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|
use clippy_utils::diagnostics::span_lint_hir_and_then;
use clippy_utils::return_ty;
use clippy_utils::source::snippet;
use clippy_utils::sugg::DiagnosticExt;
use if_chain::if_chain;
use rustc_errors::Applicability;
use rustc_hir as hir;
use rustc_hir::HirIdSet;
use rustc_lint::{LateContext, LateLintPass, LintContext};
use rustc_middle::lint::in_external_macro;
use rustc_session::{declare_tool_lint, impl_lint_pass};
use rustc_span::sym;
declare_clippy_lint! {
/// ### What it does
/// Checks for public types with a `pub fn new() -> Self` method and no
/// implementation of
/// [`Default`](https://doc.rust-lang.org/std/default/trait.Default.html).
///
/// ### Why is this bad?
/// The 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.
///
/// ### Example
/// ```ignore
/// pub struct Foo(Bar);
///
/// impl Foo {
/// pub fn new() -> Self {
/// Foo(Bar::new())
/// }
/// }
/// ```
///
/// To fix the lint, add a `Default` implementation that delegates to `new`:
///
/// ```ignore
/// pub struct Foo(Bar);
///
/// impl Default for Foo {
/// fn default() -> Self {
/// Foo::new()
/// }
/// }
/// ```
#[clippy::version = "pre 1.29.0"]
pub NEW_WITHOUT_DEFAULT,
style,
"`pub fn new() -> Self` method without `Default` implementation"
}
#[derive(Clone, Default)]
pub struct NewWithoutDefault {
impling_types: Option<HirIdSet>,
}
impl_lint_pass!(NewWithoutDefault => [NEW_WITHOUT_DEFAULT]);
impl<'tcx> LateLintPass<'tcx> for NewWithoutDefault {
fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx hir::Item<'_>) {
if let hir::ItemKind::Impl(hir::Impl {
of_trait: None,
generics,
self_ty: impl_self_ty,
items,
..
}) = item.kind
{
for assoc_item in *items {
if assoc_item.kind == (hir::AssocItemKind::Fn { has_self: false }) {
let impl_item = cx.tcx.hir().impl_item(assoc_item.id);
if in_external_macro(cx.sess(), impl_item.span) {
return;
}
if let hir::ImplItemKind::Fn(ref sig, _) = impl_item.kind {
let name = impl_item.ident.name;
let id = impl_item.hir_id();
if sig.header.constness == hir::Constness::Const {
// can't be implemented by default
return;
}
if sig.header.unsafety == hir::Unsafety::Unsafe {
// can't be implemented for unsafe new
return;
}
if cx.tcx.is_doc_hidden(impl_item.owner_id.def_id) {
// shouldn't be implemented when it is hidden in docs
return;
}
if !impl_item.generics.params.is_empty() {
// when the result of `new()` depends on a parameter we should not require
// an impl of `Default`
return;
}
if_chain! {
if sig.decl.inputs.is_empty();
if name == sym::new;
if cx.effective_visibilities.is_reachable(impl_item.owner_id.def_id);
let self_def_id = cx.tcx.hir().get_parent_item(id);
let self_ty = cx.tcx.type_of(self_def_id);
if self_ty == return_ty(cx, id);
if let Some(default_trait_id) = cx.tcx.get_diagnostic_item(sym::Default);
then {
if self.impling_types.is_none() {
let mut impls = HirIdSet::default();
cx.tcx.for_each_impl(default_trait_id, |d| {
if let Some(ty_def) = cx.tcx.type_of(d).ty_adt_def() {
if let Some(local_def_id) = ty_def.did().as_local() {
impls.insert(cx.tcx.hir().local_def_id_to_hir_id(local_def_id));
}
}
});
self.impling_types = Some(impls);
}
// Check if a Default implementation exists for the Self type, regardless of
// generics
if_chain! {
if let Some(ref impling_types) = self.impling_types;
if let Some(self_def) = cx.tcx.type_of(self_def_id).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 impling_types.contains(&self_id);
then {
return;
}
}
let generics_sugg = snippet(cx, generics.span, "");
let self_ty_fmt = self_ty.to_string();
let self_type_snip = snippet(cx, impl_self_ty.span, &self_ty_fmt);
span_lint_hir_and_then(
cx,
NEW_WITHOUT_DEFAULT,
id,
impl_item.span,
&format!(
"you should consider adding a `Default` implementation for `{self_type_snip}`"
),
|diag| {
diag.suggest_prepend_item(
cx,
item.span,
"try adding this",
&create_new_without_default_suggest_msg(&self_type_snip, &generics_sugg),
Applicability::MaybeIncorrect,
);
},
);
}
}
}
}
}
}
}
}
fn create_new_without_default_suggest_msg(self_type_snip: &str, generics_sugg: &str) -> String {
#[rustfmt::skip]
format!(
"impl{generics_sugg} Default for {self_type_snip} {{
fn default() -> Self {{
Self::new()
}}
}}")
}
|
