lint #1674: replace struct name with Self when applicable

clippy_lints/src/use_self.rs

@@ -0,0 +1,90 @@
+use rustc::lint::{LintArray, LateLintPass, LateContext, LintPass};
+use rustc::hir::*;
+use rustc::hir::intravisit::{Visitor, walk_path, NestedVisitorMap};
+use utils::span_lint;
+use syntax::ast::NodeId;
+
+/// **What it does:** Checks for unnecessary repetition of structure name when a
+/// replacement with `Self` is applicable.
+///
+/// **Why is this bad?** Unnecessary repetition. Mixed use of `Self` and struct name
+/// feels inconsistent.
+///
+/// **Known problems:** None.
+///
+/// **Example:**
+/// ```rust
+/// struct Foo {}
+/// impl Foo {
+///     fn new() -> Foo {
+///         Foo {}
+///     }
+/// }
+/// ```
+/// could be
+/// ```
+/// struct Foo {}
+/// impl Foo {
+///     fn new() -> Self {
+///         Self {}
+///     }
+/// }
+/// ```
+declare_lint! {
+    pub USE_SELF,
+    Allow,
+    "Repetitive struct name usage whereas `Self` is applicable"
+}
+
+#[derive(Copy, Clone, Default)]
+pub struct UseSelf;
+
+impl LintPass for UseSelf {
+    fn get_lints(&self) -> LintArray {
+        lint_array!(USE_SELF)
+    }
+}
+
+impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UseSelf {
+    fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx Item) {
+        if_let_chain!([
+            let ItemImpl(.., ref item_type, ref refs) = item.node,
+            let Ty_::TyPath(QPath::Resolved(_, ref item_path)) = item_type.node,
+        ], {
+            let visitor = &mut UseSelfVisitor {
+                item_path: item_path,
+                cx: cx,
+            };
+            for impl_item_ref in refs {
+                visitor.visit_impl_item(cx.tcx.hir.impl_item(impl_item_ref.id));
+            }
+        })
+    }
+}
+
+struct UseSelfVisitor<'a, 'tcx: 'a> {
+    item_path: &'a Path,
+    cx: &'a LateContext<'a, 'tcx>,
+}
+
+impl<'a, 'tcx> Visitor<'tcx> for UseSelfVisitor<'a, 'tcx> {
+    fn visit_path(&mut self, path: &'tcx Path, _id: NodeId) {
+        if self.item_path.def == path.def &&
+           path.segments
+            .last()
+            .expect("segments should be composed of at least 1 elemnt")
+            .name
+            .as_str() != "Self" {
+            span_lint(self.cx,
+                      USE_SELF,
+                      path.span,
+                      "repetitive struct name usage. Use `Self` instead.");
+        }
+
+        walk_path(self, path);
+    }
+
+    fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
+        NestedVisitorMap::OnlyBodies(&self.cx.tcx.hir)
+    }
+}