use crate::utils::{ match_def_path, match_trait_method, paths, same_tys, snippet, snippet_with_macro_callsite, span_lint_and_then, }; use rustc_errors::Applicability; use rustc_hir::{Expr, ExprKind, HirId, MatchSource}; use rustc_lint::{LateContext, LateLintPass}; use rustc_session::{declare_tool_lint, impl_lint_pass}; declare_clippy_lint! { /// **What it does:** Checks for always-identical `Into`/`From`/`IntoIter` conversions. /// /// **Why is this bad?** Redundant code. /// /// **Known problems:** None. /// /// **Example:** /// ```rust /// // format!() returns a `String` /// let s: String = format!("hello").into(); /// ``` pub IDENTITY_CONVERSION, complexity, "using always-identical `Into`/`From`/`IntoIter` conversions" } #[derive(Default)] pub struct IdentityConversion { try_desugar_arm: Vec, } impl_lint_pass!(IdentityConversion => [IDENTITY_CONVERSION]); impl<'a, 'tcx> LateLintPass<'a, 'tcx> for IdentityConversion { fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, e: &'tcx Expr<'_>) { if e.span.from_expansion() { return; } if Some(&e.hir_id) == self.try_desugar_arm.last() { return; } match e.kind { ExprKind::Match(_, ref arms, MatchSource::TryDesugar) => { let e = match arms[0].body.kind { ExprKind::Ret(Some(ref e)) | ExprKind::Break(_, Some(ref e)) => e, _ => return, }; if let ExprKind::Call(_, ref args) = e.kind { self.try_desugar_arm.push(args[0].hir_id); } }, ExprKind::MethodCall(ref name, .., ref args) => { if match_trait_method(cx, e, &paths::INTO) && &*name.ident.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_with_macro_callsite(cx, args[0].span, "").to_string(); span_lint_and_then(cx, IDENTITY_CONVERSION, e.span, "identical conversion", |db| { db.span_suggestion( e.span, "consider removing `.into()`", sugg, Applicability::MachineApplicable, // snippet ); }); } } if match_trait_method(cx, e, &paths::INTO_ITERATOR) && &*name.ident.as_str() == "into_iter" { 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_iter()`", sugg, Applicability::MachineApplicable, // snippet ); }); } } }, ExprKind::Call(ref path, ref args) => { if let ExprKind::Path(ref qpath) = path.kind { if let Some(def_id) = cx.tables.qpath_res(qpath, path.hir_id).opt_def_id() { if match_def_path(cx, 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.source_callsite(), "").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, Applicability::MachineApplicable, // snippet ); }); } } } } }, _ => {}, } } fn check_expr_post(&mut self, _: &LateContext<'a, 'tcx>, e: &'tcx Expr<'_>) { if Some(&e.hir_id) == self.try_desugar_arm.last() { self.try_desugar_arm.pop(); } } }