67 lines
2.1 KiB
Rust
67 lines
2.1 KiB
Rust
use rustc::lint::*;
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use rustc_front::hir;
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use rustc_front::intravisit::FnKind;
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use syntax::ast;
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use syntax::codemap::Span;
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use utils::{get_trait_def_id, implements_trait, in_external_macro, return_ty, same_tys, span_lint,
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DEFAULT_TRAIT_PATH};
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/// **What it does:** This lints about type with a `fn new() -> Self` method and no `Default`
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/// implementation.
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///
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/// **Why is this bad?** User might expect to be able to use `Default` as the type can be
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/// constructed without arguments.
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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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declare_lint! {
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pub NEW_WITHOUT_DEFAULT,
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Warn,
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"`fn new() -> Self` method without `Default` implementation"
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}
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#[derive(Copy,Clone)]
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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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lint_array!(NEW_WITHOUT_DEFAULT)
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}
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}
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impl LateLintPass for NewWithoutDefault {
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fn check_fn(&mut self, cx: &LateContext, kind: FnKind, decl: &hir::FnDecl, _: &hir::Block, span: Span, id: ast::NodeId) {
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if in_external_macro(cx, span) {
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return;
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}
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if let FnKind::Method(name, _, _, _) = kind {
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if decl.inputs.is_empty() && name.as_str() == "new" {
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let self_ty = cx.tcx.lookup_item_type(cx.tcx.map.local_def_id(cx.tcx.map.get_parent(id))).ty;
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if_let_chain!{[
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self_ty.walk_shallow().next().is_none(), // implements_trait does not work with generics
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let Some(ret_ty) = return_ty(cx.tcx.node_id_to_type(id)),
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same_tys(cx, self_ty, ret_ty),
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let Some(default_trait_id) = get_trait_def_id(cx, &DEFAULT_TRAIT_PATH),
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!implements_trait(cx, self_ty, default_trait_id, Vec::new())
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], {
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span_lint(cx, NEW_WITHOUT_DEFAULT, span,
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&format!("you should consider adding a `Default` implementation for `{}`", 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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