clippy_lints/src/replace_consts.rs

   1 use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
   2 use rustc::{declare_lint, lint_array};
   3 use if_chain::if_chain;
   4 use rustc::hir;
   5 use rustc::hir::def::Def;
   6 use crate::utils::{match_def_path, span_lint_and_sugg};
   7
   8 /// **What it does:** Checks for usage of `ATOMIC_X_INIT`, `ONCE_INIT`, and
   9 /// `uX/iX::MIN/MAX`.
  10 ///
  11 /// **Why is this bad?** `const fn`s exist
  12 ///
  13 /// **Known problems:** None.
  14 ///
  15 /// **Example:**
  16 /// ```rust
  17 /// static FOO: AtomicIsize = ATOMIC_ISIZE_INIT;
  18 /// ```
  19 ///
  20 /// Could be written:
  21 ///
  22 /// ```rust
  23 /// static FOO: AtomicIsize = AtomicIsize::new(0);
  24 /// ```
  25 declare_clippy_lint! {
  26     pub REPLACE_CONSTS,
  27     pedantic,
  28     "Lint usages of standard library `const`s that could be replaced by `const fn`s"
  29 }
  30
  31 pub struct ReplaceConsts;
  32
  33 impl LintPass for ReplaceConsts {
  34     fn get_lints(&self) -> LintArray {
  35         lint_array!(REPLACE_CONSTS)
  36     }
  37 }
  38
  39 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for ReplaceConsts {
  40     fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx hir::Expr) {
  41         if_chain! {
  42             if let hir::ExprKind::Path(ref qp) = expr.node;
  43             if let Def::Const(def_id) = cx.tables.qpath_def(qp, expr.hir_id);
  44             then {
  45                 for &(const_path, repl_snip) in REPLACEMENTS {
  46                     if match_def_path(cx.tcx, def_id, const_path) {
  47                         span_lint_and_sugg(
  48                             cx,
  49                             REPLACE_CONSTS,
  50                             expr.span,
  51                             &format!("using `{}`", const_path.last().expect("empty path")),
  52                             "try this",
  53                             repl_snip.to_string(),
  54                         );
  55                         return;
  56                     }
  57                 }
  58             }
  59         }
  60     }
  61 }
  62
  63 const REPLACEMENTS: &[(&[&str], &str)] = &[
  64     // Once
  65     (&["core", "sync",  "ONCE_INIT"], "Once::new()"),
  66     // Atomic
  67     (&["core", "sync", "atomic", "ATOMIC_BOOL_INIT"],  "AtomicBool::new(false)"),
  68     (&["core", "sync", "atomic", "ATOMIC_ISIZE_INIT"], "AtomicIsize::new(0)"),
  69     (&["core", "sync", "atomic", "ATOMIC_I8_INIT"],    "AtomicI8::new(0)"),
  70     (&["core", "sync", "atomic", "ATOMIC_I16_INIT"],   "AtomicI16::new(0)"),
  71     (&["core", "sync", "atomic", "ATOMIC_I32_INIT"],   "AtomicI32::new(0)"),
  72     (&["core", "sync", "atomic", "ATOMIC_I64_INIT"],   "AtomicI64::new(0)"),
  73     (&["core", "sync", "atomic", "ATOMIC_USIZE_INIT"], "AtomicUsize::new(0)"),
  74     (&["core", "sync", "atomic", "ATOMIC_U8_INIT"],    "AtomicU8::new(0)"),
  75     (&["core", "sync", "atomic", "ATOMIC_U16_INIT"],   "AtomicU16::new(0)"),
  76     (&["core", "sync", "atomic", "ATOMIC_U32_INIT"],   "AtomicU32::new(0)"),
  77     (&["core", "sync", "atomic", "ATOMIC_U64_INIT"],   "AtomicU64::new(0)"),
  78     // Min
  79     (&["core", "isize", "MIN"], "isize::min_value()"),
  80     (&["core", "i8",    "MIN"], "i8::min_value()"),
  81     (&["core", "i16",   "MIN"], "i16::min_value()"),
  82     (&["core", "i32",   "MIN"], "i32::min_value()"),
  83     (&["core", "i64",   "MIN"], "i64::min_value()"),
  84     (&["core", "i128",  "MIN"], "i128::min_value()"),
  85     (&["core", "usize", "MIN"], "usize::min_value()"),
  86     (&["core", "u8",    "MIN"], "u8::min_value()"),
  87     (&["core", "u16",   "MIN"], "u16::min_value()"),
  88     (&["core", "u32",   "MIN"], "u32::min_value()"),
  89     (&["core", "u64",   "MIN"], "u64::min_value()"),
  90     (&["core", "u128",  "MIN"], "u128::min_value()"),
  91     // Max
  92     (&["core", "isize", "MAX"], "isize::max_value()"),
  93     (&["core", "i8",    "MAX"], "i8::max_value()"),
  94     (&["core", "i16",   "MAX"], "i16::max_value()"),
  95     (&["core", "i32",   "MAX"], "i32::max_value()"),
  96     (&["core", "i64",   "MAX"], "i64::max_value()"),
  97     (&["core", "i128",  "MAX"], "i128::max_value()"),
  98     (&["core", "usize", "MAX"], "usize::max_value()"),
  99     (&["core", "u8",    "MAX"], "u8::max_value()"),
 100     (&["core", "u16",   "MAX"], "u16::max_value()"),
 101     (&["core", "u32",   "MAX"], "u32::max_value()"),
 102     (&["core", "u64",   "MAX"], "u64::max_value()"),
 103     (&["core", "u128",  "MAX"], "u128::max_value()"),
 104 ];