use reexport::*; use rustc::lint::*; use rustc::hir::*; use rustc::hir::intravisit::{Visitor, FnKind, NestedVisitorMap}; use rustc::ty; use syntax::codemap::Span; use utils::{higher, in_external_macro, snippet, span_lint_and_then, iter_input_pats}; /// **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 = &x; /// ``` declare_lint! { pub SHADOW_SAME, Allow, "rebinding a name to itself, e.g. `let mut x = &mut x`" } /// **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 = x + 1; /// ``` declare_lint! { pub SHADOW_REUSE, Allow, "rebinding a name to an expression that re-uses the original value, e.g. \ `let x = x + 1`" } /// **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 ore 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 x = y; let x = z; // shadows the earlier binding /// ``` declare_lint! { pub SHADOW_UNRELATED, Allow, "rebinding a name without even using the original value" } #[derive(Copy, Clone)] pub struct Pass; impl LintPass for Pass { fn get_lints(&self) -> LintArray { lint_array!(SHADOW_SAME, SHADOW_REUSE, SHADOW_UNRELATED) } } impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass { fn check_fn( &mut self, cx: &LateContext<'a, 'tcx>, _: FnKind<'tcx>, decl: &'tcx FnDecl, body: &'tcx Body, _: Span, _: NodeId ) { if in_external_macro(cx, 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::new(); for arg in iter_input_pats(decl, body) { if let PatKind::Binding(_, _, ident, _) = arg.pat.node { bindings.push((ident.node, 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.node { StmtDecl(ref decl, _) => check_decl(cx, decl, bindings), StmtExpr(ref e, _) | StmtSemi(ref e, _) => check_expr(cx, e, bindings), } } if let Some(ref o) = block.expr { check_expr(cx, o, bindings); } bindings.truncate(len); } fn check_decl<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, decl: &'tcx Decl, bindings: &mut Vec<(Name, Span)>) { if in_external_macro(cx, decl.span) { return; } if higher::is_from_for_desugar(decl) { return; } if let DeclLocal(ref local) = decl.node { 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: NodeId) -> bool { let var_ty = cx.tables.node_id_to_type(pat_id); match var_ty.sty { ty::TyAdt(..) => 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.node { PatKind::Binding(_, _, ref ident, ref inner) => { let name = ident.node; if is_binding(cx, pat.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(_, ref pfields, _) => { if let Some(init_struct) = init { if let ExprStruct(_, ref efields, _) = init_struct.node { for field in pfields { let name = field.node.name; let efield = efields.iter() .find(|f| f.name.node == name) .map(|f| &*f.expr); check_pat(cx, &field.node.pat, efield, span, bindings); } } else { for field in pfields { check_pat(cx, &field.node.pat, init, span, bindings); } } } else { for field in pfields { check_pat(cx, &field.node.pat, None, span, bindings); } } }, PatKind::Tuple(ref inner, _) => { if let Some(init_tup) = init { if let ExprTup(ref tup) = init_tup.node { 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 ExprBox(ref inner_init) = initp.node { 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: 'a>( 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_self(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, expr.span) { return; } match expr.node { ExprUnary(_, ref e) | ExprField(ref e, _) | ExprTupField(ref e, _) | ExprAddrOf(_, ref e) | ExprBox(ref e) => check_expr(cx, e, bindings), ExprBlock(ref block) | ExprLoop(ref block, _, _) => check_block(cx, block, bindings), // ExprCall // ExprMethodCall ExprArray(ref v) | ExprTup(ref v) => { for e in v { check_expr(cx, e, bindings) } }, ExprIf(ref cond, ref then, ref otherwise) => { check_expr(cx, cond, bindings); check_expr(cx, &**then, bindings); if let Some(ref o) = *otherwise { check_expr(cx, o, bindings); } }, ExprWhile(ref cond, ref block, _) => { check_expr(cx, cond, bindings); check_block(cx, block, bindings); }, ExprMatch(ref init, ref arms, _) => { check_expr(cx, init, bindings); let len = bindings.len(); for arm in arms { for pat in &arm.pats { check_pat(cx, pat, Some(&**init), pat.span, bindings); // This is ugly, but needed to get the right type if let Some(ref guard) = arm.guard { check_expr(cx, guard, 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.node { TySlice(ref sty) => check_ty(cx, sty, bindings), TyArray(ref fty, body_id) => { check_ty(cx, fty, bindings); check_expr(cx, &cx.tcx.hir.body(body_id).value, bindings); }, TyPtr(MutTy { ty: ref mty, .. }) | TyRptr(_, MutTy { ty: ref mty, .. }) => check_ty(cx, mty, bindings), TyTup(ref tup) => { for t in tup { check_ty(cx, t, bindings) } }, TyTypeof(body_id) => check_expr(cx, &cx.tcx.hir.body(body_id).value, bindings), _ => (), } } fn is_self_shadow(name: Name, expr: &Expr) -> bool { match expr.node { ExprBox(ref inner) | ExprAddrOf(_, ref inner) => is_self_shadow(name, inner), ExprBlock(ref block) => { block.stmts.is_empty() && block.expr.as_ref().map_or(false, |e| is_self_shadow(name, e)) }, ExprUnary(op, ref inner) => (UnDeref == op) && is_self_shadow(name, inner), ExprPath(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].name.as_str() == name.as_str() } struct ContainsSelf { name: Name, result: bool, } impl<'tcx> Visitor<'tcx> for ContainsSelf { fn visit_name(&mut self, _: Span, name: Name) { if self.name == name { self.result = true; } } fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> { NestedVisitorMap::None } } fn contains_self(name: Name, expr: &Expr) -> bool { let mut cs = ContainsSelf { name: name, result: false, }; cs.visit_expr(expr); cs.result }