--- /dev/null
+use crate::utils::{contains_name, higher, iter_input_pats, snippet, span_lint_and_then};
+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_middle::lint::in_external_macro;
+use rustc_middle::ty;
+use rustc_session::{declare_lint_pass, declare_tool_lint};
+use rustc_span::source_map::Span;
+use rustc_span::symbol::Symbol;
+
+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;
+ /// // Bad
+ /// let x = &x;
+ ///
+ /// // Good
+ /// let y = &x; // use different variable name
+ /// ```
+ 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. Note that
+ /// `allow`/`warn`/`deny`/`forbid` attributes only work on the function level
+ /// for this lint.
+ ///
+ /// **Example:**
+ /// ```rust
+ /// # let y = 1;
+ /// # let z = 2;
+ /// let x = y;
+ ///
+ /// // Bad
+ /// let x = z; // shadows the earlier binding
+ ///
+ /// // Good
+ /// let w = z; // use different variable name
+ /// ```
+ pub SHADOW_UNRELATED,
+ pedantic,
+ "rebinding a name without even using the original value"
+}
+
+declare_lint_pass!(Shadow => [SHADOW_SAME, SHADOW_REUSE, SHADOW_UNRELATED]);
+
+impl<'tcx> LateLintPass<'tcx> for Shadow {
+ fn check_fn(
+ &mut self,
+ cx: &LateContext<'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<'tcx>(cx: &LateContext<'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<'tcx>(cx: &LateContext<'tcx>, block: &'tcx Block<'_>, bindings: &mut Vec<(Symbol, 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<'tcx>(cx: &LateContext<'tcx>, local: &'tcx Local<'_>, bindings: &mut Vec<(Symbol, 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.typeck_results().node_type_opt(pat_id);
+ var_ty.map_or(false, |var_ty| !matches!(var_ty.kind(), ty::Adt(..)))
+}
+
+fn check_pat<'tcx>(
+ cx: &LateContext<'tcx>,
+ pat: &'tcx Pat<'_>,
+ init: Option<&'tcx Expr<'_>>,
+ span: Span,
+ bindings: &mut Vec<(Symbol, 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<P<Pat>>, Option<P<Pat>>, Vec<P<Pat>>),
+ _ => (),
+ }
+}
+
+fn lint_shadow<'tcx>(
+ cx: &LateContext<'tcx>,
+ name: Symbol,
+ 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, "..")
+ ),
+ |diag| {
+ diag.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, "..")
+ ),
+ |diag| {
+ diag.span_note(expr.span, "initialization happens here");
+ diag.span_note(prev_span, "previous binding is here");
+ },
+ );
+ } else {
+ span_lint_and_then(
+ cx,
+ SHADOW_UNRELATED,
+ pattern_span,
+ &format!("`{}` is being shadowed", snippet(cx, pattern_span, "_")),
+ |diag| {
+ diag.span_note(expr.span, "initialization happens here");
+ diag.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, "_")),
+ |diag| {
+ diag.span_note(prev_span, "previous binding is here");
+ },
+ );
+ }
+}
+
+fn check_expr<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>, bindings: &mut Vec<(Symbol, 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::If(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);
+ }
+ },
+ 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),
+ Guard::IfLet(guard_pat, guard_expr) => {
+ check_pat(cx, guard_pat, Some(*guard_expr), guard_pat.span, bindings);
+ check_expr(cx, guard_expr, bindings);
+ },
+ }
+ }
+ check_expr(cx, &arm.body, bindings);
+ bindings.truncate(len);
+ }
+ },
+ _ => (),
+ }
+}
+
+fn check_ty<'tcx>(cx: &LateContext<'tcx>, ty: &'tcx Ty<'_>, bindings: &mut Vec<(Symbol, 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: Symbol, 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::Deref == op) && is_self_shadow(name, inner),
+ ExprKind::Path(QPath::Resolved(_, ref path)) => path_eq_name(name, path),
+ _ => false,
+ }
+}
+
+fn path_eq_name(name: Symbol, path: &Path<'_>) -> bool {
+ !path.is_global() && path.segments.len() == 1 && path.segments[0].ident.name == name
+}
projects / rustc.git / blobdiff