2016-05-17 01:33:57 -05:00
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use rustc::hir::def_id::DefId;
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2016-04-14 11:13:15 -05:00
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use rustc::hir;
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use rustc::lint::*;
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2017-06-10 21:57:25 -05:00
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use rustc::ty::{self, Ty};
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2016-03-01 09:25:15 -06:00
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use syntax::codemap::Span;
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2018-05-30 03:15:50 -05:00
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use crate::utils::paths;
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use crate::utils::{get_trait_def_id, implements_trait, in_external_macro, return_ty, same_tys, span_lint_and_then};
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use crate::utils::sugg::DiagnosticBuilderExt;
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2016-03-01 09:25:15 -06:00
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2016-08-06 02:55:04 -05:00
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/// **What it does:** Checks for types with a `fn new() -> Self` method and no
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/// implementation of
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/// [`Default`](https://doc.rust-lang.org/std/default/trait.Default.html).
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2016-03-01 09:25:15 -06:00
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///
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2016-08-06 02:55:04 -05:00
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/// **Why is this bad?** The user might expect to be able to use
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/// [`Default`](https://doc.rust-lang.org/std/default/trait.Default.html) as the
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/// type can be constructed without arguments.
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2016-03-01 09:25:15 -06:00
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///
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/// **Known problems:** Hopefully none.
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///
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/// **Example:**
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///
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/// ```rust,ignore
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2016-05-17 01:33:57 -05:00
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/// struct Foo(Bar);
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2016-03-01 09:25:15 -06:00
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///
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/// impl Foo {
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/// fn new() -> Self {
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2016-05-17 01:33:57 -05:00
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/// Foo(Bar::new())
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2016-03-01 09:25:15 -06:00
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/// }
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/// }
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/// ```
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2016-04-24 06:45:54 -05:00
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///
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/// Instead, use:
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///
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/// ```rust
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2016-05-17 01:33:57 -05:00
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/// struct Foo(Bar);
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2016-04-24 06:45:54 -05:00
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///
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/// impl Default for Foo {
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/// fn default() -> Self {
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2016-05-17 01:33:57 -05:00
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/// Foo(Bar::new())
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2016-04-24 06:45:54 -05:00
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/// }
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/// }
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/// ```
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///
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2016-08-06 02:55:04 -05:00
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/// You can also have `new()` call `Default::default()`.
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2018-03-28 08:24:26 -05:00
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declare_clippy_lint! {
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2016-03-01 09:25:15 -06:00
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pub NEW_WITHOUT_DEFAULT,
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2018-03-28 08:24:26 -05:00
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style,
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2016-03-01 09:25:15 -06:00
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"`fn new() -> Self` method without `Default` implementation"
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}
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2016-08-06 02:55:04 -05:00
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/// **What it does:** Checks for types with a `fn new() -> Self` method
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2016-05-17 01:33:57 -05:00
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/// and no implementation of
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2016-08-06 02:55:04 -05:00
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/// [`Default`](https://doc.rust-lang.org/std/default/trait.Default.html),
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/// where the `Default` can be derived by `#[derive(Default)]`.
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2016-05-17 01:33:57 -05:00
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///
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2016-08-06 02:55:04 -05:00
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/// **Why is this bad?** The user might expect to be able to use
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/// [`Default`](https://doc.rust-lang.org/std/default/trait.Default.html) as the
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/// type can be constructed without arguments.
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2016-05-17 01:33:57 -05:00
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///
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/// **Known problems:** Hopefully none.
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///
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/// **Example:**
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///
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/// ```rust,ignore
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/// struct Foo;
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///
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/// impl Foo {
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/// fn new() -> Self {
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/// Foo
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/// }
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/// }
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/// ```
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///
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2016-08-06 02:55:04 -05:00
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/// Just prepend `#[derive(Default)]` before the `struct` definition.
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2018-03-28 08:24:26 -05:00
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declare_clippy_lint! {
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2016-05-17 01:33:57 -05:00
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pub NEW_WITHOUT_DEFAULT_DERIVE,
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2018-03-28 08:24:26 -05:00
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style,
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2016-05-17 01:33:57 -05:00
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"`fn new() -> Self` without `#[derive]`able `Default` implementation"
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}
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2017-08-09 02:30:56 -05:00
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#[derive(Copy, Clone)]
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2016-03-01 09:25:15 -06:00
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pub struct NewWithoutDefault;
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impl LintPass for NewWithoutDefault {
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fn get_lints(&self) -> LintArray {
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2016-05-17 01:33:57 -05:00
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lint_array!(NEW_WITHOUT_DEFAULT, NEW_WITHOUT_DEFAULT_DERIVE)
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2016-03-01 09:25:15 -06:00
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}
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}
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2016-12-07 06:13:40 -06:00
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impl<'a, 'tcx> LateLintPass<'a, 'tcx> for NewWithoutDefault {
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2017-11-29 10:06:27 -06:00
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fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx hir::Item) {
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if let hir::ItemImpl(_, _, _, _, None, _, ref items) = item.node {
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for assoc_item in items {
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if let hir::AssociatedItemKind::Method { has_self: false } = assoc_item.kind {
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let impl_item = cx.tcx.hir.impl_item(assoc_item.id);
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if in_external_macro(cx, impl_item.span) {
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return;
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}
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if let hir::ImplItemKind::Method(ref sig, _) = impl_item.node {
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let name = impl_item.name;
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let id = impl_item.id;
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if sig.constness == hir::Constness::Const {
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// can't be implemented by default
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return;
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}
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2017-12-21 22:42:47 -06:00
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if impl_item.generics.params.iter().any(|gen| gen.is_type_param()) {
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2017-11-29 10:06:27 -06:00
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// when the result of `new()` depends on a type parameter we should not require
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// an
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// impl of `Default`
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return;
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}
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2017-11-29 10:10:53 -06:00
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if sig.decl.inputs.is_empty() && name == "new" && cx.access_levels.is_reachable(id) {
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2017-11-29 10:06:27 -06:00
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let self_ty = cx.tcx
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.type_of(cx.tcx.hir.local_def_id(cx.tcx.hir.get_parent(id)));
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if_chain! {
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if same_tys(cx, self_ty, return_ty(cx, id));
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if let Some(default_trait_id) = get_trait_def_id(cx, &paths::DEFAULT_TRAIT);
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if !implements_trait(cx, self_ty, default_trait_id, &[]);
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then {
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if let Some(sp) = can_derive_default(self_ty, cx, default_trait_id) {
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span_lint_and_then(
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cx,
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NEW_WITHOUT_DEFAULT_DERIVE,
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2017-11-29 10:10:53 -06:00
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impl_item.span,
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2017-11-29 10:06:27 -06:00
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&format!("you should consider deriving a `Default` implementation for `{}`", self_ty),
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|db| {
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db.suggest_item_with_attr(cx, sp, "try this", "#[derive(Default)]");
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});
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} else {
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span_lint_and_then(
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cx,
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NEW_WITHOUT_DEFAULT,
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2017-11-29 10:10:53 -06:00
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impl_item.span,
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2017-11-29 10:06:27 -06:00
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&format!("you should consider adding a `Default` implementation for `{}`", self_ty),
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|db| {
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db.suggest_prepend_item(
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cx,
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2017-11-29 10:10:53 -06:00
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item.span,
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2017-11-29 10:06:27 -06:00
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"try this",
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&create_new_without_default_suggest_msg(self_ty),
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);
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},
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);
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}
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}
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}
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2017-11-04 14:25:13 -05:00
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}
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}
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2017-10-23 14:18:02 -05:00
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}
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2016-03-01 09:25:15 -06:00
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}
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}
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}
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}
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2016-05-17 01:33:57 -05:00
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2017-11-04 14:25:13 -05:00
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fn create_new_without_default_suggest_msg(ty: Ty) -> String {
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2018-05-30 03:05:06 -05:00
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#[cfg_attr(rustfmt, rustfmt_skip)]
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2017-11-04 14:25:13 -05:00
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format!(
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"impl Default for {} {{
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fn default() -> Self {{
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Self::new()
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}}
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}}", ty)
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}
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2017-06-10 21:57:25 -05:00
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fn can_derive_default<'t, 'c>(ty: Ty<'t>, cx: &LateContext<'c, 't>, default_trait_id: DefId) -> Option<Span> {
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2016-05-17 01:33:57 -05:00
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match ty.sty {
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2016-09-09 13:24:20 -05:00
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ty::TyAdt(adt_def, substs) if adt_def.is_struct() => {
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2016-05-17 01:33:57 -05:00
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for field in adt_def.all_fields() {
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let f_ty = field.ty(cx.tcx, substs);
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2017-06-10 21:34:47 -05:00
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if !implements_trait(cx, f_ty, default_trait_id, &[]) {
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2016-12-29 13:19:32 -06:00
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return None;
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2016-05-17 01:33:57 -05:00
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}
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}
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2017-06-10 22:15:53 -05:00
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Some(cx.tcx.def_span(adt_def.did))
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2016-12-20 11:21:30 -06:00
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},
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2016-12-29 13:19:32 -06:00
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_ => None,
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2016-05-17 01:33:57 -05:00
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}
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}
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