use crate::reexport::Name; use crate::utils::{contains_name, higher, iter_input_pats, snippet, span_lint_and_then}; use rustc::lint::in_external_macro; use rustc::ty; use rustc_hir::intravisit::FnKind; use rustc_hir::{ Block, Body, Expr, ExprKind, FnDecl, Guard, HirId, Local, MutTy, Pat, PatKind, Path, QPath, StmtKind, Ty, TyKind, UnOp, }; use rustc_lint::{LateContext, LateLintPass, LintContext}; use rustc_session::{declare_lint_pass, declare_tool_lint}; use rustc_span::source_map::Span; declare_clippy_lint! { /// **What it does:** Checks for bindings that shadow other bindings already in /// scope, while just changing reference level or mutability. /// /// **Why is this bad?** Not much, in fact it's a very common pattern in Rust /// code. Still, some may opt to avoid it in their code base, they can set this /// lint to `Warn`. /// /// **Known problems:** This lint, as the other shadowing related lints, /// currently only catches very simple patterns. /// /// **Example:** /// ```rust /// # let x = 1; /// let x = &x; /// ``` pub SHADOW_SAME, restriction, "rebinding a name to itself, e.g., `let mut x = &mut x`" } declare_clippy_lint! { /// **What it does:** Checks for bindings that shadow other bindings already in /// scope, while reusing the original value. /// /// **Why is this bad?** Not too much, in fact it's a common pattern in Rust /// code. Still, some argue that name shadowing like this hurts readability, /// because a value may be bound to different things depending on position in /// the code. /// /// **Known problems:** This lint, as the other shadowing related lints, /// currently only catches very simple patterns. /// /// **Example:** /// ```rust /// let x = 2; /// let x = x + 1; /// ``` /// use different variable name: /// ```rust /// let x = 2; /// let y = x + 1; /// ``` pub SHADOW_REUSE, restriction, "rebinding a name to an expression that re-uses the original value, e.g., `let x = x + 1`" } declare_clippy_lint! { /// **What it does:** Checks for bindings that shadow other bindings already in /// scope, either without a initialization or with one that does not even use /// the original value. /// /// **Why is this bad?** Name shadowing can hurt readability, especially in /// large code bases, because it is easy to lose track of the active binding at /// any place in the code. This can be alleviated by either giving more specific /// names to bindings or introducing more scopes to contain the bindings. /// /// **Known problems:** This lint, as the other shadowing related lints, /// currently only catches very simple patterns. /// /// **Example:** /// ```rust /// # let y = 1; /// # let z = 2; /// let x = y; /// let x = z; // shadows the earlier binding /// ``` pub SHADOW_UNRELATED, pedantic, "rebinding a name without even using the original value" } declare_lint_pass!(Shadow => [SHADOW_SAME, SHADOW_REUSE, SHADOW_UNRELATED]); impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Shadow { fn check_fn( &mut self, cx: &LateContext<'a, 'tcx>, _: FnKind<'tcx>, decl: &'tcx FnDecl<'_>, body: &'tcx Body<'_>, _: Span, _: HirId, ) { if in_external_macro(cx.sess(), body.value.span) { return; } check_fn(cx, decl, body); } } fn check_fn<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, decl: &'tcx FnDecl<'_>, body: &'tcx Body<'_>) { let mut bindings = Vec::with_capacity(decl.inputs.len()); for arg in iter_input_pats(decl, body) { if let PatKind::Binding(.., ident, _) = arg.pat.kind { bindings.push((ident.name, ident.span)) } } check_expr(cx, &body.value, &mut bindings); } fn check_block<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, block: &'tcx Block<'_>, bindings: &mut Vec<(Name, Span)>) { let len = bindings.len(); for stmt in block.stmts { match stmt.kind { StmtKind::Local(ref local) => check_local(cx, local, bindings), StmtKind::Expr(ref e) | StmtKind::Semi(ref e) => check_expr(cx, e, bindings), StmtKind::Item(..) => {}, } } if let Some(ref o) = block.expr { check_expr(cx, o, bindings); } bindings.truncate(len); } fn check_local<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, local: &'tcx Local<'_>, bindings: &mut Vec<(Name, Span)>) { if in_external_macro(cx.sess(), local.span) { return; } if higher::is_from_for_desugar(local) { return; } let Local { ref pat, ref ty, ref init, span, .. } = *local; if let Some(ref t) = *ty { check_ty(cx, t, bindings) } if let Some(ref o) = *init { check_expr(cx, o, bindings); check_pat(cx, pat, Some(o), span, bindings); } else { check_pat(cx, pat, None, span, bindings); } } fn is_binding(cx: &LateContext<'_, '_>, pat_id: HirId) -> bool { let var_ty = cx.tables.node_type(pat_id); match var_ty.kind { ty::Adt(..) => false, _ => true, } } fn check_pat<'a, 'tcx>( cx: &LateContext<'a, 'tcx>, pat: &'tcx Pat<'_>, init: Option<&'tcx Expr<'_>>, span: Span, bindings: &mut Vec<(Name, Span)>, ) { // TODO: match more stuff / destructuring match pat.kind { PatKind::Binding(.., ident, ref inner) => { let name = ident.name; if is_binding(cx, pat.hir_id) { let mut new_binding = true; for tup in bindings.iter_mut() { if tup.0 == name { lint_shadow(cx, name, span, pat.span, init, tup.1); tup.1 = ident.span; new_binding = false; break; } } if new_binding { bindings.push((name, ident.span)); } } if let Some(ref p) = *inner { check_pat(cx, p, init, span, bindings); } }, PatKind::Struct(_, pfields, _) => { if let Some(init_struct) = init { if let ExprKind::Struct(_, ref efields, _) = init_struct.kind { for field in pfields { let name = field.ident.name; let efield = efields .iter() .find_map(|f| if f.ident.name == name { Some(&*f.expr) } else { None }); check_pat(cx, &field.pat, efield, span, bindings); } } else { for field in pfields { check_pat(cx, &field.pat, init, span, bindings); } } } else { for field in pfields { check_pat(cx, &field.pat, None, span, bindings); } } }, PatKind::Tuple(inner, _) => { if let Some(init_tup) = init { if let ExprKind::Tup(ref tup) = init_tup.kind { for (i, p) in inner.iter().enumerate() { check_pat(cx, p, Some(&tup[i]), p.span, bindings); } } else { for p in inner { check_pat(cx, p, init, span, bindings); } } } else { for p in inner { check_pat(cx, p, None, span, bindings); } } }, PatKind::Box(ref inner) => { if let Some(initp) = init { if let ExprKind::Box(ref inner_init) = initp.kind { check_pat(cx, inner, Some(&**inner_init), span, bindings); } else { check_pat(cx, inner, init, span, bindings); } } else { check_pat(cx, inner, init, span, bindings); } }, PatKind::Ref(ref inner, _) => check_pat(cx, inner, init, span, bindings), // PatVec(Vec>, Option>, Vec>), _ => (), } } fn lint_shadow<'a, 'tcx>( cx: &LateContext<'a, 'tcx>, name: Name, span: Span, pattern_span: Span, init: Option<&'tcx Expr<'_>>, prev_span: Span, ) { if let Some(expr) = init { if is_self_shadow(name, expr) { span_lint_and_then( cx, SHADOW_SAME, span, &format!( "`{}` is shadowed by itself in `{}`", snippet(cx, pattern_span, "_"), snippet(cx, expr.span, "..") ), |db| { db.span_note(prev_span, "previous binding is here"); }, ); } else if contains_name(name, expr) { span_lint_and_then( cx, SHADOW_REUSE, pattern_span, &format!( "`{}` is shadowed by `{}` which reuses the original value", snippet(cx, pattern_span, "_"), snippet(cx, expr.span, "..") ), |db| { db.span_note(expr.span, "initialization happens here"); db.span_note(prev_span, "previous binding is here"); }, ); } else { span_lint_and_then( cx, SHADOW_UNRELATED, pattern_span, &format!( "`{}` is shadowed by `{}`", snippet(cx, pattern_span, "_"), snippet(cx, expr.span, "..") ), |db| { db.span_note(expr.span, "initialization happens here"); db.span_note(prev_span, "previous binding is here"); }, ); } } else { span_lint_and_then( cx, SHADOW_UNRELATED, span, &format!("`{}` shadows a previous declaration", snippet(cx, pattern_span, "_")), |db| { db.span_note(prev_span, "previous binding is here"); }, ); } } fn check_expr<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr<'_>, bindings: &mut Vec<(Name, Span)>) { if in_external_macro(cx.sess(), expr.span) { return; } match expr.kind { ExprKind::Unary(_, ref e) | ExprKind::Field(ref e, _) | ExprKind::AddrOf(_, _, ref e) | ExprKind::Box(ref e) => check_expr(cx, e, bindings), ExprKind::Block(ref block, _) | ExprKind::Loop(ref block, _, _) => check_block(cx, block, bindings), // ExprKind::Call // ExprKind::MethodCall ExprKind::Array(v) | ExprKind::Tup(v) => { for e in v { check_expr(cx, e, bindings) } }, ExprKind::Match(ref init, arms, _) => { check_expr(cx, init, bindings); let len = bindings.len(); for arm in arms { check_pat(cx, &arm.pat, Some(&**init), arm.pat.span, bindings); // This is ugly, but needed to get the right type if let Some(ref guard) = arm.guard { match guard { Guard::If(if_expr) => check_expr(cx, if_expr, bindings), } } check_expr(cx, &arm.body, bindings); bindings.truncate(len); } }, _ => (), } } fn check_ty<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, ty: &'tcx Ty<'_>, bindings: &mut Vec<(Name, Span)>) { match ty.kind { TyKind::Slice(ref sty) => check_ty(cx, sty, bindings), TyKind::Array(ref fty, ref anon_const) => { check_ty(cx, fty, bindings); check_expr(cx, &cx.tcx.hir().body(anon_const.body).value, bindings); }, TyKind::Ptr(MutTy { ty: ref mty, .. }) | TyKind::Rptr(_, MutTy { ty: ref mty, .. }) => { check_ty(cx, mty, bindings) }, TyKind::Tup(tup) => { for t in tup { check_ty(cx, t, bindings) } }, TyKind::Typeof(ref anon_const) => check_expr(cx, &cx.tcx.hir().body(anon_const.body).value, bindings), _ => (), } } fn is_self_shadow(name: Name, expr: &Expr<'_>) -> bool { match expr.kind { ExprKind::Box(ref inner) | ExprKind::AddrOf(_, _, ref inner) => is_self_shadow(name, inner), ExprKind::Block(ref block, _) => { block.stmts.is_empty() && block.expr.as_ref().map_or(false, |e| is_self_shadow(name, e)) }, ExprKind::Unary(op, ref inner) => (UnOp::UnDeref == op) && is_self_shadow(name, inner), ExprKind::Path(QPath::Resolved(_, ref path)) => path_eq_name(name, path), _ => false, } } fn path_eq_name(name: Name, path: &Path<'_>) -> bool { !path.is_global() && path.segments.len() == 1 && path.segments[0].ident.as_str() == name.as_str() }