377 lines
13 KiB
Rust
377 lines
13 KiB
Rust
use reexport::*;
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use rustc::lint::*;
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use rustc::hir::*;
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use rustc::hir::intravisit::{Visitor, FnKind};
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use rustc::ty;
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use std::ops::Deref;
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use syntax::codemap::Span;
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use utils::{higher, in_external_macro, snippet, span_lint_and_then};
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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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declare_lint! {
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pub SHADOW_SAME,
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Allow,
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"rebinding a name to itself, e.g. `let mut x = &mut x`"
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}
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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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declare_lint! {
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pub SHADOW_REUSE,
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Allow,
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"rebinding a name to an expression that re-uses the original value, e.g. \
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`let x = x + 1`"
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}
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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 ore 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; let x = z; // shadows the earlier binding
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/// ```
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declare_lint! {
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pub SHADOW_UNRELATED,
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Allow,
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"rebinding a name without even using the original value"
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}
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#[derive(Copy, Clone)]
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pub struct Pass;
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impl LintPass for Pass {
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fn get_lints(&self) -> LintArray {
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lint_array!(SHADOW_SAME, SHADOW_REUSE, SHADOW_UNRELATED)
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}
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}
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impl LateLintPass for Pass {
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fn check_fn(&mut self, cx: &LateContext, _: FnKind, decl: &FnDecl, expr: &Expr, _: Span, _: NodeId) {
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if in_external_macro(cx, expr.span) {
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return;
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}
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check_fn(cx, decl, expr);
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}
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}
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fn check_fn(cx: &LateContext, decl: &FnDecl, expr: &Expr) {
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let mut bindings = Vec::new();
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for arg in &decl.inputs {
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if let PatKind::Binding(_, _, ident, _) = arg.pat.node {
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bindings.push((ident.node, ident.span))
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}
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}
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check_expr(cx, expr, &mut bindings);
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}
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fn check_block(cx: &LateContext, block: &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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StmtDecl(ref decl, _) => check_decl(cx, decl, bindings),
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StmtExpr(ref e, _) |
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StmtSemi(ref e, _) => check_expr(cx, e, bindings),
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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_decl(cx: &LateContext, decl: &Decl, bindings: &mut Vec<(Name, Span)>) {
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if in_external_macro(cx, decl.span) {
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return;
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}
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if higher::is_from_for_desugar(decl) {
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return;
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}
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if let DeclLocal(ref local) = decl.node {
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let Local { ref pat, ref ty, ref init, span, .. } = **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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}
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fn is_binding(cx: &LateContext, pat_id: NodeId) -> bool {
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let var_ty = cx.tcx.tables().node_id_to_type(pat_id);
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match var_ty.sty {
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ty::TyAdt(..) => false,
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_ => true,
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}
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}
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fn check_pat(cx: &LateContext, pat: &Pat, init: &Option<&Expr>, span: Span, bindings: &mut Vec<(Name, Span)>) {
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// TODO: match more stuff / destructuring
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match pat.node {
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PatKind::Binding(_, _, ref ident, ref inner) => {
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let name = ident.node;
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if is_binding(cx, pat.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 ExprStruct(_, ref efields, _) = init_struct.node {
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for field in pfields {
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let name = field.node.name;
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let efield = efields.iter()
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.find(|f| f.name.node == name)
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.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 ExprTup(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 ExprBox(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<T>(cx: &LateContext, name: Name, span: Span, pattern_span: Span, init: &Option<T>, prev_span: Span)
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where T: Deref<Target = Expr>
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{
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if let Some(ref expr) = *init {
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if is_self_shadow(name, expr) {
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span_lint_and_then(cx,
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SHADOW_SAME,
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span,
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&format!("`{}` 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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|db| { db.span_note(prev_span, "previous binding is here"); },
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);
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} else if contains_self(name, expr) {
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span_lint_and_then(cx,
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SHADOW_REUSE,
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pattern_span,
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&format!("`{}` 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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|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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} else {
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span_lint_and_then(cx,
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SHADOW_UNRELATED,
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pattern_span,
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&format!("`{}` is shadowed by `{}`",
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snippet(cx, pattern_span, "_"),
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snippet(cx, expr.span, "..")),
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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(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| { db.span_note(prev_span, "previous binding is here"); });
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}
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}
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fn check_expr(cx: &LateContext, expr: &Expr, bindings: &mut Vec<(Name, Span)>) {
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if in_external_macro(cx, expr.span) {
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return;
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}
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match expr.node {
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ExprUnary(_, ref e) |
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ExprField(ref e, _) |
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ExprTupField(ref e, _) |
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ExprAddrOf(_, ref e) |
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ExprBox(ref e) => check_expr(cx, e, bindings),
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ExprBlock(ref block) |
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ExprLoop(ref block, _, _) => check_block(cx, block, bindings),
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// ExprCall
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// ExprMethodCall
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ExprArray(ref v) | ExprTup(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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ExprIf(ref cond, ref then, ref otherwise) => {
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check_expr(cx, cond, bindings);
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check_block(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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ExprWhile(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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ExprMatch(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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check_expr(cx, guard, bindings);
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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(cx: &LateContext, ty: &Ty, bindings: &mut Vec<(Name, Span)>) {
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match ty.node {
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TyObjectSum(ref sty, _) |
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TySlice(ref sty) => check_ty(cx, sty, bindings),
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TyArray(ref fty, ref expr) => {
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check_ty(cx, fty, bindings);
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check_expr(cx, expr, bindings);
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}
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TyPtr(MutTy { ty: ref mty, .. }) |
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TyRptr(_, MutTy { ty: ref mty, .. }) => check_ty(cx, mty, bindings),
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TyTup(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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TyTypeof(ref expr) => check_expr(cx, expr, 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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ExprBox(ref inner) |
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ExprAddrOf(_, ref inner) => is_self_shadow(name, inner),
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ExprBlock(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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ExprUnary(op, ref inner) => (UnDeref == op) && is_self_shadow(name, inner),
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ExprPath(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.global && path.segments.len() == 1 && path.segments[0].name.as_str() == name.as_str()
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}
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struct ContainsSelf {
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name: Name,
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result: bool,
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}
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impl<'v> Visitor<'v> for ContainsSelf {
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fn visit_name(&mut self, _: Span, name: Name) {
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if self.name == name {
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self.result = true;
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}
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}
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}
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fn contains_self(name: Name, expr: &Expr) -> bool {
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let mut cs = ContainsSelf {
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name: name,
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result: false,
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};
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cs.visit_expr(expr);
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cs.result
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}
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