src/librustc/lint/mod.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 //! Lints, aka compiler warnings.
  12 //!
  13 //! A 'lint' check is a kind of miscellaneous constraint that a user _might_
  14 //! want to enforce, but might reasonably want to permit as well, on a
  15 //! module-by-module basis. They contrast with static constraints enforced by
  16 //! other phases of the compiler, which are generally required to hold in order
  17 //! to compile the program at all.
  18 //!
  19 //! Most lints can be written as `LintPass` instances. These run just before
  20 //! translation to LLVM bytecode. The `LintPass`es built into rustc are defined
  21 //! within `builtin.rs`, which has further comments on how to add such a lint.
  22 //! rustc can also load user-defined lint plugins via the plugin mechanism.
  23 //!
  24 //! Some of rustc's lints are defined elsewhere in the compiler and work by
  25 //! calling `add_lint()` on the overall `Session` object. This works when
  26 //! it happens before the main lint pass, which emits the lints stored by
  27 //! `add_lint()`. To emit lints after the main lint pass (from trans, for
  28 //! example) requires more effort. See `emit_lint` and `GatherNodeLevels`
  29 //! in `context.rs`.
  30
  31 pub use self::Level::*;
  32 pub use self::LintSource::*;
  33
  34 use std::hash;
  35 use std::ascii::AsciiExt;
  36 use syntax::codemap::Span;
  37 use rustc_front::visit::FnKind;
  38 use syntax::ast;
  39 use rustc_front::hir;
  40
  41 pub use lint::context::{Context, LintStore, raw_emit_lint, check_crate, gather_attrs,
  42                         gather_attrs_from_hir, GatherNodeLevels};
  43
  44 /// Specification of a single lint.
  45 #[derive(Copy, Clone, Debug)]
  46 pub struct Lint {
  47     /// A string identifier for the lint.
  48     ///
  49     /// This identifies the lint in attributes and in command-line arguments.
  50     /// In those contexts it is always lowercase, but this field is compared
  51     /// in a way which is case-insensitive for ASCII characters. This allows
  52     /// `declare_lint!()` invocations to follow the convention of upper-case
  53     /// statics without repeating the name.
  54     ///
  55     /// The name is written with underscores, e.g. "unused_imports".
  56     /// On the command line, underscores become dashes.
  57     pub name: &'static str,
  58
  59     /// Default level for the lint.
  60     pub default_level: Level,
  61
  62     /// Description of the lint or the issue it detects.
  63     ///
  64     /// e.g. "imports that are never used"
  65     pub desc: &'static str,
  66 }
  67
  68 impl Lint {
  69     /// Get the lint's name, with ASCII letters converted to lowercase.
  70     pub fn name_lower(&self) -> String {
  71         self.name.to_ascii_lowercase()
  72     }
  73 }
  74
  75 /// Build a `Lint` initializer.
  76 #[macro_export]
  77 macro_rules! lint_initializer {
  78     ($name:ident, $level:ident, $desc:expr) => (
  79         ::rustc::lint::Lint {
  80             name: stringify!($name),
  81             default_level: ::rustc::lint::$level,
  82             desc: $desc,
  83         }
  84     )
  85 }
  86
  87 /// Declare a static item of type `&'static Lint`.
  88 #[macro_export]
  89 macro_rules! declare_lint {
  90     // FIXME(#14660): deduplicate
  91     (pub $name:ident, $level:ident, $desc:expr) => (
  92         pub static $name: &'static ::rustc::lint::Lint
  93             = &lint_initializer!($name, $level, $desc);
  94     );
  95     ($name:ident, $level:ident, $desc:expr) => (
  96         static $name: &'static ::rustc::lint::Lint
  97             = &lint_initializer!($name, $level, $desc);
  98     );
  99 }
 100
 101 /// Declare a static `LintArray` and return it as an expression.
 102 #[macro_export]
 103 macro_rules! lint_array { ($( $lint:expr ),*) => (
 104     {
 105         static ARRAY: LintArray = &[ $( &$lint ),* ];
 106         ARRAY
 107     }
 108 ) }
 109
 110 pub type LintArray = &'static [&'static &'static Lint];
 111
 112 /// Trait for types providing lint checks.
 113 ///
 114 /// Each `check` method checks a single syntax node, and should not
 115 /// invoke methods recursively (unlike `Visitor`). By default they
 116 /// do nothing.
 117 //
 118 // FIXME: eliminate the duplication with `Visitor`. But this also
 119 // contains a few lint-specific methods with no equivalent in `Visitor`.
 120 pub trait LintPass {
 121     /// Get descriptions of the lints this `LintPass` object can emit.
 122     ///
 123     /// NB: there is no enforcement that the object only emits lints it registered.
 124     /// And some `rustc` internal `LintPass`es register lints to be emitted by other
 125     /// parts of the compiler. If you want enforced access restrictions for your
 126     /// `Lint`, make it a private `static` item in its own module.
 127     fn get_lints(&self) -> LintArray;
 128
 129     fn check_crate(&mut self, _: &Context, _: &hir::Crate) { }
 130     fn check_ident(&mut self, _: &Context, _: Span, _: ast::Ident) { }
 131     fn check_mod(&mut self, _: &Context, _: &hir::Mod, _: Span, _: ast::NodeId) { }
 132     fn check_foreign_item(&mut self, _: &Context, _: &hir::ForeignItem) { }
 133     fn check_item(&mut self, _: &Context, _: &hir::Item) { }
 134     fn check_local(&mut self, _: &Context, _: &hir::Local) { }
 135     fn check_block(&mut self, _: &Context, _: &hir::Block) { }
 136     fn check_stmt(&mut self, _: &Context, _: &hir::Stmt) { }
 137     fn check_arm(&mut self, _: &Context, _: &hir::Arm) { }
 138     fn check_pat(&mut self, _: &Context, _: &hir::Pat) { }
 139     fn check_decl(&mut self, _: &Context, _: &hir::Decl) { }
 140     fn check_expr(&mut self, _: &Context, _: &hir::Expr) { }
 141     fn check_expr_post(&mut self, _: &Context, _: &hir::Expr) { }
 142     fn check_ty(&mut self, _: &Context, _: &hir::Ty) { }
 143     fn check_generics(&mut self, _: &Context, _: &hir::Generics) { }
 144     fn check_fn(&mut self, _: &Context,
 145         _: FnKind, _: &hir::FnDecl, _: &hir::Block, _: Span, _: ast::NodeId) { }
 146     fn check_trait_item(&mut self, _: &Context, _: &hir::TraitItem) { }
 147     fn check_impl_item(&mut self, _: &Context, _: &hir::ImplItem) { }
 148     fn check_struct_def(&mut self, _: &Context,
 149         _: &hir::StructDef, _: ast::Ident, _: &hir::Generics, _: ast::NodeId) { }
 150     fn check_struct_def_post(&mut self, _: &Context,
 151         _: &hir::StructDef, _: ast::Ident, _: &hir::Generics, _: ast::NodeId) { }
 152     fn check_struct_field(&mut self, _: &Context, _: &hir::StructField) { }
 153     fn check_variant(&mut self, _: &Context, _: &hir::Variant, _: &hir::Generics) { }
 154     fn check_variant_post(&mut self, _: &Context, _: &hir::Variant, _: &hir::Generics) { }
 155     fn check_opt_lifetime_ref(&mut self, _: &Context, _: Span, _: &Option<hir::Lifetime>) { }
 156     fn check_lifetime_ref(&mut self, _: &Context, _: &hir::Lifetime) { }
 157     fn check_lifetime_def(&mut self, _: &Context, _: &hir::LifetimeDef) { }
 158     fn check_explicit_self(&mut self, _: &Context, _: &hir::ExplicitSelf) { }
 159     fn check_mac(&mut self, _: &Context, _: &ast::Mac) { }
 160     fn check_path(&mut self, _: &Context, _: &hir::Path, _: ast::NodeId) { }
 161     fn check_attribute(&mut self, _: &Context, _: &hir::Attribute) { }
 162
 163     /// Called when entering a syntax node that can have lint attributes such
 164     /// as `#[allow(...)]`. Called with *all* the attributes of that node.
 165     fn enter_lint_attrs(&mut self, _: &Context, _: &[hir::Attribute]) { }
 166
 167     /// Counterpart to `enter_lint_attrs`.
 168     fn exit_lint_attrs(&mut self, _: &Context, _: &[hir::Attribute]) { }
 169 }
 170
 171 /// A lint pass boxed up as a trait object.
 172 pub type LintPassObject = Box<LintPass + 'static>;
 173
 174 /// Identifies a lint known to the compiler.
 175 #[derive(Clone, Copy)]
 176 pub struct LintId {
 177     // Identity is based on pointer equality of this field.
 178     lint: &'static Lint,
 179 }
 180
 181 impl PartialEq for LintId {
 182     fn eq(&self, other: &LintId) -> bool {
 183         (self.lint as *const Lint) == (other.lint as *const Lint)
 184     }
 185 }
 186
 187 impl Eq for LintId { }
 188
 189 impl hash::Hash for LintId {
 190     fn hash<H: hash::Hasher>(&self, state: &mut H) {
 191         let ptr = self.lint as *const Lint;
 192         ptr.hash(state);
 193     }
 194 }
 195
 196 impl LintId {
 197     /// Get the `LintId` for a `Lint`.
 198     pub fn of(lint: &'static Lint) -> LintId {
 199         LintId {
 200             lint: lint,
 201         }
 202     }
 203
 204     /// Get the name of the lint.
 205     pub fn as_str(&self) -> String {
 206         self.lint.name_lower()
 207     }
 208 }
 209
 210 /// Setting for how to handle a lint.
 211 #[derive(Clone, Copy, PartialEq, PartialOrd, Eq, Ord, Debug)]
 212 pub enum Level {
 213     Allow, Warn, Deny, Forbid
 214 }
 215
 216 impl Level {
 217     /// Convert a level to a lower-case string.
 218     pub fn as_str(self) -> &'static str {
 219         match self {
 220             Allow => "allow",
 221             Warn => "warn",
 222             Deny => "deny",
 223             Forbid => "forbid",
 224         }
 225     }
 226
 227     /// Convert a lower-case string to a level.
 228     pub fn from_str(x: &str) -> Option<Level> {
 229         match x {
 230             "allow" => Some(Allow),
 231             "warn" => Some(Warn),
 232             "deny" => Some(Deny),
 233             "forbid" => Some(Forbid),
 234             _ => None,
 235         }
 236     }
 237 }
 238
 239 /// How a lint level was set.
 240 #[derive(Clone, Copy, PartialEq, Eq)]
 241 pub enum LintSource {
 242     /// Lint is at the default level as declared
 243     /// in rustc or a plugin.
 244     Default,
 245
 246     /// Lint level was set by an attribute.
 247     Node(Span),
 248
 249     /// Lint level was set by a command-line flag.
 250     CommandLine,
 251 }
 252
 253 pub type LevelSource = (Level, LintSource);
 254
 255 pub mod builtin;
 256
 257 mod context;