Merge pull request #3478 from dtolnay/setlen

Remove unsafe_vector_initialization lint

README.md

@@ -7,7 +7,7 @@
 
 A collection of lints to catch common mistakes and improve your [Rust](https://github.com/rust-lang/rust) code.
 
-[There are 290 lints included in this crate!](https://rust-lang.github.io/rust-clippy/master/index.html)
+[There are 289 lints included in this crate!](https://rust-lang.github.io/rust-clippy/master/index.html)
 
 We have a bunch of lint categories to allow you to choose how much Clippy is supposed to ~~annoy~~ help you:
 

clippy_lints/src/deprecated_lints.rs

@@ -112,3 +112,14 @@ declare_deprecated_lint! {
     pub IF_LET_REDUNDANT_PATTERN_MATCHING,
     "this lint has been changed to redundant_pattern_matching"
 }
+
+/// **What it does:** Nothing. This lint has been deprecated.
+///
+/// **Deprecation reason:** This lint used to suggest replacing `let mut vec =
+/// Vec::with_capacity(n); vec.set_len(n);` with `let vec = vec![0; n];`. The
+/// replacement has very different performance characteristics so the lint is
+/// deprecated.
+declare_deprecated_lint! {
+    pub UNSAFE_VECTOR_INITIALIZATION,
+    "the replacement suggested by this lint had substantially different behavior"
+}

clippy_lints/src/lib.rs

@@ -330,6 +330,10 @@ pub fn register_plugins(reg: &mut rustc_plugin::Registry<'_>, conf: &Conf) {
         "if_let_redundant_pattern_matching",
         "this lint has been changed to redundant_pattern_matching",
     );
+    store.register_removed(
+        "unsafe_vector_initialization",
+        "the replacement suggested by this lint had substantially different behavior",
+    );
     // end deprecated lints, do not remove this comment, it’s used in `update_lints`
 
     reg.register_late_lint_pass(box serde_api::Serde);
@@ -727,7 +731,6 @@ pub fn register_plugins(reg: &mut rustc_plugin::Registry<'_>, conf: &Conf) {
         returns::UNUSED_UNIT,
         serde_api::SERDE_API_MISUSE,
         slow_vector_initialization::SLOW_VECTOR_INITIALIZATION,
-        slow_vector_initialization::UNSAFE_VECTOR_INITIALIZATION,
         strings::STRING_LIT_AS_BYTES,
         suspicious_trait_impl::SUSPICIOUS_ARITHMETIC_IMPL,
         suspicious_trait_impl::SUSPICIOUS_OP_ASSIGN_IMPL,
@@ -973,7 +976,6 @@ pub fn register_plugins(reg: &mut rustc_plugin::Registry<'_>, conf: &Conf) {
         ranges::ITERATOR_STEP_BY_ZERO,
         regex::INVALID_REGEX,
         serde_api::SERDE_API_MISUSE,
-        slow_vector_initialization::UNSAFE_VECTOR_INITIALIZATION,
         suspicious_trait_impl::SUSPICIOUS_ARITHMETIC_IMPL,
         suspicious_trait_impl::SUSPICIOUS_OP_ASSIGN_IMPL,
         swap::ALMOST_SWAPPED,

clippy_lints/src/slow_vector_initialization.rs

@@ -39,32 +39,12 @@ declare_clippy_lint! {
     "slow vector initialization"
 }
 
-/// **What it does:** Checks unsafe vector initialization
-///
-/// **Why is this bad?** Changing the length of a vector may expose uninitialized memory, which
-/// can lead to memory safety issues
-///
-/// **Known problems:** None.
-///
-/// **Example:**
-/// ```rust
-/// let mut vec1 = Vec::with_capacity(len);
-/// unsafe {
-///     vec1.set_len(len);
-/// }
-/// ```
-declare_clippy_lint! {
-    pub UNSAFE_VECTOR_INITIALIZATION,
-    correctness,
-    "unsafe vector initialization"
-}
-
 #[derive(Copy, Clone, Default)]
 pub struct Pass;
 
 impl LintPass for Pass {
     fn get_lints(&self) -> LintArray {
-        lint_array!(SLOW_VECTOR_INITIALIZATION, UNSAFE_VECTOR_INITIALIZATION,)
+        lint_array!(SLOW_VECTOR_INITIALIZATION,)
     }
 }
 
@@ -90,9 +70,6 @@ enum InitializationType<'tcx> {
 
     /// Resize is a slow initialization with the form `vec.resize(.., 0)`
     Resize(&'tcx Expr),
-
-    /// UnsafeSetLen is a slow initialization with the form `vec.set_len(..)`
-    UnsafeSetLen(&'tcx Expr),
 }
 
 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass {
@@ -188,14 +165,6 @@ impl Pass {
         vec_alloc: &VecAllocation<'_>,
     ) {
         match initialization {
-            InitializationType::UnsafeSetLen(e) => Self::emit_lint(
-                cx,
-                e,
-                vec_alloc,
-                "unsafe vector initialization",
-                UNSAFE_VECTOR_INITIALIZATION,
-            ),
-
             InitializationType::Extend(e) | InitializationType::Resize(e) => Self::emit_lint(
                 cx,
                 e,
@@ -282,25 +251,6 @@ impl<'a, 'tcx> VectorInitializationVisitor<'a, 'tcx> {
         }
     }
 
-    /// Checks if the given expression is using `set_len` to initialize the vector
-    fn search_unsafe_set_len(&mut self, expr: &'tcx Expr) {
-        if_chain! {
-            if self.initialization_found;
-            if let ExprKind::MethodCall(ref path, _, ref args) = expr.node;
-            if let ExprKind::Path(ref qpath_subj) = args[0].node;
-            if match_qpath(&qpath_subj, &[&self.vec_alloc.variable_name.to_string()]);
-            if path.ident.name == "set_len";
-            if let Some(ref len_arg) = args.get(1);
-
-            // Check that len expression is equals to `with_capacity` expression
-            if SpanlessEq::new(self.cx).eq_expr(len_arg, self.vec_alloc.len_expr);
-
-            then {
-                self.slow_expression = Some(InitializationType::UnsafeSetLen(expr));
-            }
-        }
-    }
-
     /// Returns `true` if give expression is `repeat(0).take(...)`
     fn is_repeat_take(&self, expr: &Expr) -> bool {
         if_chain! {
@@ -349,7 +299,6 @@ impl<'a, 'tcx> Visitor<'tcx> for VectorInitializationVisitor<'a, 'tcx> {
                 StmtKind::Expr(ref expr, _) | StmtKind::Semi(ref expr, _) => {
                     self.search_slow_extend_filling(expr);
                     self.search_slow_resize_filling(expr);
-                    self.search_unsafe_set_len(expr);
                 },
                 _ => (),
             }

tests/ui/slow_vector_initialization.rs

@@ -13,7 +13,6 @@ fn main() {
     resize_vector();
     extend_vector();
     mixed_extend_resize_vector();
-    unsafe_vector();
 }
 
 fn extend_vector() {
@@ -63,14 +62,6 @@ fn resize_vector() {
     vec1.resize(10, 0);
 }
 
-fn unsafe_vector() {
-    let mut unsafe_vec: Vec<u8> = Vec::with_capacity(200);
-
-    unsafe {
-        unsafe_vec.set_len(200);
-    }
-}
-
 fn do_stuff(vec: &mut Vec<u8>) {
 
 }

tests/ui/slow_vector_initialization.stderr

@@ -1,71 +1,60 @@
 error: slow zero-filling initialization
-  --> $DIR/slow_vector_initialization.rs:23:5
+  --> $DIR/slow_vector_initialization.rs:22:5
    |
-22 |     let mut vec1 = Vec::with_capacity(len);
+21 |     let mut vec1 = Vec::with_capacity(len);
    |                    ----------------------- help: consider replace allocation with: `vec![0; len]`
-23 |     vec1.extend(repeat(0).take(len));
+22 |     vec1.extend(repeat(0).take(len));
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: `-D clippy::slow-vector-initialization` implied by `-D warnings`
 
 error: slow zero-filling initialization
-  --> $DIR/slow_vector_initialization.rs:27:5
+  --> $DIR/slow_vector_initialization.rs:26:5
    |
-26 |     let mut vec2 = Vec::with_capacity(len - 10);
+25 |     let mut vec2 = Vec::with_capacity(len - 10);
    |                    ---------------------------- help: consider replace allocation with: `vec![0; len - 10]`
-27 |     vec2.extend(repeat(0).take(len - 10));
+26 |     vec2.extend(repeat(0).take(len - 10));
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: slow zero-filling initialization
-  --> $DIR/slow_vector_initialization.rs:41:5
+  --> $DIR/slow_vector_initialization.rs:40:5
    |
-40 |     let mut resized_vec = Vec::with_capacity(30);
+39 |     let mut resized_vec = Vec::with_capacity(30);
    |                           ---------------------- help: consider replace allocation with: `vec![0; 30]`
-41 |     resized_vec.resize(30, 0);
+40 |     resized_vec.resize(30, 0);
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: slow zero-filling initialization
-  --> $DIR/slow_vector_initialization.rs:44:5
+  --> $DIR/slow_vector_initialization.rs:43:5
    |
-43 |     let mut extend_vec = Vec::with_capacity(30);
+42 |     let mut extend_vec = Vec::with_capacity(30);
    |                          ---------------------- help: consider replace allocation with: `vec![0; 30]`
-44 |     extend_vec.extend(repeat(0).take(30));
+43 |     extend_vec.extend(repeat(0).take(30));
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: slow zero-filling initialization
-  --> $DIR/slow_vector_initialization.rs:51:5
+  --> $DIR/slow_vector_initialization.rs:50:5
    |
-50 |     let mut vec1 = Vec::with_capacity(len);
+49 |     let mut vec1 = Vec::with_capacity(len);
    |                    ----------------------- help: consider replace allocation with: `vec![0; len]`
-51 |     vec1.resize(len, 0);
+50 |     vec1.resize(len, 0);
    |     ^^^^^^^^^^^^^^^^^^^
 
 error: slow zero-filling initialization
-  --> $DIR/slow_vector_initialization.rs:59:5
+  --> $DIR/slow_vector_initialization.rs:58:5
    |
-58 |     let mut vec3 = Vec::with_capacity(len - 10);
+57 |     let mut vec3 = Vec::with_capacity(len - 10);
    |                    ---------------------------- help: consider replace allocation with: `vec![0; len - 10]`
-59 |     vec3.resize(len - 10, 0);
+58 |     vec3.resize(len - 10, 0);
    |     ^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: slow zero-filling initialization
-  --> $DIR/slow_vector_initialization.rs:63:5
+  --> $DIR/slow_vector_initialization.rs:62:5
    |
-62 |     vec1 = Vec::with_capacity(10);
+61 |     vec1 = Vec::with_capacity(10);
    |            ---------------------- help: consider replace allocation with: `vec![0; 10]`
-63 |     vec1.resize(10, 0);
+62 |     vec1.resize(10, 0);
    |     ^^^^^^^^^^^^^^^^^^
 
-error: unsafe vector initialization
+error: aborting due to 7 previous errors
-  --> $DIR/slow_vector_initialization.rs:70:9
-   |
-67 |     let mut unsafe_vec: Vec<u8> = Vec::with_capacity(200);
-   |                                   ----------------------- help: consider replace allocation with: `vec![0; 200]`
-...
-70 |         unsafe_vec.set_len(200);
-   |         ^^^^^^^^^^^^^^^^^^^^^^^
-   |
-   = note: #[deny(clippy::unsafe_vector_initialization)] on by default
-
-error: aborting due to 8 previous errors