New lint: [self_named_constructor]

CHANGELOG.md

@@ -2772,6 +2772,7 @@ Released 2018-09-13
 [`same_item_push`]: https://rust-lang.github.io/rust-clippy/master/index.html#same_item_push
 [`search_is_some`]: https://rust-lang.github.io/rust-clippy/master/index.html#search_is_some
 [`self_assignment`]: https://rust-lang.github.io/rust-clippy/master/index.html#self_assignment
+[`self_named_constructor`]: https://rust-lang.github.io/rust-clippy/master/index.html#self_named_constructor
 [`semicolon_if_nothing_returned`]: https://rust-lang.github.io/rust-clippy/master/index.html#semicolon_if_nothing_returned
 [`serde_api_misuse`]: https://rust-lang.github.io/rust-clippy/master/index.html#serde_api_misuse
 [`shadow_reuse`]: https://rust-lang.github.io/rust-clippy/master/index.html#shadow_reuse

clippy_lints/src/lib.rs

@@ -330,6 +330,7 @@ mod regex;
 mod repeat_once;
 mod returns;
 mod self_assignment;
+mod self_named_constructor;
 mod semicolon_if_nothing_returned;
 mod serde_api;
 mod shadow;
@@ -900,6 +901,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
         returns::LET_AND_RETURN,
         returns::NEEDLESS_RETURN,
         self_assignment::SELF_ASSIGNMENT,
+        self_named_constructor::SELF_NAMED_CONSTRUCTOR,
         semicolon_if_nothing_returned::SEMICOLON_IF_NOTHING_RETURNED,
         serde_api::SERDE_API_MISUSE,
         shadow::SHADOW_REUSE,
@@ -1406,6 +1408,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
         LintId::of(returns::LET_AND_RETURN),
         LintId::of(returns::NEEDLESS_RETURN),
         LintId::of(self_assignment::SELF_ASSIGNMENT),
+        LintId::of(self_named_constructor::SELF_NAMED_CONSTRUCTOR),
         LintId::of(serde_api::SERDE_API_MISUSE),
         LintId::of(single_component_path_imports::SINGLE_COMPONENT_PATH_IMPORTS),
         LintId::of(size_of_in_element_count::SIZE_OF_IN_ELEMENT_COUNT),
@@ -1559,6 +1562,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
         LintId::of(redundant_static_lifetimes::REDUNDANT_STATIC_LIFETIMES),
         LintId::of(returns::LET_AND_RETURN),
         LintId::of(returns::NEEDLESS_RETURN),
+        LintId::of(self_named_constructor::SELF_NAMED_CONSTRUCTOR),
         LintId::of(single_component_path_imports::SINGLE_COMPONENT_PATH_IMPORTS),
         LintId::of(tabs_in_doc_comments::TABS_IN_DOC_COMMENTS),
         LintId::of(to_digit_is_some::TO_DIGIT_IS_SOME),
@@ -2101,6 +2105,8 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
     let scripts = conf.allowed_scripts.clone();
     store.register_early_pass(move || box disallowed_script_idents::DisallowedScriptIdents::new(&scripts));
     store.register_late_pass(|| box strlen_on_c_strings::StrlenOnCStrings);
+    store.register_late_pass(move || box self_named_constructor::SelfNamedConstructor);
+
 }
 
 #[rustfmt::skip]

clippy_lints/src/self_named_constructor.rs

@@ -0,0 +1,91 @@
+use clippy_utils::diagnostics::span_lint;
+use clippy_utils::return_ty;
+use clippy_utils::ty::{contains_adt_constructor, contains_ty};
+use rustc_hir::{Impl, ImplItem, ImplItemKind, ItemKind, Node};
+use rustc_lint::{LateContext, LateLintPass};
+use rustc_session::{declare_lint_pass, declare_tool_lint};
+
+declare_clippy_lint! {
+    /// **What it does:** Warns when constructors have the same name as their types.
+    ///
+    /// **Why is this bad?** Repeating the name of the type is redundant.
+    ///
+    /// **Known problems:** None.
+    ///
+    /// **Example:**
+    ///
+    /// ```rust,ignore
+    /// struct Foo {}
+    ///
+    /// impl Foo {
+    ///     pub fn foo() -> Foo {
+    ///         Foo {}
+    ///     }
+    /// }
+    /// ```
+    /// Use instead:
+    /// ```rust,ignore
+    /// struct Foo {}
+    ///
+    /// impl Foo {
+    ///     pub fn new() -> Foo {
+    ///         Foo {}
+    ///     }
+    /// }
+    /// ```
+    pub SELF_NAMED_CONSTRUCTOR,
+    style,
+    "method should not have the same name as the type it is implemented for"
+}
+
+declare_lint_pass!(SelfNamedConstructor => [SELF_NAMED_CONSTRUCTOR]);
+
+impl<'tcx> LateLintPass<'tcx> for SelfNamedConstructor {
+    fn check_impl_item(&mut self, cx: &LateContext<'tcx>, impl_item: &'tcx ImplItem<'_>) {
+        match impl_item.kind {
+            ImplItemKind::Fn(ref sig, _) => {
+                if sig.decl.implicit_self.has_implicit_self() {
+                    return;
+                }
+            },
+            _ => return,
+        }
+
+        let parent = cx.tcx.hir().get_parent_item(impl_item.hir_id());
+        let item = cx.tcx.hir().expect_item(parent);
+        let self_ty = cx.tcx.type_of(item.def_id);
+        let ret_ty = return_ty(cx, impl_item.hir_id());
+
+        // Do not check trait impls
+        if matches!(item.kind, ItemKind::Impl(Impl { of_trait: Some(_), .. })) {
+            return;
+        }
+
+        // Ensure method is constructor-like
+        if let Some(self_adt) = self_ty.ty_adt_def() {
+            if !contains_adt_constructor(ret_ty, self_adt) {
+                return;
+            }
+        } else if !contains_ty(ret_ty, self_ty) {
+            return;
+        }
+
+        if_chain! {
+            if let Some(self_def) = self_ty.ty_adt_def();
+            if let Some(self_local_did) = self_def.did.as_local();
+            let self_id = cx.tcx.hir().local_def_id_to_hir_id(self_local_did);
+            if let Some(Node::Item(x)) = cx.tcx.hir().find(self_id);
+            let type_name = x.ident.name.as_str().to_lowercase();
+            if impl_item.ident.name.as_str() == type_name || impl_item.ident.name.as_str().replace("_", "") == type_name;
+
+            then {
+                span_lint(
+                    cx,
+                    SELF_NAMED_CONSTRUCTOR,
+                    impl_item.span,
+                    &format!("constructor `{}` has the same name as the type", impl_item.ident.name),
+                );
+            }
+        }
+    }
+}

tests/ui/crashes/ice-6179.rs

@@ -7,7 +7,7 @@
 struct Foo {}
 
 impl Foo {
-    fn foo() -> Self {
+    fn new() -> Self {
         impl Foo {
             fn bar() {}
         }

tests/ui/issue_4266.rs

@@ -25,7 +25,9 @@ async fn all_to_one<'a>(a: &'a str, _b: &'a str) -> &'a str {
 struct Foo;
 impl Foo {
     // ok
-    pub async fn foo(&mut self) {}
+    pub async fn new(&mut self) -> Self {
+        Foo {}
+    }
 }
 
 // rust-lang/rust#61115

tests/ui/missing-doc-impl.rs

@@ -59,7 +59,9 @@ pub trait E: Sized {
 }
 
 impl Foo {
-    pub fn foo() {}
+    pub fn new() -> Self {
+        Foo { a: 0, b: 0 }
+    }
     fn bar() {}
 }
 

tests/ui/missing-doc-impl.stderr

@@ -78,23 +78,25 @@ LL |     type AssociatedTypeDef = Self;
 error: missing documentation for an associated function
   --> $DIR/missing-doc-impl.rs:62:5
    |
-LL |     pub fn foo() {}
-   |     ^^^^^^^^^^^^^^^
+LL | /     pub fn new() -> Self {
+LL | |         Foo { a: 0, b: 0 }
+LL | |     }
+   | |_____^
 
 error: missing documentation for an associated function
-  --> $DIR/missing-doc-impl.rs:63:5
+  --> $DIR/missing-doc-impl.rs:65:5
    |
 LL |     fn bar() {}
    |     ^^^^^^^^^^^
 
 error: missing documentation for an associated function
-  --> $DIR/missing-doc-impl.rs:67:5
+  --> $DIR/missing-doc-impl.rs:69:5
    |
 LL |     pub fn foo() {}
    |     ^^^^^^^^^^^^^^^
 
 error: missing documentation for an associated function
-  --> $DIR/missing-doc-impl.rs:71:5
+  --> $DIR/missing-doc-impl.rs:73:5
    |
 LL | /     fn foo2() -> u32 {
 LL | |         1

tests/ui/missing_const_for_fn/cant_be_const.rs

@@ -84,7 +84,7 @@ mod with_drop {
 
     impl A {
         // This can not be const because the type implements `Drop`.
-        pub fn a(self) -> B {
+        pub fn b(self) -> B {
             B
         }
     }

tests/ui/needless_bool/fixable.fixed

@@ -6,7 +6,8 @@
     dead_code,
     clippy::no_effect,
     clippy::if_same_then_else,
-    clippy::needless_return
+    clippy::needless_return,
+    clippy::self_named_constructor
 )]
 
 use std::cell::Cell;

tests/ui/needless_bool/fixable.rs

@@ -6,7 +6,8 @@
     dead_code,
     clippy::no_effect,
     clippy::if_same_then_else,
-    clippy::needless_return
+    clippy::needless_return,
+    clippy::self_named_constructor
 )]
 
 use std::cell::Cell;

tests/ui/needless_bool/fixable.stderr

@@ -1,5 +1,5 @@
 error: this if-then-else expression returns a bool literal
-  --> $DIR/fixable.rs:39:5
+  --> $DIR/fixable.rs:40:5
    |
 LL | /     if x {
 LL | |         true
@@ -11,7 +11,7 @@ LL | |     };
    = note: `-D clippy::needless-bool` implied by `-D warnings`
 
 error: this if-then-else expression returns a bool literal
-  --> $DIR/fixable.rs:44:5
+  --> $DIR/fixable.rs:45:5
    |
 LL | /     if x {
 LL | |         false
@@ -21,7 +21,7 @@ LL | |     };
    | |_____^ help: you can reduce it to: `!x`
 
 error: this if-then-else expression returns a bool literal
-  --> $DIR/fixable.rs:49:5
+  --> $DIR/fixable.rs:50:5
    |
 LL | /     if x && y {
 LL | |         false
@@ -31,7 +31,7 @@ LL | |     };
    | |_____^ help: you can reduce it to: `!(x && y)`
 
 error: this if-then-else expression returns a bool literal
-  --> $DIR/fixable.rs:69:5
+  --> $DIR/fixable.rs:70:5
    |
 LL | /     if x {
 LL | |         return true;
@@ -41,7 +41,7 @@ LL | |     };
    | |_____^ help: you can reduce it to: `return x`
 
 error: this if-then-else expression returns a bool literal
-  --> $DIR/fixable.rs:77:5
+  --> $DIR/fixable.rs:78:5
    |
 LL | /     if x {
 LL | |         return false;
@@ -51,7 +51,7 @@ LL | |     };
    | |_____^ help: you can reduce it to: `return !x`
 
 error: this if-then-else expression returns a bool literal
-  --> $DIR/fixable.rs:85:5
+  --> $DIR/fixable.rs:86:5
    |
 LL | /     if x && y {
 LL | |         return true;
@@ -61,7 +61,7 @@ LL | |     };
    | |_____^ help: you can reduce it to: `return x && y`
 
 error: this if-then-else expression returns a bool literal
-  --> $DIR/fixable.rs:93:5
+  --> $DIR/fixable.rs:94:5
    |
 LL | /     if x && y {
 LL | |         return false;
@@ -71,33 +71,33 @@ LL | |     };
    | |_____^ help: you can reduce it to: `return !(x && y)`
 
 error: equality checks against true are unnecessary
-  --> $DIR/fixable.rs:101:8
+  --> $DIR/fixable.rs:102:8
    |
 LL |     if x == true {};
    |        ^^^^^^^^^ help: try simplifying it as shown: `x`
    |
    = note: `-D clippy::bool-comparison` implied by `-D warnings`
 
 error: equality checks against false can be replaced by a negation
-  --> $DIR/fixable.rs:105:8
+  --> $DIR/fixable.rs:106:8
    |
 LL |     if x == false {};
    |        ^^^^^^^^^^ help: try simplifying it as shown: `!x`
 
 error: equality checks against true are unnecessary
-  --> $DIR/fixable.rs:115:8
+  --> $DIR/fixable.rs:116:8
    |
 LL |     if x == true {};
    |        ^^^^^^^^^ help: try simplifying it as shown: `x`
 
 error: equality checks against false can be replaced by a negation
-  --> $DIR/fixable.rs:116:8
+  --> $DIR/fixable.rs:117:8
    |
 LL |     if x == false {};
    |        ^^^^^^^^^^ help: try simplifying it as shown: `!x`
 
 error: this if-then-else expression returns a bool literal
-  --> $DIR/fixable.rs:125:12
+  --> $DIR/fixable.rs:126:12
    |
 LL |       } else if returns_bool() {
    |  ____________^

tests/ui/self_named_constructor.rs

@@ -0,0 +1,59 @@
+#![warn(clippy::self_named_constructor)]
+
+struct ShouldSpawn;
+struct ShouldNotSpawn;
+
+impl ShouldSpawn {
+    pub fn should_spawn() -> ShouldSpawn {
+        ShouldSpawn
+    }
+
+    fn should_not_spawn() -> ShouldNotSpawn {
+        ShouldNotSpawn
+    }
+}
+
+impl ShouldNotSpawn {
+    pub fn new() -> ShouldNotSpawn {
+        ShouldNotSpawn
+    }
+}
+
+struct ShouldNotSpawnWithTrait;
+
+trait ShouldNotSpawnTrait {
+    type Item;
+}
+
+impl ShouldNotSpawnTrait for ShouldNotSpawnWithTrait {
+    type Item = Self;
+}
+
+impl ShouldNotSpawnWithTrait {
+    pub fn should_not_spawn_with_trait() -> impl ShouldNotSpawnTrait<Item = Self> {
+        ShouldNotSpawnWithTrait
+    }
+}
+
+// Same trait name and same type name should not spawn the lint
+#[derive(Default)]
+pub struct Default;
+
+trait TraitSameTypeName {
+    fn should_not_spawn() -> Self;
+}
+impl TraitSameTypeName for ShouldNotSpawn {
+    fn should_not_spawn() -> Self {
+        ShouldNotSpawn
+    }
+}
+
+struct SelfMethodShouldNotSpawn;
+
+impl SelfMethodShouldNotSpawn {
+    fn self_method_should_not_spawn(self) -> Self {
+        SelfMethodShouldNotSpawn
+    }
+}
+
+fn main() {}