clippy_lints/src/trait_bounds.rs

   1 use crate::utils::{in_macro, span_help_and_lint, SpanlessHash};
   2 use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
   3 use rustc::{declare_tool_lint, lint_array, impl_lint_pass};
   4 use rustc_data_structures::fx::FxHashMap;
   5 use rustc::hir::*;
   6
   7 #[derive(Copy, Clone)]
   8 pub struct TraitBounds;
   9
  10 declare_clippy_lint! {
  11     pub TYPE_REPETITION_IN_BOUNDS,
  12     complexity,
  13     "Types are repeated unnecessary in trait bounds use `+` instead of using `T: _, T: _`"
  14 }
  15
  16 impl_lint_pass!(TraitBounds => [TYPE_REPETITION_IN_BOUNDS]);
  17
  18 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for TraitBounds {
  19     fn check_generics(&mut self, cx: &LateContext<'a, 'tcx>, gen: &'tcx Generics) {
  20         if in_macro(gen.span) {
  21             return;
  22         }
  23         let hash = | ty | -> u64 {
  24             let mut hasher = SpanlessHash::new(cx, cx.tables);
  25             hasher.hash_ty(ty);
  26             hasher.finish()
  27         };
  28         let mut map = FxHashMap::default();
  29         for bound in &gen.where_clause.predicates {
  30             if let WherePredicate::BoundPredicate(ref p) = bound {
  31                 let h = hash(&p.bounded_ty.node);
  32                 if let Some(ref v) = map.insert(h, p.bounds) {
  33                     let mut hint_string = format!("consider combining the bounds: `{:?}: ", p.bounded_ty);
  34                     for &b in v.iter() {
  35                         hint_string.push_str(&format!("{:?}, ", b));
  36                     }
  37                     for &b in p.bounds.iter() {
  38                         hint_string.push_str(&format!("{:?}, ", b));
  39                     }
  40                     hint_string.truncate(hint_string.len() - 2);
  41                     hint_string.push('`');
  42                     span_help_and_lint(
  43                         cx,
  44                         TYPE_REPETITION_IN_BOUNDS,
  45                         p.span,
  46                         "this type has already been used as a bound predicate",
  47                         &hint_string,
  48                     );
  49                 }
  50             }
  51         }
  52     }
  53 }