Deprecates 4 lints

Namely STR_TO_STRING, STRING_TO_STRING, UNSTABLE_AS_SLICE and
UNSTABLE_AS_MUT_SLICE.

Author: mcarton

README.md

@@ -14,7 +14,7 @@ Table of contents:
 * [License](#license)
 
 ##Lints
-There are 138 lints included in this crate:
+There are 134 lints included in this crate:
 
 name                                                                                                                 | default | meaning
 ---------------------------------------------------------------------------------------------------------------------|---------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
@@ -124,11 +124,9 @@ name
 [single_char_pattern](https://github.com/Manishearth/rust-clippy/wiki#single_char_pattern)                           | warn    | using a single-character str where a char could be used, e.g. `_.split("x")`
 [single_match](https://github.com/Manishearth/rust-clippy/wiki#single_match)                                         | warn    | a match statement with a single nontrivial arm (i.e, where the other arm is `_ => {}`) is used; recommends `if let` instead
 [single_match_else](https://github.com/Manishearth/rust-clippy/wiki#single_match_else)                               | allow   | a match statement with a two arms where the second arm's pattern is a wildcard; recommends `if let` instead
-[str_to_string](https://github.com/Manishearth/rust-clippy/wiki#str_to_string)                                       | warn    | using `to_string()` on a str, which should be `to_owned()`
 [string_add](https://github.com/Manishearth/rust-clippy/wiki#string_add)                                             | allow   | using `x + ..` where x is a `String`; suggests using `push_str()` instead
 [string_add_assign](https://github.com/Manishearth/rust-clippy/wiki#string_add_assign)                               | allow   | using `x = x + ..` where x is a `String`; suggests using `push_str()` instead
 [string_lit_as_bytes](https://github.com/Manishearth/rust-clippy/wiki#string_lit_as_bytes)                           | warn    | calling `as_bytes` on a string literal; suggests using a byte string literal instead
-[string_to_string](https://github.com/Manishearth/rust-clippy/wiki#string_to_string)                                 | warn    | calling `String::to_string` which is inefficient
 [suspicious_assignment_formatting](https://github.com/Manishearth/rust-clippy/wiki#suspicious_assignment_formatting) | warn    | suspicious formatting of `*=`, `-=` or `!=`
 [suspicious_else_formatting](https://github.com/Manishearth/rust-clippy/wiki#suspicious_else_formatting)             | warn    | suspicious formatting of `else if`
 [temporary_assignment](https://github.com/Manishearth/rust-clippy/wiki#temporary_assignment)                         | warn    | assignments to temporaries
@@ -140,8 +138,6 @@ name
 [unit_cmp](https://github.com/Manishearth/rust-clippy/wiki#unit_cmp)                                                 | warn    | comparing unit values (which is always `true` or `false`, respectively)
 [unnecessary_mut_passed](https://github.com/Manishearth/rust-clippy/wiki#unnecessary_mut_passed)                     | warn    | an argument is passed as a mutable reference although the function/method only demands an immutable reference
 [unneeded_field_pattern](https://github.com/Manishearth/rust-clippy/wiki#unneeded_field_pattern)                     | warn    | Struct fields are bound to a wildcard instead of using `..`
-[unstable_as_mut_slice](https://github.com/Manishearth/rust-clippy/wiki#unstable_as_mut_slice)                       | warn    | as_mut_slice is not stable and can be replaced by &mut v[..]see https://github.com/rust-lang/rust/issues/27729
-[unstable_as_slice](https://github.com/Manishearth/rust-clippy/wiki#unstable_as_slice)                               | warn    | as_slice is not stable and can be replaced by & v[..]see https://github.com/rust-lang/rust/issues/27729
 [unused_collect](https://github.com/Manishearth/rust-clippy/wiki#unused_collect)                                     | warn    | `collect()`ing an iterator without using the result; this is usually better written as a for loop
 [unused_label](https://github.com/Manishearth/rust-clippy/wiki#unused_label)                                         | warn    | unused label
 [unused_lifetimes](https://github.com/Manishearth/rust-clippy/wiki#unused_lifetimes)                                 | warn    | unused lifetimes in function definitions

src/deprecated_lints.rs

@@ -0,0 +1,44 @@
+macro_rules! declare_deprecated_lint {
+    (pub $name: ident, $_reason: expr) => {
+        declare_lint!(pub $name, Allow, "deprecated lint")
+    }
+}
+
+/// **What it does:** Nothing. This lint has been deprecated.
+///
+/// **Deprecation reason:** This used to check for `Vec::as_slice`, which was unstable with good
+/// stable alternatives. `Vec::as_slice` has now been stabilized.
+declare_deprecated_lint! {
+    pub UNSTABLE_AS_SLICE,
+    "`Vec::as_slice` has been stabilized in 1.7"
+}
+
+
+/// **What it does:** Nothing. This lint has been deprecated.
+///
+/// **Deprecation reason:** This used to check for `Vec::as_mut_slice`, which was unstable with good
+/// stable alternatives. `Vec::as_mut_slice` has now been stabilized.
+declare_deprecated_lint! {
+    pub UNSTABLE_AS_MUT_SLICE,
+    "`Vec::as_mut_slice` has been stabilized in 1.7"
+}
+
+/// **What it does:** Nothing. This lint has been deprecated.
+///
+/// **Deprecation reason:** This used to check for `.to_string()` method calls on values
+/// of type `&str`. This is not unidiomatic and with specialization coming, `to_string` could be
+/// specialized to be as efficient as `to_owned`.
+declare_deprecated_lint! {
+    pub STR_TO_STRING,
+    "using `str::to_string` is common even today and specialization will likely happen soon"
+}
+
+/// **What it does:** Nothing. This lint has been deprecated.
+///
+/// **Deprecation reason:** This used to check for `.to_string()` method calls on values
+/// of type `String`. This is not unidiomatic and with specialization coming, `to_string` could be
+/// specialized to be as efficient as `clone`.
+declare_deprecated_lint! {
+    pub STRING_TO_STRING,
+    "using `string::to_string` is common even today and specialization will likely happen soon"
+}

src/lib.rs

@@ -81,7 +81,6 @@ pub mod mut_mut;
 pub mod mut_reference;
 pub mod mutex_atomic;
 pub mod needless_bool;
-pub mod needless_features;
 pub mod needless_update;
 pub mod new_without_default;
 pub mod no_effect;
@@ -141,6 +140,13 @@ pub fn plugin_registrar(reg: &mut Registry) {
         }
     };
 
+    let mut store = reg.sess.lint_store.borrow_mut();
+    store.register_removed("unstable_as_slice", "`Vec::as_slice` has been stabilized in 1.7");
+    store.register_removed("unstable_as_mut_slice", "`Vec::as_mut_slice` has been stabilized in 1.7");
+    store.register_removed("str_to_string", "using `str::to_string` is common even today and specialization will likely happen soon");
+    store.register_removed("string_to_string", "using `string::to_string` is common even today and specialization will likely happen soon");
+    // end deprecated lints, do not remove this comment, it’s used in `update_lints`
+
     reg.register_late_lint_pass(box types::TypePass);
     reg.register_late_lint_pass(box misc::TopLevelRefPass);
     reg.register_late_lint_pass(box misc::CmpNan);
@@ -185,7 +191,6 @@ pub fn plugin_registrar(reg: &mut Registry) {
     reg.register_late_lint_pass(box open_options::NonSensicalOpenOptions);
     reg.register_late_lint_pass(box zero_div_zero::ZeroDivZeroPass);
     reg.register_late_lint_pass(box mutex_atomic::MutexAtomic);
-    reg.register_late_lint_pass(box needless_features::NeedlessFeaturesPass);
     reg.register_late_lint_pass(box needless_update::NeedlessUpdatePass);
     reg.register_late_lint_pass(box no_effect::NoEffectPass);
     reg.register_late_lint_pass(box map_clone::MapClonePass);
@@ -308,8 +313,6 @@ pub fn plugin_registrar(reg: &mut Registry) {
         methods::SEARCH_IS_SOME,
         methods::SHOULD_IMPLEMENT_TRAIT,
         methods::SINGLE_CHAR_PATTERN,
-        methods::STR_TO_STRING,
-        methods::STRING_TO_STRING,
         methods::WRONG_SELF_CONVENTION,
         minmax::MIN_MAX,
         misc::CMP_NAN,
@@ -326,8 +329,6 @@ pub fn plugin_registrar(reg: &mut Registry) {
         mutex_atomic::MUTEX_ATOMIC,
         needless_bool::BOOL_COMPARISON,
         needless_bool::NEEDLESS_BOOL,
-        needless_features::UNSTABLE_AS_MUT_SLICE,
-        needless_features::UNSTABLE_AS_SLICE,
         needless_update::NEEDLESS_UPDATE,
         new_without_default::NEW_WITHOUT_DEFAULT,
         no_effect::NO_EFFECT,

src/methods.rs

@@ -6,13 +6,13 @@ use rustc::middle::subst::{Subst, TypeSpace};
 use rustc::middle::ty;
 use rustc_front::hir::*;
 use std::borrow::Cow;
-use std::{fmt, iter};
+use std::fmt;
 use syntax::codemap::Span;
 use syntax::ptr::P;
 use utils::{get_trait_def_id, implements_trait, in_external_macro, in_macro, match_path, match_trait_method,
             match_type, method_chain_args, return_ty, same_tys, snippet, snippet_opt, span_lint,
             span_lint_and_then, span_note_and_lint, walk_ptrs_ty, walk_ptrs_ty_depth};
-use utils::{BTREEMAP_ENTRY_PATH, DEFAULT_TRAIT_PATH, HASHMAP_ENTRY_PATH, OPTION_PATH, RESULT_PATH, STRING_PATH,
+use utils::{BTREEMAP_ENTRY_PATH, DEFAULT_TRAIT_PATH, HASHMAP_ENTRY_PATH, OPTION_PATH, RESULT_PATH,
             VEC_PATH};
 use utils::MethodArgs;
 
@@ -45,31 +45,6 @@ declare_lint! {
     "using `Result.unwrap()`, which might be better handled"
 }
 
-/// **What it does:** This lint checks for `.to_string()` method calls on values of type `&str`.
-///
-/// **Why is this bad?** This uses the whole formatting machinery just to clone a string. Using `.to_owned()` is lighter on resources. You can also consider using a [`Cow<'a, str>`](http://doc.rust-lang.org/std/borrow/enum.Cow.html) instead in some cases.
-///
-/// **Known problems:** None
-///
-/// **Example:** `s.to_string()` where `s: &str`
-declare_lint! {
-    pub STR_TO_STRING, Warn,
-    "using `to_string()` on a str, which should be `to_owned()`"
-}
-
-/// **What it does:** This lint checks for `.to_string()` method calls on values of type `String`.
-///
-/// **Why is this bad?** This is an non-efficient way to clone a `String`, `.clone()` should be used
-/// instead. `String` implements `ToString` mostly for generics.
-///
-/// **Known problems:** None
-///
-/// **Example:** `s.to_string()` where `s: String`
-declare_lint! {
-    pub STRING_TO_STRING, Warn,
-    "calling `String::to_string` which is inefficient"
-}
-
 /// **What it does:** This lint checks for methods that should live in a trait implementation of a `std` trait (see [llogiq's blog post](http://llogiq.github.io/2015/07/30/traits.html) for further information) instead of an inherent implementation.
 ///
 /// **Why is this bad?** Implementing the traits improve ergonomics for users of the code, often with very little cost. Also people seeing a `mul(..)` method may expect `*` to work equally, so you should have good reason to disappoint them.
@@ -315,8 +290,6 @@ impl LintPass for MethodsPass {
         lint_array!(EXTEND_FROM_SLICE,
                     OPTION_UNWRAP_USED,
                     RESULT_UNWRAP_USED,
-                    STR_TO_STRING,
-                    STRING_TO_STRING,
                     SHOULD_IMPLEMENT_TRAIT,
                     WRONG_SELF_CONVENTION,
                     WRONG_PUB_SELF_CONVENTION,
@@ -343,8 +316,6 @@ impl LateLintPass for MethodsPass {
                 // Chain calls
                 if let Some(arglists) = method_chain_args(expr, &["unwrap"]) {
                     lint_unwrap(cx, expr, arglists[0]);
-                } else if let Some(arglists) = method_chain_args(expr, &["to_string"]) {
-                    lint_to_string(cx, expr, arglists[0]);
                 } else if let Some(arglists) = method_chain_args(expr, &["ok", "expect"]) {
                     lint_ok_expect(cx, expr, arglists[0]);
                 } else if let Some(arglists) = method_chain_args(expr, &["map", "unwrap_or"]) {
@@ -640,26 +611,6 @@ fn lint_unwrap(cx: &LateContext, expr: &Expr, unwrap_args: &MethodArgs) {
     }
 }
 
-#[allow(ptr_arg)]
-// Type of MethodArgs is potentially a Vec
-/// lint use of `to_string()` for `&str`s and `String`s
-fn lint_to_string(cx: &LateContext, expr: &Expr, to_string_args: &MethodArgs) {
-    let (obj_ty, ptr_depth) = walk_ptrs_ty_depth(cx.tcx.expr_ty(&to_string_args[0]));
-
-    if obj_ty.sty == ty::TyStr {
-        let mut arg_str = snippet(cx, to_string_args[0].span, "_");
-        if ptr_depth > 1 {
-            arg_str = Cow::Owned(format!("({}{})", iter::repeat('*').take(ptr_depth - 1).collect::<String>(), arg_str));
-        }
-        span_lint(cx, STR_TO_STRING, expr.span, &format!("`{}.to_owned()` is faster", arg_str));
-    } else if match_type(cx, obj_ty, &STRING_PATH) {
-        span_lint(cx,
-                  STRING_TO_STRING,
-                  expr.span,
-                  "`String::to_string` is an inefficient way to clone a `String`; use `clone()` instead");
-    }
-}
-
 #[allow(ptr_arg)]
 // Type of MethodArgs is potentially a Vec
 /// lint use of `ok().expect()` for `Result`s

src/needless_features.rs

@@ -3,7 +3,6 @@
 
 #[deny(cmp_owned)]
 fn main() {
-    #[allow(str_to_string)]
     fn with_to_string(x : &str) {
         x != "foo".to_string();
         //~^ ERROR this creates an owned instance just for comparison. Consider using `x != "foo"` to compare without allocation

tests/compile-fail/cmp_owned.rs

@@ -296,12 +296,6 @@ fn main() {
     let res: Result<i32, ()> = Ok(0);
     let _ = res.unwrap();  //~ERROR used unwrap() on a Result
 
-    let _ = "str".to_string();  //~ERROR `"str".to_owned()` is faster
-
-    let v = &"str";
-    let string = v.to_string();  //~ERROR `(*v).to_owned()` is faster
-    let _again = string.to_string();  //~ERROR `String::to_string` is an inefficient way to clone a `String`; use `clone()` instead
-
     res.ok().expect("disaster!"); //~ERROR called `ok().expect()`
     // the following should not warn, since `expect` isn't implemented unless
     // the error type implements `Debug`

tests/compile-fail/methods.rs

@@ -0,0 +1,12 @@
+#![feature(plugin)]
+#![plugin(clippy)]
+
+#[warn(str_to_string)]
+//~^WARNING: warning: lint str_to_string has been removed: using `str::to_string`
+#[warn(string_to_string)]
+//~^WARNING: warning: lint string_to_string has been removed: using `string::to_string`
+#[warn(unstable_as_slice)]
+//~^WARNING: warning: lint unstable_as_slice has been removed: `Vec::as_slice` has been stabilized
+#[warn(unstable_as_mut_slice)]
+//~^WARNING: warning: lint unstable_as_mut_slice has been removed: `Vec::as_mut_slice` has been stabilized
+fn main() {}