## Lints
-There are 150 lints included in this crate:
+There are 151 lints included in this crate:
name | default | meaning
---------------------------------------------------------------------------------------------------------------------|---------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
[neg_multiply](https://github.com/Manishearth/rust-clippy/wiki#neg_multiply) | warn | Warns on multiplying integers with -1
[new_ret_no_self](https://github.com/Manishearth/rust-clippy/wiki#new_ret_no_self) | warn | not returning `Self` in a `new` method
[new_without_default](https://github.com/Manishearth/rust-clippy/wiki#new_without_default) | warn | `fn new() -> Self` method without `Default` implementation
+[new_without_default_derive](https://github.com/Manishearth/rust-clippy/wiki#new_without_default_derive) | warn | `fn new() -> Self` without `#[derive]`able `Default` implementation
[no_effect](https://github.com/Manishearth/rust-clippy/wiki#no_effect) | warn | statements with no effect
[non_ascii_literal](https://github.com/Manishearth/rust-clippy/wiki#non_ascii_literal) | allow | using any literal non-ASCII chars in a string literal; suggests using the \\u escape instead
[nonminimal_bool](https://github.com/Manishearth/rust-clippy/wiki#nonminimal_bool) | allow | checks for boolean expressions that can be written more concisely
use rustc::hir::intravisit::FnKind;
+use rustc::hir::def_id::DefId;
use rustc::hir;
use rustc::lint::*;
+use rustc::ty;
use syntax::ast;
use syntax::codemap::Span;
use utils::paths;
/// **Example:**
///
/// ```rust,ignore
-/// struct Foo;
+/// struct Foo(Bar);
///
/// impl Foo {
/// fn new() -> Self {
-/// Foo
+/// Foo(Bar::new())
/// }
/// }
/// ```
/// Instead, use:
///
/// ```rust
-/// struct Foo;
+/// struct Foo(Bar);
///
/// impl Default for Foo {
/// fn default() -> Self {
-/// Foo
+/// Foo(Bar::new())
/// }
/// }
/// ```
///
/// You can also have `new()` call `Default::default()`
-///
declare_lint! {
pub NEW_WITHOUT_DEFAULT,
Warn,
"`fn new() -> Self` method without `Default` implementation"
}
+/// **What it does:** This lints about type with a `fn new() -> Self` method
+/// and no implementation of
+/// [`Default`](https://doc.rust-lang.org/std/default/trait.Default.html)
+///
+/// **Why is this bad?** User might expect to be able to use
+/// [`Default`](https://doc.rust-lang.org/std/default/trait.Default.html)
+/// as the type can be
+/// constructed without arguments.
+///
+/// **Known problems:** Hopefully none.
+///
+/// **Example:**
+///
+/// ```rust,ignore
+/// struct Foo;
+///
+/// impl Foo {
+/// fn new() -> Self {
+/// Foo
+/// }
+/// }
+/// ```
+///
+/// Just prepend `#[derive(Default)]` before the `struct` definition
+declare_lint! {
+ pub NEW_WITHOUT_DEFAULT_DERIVE,
+ Warn,
+ "`fn new() -> Self` without `#[derive]`able `Default` implementation"
+}
+
#[derive(Copy,Clone)]
pub struct NewWithoutDefault;
impl LintPass for NewWithoutDefault {
fn get_lints(&self) -> LintArray {
- lint_array!(NEW_WITHOUT_DEFAULT)
+ lint_array!(NEW_WITHOUT_DEFAULT, NEW_WITHOUT_DEFAULT_DERIVE)
}
}
if let FnKind::Method(name, _, _, _) = kind {
if decl.inputs.is_empty() && name.as_str() == "new" {
- let self_ty = cx.tcx.lookup_item_type(cx.tcx.map.local_def_id(cx.tcx.map.get_parent(id))).ty;
-
+ let self_ty = cx.tcx.lookup_item_type(cx.tcx.map.local_def_id(
+ cx.tcx.map.get_parent(id))).ty;
if_let_chain!{[
self_ty.walk_shallow().next().is_none(), // implements_trait does not work with generics
let Some(ret_ty) = return_ty(cx, id),
let Some(default_trait_id) = get_trait_def_id(cx, &paths::DEFAULT_TRAIT),
!implements_trait(cx, self_ty, default_trait_id, Vec::new())
], {
- span_lint(cx, NEW_WITHOUT_DEFAULT, span,
- &format!("you should consider adding a `Default` implementation for `{}`", self_ty));
+ if can_derive_default(self_ty, cx, default_trait_id) {
+ span_lint(cx,
+ NEW_WITHOUT_DEFAULT_DERIVE, span,
+ &format!("you should consider deriving a \
+ `Default` implementation for `{}`",
+ self_ty)).
+ span_suggestion(span,
+ "try this",
+ "#[derive(Default)]".into());
+ } else {
+ span_lint(cx,
+ NEW_WITHOUT_DEFAULT, span,
+ &format!("you should consider adding a \
+ `Default` implementation for `{}`",
+ self_ty)).
+ span_suggestion(span,
+ "try this",
+ format!("impl Default for {} {{ fn default() -> \
+ Self {{ {}::new() }} }}", self_ty, self_ty));
+ }
}}
}
}
}
}
+
+fn can_derive_default<'t, 'c>(ty: ty::Ty<'t>, cx: &LateContext<'c, 't>, default_trait_id: DefId) -> bool {
+ match ty.sty {
+ ty::TyStruct(ref adt_def, ref substs) => {
+ for field in adt_def.all_fields() {
+ let f_ty = field.ty(cx.tcx, substs);
+ if !implements_trait(cx, f_ty, default_trait_id, Vec::new()) {
+ return false
+ }
+ }
+ true
+ },
+ _ => false
+ }
+}