2 in_macro, match_def_path, match_trait_method, same_tys, snippet, snippet_with_macro_callsite, span_lint_and_then,
4 use crate::utils::{opt_def_id, paths, resolve_node};
6 use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
7 use rustc::{declare_tool_lint, lint_array};
8 use rustc_errors::Applicability;
10 /// **What it does:** Checks for always-identical `Into`/`From`/`IntoIter` conversions.
12 /// **Why is this bad?** Redundant code.
14 /// **Known problems:** None.
18 /// // format!() returns a `String`
19 /// let s: String = format!("hello").into();
21 declare_clippy_lint! {
22 pub IDENTITY_CONVERSION,
24 "using always-identical `Into`/`From`/`IntoIter` conversions"
28 pub struct IdentityConversion {
29 try_desugar_arm: Vec<HirId>,
32 impl LintPass for IdentityConversion {
33 fn get_lints(&self) -> LintArray {
34 lint_array!(IDENTITY_CONVERSION)
37 fn name(&self) -> &'static str {
42 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for IdentityConversion {
43 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, e: &'tcx Expr) {
48 if Some(&e.hir_id) == self.try_desugar_arm.last() {
53 ExprKind::Match(_, ref arms, MatchSource::TryDesugar) => {
54 let e = match arms[0].body.node {
55 ExprKind::Ret(Some(ref e)) | ExprKind::Break(_, Some(ref e)) => e,
58 if let ExprKind::Call(_, ref args) = e.node {
59 self.try_desugar_arm.push(args[0].hir_id);
65 ExprKind::MethodCall(ref name, .., ref args) => {
66 if match_trait_method(cx, e, &paths::INTO[..]) && &*name.ident.as_str() == "into" {
67 let a = cx.tables.expr_ty(e);
68 let b = cx.tables.expr_ty(&args[0]);
69 if same_tys(cx, a, b) {
70 let sugg = snippet_with_macro_callsite(cx, args[0].span, "<expr>").to_string();
72 span_lint_and_then(cx, IDENTITY_CONVERSION, e.span, "identical conversion", |db| {
75 "consider removing `.into()`",
77 Applicability::MachineApplicable, // snippet
82 if match_trait_method(cx, e, &paths::INTO_ITERATOR) && &*name.ident.as_str() == "into_iter" {
83 let a = cx.tables.expr_ty(e);
84 let b = cx.tables.expr_ty(&args[0]);
85 if same_tys(cx, a, b) {
86 let sugg = snippet(cx, args[0].span, "<expr>").into_owned();
87 span_lint_and_then(cx, IDENTITY_CONVERSION, e.span, "identical conversion", |db| {
90 "consider removing `.into_iter()`",
92 Applicability::MachineApplicable, // snippet
99 ExprKind::Call(ref path, ref args) => {
100 if let ExprKind::Path(ref qpath) = path.node {
101 if let Some(def_id) = opt_def_id(resolve_node(cx, qpath, path.hir_id)) {
102 if match_def_path(cx.tcx, def_id, &paths::FROM_FROM[..]) {
103 let a = cx.tables.expr_ty(e);
104 let b = cx.tables.expr_ty(&args[0]);
105 if same_tys(cx, a, b) {
106 let sugg = snippet(cx, args[0].span.source_callsite(), "<expr>").into_owned();
108 format!("consider removing `{}()`", snippet(cx, path.span, "From::from"));
109 span_lint_and_then(cx, IDENTITY_CONVERSION, e.span, "identical conversion", |db| {
114 Applicability::MachineApplicable, // snippet
127 fn check_expr_post(&mut self, _: &LateContext<'a, 'tcx>, e: &'tcx Expr) {
128 if Some(&e.hir_id) == self.try_desugar_arm.last() {
129 self.try_desugar_arm.pop();