1 use if_chain::if_chain;
2 use rustc_errors::Applicability;
3 use rustc_hir::{Expr, ExprKind, QPath};
4 use rustc_lint::{LateContext, LateLintPass};
6 use rustc_session::{declare_lint_pass, declare_tool_lint};
8 use crate::utils::{any_parent_is_automatically_derived, match_def_path, paths, span_lint_and_sugg};
10 declare_clippy_lint! {
11 /// **What it does:** Checks for literal calls to `Default::default()`.
13 /// **Why is this bad?** It's more clear to the reader to use the name of the type whose default is
14 /// being gotten than the generic `Default`.
16 /// **Known problems:** None.
21 /// let s: String = Default::default();
24 /// let s = String::default();
26 pub DEFAULT_TRAIT_ACCESS,
28 "checks for literal calls to `Default::default()`"
31 declare_lint_pass!(DefaultTraitAccess => [DEFAULT_TRAIT_ACCESS]);
33 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for DefaultTraitAccess {
34 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr<'_>) {
36 if let ExprKind::Call(ref path, ..) = expr.kind;
37 if !any_parent_is_automatically_derived(cx.tcx, expr.hir_id);
38 if let ExprKind::Path(ref qpath) = path.kind;
39 if let Some(def_id) = cx.tables.qpath_res(qpath, path.hir_id).opt_def_id();
40 if match_def_path(cx, def_id, &paths::DEFAULT_TRAIT_METHOD);
43 QPath::Resolved(..) => {
45 // Detect and ignore <Foo as Default>::default() because these calls do
46 // explicitly name the type.
47 if let ExprKind::Call(ref method, ref _args) = expr.kind;
48 if let ExprKind::Path(ref p) = method.kind;
49 if let QPath::Resolved(Some(_ty), _path) = p;
55 // TODO: Work out a way to put "whatever the imported way of referencing
56 // this type in this file" rather than a fully-qualified type.
57 let expr_ty = cx.tables.expr_ty(expr);
58 if let ty::Adt(..) = expr_ty.kind {
59 let replacement = format!("{}::default()", expr_ty);
64 &format!("Calling `{}` is more clear than this expression", replacement),
67 Applicability::Unspecified, // First resolve the TODO above
71 QPath::TypeRelative(..) => {},