From ccc4747f468e0887f6d1c460237e2e6313ae97b9 Mon Sep 17 00:00:00 2001 From: Ryan1729 Date: Mon, 3 Aug 2020 02:47:25 -0600 Subject: [PATCH] get the expected number of errors by acknowledging that other lints are covering the same ground --- clippy_lints/src/transmute.rs | 80 +++++++++---------- tests/ui/transmute.rs | 2 +- tests/ui/transmute_ptr_to_ptr.rs | 2 +- .../ui/transmutes_expressible_as_ptr_casts.rs | 10 ++- ...transmutes_expressible_as_ptr_casts.stderr | 51 +++++++++++- 5 files changed, 100 insertions(+), 45 deletions(-) diff --git a/clippy_lints/src/transmute.rs b/clippy_lints/src/transmute.rs index 7ab3f0d9676..269d2f00353 100644 --- a/clippy_lints/src/transmute.rs +++ b/clippy_lints/src/transmute.rs @@ -50,6 +50,29 @@ "transmutes that have the same to and from types or could be a cast/coercion" } +// FIXME: Merge this lint with USELESS_TRANSMUTE once that is out of the nursery. +declare_clippy_lint! { + /// **What it does:**Checks for transmutes that could be a pointer cast. + /// + /// **Why is this bad?** Readability. The code tricks people into thinking that + /// something complex is going on. + /// + /// **Known problems:** None. + /// + /// **Example:** + /// + /// ```rust,ignore + /// core::intrinsics::transmute::<*const [i32], *const [u16]>(p) + /// ``` + /// Use instead: + /// ```rust + /// p as *const [u16] + /// ``` + pub TRANSMUTES_EXPRESSIBLE_AS_PTR_CASTS, + complexity, + "transmutes that could be a pointer cast" +} + declare_clippy_lint! { /// **What it does:** Checks for transmutes between a type `T` and `*T`. /// @@ -272,27 +295,6 @@ "transmute between collections of layout-incompatible types" } -declare_clippy_lint! { - /// **What it does:** - /// - /// **Why is this bad?** - /// - /// **Known problems:** None. - /// - /// **Example:** - /// - /// ```rust - /// // example code where clippy issues a warning - /// ``` - /// Use instead: - /// ```rust - /// // example code which does not raise clippy warning - /// ``` - pub TRANSMUTES_EXPRESSIBLE_AS_PTR_CASTS, - complexity, - "default lint description" -} - declare_lint_pass!(Transmute => [ CROSSPOINTER_TRANSMUTE, TRANSMUTE_PTR_TO_REF, @@ -330,26 +332,6 @@ fn check_expr(&mut self, cx: &LateContext<'tcx>, e: &'tcx Expr<'_>) { let from_ty = cx.typeck_results().expr_ty(&args[0]); let to_ty = cx.typeck_results().expr_ty(e); - if can_be_expressed_as_pointer_cast(cx, e, from_ty, to_ty) { - span_lint_and_then( - cx, - TRANSMUTES_EXPRESSIBLE_AS_PTR_CASTS, - e.span, - &format!( - "transmute from `{}` to `{}` which could be expressed as a pointer cast instead", - from_ty, - to_ty - ), - |diag| { - if let Some(arg) = sugg::Sugg::hir_opt(cx, &args[0]) { - let sugg = format!("{} as {}", arg, to_ty); - diag.span_suggestion(e.span, "try", sugg, Applicability::Unspecified); - } - } - ); - return - } - match (&from_ty.kind, &to_ty.kind) { _ if from_ty == to_ty => span_lint( cx, @@ -646,6 +628,22 @@ fn check_expr(&mut self, cx: &LateContext<'tcx>, e: &'tcx Expr<'_>) { ); } }, + (_, _) if can_be_expressed_as_pointer_cast(cx, e, from_ty, to_ty) => span_lint_and_then( + cx, + TRANSMUTES_EXPRESSIBLE_AS_PTR_CASTS, + e.span, + &format!( + "transmute from `{}` to `{}` which could be expressed as a pointer cast instead", + from_ty, + to_ty + ), + |diag| { + if let Some(arg) = sugg::Sugg::hir_opt(cx, &args[0]) { + let sugg = arg.as_ty(&to_ty.to_string()).to_string(); + diag.span_suggestion(e.span, "try", sugg, Applicability::Unspecified); + } + } + ), _ => { return; }, diff --git a/tests/ui/transmute.rs b/tests/ui/transmute.rs index b3171d2e7dc..bb853d23704 100644 --- a/tests/ui/transmute.rs +++ b/tests/ui/transmute.rs @@ -1,7 +1,7 @@ #![allow(dead_code)] -#![allow(clippy::transmutes_expressible_as_ptr_casts)] extern crate core; + use std::mem::transmute as my_transmute; use std::vec::Vec as MyVec; diff --git a/tests/ui/transmute_ptr_to_ptr.rs b/tests/ui/transmute_ptr_to_ptr.rs index 009b5fa534c..0d8a322f2b2 100644 --- a/tests/ui/transmute_ptr_to_ptr.rs +++ b/tests/ui/transmute_ptr_to_ptr.rs @@ -1,5 +1,5 @@ #![warn(clippy::transmute_ptr_to_ptr)] -#![allow(clippy::transmutes_expressible_as_ptr_casts)] + // Make sure we can modify lifetimes, which is one of the recommended uses // of transmute diff --git a/tests/ui/transmutes_expressible_as_ptr_casts.rs b/tests/ui/transmutes_expressible_as_ptr_casts.rs index e6b9dddd342..db544b438a2 100644 --- a/tests/ui/transmutes_expressible_as_ptr_casts.rs +++ b/tests/ui/transmutes_expressible_as_ptr_casts.rs @@ -1,10 +1,18 @@ #![warn(clippy::transmutes_expressible_as_ptr_casts)] +// These two warnings currrently cover the cases transmutes_expressible_as_ptr_casts +// would otherwise be responsible for +#![warn(clippy::useless_transmute)] +#![warn(clippy::transmute_ptr_to_ptr)] + +use std::mem::transmute; // rustc_typeck::check::cast contains documentation about when a cast `e as U` is // valid, which we quote from below. -use std::mem::transmute; fn main() { + // We should see an error message for each transmute, and no error messages for + // the casts, since the casts are the recommended fixes. + // e is an integer and U is *U_0, while U_0: Sized; addr-ptr-cast let ptr_i32_transmute = unsafe { transmute::(-1) diff --git a/tests/ui/transmutes_expressible_as_ptr_casts.stderr b/tests/ui/transmutes_expressible_as_ptr_casts.stderr index 6bae1fa1b4f..7cd316bf38a 100644 --- a/tests/ui/transmutes_expressible_as_ptr_casts.stderr +++ b/tests/ui/transmutes_expressible_as_ptr_casts.stderr @@ -1 +1,50 @@ -Should have 7 errors, one for each transmute +error: transmute from an integer to a pointer + --> $DIR/transmutes_expressible_as_ptr_casts.rs:18:9 + | +LL | transmute::(-1) + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `-1 as *const i32` + | + = note: `-D clippy::useless-transmute` implied by `-D warnings` + +error: transmute from a pointer to a pointer + --> $DIR/transmutes_expressible_as_ptr_casts.rs:24:9 + | +LL | transmute::<*const i32, *const i8>(ptr_i32) + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `ptr_i32 as *const i8` + | + = note: `-D clippy::transmute-ptr-to-ptr` implied by `-D warnings` + +error: transmute from a pointer to a pointer + --> $DIR/transmutes_expressible_as_ptr_casts.rs:32:9 + | +LL | transmute::<*const [i32], *const [u16]>(slice_ptr) + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `slice_ptr as *const [u16]` + +error: transmute from `*const i32` to `usize` which could be expressed as a pointer cast instead + --> $DIR/transmutes_expressible_as_ptr_casts.rs:40:9 + | +LL | transmute::<*const i32, usize>(ptr_i32) + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `ptr_i32 as usize` + | + = note: `-D clippy::transmutes-expressible-as-ptr-casts` implied by `-D warnings` + +error: transmute from a reference to a pointer + --> $DIR/transmutes_expressible_as_ptr_casts.rs:48:9 + | +LL | transmute::<&[i32; 4], *const [i32; 4]>(array_ref) + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `array_ref as *const [i32; 4]` + +error: transmute from `fn(usize) -> u8 {main::foo}` to `*const usize` which could be expressed as a pointer cast instead + --> $DIR/transmutes_expressible_as_ptr_casts.rs:56:9 + | +LL | transmute:: u8, *const usize>(foo) + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `foo as *const usize` + +error: transmute from `fn(usize) -> u8 {main::foo}` to `usize` which could be expressed as a pointer cast instead + --> $DIR/transmutes_expressible_as_ptr_casts.rs:62:9 + | +LL | transmute:: u8, usize>(foo) + | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `foo as usize` + +error: aborting due to 7 previous errors +