Auto merge of #4839 - flip1995:rollup-new-lints, r=flip1995

Rollup of 4 Pull requests with new lints

Rollup of pull requests

- #4816 (New lint: zst_offset)
- #4814 (New lint: Implement ifs_same_cond_fn)
- #4807 (Add `large_stack_arrays` lint)
- #4806 (Issue/4623)

changelog: add [`zst_offset`] lint
changelog: New lint: [`ifs_same_cond_fn`]
cahngelog: Add new lint [large_stack_arrays]
changelog: added lint [`tabs_in_doc_comments`]

Author: bors

CHANGELOG.md

@@ -1059,6 +1059,7 @@ Released 2018-09-13
 [`just_underscores_and_digits`]: https://rust-lang.github.io/rust-clippy/master/index.html#just_underscores_and_digits
 [`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
 [`len_without_is_empty`]: https://rust-lang.github.io/rust-clippy/master/index.html#len_without_is_empty
 [`len_zero`]: https://rust-lang.github.io/rust-clippy/master/index.html#len_zero
 [`let_and_return`]: https://rust-lang.github.io/rust-clippy/master/index.html#let_and_return
@@ -1176,6 +1177,7 @@ Released 2018-09-13
 [`result_map_unwrap_or_else`]: https://rust-lang.github.io/rust-clippy/master/index.html#result_map_unwrap_or_else
 [`result_unwrap_used`]: https://rust-lang.github.io/rust-clippy/master/index.html#result_unwrap_used
 [`reverse_range_loop`]: https://rust-lang.github.io/rust-clippy/master/index.html#reverse_range_loop
+[`same_functions_in_if_condition`]: https://rust-lang.github.io/rust-clippy/master/index.html#same_functions_in_if_condition
 [`search_is_some`]: https://rust-lang.github.io/rust-clippy/master/index.html#search_is_some
 [`serde_api_misuse`]: https://rust-lang.github.io/rust-clippy/master/index.html#serde_api_misuse
 [`shadow_reuse`]: https://rust-lang.github.io/rust-clippy/master/index.html#shadow_reuse
@@ -1201,6 +1203,7 @@ Released 2018-09-13
 [`suspicious_map`]: https://rust-lang.github.io/rust-clippy/master/index.html#suspicious_map
 [`suspicious_op_assign_impl`]: https://rust-lang.github.io/rust-clippy/master/index.html#suspicious_op_assign_impl
 [`suspicious_unary_op_formatting`]: https://rust-lang.github.io/rust-clippy/master/index.html#suspicious_unary_op_formatting
+[`tabs_in_doc_comments`]: https://rust-lang.github.io/rust-clippy/master/index.html#tabs_in_doc_comments
 [`temporary_assignment`]: https://rust-lang.github.io/rust-clippy/master/index.html#temporary_assignment
 [`temporary_cstring_as_ptr`]: https://rust-lang.github.io/rust-clippy/master/index.html#temporary_cstring_as_ptr
 [`to_digit_is_some`]: https://rust-lang.github.io/rust-clippy/master/index.html#to_digit_is_some
@@ -1273,4 +1276,5 @@ Released 2018-09-13
 [`zero_prefixed_literal`]: https://rust-lang.github.io/rust-clippy/master/index.html#zero_prefixed_literal
 [`zero_ptr`]: https://rust-lang.github.io/rust-clippy/master/index.html#zero_ptr
 [`zero_width_space`]: https://rust-lang.github.io/rust-clippy/master/index.html#zero_width_space
+[`zst_offset`]: https://rust-lang.github.io/rust-clippy/master/index.html#zst_offset
 <!-- end autogenerated links to lint list -->

README.md

@@ -6,7 +6,7 @@
 
 A collection of lints to catch common mistakes and improve your [Rust](https://github.com/rust-lang/rust) code.
 
-[There are 333 lints included in this crate!](https://rust-lang.github.io/rust-clippy/master/index.html)
+[There are 337 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/copies.rs

@@ -40,6 +40,53 @@ declare_clippy_lint! {
     "consecutive `ifs` with the same condition"
 }
 
+declare_clippy_lint! {
+    /// **What it does:** Checks for consecutive `if`s with the same function call.
+    ///
+    /// **Why is this bad?** This is probably a copy & paste error.
+    /// Despite the fact that function can have side effects and `if` works as
+    /// intended, such an approach is implicit and can be considered a "code smell".
+    ///
+    /// **Known problems:** Hopefully none.
+    ///
+    /// **Example:**
+    /// ```ignore
+    /// if foo() == bar {
+    ///     …
+    /// } else if foo() == bar {
+    ///     …
+    /// }
+    /// ```
+    ///
+    /// This probably should be:
+    /// ```ignore
+    /// if foo() == bar {
+    ///     …
+    /// } else if foo() == baz {
+    ///     …
+    /// }
+    /// ```
+    ///
+    /// or if the original code was not a typo and called function mutates a state,
+    /// consider move the mutation out of the `if` condition to avoid similarity to
+    /// a copy & paste error:
+    ///
+    /// ```ignore
+    /// let first = foo();
+    /// if first == bar {
+    ///     …
+    /// } else {
+    ///     let second = foo();
+    ///     if second == bar {
+    ///     …
+    ///     }
+    /// }
+    /// ```
+    pub SAME_FUNCTIONS_IN_IF_CONDITION,
+    pedantic,
+    "consecutive `ifs` with the same function call"
+}
+
 declare_clippy_lint! {
     /// **What it does:** Checks for `if/else` with the same body as the *then* part
     /// and the *else* part.
@@ -102,7 +149,7 @@ declare_clippy_lint! {
     "`match` with identical arm bodies"
 }
 
-declare_lint_pass!(CopyAndPaste => [IFS_SAME_COND, IF_SAME_THEN_ELSE, MATCH_SAME_ARMS]);
+declare_lint_pass!(CopyAndPaste => [IFS_SAME_COND, SAME_FUNCTIONS_IN_IF_CONDITION, IF_SAME_THEN_ELSE, MATCH_SAME_ARMS]);
 
 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for CopyAndPaste {
     fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
@@ -119,6 +166,7 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for CopyAndPaste {
             let (conds, blocks) = if_sequence(expr);
             lint_same_then_else(cx, &blocks);
             lint_same_cond(cx, &conds);
+            lint_same_fns_in_if_cond(cx, &conds);
             lint_match_arms(cx, expr);
         }
     }
@@ -163,6 +211,34 @@ fn lint_same_cond(cx: &LateContext<'_, '_>, conds: &[&Expr]) {
     }
 }
 
+/// Implementation of `SAME_FUNCTIONS_IN_IF_CONDITION`.
+fn lint_same_fns_in_if_cond(cx: &LateContext<'_, '_>, conds: &[&Expr]) {
+    let hash: &dyn Fn(&&Expr) -> u64 = &|expr| -> u64 {
+        let mut h = SpanlessHash::new(cx, cx.tables);
+        h.hash_expr(expr);
+        h.finish()
+    };
+
+    let eq: &dyn Fn(&&Expr, &&Expr) -> bool = &|&lhs, &rhs| -> bool {
+        // Do not spawn warning if `IFS_SAME_COND` already produced it.
+        if SpanlessEq::new(cx).ignore_fn().eq_expr(lhs, rhs) {
+            return false;
+        }
+        SpanlessEq::new(cx).eq_expr(lhs, rhs)
+    };
+
+    for (i, j) in search_same(conds, hash, eq) {
+        span_note_and_lint(
+            cx,
+            SAME_FUNCTIONS_IN_IF_CONDITION,
+            j.span,
+            "this `if` has the same function call as a previous if",
+            i.span,
+            "same as this",
+        );
+    }
+}
+
 /// Implementation of `MATCH_SAME_ARMS`.
 fn lint_match_arms<'tcx>(cx: &LateContext<'_, 'tcx>, expr: &Expr) {
     fn same_bindings<'tcx>(

clippy_lints/src/large_stack_arrays.rs

@@ -0,0 +1,68 @@
+use rustc::hir::*;
+use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
+use rustc::mir::interpret::ConstValue;
+use rustc::ty::{self, ConstKind};
+use rustc::{declare_tool_lint, impl_lint_pass};
+
+use if_chain::if_chain;
+
+use crate::rustc_target::abi::LayoutOf;
+use crate::utils::{snippet, span_help_and_lint};
+
+declare_clippy_lint! {
+    /// **What it does:** Checks for local arrays that may be too large.
+    ///
+    /// **Why is this bad?** Large local arrays may cause stack overflow.
+    ///
+    /// **Known problems:** None.
+    ///
+    /// **Example:**
+    /// ```rust,ignore
+    /// let a = [0u32; 1_000_000];
+    /// ```
+    pub LARGE_STACK_ARRAYS,
+    pedantic,
+    "allocating large arrays on stack may cause stack overflow"
+}
+
+pub struct LargeStackArrays {
+    maximum_allowed_size: u64,
+}
+
+impl LargeStackArrays {
+    #[must_use]
+    pub fn new(maximum_allowed_size: u64) -> Self {
+        Self { maximum_allowed_size }
+    }
+}
+
+impl_lint_pass!(LargeStackArrays => [LARGE_STACK_ARRAYS]);
+
+impl<'a, 'tcx> LateLintPass<'a, 'tcx> for LargeStackArrays {
+    fn check_expr(&mut self, cx: &LateContext<'_, '_>, expr: &Expr) {
+        if_chain! {
+            if let ExprKind::Repeat(_, _) = expr.kind;
+            if let ty::Array(element_type, cst) = cx.tables.expr_ty(expr).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 {
+                span_help_and_lint(
+                    cx,
+                    LARGE_STACK_ARRAYS,
+                    expr.span,
+                    &format!(
+                        "allocating a local array larger than {} bytes",
+                        self.maximum_allowed_size
+                    ),
+                    &format!(
+                        "consider allocating on the heap with vec!{}.into_boxed_slice()",
+                        snippet(cx, expr.span, "[...]")
+                    ),
+                );
+            }
+        }
+    }
+}

clippy_lints/src/lib.rs

@@ -212,6 +212,7 @@ pub mod int_plus_one;
 pub mod integer_division;
 pub mod items_after_statements;
 pub mod large_enum_variant;
+pub mod large_stack_arrays;
 pub mod len_zero;
 pub mod let_if_seq;
 pub mod lifetimes;
@@ -274,6 +275,7 @@ pub mod slow_vector_initialization;
 pub mod strings;
 pub mod suspicious_trait_impl;
 pub mod swap;
+pub mod tabs_in_doc_comments;
 pub mod temporary_assignment;
 pub mod to_digit_is_some;
 pub mod trait_bounds;
@@ -472,6 +474,7 @@ pub fn register_plugins(store: &mut lint::LintStore, sess: &Session, conf: &Conf
         &copies::IFS_SAME_COND,
         &copies::IF_SAME_THEN_ELSE,
         &copies::MATCH_SAME_ARMS,
+        &copies::SAME_FUNCTIONS_IN_IF_CONDITION,
         &copy_iterator::COPY_ITERATOR,
         &dbg_macro::DBG_MACRO,
         &default_trait_access::DEFAULT_TRAIT_ACCESS,
@@ -538,6 +541,7 @@ pub fn register_plugins(store: &mut lint::LintStore, sess: &Session, conf: &Conf
         &integer_division::INTEGER_DIVISION,
         &items_after_statements::ITEMS_AFTER_STATEMENTS,
         &large_enum_variant::LARGE_ENUM_VARIANT,
+        &large_stack_arrays::LARGE_STACK_ARRAYS,
         &len_zero::LEN_WITHOUT_IS_EMPTY,
         &len_zero::LEN_ZERO,
         &let_if_seq::USELESS_LET_IF_SEQ,
@@ -624,6 +628,7 @@ pub fn register_plugins(store: &mut lint::LintStore, sess: &Session, conf: &Conf
         &methods::USELESS_ASREF,
         &methods::WRONG_PUB_SELF_CONVENTION,
         &methods::WRONG_SELF_CONVENTION,
+        &methods::ZST_OFFSET,
         &minmax::MIN_MAX,
         &misc::CMP_NAN,
         &misc::CMP_OWNED,
@@ -716,6 +721,7 @@ pub fn register_plugins(store: &mut lint::LintStore, sess: &Session, conf: &Conf
         &suspicious_trait_impl::SUSPICIOUS_OP_ASSIGN_IMPL,
         &swap::ALMOST_SWAPPED,
         &swap::MANUAL_SWAP,
+        &tabs_in_doc_comments::TABS_IN_DOC_COMMENTS,
         &temporary_assignment::TEMPORARY_ASSIGNMENT,
         &to_digit_is_some::TO_DIGIT_IS_SOME,
         &trait_bounds::TYPE_REPETITION_IN_BOUNDS,
@@ -946,10 +952,13 @@ pub fn register_plugins(store: &mut lint::LintStore, sess: &Session, conf: &Conf
     store.register_early_pass(|| box utils::internal_lints::ClippyLintsInternal);
     let enum_variant_name_threshold = conf.enum_variant_name_threshold;
     store.register_early_pass(move || box enum_variants::EnumVariantNames::new(enum_variant_name_threshold));
+    store.register_early_pass(|| box tabs_in_doc_comments::TabsInDocComments);
     store.register_late_pass(|| box unused_self::UnusedSelf);
     store.register_late_pass(|| box mutable_debug_assertion::DebugAssertWithMutCall);
     store.register_late_pass(|| box exit::Exit);
     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_group(true, "clippy::restriction", Some("clippy_restriction"), vec![
         LintId::of(&arithmetic::FLOAT_ARITHMETIC),
@@ -989,6 +998,7 @@ pub fn register_plugins(store: &mut lint::LintStore, sess: &Session, conf: &Conf
         LintId::of(&attrs::INLINE_ALWAYS),
         LintId::of(&checked_conversions::CHECKED_CONVERSIONS),
         LintId::of(&copies::MATCH_SAME_ARMS),
+        LintId::of(&copies::SAME_FUNCTIONS_IN_IF_CONDITION),
         LintId::of(&copy_iterator::COPY_ITERATOR),
         LintId::of(&default_trait_access::DEFAULT_TRAIT_ACCESS),
         LintId::of(&derive::EXPL_IMPL_CLONE_ON_COPY),
@@ -1003,6 +1013,7 @@ pub fn register_plugins(store: &mut lint::LintStore, sess: &Session, conf: &Conf
         LintId::of(&if_not_else::IF_NOT_ELSE),
         LintId::of(&infinite_iter::MAYBE_INFINITE_ITER),
         LintId::of(&items_after_statements::ITEMS_AFTER_STATEMENTS),
+        LintId::of(&large_stack_arrays::LARGE_STACK_ARRAYS),
         LintId::of(&literal_representation::LARGE_DIGIT_GROUPS),
         LintId::of(&loops::EXPLICIT_INTO_ITER_LOOP),
         LintId::of(&loops::EXPLICIT_ITER_LOOP),
@@ -1176,6 +1187,7 @@ pub fn register_plugins(store: &mut lint::LintStore, sess: &Session, conf: &Conf
         LintId::of(&methods::UNNECESSARY_FOLD),
         LintId::of(&methods::USELESS_ASREF),
         LintId::of(&methods::WRONG_SELF_CONVENTION),
+        LintId::of(&methods::ZST_OFFSET),
         LintId::of(&minmax::MIN_MAX),
         LintId::of(&misc::CMP_NAN),
         LintId::of(&misc::CMP_OWNED),
@@ -1243,6 +1255,7 @@ pub fn register_plugins(store: &mut lint::LintStore, sess: &Session, conf: &Conf
         LintId::of(&suspicious_trait_impl::SUSPICIOUS_OP_ASSIGN_IMPL),
         LintId::of(&swap::ALMOST_SWAPPED),
         LintId::of(&swap::MANUAL_SWAP),
+        LintId::of(&tabs_in_doc_comments::TABS_IN_DOC_COMMENTS),
         LintId::of(&temporary_assignment::TEMPORARY_ASSIGNMENT),
         LintId::of(&to_digit_is_some::TO_DIGIT_IS_SOME),
         LintId::of(&transmute::CROSSPOINTER_TRANSMUTE),
@@ -1370,6 +1383,7 @@ pub fn register_plugins(store: &mut lint::LintStore, sess: &Session, conf: &Conf
         LintId::of(&returns::NEEDLESS_RETURN),
         LintId::of(&returns::UNUSED_UNIT),
         LintId::of(&strings::STRING_LIT_AS_BYTES),
+        LintId::of(&tabs_in_doc_comments::TABS_IN_DOC_COMMENTS),
         LintId::of(&to_digit_is_some::TO_DIGIT_IS_SOME),
         LintId::of(&try_err::TRY_ERR),
         LintId::of(&types::FN_TO_NUMERIC_CAST),
@@ -1497,6 +1511,7 @@ pub fn register_plugins(store: &mut lint::LintStore, sess: &Session, conf: &Conf
         LintId::of(&methods::CLONE_DOUBLE_REF),
         LintId::of(&methods::TEMPORARY_CSTRING_AS_PTR),
         LintId::of(&methods::UNINIT_ASSUMED_INIT),
+        LintId::of(&methods::ZST_OFFSET),
         LintId::of(&minmax::MIN_MAX),
         LintId::of(&misc::CMP_NAN),
         LintId::of(&misc::FLOAT_CMP),

clippy_lints/src/methods/mod.rs

@@ -1065,6 +1065,23 @@ declare_clippy_lint! {
     "`.chcked_add/sub(x).unwrap_or(MAX/MIN)`"
 }
 
+declare_clippy_lint! {
+    /// **What it does:** Checks for `offset(_)`, `wrapping_`{`add`, `sub`}, etc. on raw pointers to
+    /// zero-sized types
+    ///
+    /// **Why is this bad?** This is a no-op, and likely unintended
+    ///
+    /// **Known problems:** None
+    ///
+    /// **Example:**
+    /// ```ignore
+    /// unsafe { (&() as *const ()).offest(1) };
+    /// ```
+    pub ZST_OFFSET,
+    correctness,
+    "Check for offset calculations on raw pointers to zero-sized types"
+}
+
 declare_lint_pass!(Methods => [
     OPTION_UNWRAP_USED,
     RESULT_UNWRAP_USED,
@@ -1109,6 +1126,7 @@ declare_lint_pass!(Methods => [
     SUSPICIOUS_MAP,
     UNINIT_ASSUMED_INIT,
     MANUAL_SATURATING_ARITHMETIC,
+    ZST_OFFSET,
 ]);
 
 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Methods {
@@ -1167,6 +1185,9 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Methods {
             | ["unwrap_or", arith @ "checked_mul"] => {
                 manual_saturating_arithmetic::lint(cx, expr, &arg_lists, &arith["checked_".len()..])
             },
+            ["add"] | ["offset"] | ["sub"] | ["wrapping_offset"] | ["wrapping_add"] | ["wrapping_sub"] => {
+                check_pointer_offset(cx, expr, arg_lists[0])
+            },
             _ => {},
         }
 
@@ -3063,3 +3084,15 @@ fn contains_return(expr: &hir::Expr) -> bool {
     visitor.visit_expr(expr);
     visitor.found
 }
+
+fn check_pointer_offset(cx: &LateContext<'_, '_>, expr: &hir::Expr, args: &[hir::Expr]) {
+    if_chain! {
+        if args.len() == 2;
+        if let ty::RawPtr(ty::TypeAndMut { ref ty, .. }) = cx.tables.expr_ty(&args[0]).kind;
+        if let Ok(layout) = cx.tcx.layout_of(cx.param_env.and(ty));
+        if layout.is_zst();
+        then {
+            span_lint(cx, ZST_OFFSET, expr.span, "offset calculation on zero-sized value");
+        }
+    }
+}