clippy_lints/src/replace_consts.rs

   1 use crate::utils::{match_def_path, span_lint_and_sugg};
   2 use if_chain::if_chain;
   3 use rustc::hir;
   4 use rustc::hir::def::Def;
   5 use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
   6 use rustc::{declare_tool_lint, lint_array};
   7 use rustc_errors::Applicability;
   8
   9 /// **What it does:** Checks for usage of `ATOMIC_X_INIT`, `ONCE_INIT`, and
  10 /// `uX/iX::MIN/MAX`.
  11 ///
  12 /// **Why is this bad?** `const fn`s exist
  13 ///
  14 /// **Known problems:** None.
  15 ///
  16 /// **Example:**
  17 /// ```rust
  18 /// static FOO: AtomicIsize = ATOMIC_ISIZE_INIT;
  19 /// ```
  20 ///
  21 /// Could be written:
  22 ///
  23 /// ```rust
  24 /// static FOO: AtomicIsize = AtomicIsize::new(0);
  25 /// ```
  26 declare_clippy_lint! {
  27     pub REPLACE_CONSTS,
  28     pedantic,
  29     "Lint usages of standard library `const`s that could be replaced by `const fn`s"
  30 }
  31
  32 pub struct ReplaceConsts;
  33
  34 impl LintPass for ReplaceConsts {
  35     fn get_lints(&self) -> LintArray {
  36         lint_array!(REPLACE_CONSTS)
  37     }
  38
  39     fn name(&self) -> &'static str {
  40         "ReplaceConsts"
  41     }
  42 }
  43
  44 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for ReplaceConsts {
  45     fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx hir::Expr) {
  46         if_chain! {
  47             if let hir::ExprKind::Path(ref qp) = expr.node;
  48             if let Def::Const(def_id) = cx.tables.qpath_def(qp, expr.hir_id);
  49             then {
  50                 for &(const_path, repl_snip) in REPLACEMENTS {
  51                     if match_def_path(cx.tcx, def_id, const_path) {
  52                         span_lint_and_sugg(
  53                             cx,
  54                             REPLACE_CONSTS,
  55                             expr.span,
  56                             &format!("using `{}`", const_path.last().expect("empty path")),
  57                             "try this",
  58                             repl_snip.to_string(),
  59                             Applicability::MachineApplicable,
  60                         );
  61                         return;
  62                     }
  63                 }
  64             }
  65         }
  66     }
  67 }
  68
  69 const REPLACEMENTS: &[(&[&str], &str)] = &[
  70     // Once
  71     (&["core", "sync", "ONCE_INIT"], "Once::new()"),
  72     // Atomic
  73     (
  74         &["core", "sync", "atomic", "ATOMIC_BOOL_INIT"],
  75         "AtomicBool::new(false)",
  76     ),
  77     (&["core", "sync", "atomic", "ATOMIC_ISIZE_INIT"], "AtomicIsize::new(0)"),
  78     (&["core", "sync", "atomic", "ATOMIC_I8_INIT"], "AtomicI8::new(0)"),
  79     (&["core", "sync", "atomic", "ATOMIC_I16_INIT"], "AtomicI16::new(0)"),
  80     (&["core", "sync", "atomic", "ATOMIC_I32_INIT"], "AtomicI32::new(0)"),
  81     (&["core", "sync", "atomic", "ATOMIC_I64_INIT"], "AtomicI64::new(0)"),
  82     (&["core", "sync", "atomic", "ATOMIC_USIZE_INIT"], "AtomicUsize::new(0)"),
  83     (&["core", "sync", "atomic", "ATOMIC_U8_INIT"], "AtomicU8::new(0)"),
  84     (&["core", "sync", "atomic", "ATOMIC_U16_INIT"], "AtomicU16::new(0)"),
  85     (&["core", "sync", "atomic", "ATOMIC_U32_INIT"], "AtomicU32::new(0)"),
  86     (&["core", "sync", "atomic", "ATOMIC_U64_INIT"], "AtomicU64::new(0)"),
  87     // Min
  88     (&["core", "isize", "MIN"], "isize::min_value()"),
  89     (&["core", "i8", "MIN"], "i8::min_value()"),
  90     (&["core", "i16", "MIN"], "i16::min_value()"),
  91     (&["core", "i32", "MIN"], "i32::min_value()"),
  92     (&["core", "i64", "MIN"], "i64::min_value()"),
  93     (&["core", "i128", "MIN"], "i128::min_value()"),
  94     (&["core", "usize", "MIN"], "usize::min_value()"),
  95     (&["core", "u8", "MIN"], "u8::min_value()"),
  96     (&["core", "u16", "MIN"], "u16::min_value()"),
  97     (&["core", "u32", "MIN"], "u32::min_value()"),
  98     (&["core", "u64", "MIN"], "u64::min_value()"),
  99     (&["core", "u128", "MIN"], "u128::min_value()"),
 100     // Max
 101     (&["core", "isize", "MAX"], "isize::max_value()"),
 102     (&["core", "i8", "MAX"], "i8::max_value()"),
 103     (&["core", "i16", "MAX"], "i16::max_value()"),
 104     (&["core", "i32", "MAX"], "i32::max_value()"),
 105     (&["core", "i64", "MAX"], "i64::max_value()"),
 106     (&["core", "i128", "MAX"], "i128::max_value()"),
 107     (&["core", "usize", "MAX"], "usize::max_value()"),
 108     (&["core", "u8", "MAX"], "u8::max_value()"),
 109     (&["core", "u16", "MAX"], "u16::max_value()"),
 110     (&["core", "u32", "MAX"], "u32::max_value()"),
 111     (&["core", "u64", "MAX"], "u64::max_value()"),
 112     (&["core", "u128", "MAX"], "u128::max_value()"),
 113 ];