clippy_lints/src/replace_consts.rs

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