clippy_lints/src/replace_consts.rs

   1 use crate::utils::sym;
   2 use crate::utils::{match_def_path, span_lint_and_sugg};
   3 use if_chain::if_chain;
   4 use lazy_static::lazy_static;
   5 use rustc::hir;
   6 use rustc::hir::def::{DefKind, Res};
   7 use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
   8 use rustc::{declare_lint_pass, declare_tool_lint};
   9 use rustc_errors::Applicability;
  10 use syntax::symbol::Symbol;
  11
  12 declare_clippy_lint! {
  13     /// **What it does:** Checks for usage of `ATOMIC_X_INIT`, `ONCE_INIT`, and
  14     /// `uX/iX::MIN/MAX`.
  15     ///
  16     /// **Why is this bad?** `const fn`s exist
  17     ///
  18     /// **Known problems:** None.
  19     ///
  20     /// **Example:**
  21     /// ```rust
  22     /// static FOO: AtomicIsize = ATOMIC_ISIZE_INIT;
  23     /// ```
  24     ///
  25     /// Could be written:
  26     ///
  27     /// ```rust
  28     /// static FOO: AtomicIsize = AtomicIsize::new(0);
  29     /// ```
  30     pub REPLACE_CONSTS,
  31     pedantic,
  32     "Lint usages of standard library `const`s that could be replaced by `const fn`s"
  33 }
  34
  35 declare_lint_pass!(ReplaceConsts => [REPLACE_CONSTS]);
  36
  37 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for ReplaceConsts {
  38     fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx hir::Expr) {
  39         if_chain! {
  40             if let hir::ExprKind::Path(ref qp) = expr.node;
  41             if let Res::Def(DefKind::Const, def_id) = cx.tables.qpath_res(qp, expr.hir_id);
  42             then {
  43                 for (const_path, repl_snip) in REPLACEMENTS.iter() {
  44                     if match_def_path(cx, def_id, const_path) {
  45                         span_lint_and_sugg(
  46                             cx,
  47                             REPLACE_CONSTS,
  48                             expr.span,
  49                             &format!("using `{}`", const_path.last().expect("empty path")),
  50                             "try this",
  51                             repl_snip.to_string(),
  52                             Applicability::MachineApplicable,
  53                         );
  54                         return;
  55                     }
  56                 }
  57             }
  58         }
  59     }
  60 }
  61
  62 lazy_static! {
  63 static ref REPLACEMENTS: [([Symbol; 3], &'static str); 25] = [
  64     // Once
  65     ([*sym::core, *sym::sync, *sym::ONCE_INIT], "Once::new()"),
  66     // Min
  67     ([*sym::core, *sym::isize, *sym::MIN], "isize::min_value()"),
  68     ([*sym::core, *sym::i8, *sym::MIN], "i8::min_value()"),
  69     ([*sym::core, *sym::i16, *sym::MIN], "i16::min_value()"),
  70     ([*sym::core, *sym::i32, *sym::MIN], "i32::min_value()"),
  71     ([*sym::core, *sym::i64, *sym::MIN], "i64::min_value()"),
  72     ([*sym::core, *sym::i128, *sym::MIN], "i128::min_value()"),
  73     ([*sym::core, *sym::usize, *sym::MIN], "usize::min_value()"),
  74     ([*sym::core, *sym::u8, *sym::MIN], "u8::min_value()"),
  75     ([*sym::core, *sym::u16, *sym::MIN], "u16::min_value()"),
  76     ([*sym::core, *sym::u32, *sym::MIN], "u32::min_value()"),
  77     ([*sym::core, *sym::u64, *sym::MIN], "u64::min_value()"),
  78     ([*sym::core, *sym::u128, *sym::MIN], "u128::min_value()"),
  79     // Max
  80     ([*sym::core, *sym::isize, *sym::MAX], "isize::max_value()"),
  81     ([*sym::core, *sym::i8, *sym::MAX], "i8::max_value()"),
  82     ([*sym::core, *sym::i16, *sym::MAX], "i16::max_value()"),
  83     ([*sym::core, *sym::i32, *sym::MAX], "i32::max_value()"),
  84     ([*sym::core, *sym::i64, *sym::MAX], "i64::max_value()"),
  85     ([*sym::core, *sym::i128, *sym::MAX], "i128::max_value()"),
  86     ([*sym::core, *sym::usize, *sym::MAX], "usize::max_value()"),
  87     ([*sym::core, *sym::u8, *sym::MAX], "u8::max_value()"),
  88     ([*sym::core, *sym::u16, *sym::MAX], "u16::max_value()"),
  89     ([*sym::core, *sym::u32, *sym::MAX], "u32::max_value()"),
  90     ([*sym::core, *sym::u64, *sym::MAX], "u64::max_value()"),
  91     ([*sym::core, *sym::u128, *sym::MAX], "u128::max_value()"),
  92 ];
  93 }