point to issues.
 525         // FIXME: uncomment this error
 526         // diagnostic.span_err(item_sp,
 527         //                     "non-deprecated unstable items need to point \
 528         //                      to an issue with `issue = \"NNN\"`");
 529     }
 530
 531     (stab, used_attrs)
 532 }
 533
 534 /// Find the first stability attribute. `None` if none exists.
 535 pub fn find_stability(diagnostic: &SpanHandler, attrs: &[Attribute],
 536                       item_sp: Span) -> Option<Stability> {
 537     let (s, used) = find_stability_generic(diagnostic, attrs.iter(), item_sp);
 538     for used in used { mark_used(used) }
 539     return s;
 540 }
 541
 542 pub fn require_unique_names(diagnostic: &SpanHandler, metas: &[P<MetaItem>]) {
 543     let mut set = HashSet::new();
 544     for meta in metas {
 545         let name = meta.name();
 546
 547         if !set.insert(name.clone()) {
 548             panic!(diagnostic.span_fatal(meta.span,
 549                                   &format!("duplicate meta item `{}`", name)));
 550         }
 551     }
 552 }
 553
 554
 555 /// Parse #[repr(...)] forms.
 556 ///
 557 /// Valid repr contents: any of the primitive integral type names (see
 558 /// `int_type_of_word`, below) to specify enum discriminant type; `C`, to use
 559 /// the same discriminant size that the corresponding C enum would or C
 560 /// structure layout, and `packed` to remove padding.
 561 pub fn find_repr_attrs(diagnostic: &SpanHandler, attr: &Attribute) -> Vec<ReprAttr> {
 562     let mut acc = Vec::new();
 563     match attr.node.value.node {
 564         ast::MetaList(ref s, ref items) if *s == "repr" => {
 565             mark_used(attr);
 566             for item in items {
 567                 match item.node {
 568                     ast::MetaWord(ref word) => {
 569                         let hint = match &word[..] {
 570                             // Can't use "extern" because it's not a lexical identifier.
 571                             "C" => Some(ReprExtern),
 572                             "packed" => Some(ReprPacked),
 573                             _ => match int_type_of_word(&word) {
 574                                 Some(ity) => Some(ReprInt(item.span, ity)),
 575                                 None => {
 576                                     // Not a word we recognize
 577                                     diagnostic.span_err(item.span,
 578                                                         "unrecognized representation hint");
 579                                     None
 580                                 }
 581                             }
 582                         };
 583
 584                         match hint {
 585                             Some(h) => acc.push(h),
 586                             None => { }
 587                         }
 588                     }
 589                     // Not a word:
 590                     _ => diagnostic.span_err(item.span, "unrecognized enum representation hint")
 591                 }
 592             }
 593         }
 594         // Not a "repr" hint: ignore.
 595         _ => { }
 596     }
 597     acc
 598 }
 599
 600 fn int_type_of_word(s: &str) -> Option<IntType> {
 601     match s {
 602         "i8" => Some(SignedInt(ast::TyI8)),
 603         "u8" => Some(UnsignedInt(ast::TyU8)),
 604         "i16" => Some(SignedInt(ast::TyI16)),
 605         "u16" => Some(UnsignedInt(ast::TyU16)),
 606         "i32" => Some(SignedInt(ast::TyI32)),
 607         "u32" => Some(UnsignedInt(ast::TyU32)),
 608         "i64" => Some(SignedInt(ast::TyI64)),
 609         "u64" => Some(UnsignedInt(ast::TyU64)),
 610         "isize" => Some(SignedInt(ast::TyIs)),
 611         "usize" => Some(UnsignedInt(ast::TyUs)),
 612         _ => None
 613     }
 614 }
 615
 616 #[derive(PartialEq, Debug, RustcEncodable, RustcDecodable, Copy, Clone)]
 617 pub enum ReprAttr {
 618     ReprAny,
 619     ReprInt(Span, IntType),
 620     ReprExtern,
 621     ReprPacked,
 622 }
 623
 624 impl ReprAttr {
 625     pub fn is_ffi_safe(&self) -> bool {
 626         match *self {
 627             ReprAny => false,
 628             ReprInt(_sp, ity) => ity.is_ffi_safe(),
 629             ReprExtern => true,
 630             ReprPacked => false
 631         }
 632     }
 633 }
 634
 635 #[derive(Eq, Hash, PartialEq, Debug, RustcEncodable, RustcDecodable, Copy, Clone)]
 636 pub enum IntType {
 637     SignedInt(ast::IntTy),
 638     UnsignedInt(ast::UintTy)
 639 }
 640
 641 impl IntType {
 642     #[inline]
 643     pub fn is_signed(self) -> bool {
 644         match self {
 645             SignedInt(..) => true,
 646             UnsignedInt(..) => false
 647         }
 648     }
 649     fn is_ffi_safe(self) -> bool {
 650         match self {
 651             SignedInt(ast::TyI8) | UnsignedInt(ast::TyU8) |
 652             SignedInt(ast::TyI16) | UnsignedInt(ast::TyU16) |
 653             SignedInt(ast::TyI32) | UnsignedInt(ast::TyU32) |
 654             SignedInt(ast::TyI64) | UnsignedInt(ast::TyU64) => true,
 655             SignedInt(ast::TyIs) | UnsignedInt(ast::TyUs) => false
 656         }
 657     }
 658 }