Auto merge of #5470 - flip1995:rollup-cvkuiza, r=flip1995

Rollup of 5 pull requests

Successful merges:

 - #5226 (Add lint for explicit deref and deref_mut method calls)
 - #5248 (Add lint on large non scalar const)
 - #5430 (Disallow bit-shifting in integer_arithmetic)
 - #5466 (large_enum_variant: Report sizes of variants)
 - #5468 (Zero single char names)

Failed merges:

r? @ghost

changelog: rollup

CHANGELOG.md

@@ -1256,6 +1256,7 @@ Released 2018-09-13
 [`expect_fun_call`]: https://rust-lang.github.io/rust-clippy/master/index.html#expect_fun_call
 [`expl_impl_clone_on_copy`]: https://rust-lang.github.io/rust-clippy/master/index.html#expl_impl_clone_on_copy
 [`explicit_counter_loop`]: https://rust-lang.github.io/rust-clippy/master/index.html#explicit_counter_loop
+[`explicit_deref_methods`]: https://rust-lang.github.io/rust-clippy/master/index.html#explicit_deref_methods
 [`explicit_into_iter_loop`]: https://rust-lang.github.io/rust-clippy/master/index.html#explicit_into_iter_loop
 [`explicit_iter_loop`]: https://rust-lang.github.io/rust-clippy/master/index.html#explicit_iter_loop
 [`explicit_write`]: https://rust-lang.github.io/rust-clippy/master/index.html#explicit_write
@@ -1319,6 +1320,7 @@ Released 2018-09-13
 [`iter_skip_next`]: https://rust-lang.github.io/rust-clippy/master/index.html#iter_skip_next
 [`iterator_step_by_zero`]: https://rust-lang.github.io/rust-clippy/master/index.html#iterator_step_by_zero
 [`just_underscores_and_digits`]: https://rust-lang.github.io/rust-clippy/master/index.html#just_underscores_and_digits
+[`large_const_arrays`]: https://rust-lang.github.io/rust-clippy/master/index.html#large_const_arrays
 [`large_digit_groups`]: https://rust-lang.github.io/rust-clippy/master/index.html#large_digit_groups
 [`large_enum_variant`]: https://rust-lang.github.io/rust-clippy/master/index.html#large_enum_variant
 [`large_stack_arrays`]: https://rust-lang.github.io/rust-clippy/master/index.html#large_stack_arrays

clippy_lints/src/arithmetic.rs

@@ -6,11 +6,17 @@ use rustc_session::{declare_tool_lint, impl_lint_pass};
 use rustc_span::source_map::Span;
 
 declare_clippy_lint! {
-    /// **What it does:** Checks for plain integer arithmetic.
+    /// **What it does:** Checks for integer arithmetic operations which could overflow or panic.
     ///
-    /// **Why is this bad?** This is only checked against overflow in debug builds.
+    /// Specifically, checks for any operators (`+`, `-`, `*`, `<<`, etc) which are capable
-    /// In some applications one wants explicitly checked, wrapping or saturating
+    /// of overflowing according to the [Rust
-    /// arithmetic.
+    /// Reference](https://doc.rust-lang.org/reference/expressions/operator-expr.html#overflow),
+    /// or which can panic (`/`, `%`). No bounds analysis or sophisticated reasoning is
+    /// attempted.
+    ///
+    /// **Why is this bad?** Integer overflow will trigger a panic in debug builds or will wrap in
+    /// release mode. Division by zero will cause a panic in either mode. In some applications one
+    /// wants explicitly checked, wrapping or saturating arithmetic.
     ///
     /// **Known problems:** None.
     ///
@@ -21,7 +27,7 @@ declare_clippy_lint! {
     /// ```
     pub INTEGER_ARITHMETIC,
     restriction,
-    "any integer arithmetic statement"
+    "any integer arithmetic expression which could overflow or panic"
 }
 
 declare_clippy_lint! {
@@ -71,8 +77,6 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Arithmetic {
                     | hir::BinOpKind::BitAnd
                     | hir::BinOpKind::BitOr
                     | hir::BinOpKind::BitXor
-                    | hir::BinOpKind::Shl
-                    | hir::BinOpKind::Shr
                     | hir::BinOpKind::Eq
                     | hir::BinOpKind::Lt
                     | hir::BinOpKind::Le

clippy_lints/src/dereference.rs

@@ -0,0 +1,113 @@
+use crate::utils::{get_parent_expr, implements_trait, snippet, span_lint_and_sugg};
+use if_chain::if_chain;
+use rustc_ast::util::parser::{ExprPrecedence, PREC_POSTFIX, PREC_PREFIX};
+use rustc_errors::Applicability;
+use rustc_hir::{Expr, ExprKind};
+use rustc_lint::{LateContext, LateLintPass};
+use rustc_session::{declare_lint_pass, declare_tool_lint};
+use rustc_span::source_map::Span;
+
+declare_clippy_lint! {
+    /// **What it does:** Checks for explicit `deref()` or `deref_mut()` method calls.
+    ///
+    /// **Why is this bad?** Derefencing by `&*x` or `&mut *x` is clearer and more concise,
+    /// when not part of a method chain.
+    ///
+    /// **Example:**
+    /// ```rust
+    /// use std::ops::Deref;
+    /// let a: &mut String = &mut String::from("foo");
+    /// let b: &str = a.deref();
+    /// ```
+    /// Could be written as:
+    /// ```rust
+    /// let a: &mut String = &mut String::from("foo");
+    /// let b = &*a;
+    /// ```
+    ///
+    /// This lint excludes
+    /// ```rust,ignore
+    /// let _ = d.unwrap().deref();
+    /// ```
+    pub EXPLICIT_DEREF_METHODS,
+    pedantic,
+    "Explicit use of deref or deref_mut method while not in a method chain."
+}
+
+declare_lint_pass!(Dereferencing => [
+    EXPLICIT_DEREF_METHODS
+]);
+
+impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Dereferencing {
+    fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr<'_>) {
+        if_chain! {
+            if !expr.span.from_expansion();
+            if let ExprKind::MethodCall(ref method_name, _, ref args) = &expr.kind;
+            if args.len() == 1;
+
+            then {
+                if let Some(parent_expr) = get_parent_expr(cx, expr) {
+                    // Check if we have the whole call chain here
+                    if let ExprKind::MethodCall(..) = parent_expr.kind {
+                        return;
+                    }
+                    // Check for Expr that we don't want to be linted
+                    let precedence = parent_expr.precedence();
+                    match precedence {
+                        // Lint a Call is ok though
+                        ExprPrecedence::Call | ExprPrecedence::AddrOf => (),
+                        _ => {
+                            if precedence.order() >= PREC_PREFIX && precedence.order() <= PREC_POSTFIX {
+                                return;
+                            }
+                        }
+                    }
+                }
+                let name = method_name.ident.as_str();
+                lint_deref(cx, &*name, &args[0], args[0].span, expr.span);
+            }
+        }
+    }
+}
+
+fn lint_deref(cx: &LateContext<'_, '_>, method_name: &str, call_expr: &Expr<'_>, var_span: Span, expr_span: Span) {
+    match method_name {
+        "deref" => {
+            if cx
+                .tcx
+                .lang_items()
+                .deref_trait()
+                .map_or(false, |id| implements_trait(cx, cx.tables.expr_ty(&call_expr), id, &[]))
+            {
+                span_lint_and_sugg(
+                    cx,
+                    EXPLICIT_DEREF_METHODS,
+                    expr_span,
+                    "explicit deref method call",
+                    "try this",
+                    format!("&*{}", &snippet(cx, var_span, "..")),
+                    Applicability::MachineApplicable,
+                );
+            }
+        },
+        "deref_mut" => {
+            if cx
+                .tcx
+                .lang_items()
+                .deref_mut_trait()
+                .map_or(false, |id| implements_trait(cx, cx.tables.expr_ty(&call_expr), id, &[]))
+            {
+                span_lint_and_sugg(
+                    cx,
+                    EXPLICIT_DEREF_METHODS,
+                    expr_span,
+                    "explicit deref_mut method call",
+                    "try this",
+                    format!("&mut *{}", &snippet(cx, var_span, "..")),
+                    Applicability::MachineApplicable,
+                );
+            }
+        },
+        _ => (),
+    }
+}

clippy_lints/src/large_const_arrays.rs

@@ -0,0 +1,85 @@
+use crate::rustc_target::abi::LayoutOf;
+use crate::utils::span_lint_and_then;
+use if_chain::if_chain;
+use rustc_errors::Applicability;
+use rustc_hir::{Item, ItemKind};
+use rustc_lint::{LateContext, LateLintPass};
+use rustc_middle::mir::interpret::ConstValue;
+use rustc_middle::ty::{self, ConstKind};
+use rustc_session::{declare_tool_lint, impl_lint_pass};
+use rustc_span::{BytePos, Pos, Span};
+use rustc_typeck::hir_ty_to_ty;
+
+declare_clippy_lint! {
+    /// **What it does:** Checks for large `const` arrays that should
+    /// be defined as `static` instead.
+    ///
+    /// **Why is this bad?** Performance: const variables are inlined upon use.
+    /// Static items result in only one instance and has a fixed location in memory.
+    ///
+    /// **Known problems:** None.
+    ///
+    /// **Example:**
+    /// ```rust,ignore
+    /// // Bad
+    /// pub const a = [0u32; 1_000_000];
+    ///
+    /// // Good
+    /// pub static a = [0u32; 1_000_000];
+    /// ```
+    pub LARGE_CONST_ARRAYS,
+    perf,
+    "large non-scalar const array may cause performance overhead"
+}
+
+pub struct LargeConstArrays {
+    maximum_allowed_size: u64,
+}
+
+impl LargeConstArrays {
+    #[must_use]
+    pub fn new(maximum_allowed_size: u64) -> Self {
+        Self { maximum_allowed_size }
+    }
+}
+
+impl_lint_pass!(LargeConstArrays => [LARGE_CONST_ARRAYS]);
+
+impl<'a, 'tcx> LateLintPass<'a, 'tcx> for LargeConstArrays {
+    fn check_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx Item<'_>) {
+        if_chain! {
+            if !item.span.from_expansion();
+            if let ItemKind::Const(hir_ty, _) = &item.kind;
+            let ty = hir_ty_to_ty(cx.tcx, hir_ty);
+            if let ty::Array(element_type, cst) = ty.kind;
+            if let ConstKind::Value(val) = cst.val;
+            if let ConstValue::Scalar(element_count) = val;
+            if let Ok(element_count) = element_count.to_machine_usize(&cx.tcx);
+            if let Ok(element_size) = cx.layout_of(element_type).map(|l| l.size.bytes());
+            if self.maximum_allowed_size < element_count * element_size;
+
+            then {
+                let hi_pos = item.ident.span.lo() - BytePos::from_usize(1);
+                let sugg_span = Span::new(
+                    hi_pos - BytePos::from_usize("const".len()),
+                    hi_pos,
+                    item.span.ctxt(),
+                );
+                span_lint_and_then(
+                    cx,
+                    LARGE_CONST_ARRAYS,
+                    item.span,
+                    "large array defined as const",
+                    |db| {
+                        db.span_suggestion(
+                            sugg_span,
+                            "make this a static item",
+                            "static".to_string(),
+                            Applicability::MachineApplicable,
+                        );
+                    }
+                );
+            }
+        }
+    }
+}

clippy_lints/src/large_enum_variant.rs

@@ -21,11 +21,19 @@ declare_clippy_lint! {
     /// measure the change this lint suggests.
     ///
     /// **Example:**
+    ///
     /// ```rust
+    /// // Bad
     /// enum Test {
     ///     A(i32),
     ///     B([i32; 8000]),
     /// }
+    ///
+    /// // Possibly better
+    /// enum Test2 {
+    ///     A(i32),
+    ///     B(Box<[i32; 8000]>),
+    /// }
     /// ```
     pub LARGE_ENUM_VARIANT,
     perf,
@@ -84,12 +92,21 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for LargeEnumVariant {
                 if difference > self.maximum_size_difference_allowed {
                     let (i, variant) = largest.1;
 
+                    let help_text = "consider boxing the large fields to reduce the total size of the enum";
                     span_lint_and_then(
                         cx,
                         LARGE_ENUM_VARIANT,
                         def.variants[i].span,
                         "large size difference between variants",
                         |db| {
+                            db.span_label(
+                                def.variants[(largest.1).0].span,
+                                &format!("this variant is {} bytes", largest.0),
+                            );
+                            db.span_note(
+                                def.variants[(second.1).0].span,
+                                &format!("and the second-largest variant is {} bytes:", second.0),
+                            );
                             if variant.fields.len() == 1 {
                                 let span = match def.variants[i].data {
                                     VariantData::Struct(ref fields, ..) | VariantData::Tuple(ref fields, ..) => {
@@ -100,18 +117,14 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for LargeEnumVariant {
                                 if let Some(snip) = snippet_opt(cx, span) {
                                     db.span_suggestion(
                                         span,
-                                        "consider boxing the large fields to reduce the total size of the \
+                                        help_text,
-                                         enum",
                                         format!("Box<{}>", snip),
                                         Applicability::MaybeIncorrect,
                                     );
                                     return;
                                 }
                             }
-                            db.span_help(
+                            db.span_help(def.variants[i].span, help_text);
-                                def.variants[i].span,
-                                "consider boxing the large fields to reduce the total size of the enum",
-                            );
                         },
                     );
                 }

clippy_lints/src/lib.rs

@@ -191,6 +191,7 @@ mod copies;
 mod copy_iterator;
 mod dbg_macro;
 mod default_trait_access;
+mod dereference;
 mod derive;
 mod doc;
 mod double_comparison;
@@ -231,6 +232,7 @@ mod inline_fn_without_body;
 mod int_plus_one;
 mod integer_division;
 mod items_after_statements;
+mod large_const_arrays;
 mod large_enum_variant;
 mod large_stack_arrays;
 mod len_zero;
@@ -513,6 +515,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
         &copy_iterator::COPY_ITERATOR,
         &dbg_macro::DBG_MACRO,
         &default_trait_access::DEFAULT_TRAIT_ACCESS,
+        &dereference::EXPLICIT_DEREF_METHODS,
         &derive::DERIVE_HASH_XOR_EQ,
         &derive::EXPL_IMPL_CLONE_ON_COPY,
         &doc::DOC_MARKDOWN,
@@ -580,6 +583,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
         &int_plus_one::INT_PLUS_ONE,
         &integer_division::INTEGER_DIVISION,
         &items_after_statements::ITEMS_AFTER_STATEMENTS,
+        &large_const_arrays::LARGE_CONST_ARRAYS,
         &large_enum_variant::LARGE_ENUM_VARIANT,
         &large_stack_arrays::LARGE_STACK_ARRAYS,
         &len_zero::LEN_WITHOUT_IS_EMPTY,
@@ -1024,6 +1028,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
     store.register_late_pass(|| box to_digit_is_some::ToDigitIsSome);
     let array_size_threshold = conf.array_size_threshold;
     store.register_late_pass(move || box large_stack_arrays::LargeStackArrays::new(array_size_threshold));
+    store.register_late_pass(move || box large_const_arrays::LargeConstArrays::new(array_size_threshold));
     store.register_late_pass(move || box floating_point_arithmetic::FloatingPointArithmetic);
     store.register_early_pass(|| box as_conversions::AsConversions);
     store.register_early_pass(|| box utils::internal_lints::ProduceIce);
@@ -1039,6 +1044,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
     store.register_late_pass(|| box verbose_file_reads::VerboseFileReads);
     store.register_late_pass(|| box redundant_pub_crate::RedundantPubCrate::default());
     store.register_late_pass(|| box unnamed_address::UnnamedAddress);
+    store.register_late_pass(|| box dereference::Dereferencing);
 
     store.register_group(true, "clippy::restriction", Some("clippy_restriction"), vec![
         LintId::of(&arithmetic::FLOAT_ARITHMETIC),
@@ -1089,6 +1095,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
         LintId::of(&copies::SAME_FUNCTIONS_IN_IF_CONDITION),
         LintId::of(&copy_iterator::COPY_ITERATOR),
         LintId::of(&default_trait_access::DEFAULT_TRAIT_ACCESS),
+        LintId::of(&dereference::EXPLICIT_DEREF_METHODS),
         LintId::of(&derive::EXPL_IMPL_CLONE_ON_COPY),
         LintId::of(&doc::DOC_MARKDOWN),
         LintId::of(&doc::MISSING_ERRORS_DOC),
@@ -1221,6 +1228,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
         LintId::of(&inherent_to_string::INHERENT_TO_STRING_SHADOW_DISPLAY),
         LintId::of(&inline_fn_without_body::INLINE_FN_WITHOUT_BODY),
         LintId::of(&int_plus_one::INT_PLUS_ONE),
+        LintId::of(&large_const_arrays::LARGE_CONST_ARRAYS),
         LintId::of(&large_enum_variant::LARGE_ENUM_VARIANT),
         LintId::of(&len_zero::LEN_WITHOUT_IS_EMPTY),
         LintId::of(&len_zero::LEN_ZERO),
@@ -1652,6 +1660,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
         LintId::of(&bytecount::NAIVE_BYTECOUNT),
         LintId::of(&entry::MAP_ENTRY),
         LintId::of(&escape::BOXED_LOCAL),
+        LintId::of(&large_const_arrays::LARGE_CONST_ARRAYS),
         LintId::of(&large_enum_variant::LARGE_ENUM_VARIANT),
         LintId::of(&loops::MANUAL_MEMCPY),
         LintId::of(&loops::NEEDLESS_COLLECT),

clippy_lints/src/non_expressive_names.rs

@@ -93,7 +93,7 @@ impl<'a, 'tcx> SimilarNamesLocalVisitor<'a, 'tcx> {
     fn check_single_char_names(&self) {
         let num_single_char_names = self.single_char_names.iter().flatten().count();
         let threshold = self.lint.single_char_binding_names_threshold;
-        if num_single_char_names as u64 >= threshold {
+        if num_single_char_names as u64 > threshold {
             let span = self
                 .single_char_names
                 .iter()

clippy_lints/src/utils/conf.rs

@@ -135,7 +135,7 @@ define_Conf! {
     /// Lint: TYPE_COMPLEXITY. The maximum complexity a type can have
     (type_complexity_threshold, "type_complexity_threshold": u64, 250),
     /// Lint: MANY_SINGLE_CHAR_NAMES. The maximum number of single char bindings a scope may have
-    (single_char_binding_names_threshold, "single_char_binding_names_threshold": u64, 5),
+    (single_char_binding_names_threshold, "single_char_binding_names_threshold": u64, 4),
     /// Lint: BOXED_LOCAL. The maximum size of objects (in bytes) that will be linted. Larger objects are ok on the heap
     (too_large_for_stack, "too_large_for_stack": u64, 200),
     /// Lint: ENUM_VARIANT_NAMES. The minimum number of enum variants for the lints about variant names to trigger
@@ -150,7 +150,7 @@ define_Conf! {
     (trivial_copy_size_limit, "trivial_copy_size_limit": Option<u64>, None),
     /// Lint: TOO_MANY_LINES. The maximum number of lines a function or method can have
     (too_many_lines_threshold, "too_many_lines_threshold": u64, 100),
-    /// Lint: LARGE_STACK_ARRAYS. The maximum allowed size for arrays on the stack
+    /// Lint: LARGE_STACK_ARRAYS, LARGE_CONST_ARRAYS. The maximum allowed size for arrays on the stack
     (array_size_threshold, "array_size_threshold": u64, 512_000),
     /// Lint: VEC_BOX. The size of the boxed type in bytes, where boxing in a `Vec` is allowed
     (vec_box_size_threshold, "vec_box_size_threshold": u64, 4096),

src/lintlist/mod.rs

@@ -528,6 +528,13 @@ pub static ref ALL_LINTS: Vec<Lint> = vec![
         deprecation: None,
         module: "loops",
     },
+    Lint {
+        name: "explicit_deref_methods",
+        group: "pedantic",
+        desc: "Explicit use of deref or deref_mut method while not in a method chain.",
+        deprecation: None,
+        module: "dereference",
+    },
     Lint {
         name: "explicit_into_iter_loop",
         group: "pedantic",
@@ -846,7 +853,7 @@ pub static ref ALL_LINTS: Vec<Lint> = vec![
     Lint {
         name: "integer_arithmetic",
         group: "restriction",
-        desc: "any integer arithmetic statement",
+        desc: "any integer arithmetic expression which could overflow or panic",
         deprecation: None,
         module: "arithmetic",
     },
@@ -941,6 +948,13 @@ pub static ref ALL_LINTS: Vec<Lint> = vec![
         deprecation: None,
         module: "non_expressive_names",
     },
+    Lint {
+        name: "large_const_arrays",
+        group: "perf",
+        desc: "large non-scalar const array may cause performance overhead",
+        deprecation: None,
+        module: "large_const_arrays",
+    },
     Lint {
         name: "large_digit_groups",
         group: "pedantic",

tests/ui-toml/zero_single_char_names/clippy.toml

@@ -0,0 +1 @@
+single-char-binding-names-threshold = 0

tests/ui-toml/zero_single_char_names/zero_single_char_names.rs

@@ -0,0 +1,3 @@
+#![warn(clippy::many_single_char_names)]
+
+fn main() {}

tests/ui/dereference.fixed

@@ -0,0 +1,93 @@
+// run-rustfix
+
+#![allow(unused_variables, clippy::many_single_char_names, clippy::clone_double_ref)]
+#![warn(clippy::explicit_deref_methods)]
+
+use std::ops::{Deref, DerefMut};
+
+fn concat(deref_str: &str) -> String {
+    format!("{}bar", deref_str)
+}
+
+fn just_return(deref_str: &str) -> &str {
+    deref_str
+}
+
+struct CustomVec(Vec<u8>);
+impl Deref for CustomVec {
+    type Target = Vec<u8>;
+
+    fn deref(&self) -> &Vec<u8> {
+        &self.0
+    }
+}
+
+fn main() {
+    let a: &mut String = &mut String::from("foo");
+
+    // these should require linting
+
+    let b: &str = &*a;
+
+    let b: &mut str = &mut *a;
+
+    // both derefs should get linted here
+    let b: String = format!("{}, {}", &*a, &*a);
+
+    println!("{}", &*a);
+
+    #[allow(clippy::match_single_binding)]
+    match &*a {
+        _ => (),
+    }
+
+    let b: String = concat(&*a);
+
+    let b = &*just_return(a);
+
+    let b: String = concat(&*just_return(a));
+
+    let b: &str = &*a.deref();
+
+    let opt_a = Some(a.clone());
+    let b = &*opt_a.unwrap();
+
+    // following should not require linting
+
+    let cv = CustomVec(vec![0, 42]);
+    let c = cv.deref()[0];
+
+    let b: &str = &*a.deref();
+
+    let b: String = a.deref().clone();
+
+    let b: usize = a.deref_mut().len();
+
+    let b: &usize = &a.deref().len();
+
+    let b: &str = &*a;
+
+    let b: &mut str = &mut *a;
+
+    macro_rules! expr_deref {
+        ($body:expr) => {
+            $body.deref()
+        };
+    }
+    let b: &str = expr_deref!(a);
+
+    // The struct does not implement Deref trait
+    #[derive(Copy, Clone)]
+    struct NoLint(u32);
+    impl NoLint {
+        pub fn deref(self) -> u32 {
+            self.0
+        }
+        pub fn deref_mut(self) -> u32 {
+            self.0
+        }
+    }
+    let no_lint = NoLint(42);
+    let b = no_lint.deref();
+    let b = no_lint.deref_mut();
+}

tests/ui/dereference.rs

@@ -0,0 +1,93 @@
+// run-rustfix
+
+#![allow(unused_variables, clippy::many_single_char_names, clippy::clone_double_ref)]
+#![warn(clippy::explicit_deref_methods)]
+
+use std::ops::{Deref, DerefMut};
+
+fn concat(deref_str: &str) -> String {
+    format!("{}bar", deref_str)
+}
+
+fn just_return(deref_str: &str) -> &str {
+    deref_str
+}
+
+struct CustomVec(Vec<u8>);
+impl Deref for CustomVec {
+    type Target = Vec<u8>;
+
+    fn deref(&self) -> &Vec<u8> {
+        &self.0
+    }
+}
+
+fn main() {
+    let a: &mut String = &mut String::from("foo");
+
+    // these should require linting
+
+    let b: &str = a.deref();
+
+    let b: &mut str = a.deref_mut();
+
+    // both derefs should get linted here
+    let b: String = format!("{}, {}", a.deref(), a.deref());
+
+    println!("{}", a.deref());
+
+    #[allow(clippy::match_single_binding)]
+    match a.deref() {
+        _ => (),
+    }
+
+    let b: String = concat(a.deref());
+
+    let b = just_return(a).deref();
+
+    let b: String = concat(just_return(a).deref());
+
+    let b: &str = a.deref().deref();
+
+    let opt_a = Some(a.clone());
+    let b = opt_a.unwrap().deref();
+
+    // following should not require linting
+
+    let cv = CustomVec(vec![0, 42]);
+    let c = cv.deref()[0];
+
+    let b: &str = &*a.deref();
+
+    let b: String = a.deref().clone();
+
+    let b: usize = a.deref_mut().len();
+
+    let b: &usize = &a.deref().len();
+
+    let b: &str = &*a;
+
+    let b: &mut str = &mut *a;
+
+    macro_rules! expr_deref {
+        ($body:expr) => {
+            $body.deref()
+        };
+    }
+    let b: &str = expr_deref!(a);
+
+    // The struct does not implement Deref trait
+    #[derive(Copy, Clone)]
+    struct NoLint(u32);
+    impl NoLint {
+        pub fn deref(self) -> u32 {
+            self.0
+        }
+        pub fn deref_mut(self) -> u32 {
+            self.0
+        }
+    }
+    let no_lint = NoLint(42);
+    let b = no_lint.deref();
+    let b = no_lint.deref_mut();
+}

tests/ui/dereference.stderr

@@ -0,0 +1,70 @@
+error: explicit deref method call
+  --> $DIR/dereference.rs:30:19
+   |
+LL |     let b: &str = a.deref();
+   |                   ^^^^^^^^^ help: try this: `&*a`
+   |
+   = note: `-D clippy::explicit-deref-methods` implied by `-D warnings`
+
+error: explicit deref_mut method call
+  --> $DIR/dereference.rs:32:23
+   |
+LL |     let b: &mut str = a.deref_mut();
+   |                       ^^^^^^^^^^^^^ help: try this: `&mut *a`
+
+error: explicit deref method call
+  --> $DIR/dereference.rs:35:39
+   |
+LL |     let b: String = format!("{}, {}", a.deref(), a.deref());
+   |                                       ^^^^^^^^^ help: try this: `&*a`
+
+error: explicit deref method call
+  --> $DIR/dereference.rs:35:50
+   |
+LL |     let b: String = format!("{}, {}", a.deref(), a.deref());
+   |                                                  ^^^^^^^^^ help: try this: `&*a`
+
+error: explicit deref method call
+  --> $DIR/dereference.rs:37:20
+   |
+LL |     println!("{}", a.deref());
+   |                    ^^^^^^^^^ help: try this: `&*a`
+
+error: explicit deref method call
+  --> $DIR/dereference.rs:40:11
+   |
+LL |     match a.deref() {
+   |           ^^^^^^^^^ help: try this: `&*a`
+
+error: explicit deref method call
+  --> $DIR/dereference.rs:44:28
+   |
+LL |     let b: String = concat(a.deref());
+   |                            ^^^^^^^^^ help: try this: `&*a`
+
+error: explicit deref method call
+  --> $DIR/dereference.rs:46:13
+   |
+LL |     let b = just_return(a).deref();
+   |             ^^^^^^^^^^^^^^^^^^^^^^ help: try this: `&*just_return(a)`
+
+error: explicit deref method call
+  --> $DIR/dereference.rs:48:28
+   |
+LL |     let b: String = concat(just_return(a).deref());
+   |                            ^^^^^^^^^^^^^^^^^^^^^^ help: try this: `&*just_return(a)`
+
+error: explicit deref method call
+  --> $DIR/dereference.rs:50:19
+   |
+LL |     let b: &str = a.deref().deref();
+   |                   ^^^^^^^^^^^^^^^^^ help: try this: `&*a.deref()`
+
+error: explicit deref method call
+  --> $DIR/dereference.rs:53:13
+   |
+LL |     let b = opt_a.unwrap().deref();
+   |             ^^^^^^^^^^^^^^^^^^^^^^ help: try this: `&*opt_a.unwrap()`
+
+error: aborting due to 11 previous errors
+

tests/ui/integer_arithmetic.rs

@@ -17,6 +17,8 @@ fn main() {
     i / 2; // no error, this is part of the expression in the preceding line
     i - 2 + 2 - i;
     -i;
+    i >> 1;
+    i << 1;
 
     // no error, overflows are checked by `overflowing_literals`
     -1;
@@ -25,18 +27,16 @@ fn main() {
     i & 1; // no wrapping
     i | 1;
     i ^ 1;
-    i >> 1;
-    i << 1;
 
     i += 1;
     i -= 1;
     i *= 2;
     i /= 2;
     i %= 2;
-
-    // no errors
     i <<= 3;
     i >>= 2;
+
+    // no errors
     i |= 1;
     i &= 1;
     i ^= i;
@@ -72,8 +72,6 @@ fn main() {
             1 + 1
         };
     }
-
-
 }
 
 // warn on references as well! (#5328)

tests/ui/integer_arithmetic.stderr

@@ -31,6 +31,18 @@ error: integer arithmetic detected
 LL |     -i;
    |     ^^
 
+error: integer arithmetic detected
+  --> $DIR/integer_arithmetic.rs:20:5
+   |
+LL |     i >> 1;
+   |     ^^^^^^
+
+error: integer arithmetic detected
+  --> $DIR/integer_arithmetic.rs:21:5
+   |
+LL |     i << 1;
+   |     ^^^^^^
+
 error: integer arithmetic detected
   --> $DIR/integer_arithmetic.rs:31:5
    |
@@ -62,46 +74,58 @@ LL |     i %= 2;
    |     ^^^^^^
 
 error: integer arithmetic detected
-  --> $DIR/integer_arithmetic.rs:81:5
+  --> $DIR/integer_arithmetic.rs:36:5
+   |
+LL |     i <<= 3;
+   |     ^^^^^^^
+
+error: integer arithmetic detected
+  --> $DIR/integer_arithmetic.rs:37:5
+   |
+LL |     i >>= 2;
+   |     ^^^^^^^
+
+error: integer arithmetic detected
+  --> $DIR/integer_arithmetic.rs:79:5
    |
 LL |     3 + &1;
    |     ^^^^^^
 
 error: integer arithmetic detected
-  --> $DIR/integer_arithmetic.rs:82:5
+  --> $DIR/integer_arithmetic.rs:80:5
    |
 LL |     &3 + 1;
    |     ^^^^^^
 
 error: integer arithmetic detected
-  --> $DIR/integer_arithmetic.rs:83:5
+  --> $DIR/integer_arithmetic.rs:81:5
    |
 LL |     &3 + &1;
    |     ^^^^^^^
 
 error: integer arithmetic detected
-  --> $DIR/integer_arithmetic.rs:88:5
+  --> $DIR/integer_arithmetic.rs:86:5
    |
 LL |     a + x
    |     ^^^^^
 
 error: integer arithmetic detected
-  --> $DIR/integer_arithmetic.rs:92:5
+  --> $DIR/integer_arithmetic.rs:90:5
    |
 LL |     x + y
    |     ^^^^^
 
 error: integer arithmetic detected
-  --> $DIR/integer_arithmetic.rs:96:5
+  --> $DIR/integer_arithmetic.rs:94:5
    |
 LL |     x + y
    |     ^^^^^
 
 error: integer arithmetic detected
-  --> $DIR/integer_arithmetic.rs:100:5
+  --> $DIR/integer_arithmetic.rs:98:5
    |
 LL |     (&x + &y)
    |     ^^^^^^^^^
 
-error: aborting due to 17 previous errors
+error: aborting due to 21 previous errors
 

tests/ui/large_const_arrays.fixed

@@ -0,0 +1,37 @@
+// run-rustfix
+
+#![warn(clippy::large_const_arrays)]
+#![allow(dead_code)]
+
+#[derive(Clone, Copy)]
+pub struct S {
+    pub data: [u64; 32],
+}
+
+// Should lint
+pub(crate) static FOO_PUB_CRATE: [u32; 1_000_000] = [0u32; 1_000_000];
+pub static FOO_PUB: [u32; 1_000_000] = [0u32; 1_000_000];
+static FOO: [u32; 1_000_000] = [0u32; 1_000_000];
+
+// Good
+pub(crate) const G_FOO_PUB_CRATE: [u32; 1_000] = [0u32; 1_000];
+pub const G_FOO_PUB: [u32; 1_000] = [0u32; 1_000];
+const G_FOO: [u32; 1_000] = [0u32; 1_000];
+
+fn main() {
+    // Should lint
+    pub static BAR_PUB: [u32; 1_000_000] = [0u32; 1_000_000];
+    static BAR: [u32; 1_000_000] = [0u32; 1_000_000];
+    pub static BAR_STRUCT_PUB: [S; 5_000] = [S { data: [0; 32] }; 5_000];
+    static BAR_STRUCT: [S; 5_000] = [S { data: [0; 32] }; 5_000];
+    pub static BAR_S_PUB: [Option<&str>; 200_000] = [Some("str"); 200_000];
+    static BAR_S: [Option<&str>; 200_000] = [Some("str"); 200_000];
+
+    // Good
+    pub const G_BAR_PUB: [u32; 1_000] = [0u32; 1_000];
+    const G_BAR: [u32; 1_000] = [0u32; 1_000];
+    pub const G_BAR_STRUCT_PUB: [S; 500] = [S { data: [0; 32] }; 500];
+    const G_BAR_STRUCT: [S; 500] = [S { data: [0; 32] }; 500];
+    pub const G_BAR_S_PUB: [Option<&str>; 200] = [Some("str"); 200];
+    const G_BAR_S: [Option<&str>; 200] = [Some("str"); 200];
+}

tests/ui/large_const_arrays.rs

@@ -0,0 +1,37 @@
+// run-rustfix
+
+#![warn(clippy::large_const_arrays)]
+#![allow(dead_code)]
+
+#[derive(Clone, Copy)]
+pub struct S {
+    pub data: [u64; 32],
+}
+
+// Should lint
+pub(crate) const FOO_PUB_CRATE: [u32; 1_000_000] = [0u32; 1_000_000];
+pub const FOO_PUB: [u32; 1_000_000] = [0u32; 1_000_000];
+const FOO: [u32; 1_000_000] = [0u32; 1_000_000];
+
+// Good
+pub(crate) const G_FOO_PUB_CRATE: [u32; 1_000] = [0u32; 1_000];
+pub const G_FOO_PUB: [u32; 1_000] = [0u32; 1_000];
+const G_FOO: [u32; 1_000] = [0u32; 1_000];
+
+fn main() {
+    // Should lint
+    pub const BAR_PUB: [u32; 1_000_000] = [0u32; 1_000_000];
+    const BAR: [u32; 1_000_000] = [0u32; 1_000_000];
+    pub const BAR_STRUCT_PUB: [S; 5_000] = [S { data: [0; 32] }; 5_000];
+    const BAR_STRUCT: [S; 5_000] = [S { data: [0; 32] }; 5_000];
+    pub const BAR_S_PUB: [Option<&str>; 200_000] = [Some("str"); 200_000];
+    const BAR_S: [Option<&str>; 200_000] = [Some("str"); 200_000];
+
+    // Good
+    pub const G_BAR_PUB: [u32; 1_000] = [0u32; 1_000];
+    const G_BAR: [u32; 1_000] = [0u32; 1_000];
+    pub const G_BAR_STRUCT_PUB: [S; 500] = [S { data: [0; 32] }; 500];
+    const G_BAR_STRUCT: [S; 500] = [S { data: [0; 32] }; 500];
+    pub const G_BAR_S_PUB: [Option<&str>; 200] = [Some("str"); 200];
+    const G_BAR_S: [Option<&str>; 200] = [Some("str"); 200];
+}

tests/ui/large_const_arrays.stderr

@@ -0,0 +1,76 @@
+error: large array defined as const
+  --> $DIR/large_const_arrays.rs:12:1
+   |
+LL | pub(crate) const FOO_PUB_CRATE: [u32; 1_000_000] = [0u32; 1_000_000];
+   | ^^^^^^^^^^^-----^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |            |
+   |            help: make this a static item: `static`
+   |
+   = note: `-D clippy::large-const-arrays` implied by `-D warnings`
+
+error: large array defined as const
+  --> $DIR/large_const_arrays.rs:13:1
+   |
+LL | pub const FOO_PUB: [u32; 1_000_000] = [0u32; 1_000_000];
+   | ^^^^-----^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |     |
+   |     help: make this a static item: `static`
+
+error: large array defined as const
+  --> $DIR/large_const_arrays.rs:14:1
+   |
+LL | const FOO: [u32; 1_000_000] = [0u32; 1_000_000];
+   | -----^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   | |
+   | help: make this a static item: `static`
+
+error: large array defined as const
+  --> $DIR/large_const_arrays.rs:23:5
+   |
+LL |     pub const BAR_PUB: [u32; 1_000_000] = [0u32; 1_000_000];
+   |     ^^^^-----^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |         |
+   |         help: make this a static item: `static`
+
+error: large array defined as const
+  --> $DIR/large_const_arrays.rs:24:5
+   |
+LL |     const BAR: [u32; 1_000_000] = [0u32; 1_000_000];
+   |     -----^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |     |
+   |     help: make this a static item: `static`
+
+error: large array defined as const
+  --> $DIR/large_const_arrays.rs:25:5
+   |
+LL |     pub const BAR_STRUCT_PUB: [S; 5_000] = [S { data: [0; 32] }; 5_000];
+   |     ^^^^-----^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |         |
+   |         help: make this a static item: `static`
+
+error: large array defined as const
+  --> $DIR/large_const_arrays.rs:26:5
+   |
+LL |     const BAR_STRUCT: [S; 5_000] = [S { data: [0; 32] }; 5_000];
+   |     -----^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |     |
+   |     help: make this a static item: `static`
+
+error: large array defined as const
+  --> $DIR/large_const_arrays.rs:27:5
+   |
+LL |     pub const BAR_S_PUB: [Option<&str>; 200_000] = [Some("str"); 200_000];
+   |     ^^^^-----^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |         |
+   |         help: make this a static item: `static`
+
+error: large array defined as const
+  --> $DIR/large_const_arrays.rs:28:5
+   |
+LL |     const BAR_S: [Option<&str>; 200_000] = [Some("str"); 200_000];
+   |     -----^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |     |
+   |     help: make this a static item: `static`
+
+error: aborting due to 9 previous errors
+

tests/ui/large_enum_variant.stderr

@@ -2,9 +2,14 @@ error: large size difference between variants
   --> $DIR/large_enum_variant.rs:7:5
    |
 LL |     B([i32; 8000]),
-   |     ^^^^^^^^^^^^^^
+   |     ^^^^^^^^^^^^^^ this variant is 32000 bytes
    |
    = note: `-D clippy::large-enum-variant` implied by `-D warnings`
+note: and the second-largest variant is 4 bytes:
+  --> $DIR/large_enum_variant.rs:6:5
+   |
+LL |     A(i32),
+   |     ^^^^^^
 help: consider boxing the large fields to reduce the total size of the enum
    |
 LL |     B(Box<[i32; 8000]>),
@@ -14,8 +19,13 @@ error: large size difference between variants
   --> $DIR/large_enum_variant.rs:31:5
    |
 LL |     ContainingLargeEnum(LargeEnum),
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ this variant is 32004 bytes
    |
+note: and the second-largest variant is 8 bytes:
+  --> $DIR/large_enum_variant.rs:30:5
+   |
+LL |     VariantOk(i32, u32),
+   |     ^^^^^^^^^^^^^^^^^^^
 help: consider boxing the large fields to reduce the total size of the enum
    |
 LL |     ContainingLargeEnum(Box<LargeEnum>),
@@ -25,8 +35,13 @@ error: large size difference between variants
   --> $DIR/large_enum_variant.rs:41:5
    |
 LL |     StructLikeLarge { x: [i32; 8000], y: i32 },
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ this variant is 32004 bytes
    |
+note: and the second-largest variant is 8 bytes:
+  --> $DIR/large_enum_variant.rs:40:5
+   |
+LL |     VariantOk(i32, u32),
+   |     ^^^^^^^^^^^^^^^^^^^
 help: consider boxing the large fields to reduce the total size of the enum
   --> $DIR/large_enum_variant.rs:41:5
    |
@@ -37,8 +52,13 @@ error: large size difference between variants
   --> $DIR/large_enum_variant.rs:46:5
    |
 LL |     StructLikeLarge2 { x: [i32; 8000] },
-   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+   |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ this variant is 32000 bytes
    |
+note: and the second-largest variant is 8 bytes:
+  --> $DIR/large_enum_variant.rs:45:5
+   |
+LL |     VariantOk(i32, u32),
+   |     ^^^^^^^^^^^^^^^^^^^
 help: consider boxing the large fields to reduce the total size of the enum
    |
 LL |     StructLikeLarge2 { x: Box<[i32; 8000]> },

util/lintlib.py

@@ -14,7 +14,7 @@ lintname_re = re.compile(r'''pub\s+([A-Z_][A-Z_0-9]*)''')
 group_re = re.compile(r'''\s*([a-z_][a-z_0-9]+)''')
 conf_re = re.compile(r'''define_Conf! {\n([^}]*)\n}''', re.MULTILINE)
 confvar_re = re.compile(
-    r'''/// Lint: (\w+)\. (.*)\n\s*\([^,]+,\s+"([^"]+)":\s+([^,]+),\s+([^\.\)]+).*\),''', re.MULTILINE)
+    r'''/// Lint: ([\w,\s]+)\. (.*)\n\s*\([^,]+,\s+"([^"]+)":\s+([^,]+),\s+([^\.\)]+).*\),''', re.MULTILINE)
 comment_re = re.compile(r'''\s*/// ?(.*)''')
 
 lint_levels = {
@@ -93,9 +93,9 @@ def parse_configs(path):
     match = re.search(conf_re, contents)
     confvars = re.findall(confvar_re, match.group(1))
 
-    for (lint, doc, name, ty, default) in confvars:
+    for (lints, doc, name, ty, default) in confvars:
-        configs[lint.lower()] = Config(name.replace("_", "-"), ty, doc, default)
+        for lint in lints.split(','):
-
+            configs[lint.strip().lower()] = Config(name.replace("_", "-"), ty, doc, default)
     return configs