109 lines
3.0 KiB
Rust
109 lines
3.0 KiB
Rust
use syntax::ast::{Expr, ExprKind, UnOp};
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use rustc::lint::*;
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use rustc::{declare_lint, lint_array};
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use if_chain::if_chain;
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use crate::utils::{snippet, span_lint_and_sugg};
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/// **What it does:** Checks for usage of `*&` and `*&mut` in expressions.
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///
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/// **Why is this bad?** Immediately dereferencing a reference is no-op and
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/// makes the code less clear.
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///
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/// **Known problems:** Multiple dereference/addrof pairs are not handled so
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/// the suggested fix for `x = **&&y` is `x = *&y`, which is still incorrect.
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///
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/// **Example:**
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/// ```rust
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/// let a = f(*&mut b);
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/// let c = *&d;
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/// ```
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declare_clippy_lint! {
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pub DEREF_ADDROF,
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complexity,
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"use of `*&` or `*&mut` in an expression"
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}
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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!(DEREF_ADDROF)
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}
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}
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fn without_parens(mut e: &Expr) -> &Expr {
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while let ExprKind::Paren(ref child_e) = e.node {
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e = child_e;
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}
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e
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}
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impl EarlyLintPass for Pass {
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fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &Expr) {
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if_chain! {
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if let ExprKind::Unary(UnOp::Deref, ref deref_target) = e.node;
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if let ExprKind::AddrOf(_, ref addrof_target) = without_parens(deref_target).node;
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then {
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span_lint_and_sugg(
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cx,
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DEREF_ADDROF,
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e.span,
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"immediately dereferencing a reference",
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"try this",
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format!("{}", snippet(cx, addrof_target.span, "_")),
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);
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}
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}
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}
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}
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/// **What it does:** Checks for references in expressions that use
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/// auto dereference.
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///
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/// **Why is this bad?** The reference is a no-op and is automatically
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/// dereferenced by the compiler and makes the code less clear.
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///
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/// **Example:**
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/// ```rust
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/// struct Point(u32, u32);
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/// let point = Foo(30, 20);
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/// let x = (&point).x;
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/// ```
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declare_clippy_lint! {
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pub REF_IN_DEREF,
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complexity,
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"Use of reference in auto dereference expression."
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}
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pub struct DerefPass;
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impl LintPass for DerefPass {
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fn get_lints(&self) -> LintArray {
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lint_array!(REF_IN_DEREF)
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}
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}
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impl EarlyLintPass for DerefPass {
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fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &Expr) {
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if_chain! {
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if let ExprKind::Field(ref object, ref field_name) = e.node;
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if let ExprKind::Paren(ref parened) = object.node;
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if let ExprKind::AddrOf(_, ref inner) = parened.node;
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then {
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span_lint_and_sugg(
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cx,
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REF_IN_DEREF,
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object.span,
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"Creating a reference that is immediately dereferenced.",
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"try this",
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format!(
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"{}.{}",
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snippet(cx, inner.span, "_"),
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snippet(cx, field_name.span, "_")
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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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