lint #1674: replace struct name with Self when applicable

clippy_lints/src/lib.rs

@@ -148,6 +148,7 @@ pub mod unicode;
 pub mod unsafe_removed_from_name;
 pub mod unused_io_amount;
 pub mod unused_label;
+pub mod use_self;
 pub mod vec;
 pub mod zero_div_zero;
 // end lints modules, do not remove this comment, it’s used in `update_lints`
@@ -319,6 +320,7 @@ pub fn register_plugins(reg: &mut rustc_plugin::Registry) {
     reg.register_late_lint_pass(box should_assert_eq::ShouldAssertEq);
     reg.register_late_lint_pass(box needless_pass_by_value::NeedlessPassByValue);
     reg.register_early_lint_pass(box literal_digit_grouping::LiteralDigitGrouping);
+    reg.register_late_lint_pass(box use_self::UseSelf);
 
     reg.register_lint_group("clippy_restrictions", vec![
         arithmetic::FLOAT_ARITHMETIC,

clippy_lints/src/use_self.rs

@@ -0,0 +1,91 @@
+use rustc::lint::{LintArray, LateLintPass, LateContext, LintPass};
+use rustc::hir::*;
+use rustc::hir::intravisit::{Visitor, walk_path, NestedVisitorMap};
+use utils::span_lint_and_then;
+use syntax::ast::NodeId;
+use syntax_pos::symbol::keywords::SelfType;
+
+/// **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,
+    "Unnecessary structure name repetition 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 element")
+            .name != SelfType.name() {
+            span_lint_and_then(self.cx, USE_SELF, path.span, "unnecessary structure name repetition", |db| {
+                db.span_suggestion(path.span,
+                                   "use the applicable keyword",
+                                   "Self".to_owned());
+            });
+        }
+
+        walk_path(self, path);
+    }
+
+    fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
+        NestedVisitorMap::OnlyBodies(&self.cx.tcx.hir)
+    }
+}

tests/ui/use_self.rs

@@ -0,0 +1,45 @@
+#![feature(plugin)]
+#![plugin(clippy)]
+#![warn(use_self)]
+#![allow(dead_code)]
+
+
+fn main() {}
+
+mod use_self {
+    struct Foo {}
+
+    impl Foo {
+        fn new() -> Foo {
+            Foo {}
+        }
+        fn test() -> Foo {
+            Foo::new()
+        }
+    }
+
+    impl Default for Foo {
+        fn default() -> Foo {
+            Foo::new()
+        }
+    }
+}
+
+mod better {
+    struct Foo {}
+
+    impl Foo {
+        fn new() -> Self {
+            Self {}
+        }
+        fn test() -> Self {
+            Self::new()
+        }
+    }
+
+    impl Default for Foo {
+        fn default() -> Self {
+            Self::new()
+        }
+    }
+}

tests/ui/use_self.stderr

@@ -0,0 +1,40 @@
+error: unnecessary structure name repetition
+  --> $DIR/use_self.rs:13:21
+   |
+13 |         fn new() -> Foo {
+   |                     ^^^ help: use the applicable keyword: `Self`
+   |
+   = note: `-D use-self` implied by `-D warnings`
+
+error: unnecessary structure name repetition
+  --> $DIR/use_self.rs:14:13
+   |
+14 |             Foo {}
+   |             ^^^ help: use the applicable keyword: `Self`
+
+error: unnecessary structure name repetition
+  --> $DIR/use_self.rs:16:22
+   |
+16 |         fn test() -> Foo {
+   |                      ^^^ help: use the applicable keyword: `Self`
+
+error: unnecessary structure name repetition
+  --> $DIR/use_self.rs:17:13
+   |
+17 |             Foo::new()
+   |             ^^^^^^^^ help: use the applicable keyword: `Self`
+
+error: unnecessary structure name repetition
+  --> $DIR/use_self.rs:22:25
+   |
+22 |         fn default() -> Foo {
+   |                         ^^^ help: use the applicable keyword: `Self`
+
+error: unnecessary structure name repetition
+  --> $DIR/use_self.rs:23:13
+   |
+23 |             Foo::new()
+   |             ^^^^^^^^ help: use the applicable keyword: `Self`
+
+error: aborting due to 6 previous errors
+