use rustc::lint::*; use rustc::hir::*; use syntax::ast::NodeId; use crate::utils::{in_macro, match_def_path, match_trait_method, same_tys, snippet, span_lint_and_then}; use crate::utils::{opt_def_id, paths, resolve_node}; /// **What it does:** Checks for always-identical `Into`/`From` conversions. /// /// **Why is this bad?** Redundant code. /// /// **Known problems:** None. /// /// **Example:** /// ```rust /// // format!() returns a `String` /// let s: String = format!("hello").into(); /// ``` declare_clippy_lint! { pub IDENTITY_CONVERSION, complexity, "using always-identical `Into`/`From` conversions" } #[derive(Default)] pub struct IdentityConversion { try_desugar_arm: Vec, } impl LintPass for IdentityConversion { fn get_lints(&self) -> LintArray { lint_array!(IDENTITY_CONVERSION) } } impl<'a, 'tcx> LateLintPass<'a, 'tcx> for IdentityConversion { fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, e: &'tcx Expr) { if in_macro(e.span) { return; } if Some(&e.id) == self.try_desugar_arm.last() { return; } match e.node { ExprMatch(_, ref arms, MatchSource::TryDesugar) => { let e = match arms[0].body.node { ExprRet(Some(ref e)) | ExprBreak(_, Some(ref e)) => e, _ => return, }; if let ExprCall(_, ref args) = e.node { self.try_desugar_arm.push(args[0].id); } else { return; } }, ExprMethodCall(ref name, .., ref args) => { if match_trait_method(cx, e, &paths::INTO[..]) && &*name.name.as_str() == "into" { let a = cx.tables.expr_ty(e); let b = cx.tables.expr_ty(&args[0]); if same_tys(cx, a, b) { let sugg = snippet(cx, args[0].span, "").into_owned(); span_lint_and_then(cx, IDENTITY_CONVERSION, e.span, "identical conversion", |db| { db.span_suggestion(e.span, "consider removing `.into()`", sugg); }); } } }, ExprCall(ref path, ref args) => if let ExprPath(ref qpath) = path.node { if let Some(def_id) = opt_def_id(resolve_node(cx, qpath, path.hir_id)) { if match_def_path(cx.tcx, def_id, &paths::FROM_FROM[..]) { let a = cx.tables.expr_ty(e); let b = cx.tables.expr_ty(&args[0]); if same_tys(cx, a, b) { let sugg = snippet(cx, args[0].span, "").into_owned(); let sugg_msg = format!("consider removing `{}()`", snippet(cx, path.span, "From::from")); span_lint_and_then(cx, IDENTITY_CONVERSION, e.span, "identical conversion", |db| { db.span_suggestion(e.span, &sugg_msg, sugg); }); } } } }, _ => {}, } } fn check_expr_post(&mut self, _: &LateContext<'a, 'tcx>, e: &'tcx Expr) { if Some(&e.id) == self.try_desugar_arm.last() { self.try_desugar_arm.pop(); } } }