1 use crate::utils::{in_macro, match_trait_method, same_tys, snippet, snippet_with_macro_callsite, span_lint_and_then};
2 use crate::utils::{paths, resolve_node};
4 use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
5 use rustc::{declare_tool_lint, impl_lint_pass};
6 use rustc_errors::Applicability;
9 /// **What it does:** Checks for always-identical `Into`/`From`/`IntoIter` conversions.
11 /// **Why is this bad?** Redundant code.
13 /// **Known problems:** None.
17 /// // format!() returns a `String`
18 /// let s: String = format!("hello").into();
20 pub IDENTITY_CONVERSION,
22 "using always-identical `Into`/`From`/`IntoIter` conversions"
26 pub struct IdentityConversion {
27 try_desugar_arm: Vec<HirId>,
30 impl_lint_pass!(IdentityConversion => [IDENTITY_CONVERSION]);
32 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for IdentityConversion {
33 fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, e: &'tcx Expr) {
38 if Some(&e.hir_id) == self.try_desugar_arm.last() {
43 ExprKind::Match(_, ref arms, MatchSource::TryDesugar) => {
44 let e = match arms[0].body.node {
45 ExprKind::Ret(Some(ref e)) | ExprKind::Break(_, Some(ref e)) => e,
48 if let ExprKind::Call(_, ref args) = e.node {
49 self.try_desugar_arm.push(args[0].hir_id);
55 ExprKind::MethodCall(ref name, .., ref args) => {
56 if match_trait_method(cx, e, &paths::INTO[..]) && &*name.ident.as_str() == "into" {
57 let a = cx.tables.expr_ty(e);
58 let b = cx.tables.expr_ty(&args[0]);
59 if same_tys(cx, a, b) {
60 let sugg = snippet_with_macro_callsite(cx, args[0].span, "<expr>").to_string();
62 span_lint_and_then(cx, IDENTITY_CONVERSION, e.span, "identical conversion", |db| {
65 "consider removing `.into()`",
67 Applicability::MachineApplicable, // snippet
72 if match_trait_method(cx, e, &paths::INTO_ITERATOR) && &*name.ident.as_str() == "into_iter" {
73 let a = cx.tables.expr_ty(e);
74 let b = cx.tables.expr_ty(&args[0]);
75 if same_tys(cx, a, b) {
76 let sugg = snippet(cx, args[0].span, "<expr>").into_owned();
77 span_lint_and_then(cx, IDENTITY_CONVERSION, e.span, "identical conversion", |db| {
80 "consider removing `.into_iter()`",
82 Applicability::MachineApplicable, // snippet
89 ExprKind::Call(ref path, ref args) => {
90 if let ExprKind::Path(ref qpath) = path.node {
91 if let Some(def_id) = resolve_node(cx, qpath, path.hir_id).opt_def_id() {
92 if cx.match_def_path(def_id, &paths::FROM_FROM[..]) {
93 let a = cx.tables.expr_ty(e);
94 let b = cx.tables.expr_ty(&args[0]);
95 if same_tys(cx, a, b) {
96 let sugg = snippet(cx, args[0].span.source_callsite(), "<expr>").into_owned();
98 format!("consider removing `{}()`", snippet(cx, path.span, "From::from"));
99 span_lint_and_then(cx, IDENTITY_CONVERSION, e.span, "identical conversion", |db| {
104 Applicability::MachineApplicable, // snippet
117 fn check_expr_post(&mut self, _: &LateContext<'a, 'tcx>, e: &'tcx Expr) {
118 if Some(&e.hir_id) == self.try_desugar_arm.last() {
119 self.try_desugar_arm.pop();