clippy_lints/src/replace_consts.rs

   1 // Copyright 2014-2018 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution.
   3 //
   4 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   5 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   6 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   7 // option. This file may not be copied, modified, or distributed
   8 // except according to those terms.
   9
  10
  11 use crate::rustc::hir;
  12 use crate::rustc::hir::def::Def;
  13 use crate::rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
  14 use crate::rustc::{declare_tool_lint, lint_array};
  15 use crate::rustc_errors::Applicability;
  16 use crate::utils::{match_def_path, span_lint_and_sugg};
  17 use if_chain::if_chain;
  18
  19 /// **What it does:** Checks for usage of `ATOMIC_X_INIT`, `ONCE_INIT`, and
  20 /// `uX/iX::MIN/MAX`.
  21 ///
  22 /// **Why is this bad?** `const fn`s exist
  23 ///
  24 /// **Known problems:** None.
  25 ///
  26 /// **Example:**
  27 /// ```rust
  28 /// static FOO: AtomicIsize = ATOMIC_ISIZE_INIT;
  29 /// ```
  30 ///
  31 /// Could be written:
  32 ///
  33 /// ```rust
  34 /// static FOO: AtomicIsize = AtomicIsize::new(0);
  35 /// ```
  36 declare_clippy_lint! {
  37     pub REPLACE_CONSTS,
  38     pedantic,
  39     "Lint usages of standard library `const`s that could be replaced by `const fn`s"
  40 }
  41
  42 pub struct ReplaceConsts;
  43
  44 impl LintPass for ReplaceConsts {
  45     fn get_lints(&self) -> LintArray {
  46         lint_array!(REPLACE_CONSTS)
  47     }
  48 }
  49
  50 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for ReplaceConsts {
  51     fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx hir::Expr) {
  52         if_chain! {
  53             if let hir::ExprKind::Path(ref qp) = expr.node;
  54             if let Def::Const(def_id) = cx.tables.qpath_def(qp, expr.hir_id);
  55             then {
  56                 for &(const_path, repl_snip) in REPLACEMENTS {
  57                     if match_def_path(cx.tcx, def_id, const_path) {
  58                         span_lint_and_sugg(
  59                             cx,
  60                             REPLACE_CONSTS,
  61                             expr.span,
  62                             &format!("using `{}`", const_path.last().expect("empty path")),
  63                             "try this",
  64                             repl_snip.to_string(),
  65                             Applicability::MachineApplicable,
  66                         );
  67                         return;
  68                     }
  69                 }
  70             }
  71         }
  72     }
  73 }
  74
  75 const REPLACEMENTS: &[(&[&str], &str)] = &[
  76     // Once
  77     (&["core", "sync",  "ONCE_INIT"], "Once::new()"),
  78     // Atomic
  79     (&["core", "sync", "atomic", "ATOMIC_BOOL_INIT"],  "AtomicBool::new(false)"),
  80     (&["core", "sync", "atomic", "ATOMIC_ISIZE_INIT"], "AtomicIsize::new(0)"),
  81     (&["core", "sync", "atomic", "ATOMIC_I8_INIT"],    "AtomicI8::new(0)"),
  82     (&["core", "sync", "atomic", "ATOMIC_I16_INIT"],   "AtomicI16::new(0)"),
  83     (&["core", "sync", "atomic", "ATOMIC_I32_INIT"],   "AtomicI32::new(0)"),
  84     (&["core", "sync", "atomic", "ATOMIC_I64_INIT"],   "AtomicI64::new(0)"),
  85     (&["core", "sync", "atomic", "ATOMIC_USIZE_INIT"], "AtomicUsize::new(0)"),
  86     (&["core", "sync", "atomic", "ATOMIC_U8_INIT"],    "AtomicU8::new(0)"),
  87     (&["core", "sync", "atomic", "ATOMIC_U16_INIT"],   "AtomicU16::new(0)"),
  88     (&["core", "sync", "atomic", "ATOMIC_U32_INIT"],   "AtomicU32::new(0)"),
  89     (&["core", "sync", "atomic", "ATOMIC_U64_INIT"],   "AtomicU64::new(0)"),
  90     // Min
  91     (&["core", "isize", "MIN"], "isize::min_value()"),
  92     (&["core", "i8",    "MIN"], "i8::min_value()"),
  93     (&["core", "i16",   "MIN"], "i16::min_value()"),
  94     (&["core", "i32",   "MIN"], "i32::min_value()"),
  95     (&["core", "i64",   "MIN"], "i64::min_value()"),
  96     (&["core", "i128",  "MIN"], "i128::min_value()"),
  97     (&["core", "usize", "MIN"], "usize::min_value()"),
  98     (&["core", "u8",    "MIN"], "u8::min_value()"),
  99     (&["core", "u16",   "MIN"], "u16::min_value()"),
 100     (&["core", "u32",   "MIN"], "u32::min_value()"),
 101     (&["core", "u64",   "MIN"], "u64::min_value()"),
 102     (&["core", "u128",  "MIN"], "u128::min_value()"),
 103     // Max
 104     (&["core", "isize", "MAX"], "isize::max_value()"),
 105     (&["core", "i8",    "MAX"], "i8::max_value()"),
 106     (&["core", "i16",   "MAX"], "i16::max_value()"),
 107     (&["core", "i32",   "MAX"], "i32::max_value()"),
 108     (&["core", "i64",   "MAX"], "i64::max_value()"),
 109     (&["core", "i128",  "MAX"], "i128::max_value()"),
 110     (&["core", "usize", "MAX"], "usize::max_value()"),
 111     (&["core", "u8",    "MAX"], "u8::max_value()"),
 112     (&["core", "u16",   "MAX"], "u16::max_value()"),
 113     (&["core", "u32",   "MAX"], "u32::max_value()"),
 114     (&["core", "u64",   "MAX"], "u64::max_value()"),
 115     (&["core", "u128",  "MAX"], "u128::max_value()"),
 116 ];