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