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::intravisit::FnKind;
  38 use syntax::visit as ast_visit;
  39 use syntax::ast;
  40 use rustc_front::hir;
  41
  42 pub use lint::context::{LateContext, EarlyContext, LintContext, LintStore,
  43                         raw_emit_lint, check_crate, check_ast_crate, gather_attrs,
  44                         GatherNodeLevels};
  45
  46 /// Specification of a single lint.
  47 #[derive(Copy, Clone, Debug)]
  48 pub struct Lint {
  49     /// A string identifier for the lint.
  50     ///
  51     /// This identifies the lint in attributes and in command-line arguments.
  52     /// In those contexts it is always lowercase, but this field is compared
  53     /// in a way which is case-insensitive for ASCII characters. This allows
  54     /// `declare_lint!()` invocations to follow the convention of upper-case
  55     /// statics without repeating the name.
  56     ///
  57     /// The name is written with underscores, e.g. "unused_imports".
  58     /// On the command line, underscores become dashes.
  59     pub name: &'static str,
  60
  61     /// Default level for the lint.
  62     pub default_level: Level,
  63
  64     /// Description of the lint or the issue it detects.
  65     ///
  66     /// e.g. "imports that are never used"
  67     pub desc: &'static str,
  68 }
  69
  70 impl Lint {
  71     /// Get the lint's name, with ASCII letters converted to lowercase.
  72     pub fn name_lower(&self) -> String {
  73         self.name.to_ascii_lowercase()
  74     }
  75 }
  76
  77 /// Build a `Lint` initializer.
  78 #[macro_export]
  79 macro_rules! lint_initializer {
  80     ($name:ident, $level:ident, $desc:expr) => (
  81         ::rustc::lint::Lint {
  82             name: stringify!($name),
  83             default_level: ::rustc::lint::$level,
  84             desc: $desc,
  85         }
  86     )
  87 }
  88
  89 /// Declare a static item of type `&'static Lint`.
  90 #[macro_export]
  91 macro_rules! declare_lint {
  92     (pub $name:ident, $level:ident, $desc:expr) => (
  93         pub static $name: &'static ::rustc::lint::Lint
  94             = &lint_initializer!($name, $level, $desc);
  95     );
  96     ($name:ident, $level:ident, $desc:expr) => (
  97         static $name: &'static ::rustc::lint::Lint
  98             = &lint_initializer!($name, $level, $desc);
  99     );
 100 }
 101
 102 /// Declare a static `LintArray` and return it as an expression.
 103 #[macro_export]
 104 macro_rules! lint_array { ($( $lint:expr ),*) => (
 105     {
 106         static ARRAY: LintArray = &[ $( &$lint ),* ];
 107         ARRAY
 108     }
 109 ) }
 110
 111 pub type LintArray = &'static [&'static &'static Lint];
 112
 113 pub trait LintPass {
 114     /// Get descriptions of the lints this `LintPass` object can emit.
 115     ///
 116     /// NB: there is no enforcement that the object only emits lints it registered.
 117     /// And some `rustc` internal `LintPass`es register lints to be emitted by other
 118     /// parts of the compiler. If you want enforced access restrictions for your
 119     /// `Lint`, make it a private `static` item in its own module.
 120     fn get_lints(&self) -> LintArray;
 121 }
 122
 123
 124 /// Trait for types providing lint checks.
 125 ///
 126 /// Each `check` method checks a single syntax node, and should not
 127 /// invoke methods recursively (unlike `Visitor`). By default they
 128 /// do nothing.
 129 //
 130 // FIXME: eliminate the duplication with `Visitor`. But this also
 131 // contains a few lint-specific methods with no equivalent in `Visitor`.
 132 pub trait LateLintPass: LintPass {
 133     fn check_name(&mut self, _: &LateContext, _: Span, _: ast::Name) { }
 134     fn check_crate(&mut self, _: &LateContext, _: &hir::Crate) { }
 135     fn check_mod(&mut self, _: &LateContext, _: &hir::Mod, _: Span, _: ast::NodeId) { }
 136     fn check_foreign_item(&mut self, _: &LateContext, _: &hir::ForeignItem) { }
 137     fn check_item(&mut self, _: &LateContext, _: &hir::Item) { }
 138     fn check_local(&mut self, _: &LateContext, _: &hir::Local) { }
 139     fn check_block(&mut self, _: &LateContext, _: &hir::Block) { }
 140     fn check_stmt(&mut self, _: &LateContext, _: &hir::Stmt) { }
 141     fn check_arm(&mut self, _: &LateContext, _: &hir::Arm) { }
 142     fn check_pat(&mut self, _: &LateContext, _: &hir::Pat) { }
 143     fn check_decl(&mut self, _: &LateContext, _: &hir::Decl) { }
 144     fn check_expr(&mut self, _: &LateContext, _: &hir::Expr) { }
 145     fn check_expr_post(&mut self, _: &LateContext, _: &hir::Expr) { }
 146     fn check_ty(&mut self, _: &LateContext, _: &hir::Ty) { }
 147     fn check_generics(&mut self, _: &LateContext, _: &hir::Generics) { }
 148     fn check_fn(&mut self, _: &LateContext,
 149         _: FnKind, _: &hir::FnDecl, _: &hir::Block, _: Span, _: ast::NodeId) { }
 150     fn check_trait_item(&mut self, _: &LateContext, _: &hir::TraitItem) { }
 151     fn check_impl_item(&mut self, _: &LateContext, _: &hir::ImplItem) { }
 152     fn check_struct_def(&mut self, _: &LateContext,
 153         _: &hir::VariantData, _: ast::Name, _: &hir::Generics, _: ast::NodeId) { }
 154     fn check_struct_def_post(&mut self, _: &LateContext,
 155         _: &hir::VariantData, _: ast::Name, _: &hir::Generics, _: ast::NodeId) { }
 156     fn check_struct_field(&mut self, _: &LateContext, _: &hir::StructField) { }
 157     fn check_variant(&mut self, _: &LateContext, _: &hir::Variant, _: &hir::Generics) { }
 158     fn check_variant_post(&mut self, _: &LateContext, _: &hir::Variant, _: &hir::Generics) { }
 159     fn check_lifetime(&mut self, _: &LateContext, _: &hir::Lifetime) { }
 160     fn check_lifetime_def(&mut self, _: &LateContext, _: &hir::LifetimeDef) { }
 161     fn check_explicit_self(&mut self, _: &LateContext, _: &hir::ExplicitSelf) { }
 162     fn check_path(&mut self, _: &LateContext, _: &hir::Path, _: ast::NodeId) { }
 163     fn check_path_list_item(&mut self, _: &LateContext, _: &hir::PathListItem) { }
 164     fn check_attribute(&mut self, _: &LateContext, _: &ast::Attribute) { }
 165
 166     /// Called when entering a syntax node that can have lint attributes such
 167     /// as `#[allow(...)]`. Called with *all* the attributes of that node.
 168     fn enter_lint_attrs(&mut self, _: &LateContext, _: &[ast::Attribute]) { }
 169
 170     /// Counterpart to `enter_lint_attrs`.
 171     fn exit_lint_attrs(&mut self, _: &LateContext, _: &[ast::Attribute]) { }
 172 }
 173
 174 pub trait EarlyLintPass: LintPass {
 175     fn check_ident(&mut self, _: &EarlyContext, _: Span, _: ast::Ident) { }
 176     fn check_crate(&mut self, _: &EarlyContext, _: &ast::Crate) { }
 177     fn check_mod(&mut self, _: &EarlyContext, _: &ast::Mod, _: Span, _: ast::NodeId) { }
 178     fn check_foreign_item(&mut self, _: &EarlyContext, _: &ast::ForeignItem) { }
 179     fn check_item(&mut self, _: &EarlyContext, _: &ast::Item) { }
 180     fn check_local(&mut self, _: &EarlyContext, _: &ast::Local) { }
 181     fn check_block(&mut self, _: &EarlyContext, _: &ast::Block) { }
 182     fn check_stmt(&mut self, _: &EarlyContext, _: &ast::Stmt) { }
 183     fn check_arm(&mut self, _: &EarlyContext, _: &ast::Arm) { }
 184     fn check_pat(&mut self, _: &EarlyContext, _: &ast::Pat) { }
 185     fn check_decl(&mut self, _: &EarlyContext, _: &ast::Decl) { }
 186     fn check_expr(&mut self, _: &EarlyContext, _: &ast::Expr) { }
 187     fn check_expr_post(&mut self, _: &EarlyContext, _: &ast::Expr) { }
 188     fn check_ty(&mut self, _: &EarlyContext, _: &ast::Ty) { }
 189     fn check_generics(&mut self, _: &EarlyContext, _: &ast::Generics) { }
 190     fn check_fn(&mut self, _: &EarlyContext,
 191         _: ast_visit::FnKind, _: &ast::FnDecl, _: &ast::Block, _: Span, _: ast::NodeId) { }
 192     fn check_trait_item(&mut self, _: &EarlyContext, _: &ast::TraitItem) { }
 193     fn check_impl_item(&mut self, _: &EarlyContext, _: &ast::ImplItem) { }
 194     fn check_struct_def(&mut self, _: &EarlyContext,
 195         _: &ast::VariantData, _: ast::Ident, _: &ast::Generics, _: ast::NodeId) { }
 196     fn check_struct_def_post(&mut self, _: &EarlyContext,
 197         _: &ast::VariantData, _: ast::Ident, _: &ast::Generics, _: ast::NodeId) { }
 198     fn check_struct_field(&mut self, _: &EarlyContext, _: &ast::StructField) { }
 199     fn check_variant(&mut self, _: &EarlyContext, _: &ast::Variant, _: &ast::Generics) { }
 200     fn check_variant_post(&mut self, _: &EarlyContext, _: &ast::Variant, _: &ast::Generics) { }
 201     fn check_lifetime(&mut self, _: &EarlyContext, _: &ast::Lifetime) { }
 202     fn check_lifetime_def(&mut self, _: &EarlyContext, _: &ast::LifetimeDef) { }
 203     fn check_explicit_self(&mut self, _: &EarlyContext, _: &ast::ExplicitSelf) { }
 204     fn check_path(&mut self, _: &EarlyContext, _: &ast::Path, _: ast::NodeId) { }
 205     fn check_path_list_item(&mut self, _: &EarlyContext, _: &ast::PathListItem) { }
 206     fn check_attribute(&mut self, _: &EarlyContext, _: &ast::Attribute) { }
 207
 208     /// Called when entering a syntax node that can have lint attributes such
 209     /// as `#[allow(...)]`. Called with *all* the attributes of that node.
 210     fn enter_lint_attrs(&mut self, _: &EarlyContext, _: &[ast::Attribute]) { }
 211
 212     /// Counterpart to `enter_lint_attrs`.
 213     fn exit_lint_attrs(&mut self, _: &EarlyContext, _: &[ast::Attribute]) { }
 214 }
 215
 216 /// A lint pass boxed up as a trait object.
 217 pub type EarlyLintPassObject = Box<EarlyLintPass + 'static>;
 218 pub type LateLintPassObject = Box<LateLintPass + 'static>;
 219
 220 /// Identifies a lint known to the compiler.
 221 #[derive(Clone, Copy, Debug)]
 222 pub struct LintId {
 223     // Identity is based on pointer equality of this field.
 224     lint: &'static Lint,
 225 }
 226
 227 impl PartialEq for LintId {
 228     fn eq(&self, other: &LintId) -> bool {
 229         (self.lint as *const Lint) == (other.lint as *const Lint)
 230     }
 231 }
 232
 233 impl Eq for LintId { }
 234
 235 impl hash::Hash for LintId {
 236     fn hash<H: hash::Hasher>(&self, state: &mut H) {
 237         let ptr = self.lint as *const Lint;
 238         ptr.hash(state);
 239     }
 240 }
 241
 242 impl LintId {
 243     /// Get the `LintId` for a `Lint`.
 244     pub fn of(lint: &'static Lint) -> LintId {
 245         LintId {
 246             lint: lint,
 247         }
 248     }
 249
 250     /// Get the name of the lint.
 251     pub fn as_str(&self) -> String {
 252         self.lint.name_lower()
 253     }
 254 }
 255
 256 /// Setting for how to handle a lint.
 257 #[derive(Clone, Copy, PartialEq, PartialOrd, Eq, Ord, Debug)]
 258 pub enum Level {
 259     Allow, Warn, Deny, Forbid
 260 }
 261
 262 impl Level {
 263     /// Convert a level to a lower-case string.
 264     pub fn as_str(self) -> &'static str {
 265         match self {
 266             Allow => "allow",
 267             Warn => "warn",
 268             Deny => "deny",
 269             Forbid => "forbid",
 270         }
 271     }
 272
 273     /// Convert a lower-case string to a level.
 274     pub fn from_str(x: &str) -> Option<Level> {
 275         match x {
 276             "allow" => Some(Allow),
 277             "warn" => Some(Warn),
 278             "deny" => Some(Deny),
 279             "forbid" => Some(Forbid),
 280             _ => None,
 281         }
 282     }
 283 }
 284
 285 /// How a lint level was set.
 286 #[derive(Clone, Copy, PartialEq, Eq)]
 287 pub enum LintSource {
 288     /// Lint is at the default level as declared
 289     /// in rustc or a plugin.
 290     Default,
 291
 292     /// Lint level was set by an attribute.
 293     Node(Span),
 294
 295     /// Lint level was set by a command-line flag.
 296     CommandLine,
 297 }
 298
 299 pub type LevelSource = (Level, LintSource);
 300
 301 pub mod builtin;
 302
 303 mod context;