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New lint: Recommend using
ptr::eq when possible
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,91 @@ | ||
| use crate::utils; | ||
| use if_chain::if_chain; | ||
| use rustc::hir::{BinOpKind, Expr, ExprKind}; | ||
| use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass}; | ||
| use rustc::{declare_lint_pass, declare_tool_lint}; | ||
| use rustc_errors::Applicability; | ||
|
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||
| declare_clippy_lint! { | ||
| /// **What it does:** Use `std::ptr::eq` when applicable | ||
| /// | ||
| /// **Why is this bad?** This can be used to compare `&T` references | ||
| /// (which coerce to `*const T` implicitly) by their address rather than | ||
| /// comparing the values they point to. | ||
| /// | ||
| /// **Known problems:** None | ||
| /// | ||
| /// **Example:** | ||
| /// ```rust | ||
| /// let a = &[1, 2, 3]; | ||
| /// let b = &[1, 2, 3]; | ||
| /// | ||
| /// let _ = a as *const _ as usize == b as *const _ as usize; | ||
| /// // Could be written | ||
| /// let _ = std::ptr::eq(a, b); | ||
| /// ``` | ||
| pub PTR_EQ, | ||
| style, | ||
| "use `std::ptr::eq` when applicable" | ||
| } | ||
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| declare_lint_pass!(PtrEqLint => [PTR_EQ]); | ||
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| static LINT_MSG: &str = "use `std::ptr::eq` when applicable"; | ||
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| impl<'a, 'tcx> LateLintPass<'a, 'tcx> for PtrEqLint { | ||
| fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) { | ||
| if let ExprKind::Binary(ref op, ref left, ref right) = expr.kind { | ||
| if BinOpKind::Eq == op.node { | ||
| let (left, right) = if_chain! { | ||
| if let Some(lhs) = expr_as_cast_to_usize(cx, left); | ||
| if let Some(rhs) = expr_as_cast_to_usize(cx, right); | ||
| then { | ||
| (lhs, rhs) | ||
| } | ||
| else { | ||
| (&**left, &**right) | ||
| } | ||
| }; | ||
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||
| if let Some(left_var) = expr_as_cast_to_raw_pointer(cx, left) { | ||
| if let Some(right_var) = expr_as_cast_to_raw_pointer(cx, right) { | ||
| let left_snip = utils::snippet(cx, left_var.span, ".."); | ||
| let right_snip = utils::snippet(cx, right_var.span, ".."); | ||
| let sugg = format!("std::ptr::eq({}, {})", left_snip, right_snip); | ||
| utils::span_lint_and_sugg( | ||
| cx, | ||
| PTR_EQ, | ||
| expr.span, | ||
| LINT_MSG, | ||
| "try", | ||
| sugg, | ||
| Applicability::MachineApplicable, | ||
| ); | ||
| } | ||
| } | ||
| } | ||
| } | ||
| } | ||
| } | ||
|
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||
| // If the given expression is a cast to an usize, return the lhs of the cast | ||
| // E.g., `foo as *const _ as usize` returns `foo as *const _`. | ||
| fn expr_as_cast_to_usize<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, cast_expr: &'tcx Expr) -> Option<&'tcx Expr> { | ||
| if cx.tables.expr_ty(cast_expr) == cx.tcx.types.usize { | ||
| if let ExprKind::Cast(ref expr, _) = cast_expr.kind { | ||
| return Some(expr); | ||
| } | ||
| } | ||
| None | ||
| } | ||
|
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||
| // If the given expression is a cast to a `*const` pointer, return the lhs of the cast | ||
| // E.g., `foo as *const _` returns `foo`. | ||
| fn expr_as_cast_to_raw_pointer<'a, 'tcx>(cx: &LateContext<'a, 'tcx>, cast_expr: &'tcx Expr) -> Option<&'tcx Expr> { | ||
| if cx.tables.expr_ty(cast_expr).is_unsafe_ptr() { | ||
| if let ExprKind::Cast(ref expr, _) = cast_expr.kind { | ||
| return Some(expr); | ||
| } | ||
| } | ||
| None | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,23 @@ | ||
| // run-rustfix | ||
| #![warn(clippy::ptr_eq)] | ||
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| fn main() { | ||
| let a = &[1, 2, 3]; | ||
| let b = &[1, 2, 3]; | ||
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| let _ = std::ptr::eq(a, b); | ||
| let _ = std::ptr::eq(a, b); | ||
| let _ = a.as_ptr() == b as *const _; | ||
| let _ = a.as_ptr() == b.as_ptr(); | ||
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| // Do not lint | ||
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| let a = &mut [1, 2, 3]; | ||
| let b = &mut [1, 2, 3]; | ||
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| let _ = a.as_mut_ptr() == b as *mut [i32] as *mut _; | ||
| let _ = a.as_mut_ptr() == b.as_mut_ptr(); | ||
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| let _ = a == b; | ||
| let _ = core::ptr::eq(a, b); | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,23 @@ | ||
| // run-rustfix | ||
| #![warn(clippy::ptr_eq)] | ||
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| fn main() { | ||
| let a = &[1, 2, 3]; | ||
| let b = &[1, 2, 3]; | ||
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| let _ = a as *const _ as usize == b as *const _ as usize; | ||
| let _ = a as *const _ == b as *const _; | ||
| let _ = a.as_ptr() == b as *const _; | ||
| let _ = a.as_ptr() == b.as_ptr(); | ||
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| // Do not lint | ||
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| let a = &mut [1, 2, 3]; | ||
| let b = &mut [1, 2, 3]; | ||
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| let _ = a.as_mut_ptr() == b as *mut [i32] as *mut _; | ||
| let _ = a.as_mut_ptr() == b.as_mut_ptr(); | ||
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| let _ = a == b; | ||
| let _ = core::ptr::eq(a, b); | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,16 @@ | ||
| error: use `std::ptr::eq` when applicable | ||
| --> $DIR/ptr_eq.rs:8:13 | ||
| | | ||
| LL | let _ = a as *const _ as usize == b as *const _ as usize; | ||
| | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `std::ptr::eq(a, b)` | ||
| | | ||
| = note: `-D clippy::ptr-eq` implied by `-D warnings` | ||
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| error: use `std::ptr::eq` when applicable | ||
| --> $DIR/ptr_eq.rs:9:13 | ||
| | | ||
| LL | let _ = a as *const _ == b as *const _; | ||
| | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `std::ptr::eq(a, b)` | ||
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| error: aborting due to 2 previous errors | ||
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