Add boilerplate and basic tests

Author: nhamovitz

CHANGELOG.md

@@ -3021,6 +3021,7 @@ Released 2018-09-13
 [`too_many_arguments`]: https://rust-lang.github.io/rust-clippy/master/index.html#too_many_arguments
 [`too_many_lines`]: https://rust-lang.github.io/rust-clippy/master/index.html#too_many_lines
 [`toplevel_ref_arg`]: https://rust-lang.github.io/rust-clippy/master/index.html#toplevel_ref_arg
+[`trailing_zero_sized_array_without_repr_c`]: https://rust-lang.github.io/rust-clippy/master/index.html#trailing_zero_sized_array_without_repr_c
 [`trait_duplication_in_bounds`]: https://rust-lang.github.io/rust-clippy/master/index.html#trait_duplication_in_bounds
 [`transmute_bytes_to_str`]: https://rust-lang.github.io/rust-clippy/master/index.html#transmute_bytes_to_str
 [`transmute_float_to_int`]: https://rust-lang.github.io/rust-clippy/master/index.html#transmute_float_to_int

clippy_lints/src/lib.register_lints.rs

@@ -443,6 +443,7 @@ store.register_lints(&[
     temporary_assignment::TEMPORARY_ASSIGNMENT,
     to_digit_is_some::TO_DIGIT_IS_SOME,
     to_string_in_display::TO_STRING_IN_DISPLAY,
+    trailing_zero_sized_array_without_repr_c::TRAILING_ZERO_SIZED_ARRAY_WITHOUT_REPR_C,
     trait_bounds::TRAIT_DUPLICATION_IN_BOUNDS,
     trait_bounds::TYPE_REPETITION_IN_BOUNDS,
     transmute::CROSSPOINTER_TRANSMUTE,

clippy_lints/src/lib.register_nursery.rs

@@ -25,6 +25,7 @@ store.register_group(true, "clippy::nursery", Some("clippy_nursery"), vec![
     LintId::of(regex::TRIVIAL_REGEX),
     LintId::of(strings::STRING_LIT_AS_BYTES),
     LintId::of(suspicious_operation_groupings::SUSPICIOUS_OPERATION_GROUPINGS),
+    LintId::of(trailing_zero_sized_array_without_repr_c::TRAILING_ZERO_SIZED_ARRAY_WITHOUT_REPR_C),
     LintId::of(transmute::USELESS_TRANSMUTE),
     LintId::of(use_self::USE_SELF),
 ])

clippy_lints/src/lib.rs

@@ -355,6 +355,7 @@ mod tabs_in_doc_comments;
 mod temporary_assignment;
 mod to_digit_is_some;
 mod to_string_in_display;
+mod trailing_zero_sized_array_without_repr_c;
 mod trait_bounds;
 mod transmute;
 mod transmuting_null;

clippy_lints/src/trailing_zero_sized_array_without_repr_c.rs

@@ -0,0 +1,58 @@
+use clippy_utils::diagnostics::span_lint_and_sugg;
+use rustc_hir::*;
+use rustc_lint::{LateContext, LateLintPass};
+use rustc_session::{declare_lint_pass, declare_tool_lint};
+
+declare_clippy_lint! {
+    /// ### What it does
+    /// Displays a warning when a struct with a trailing zero-sized array is declared without the `repr(C)` attribute.
+    ///
+    /// ### Why is this bad?
+    /// Zero-sized arrays aren't very useful in Rust itself, so such a struct is likely being created to pass to C code (or in conjuction with manual allocation to make it easy to compute the offset of the array). Either way, `#[repr(C)]` is needed.
+    ///
+    /// ### Example
+    /// ```rust
+    /// struct RarelyUseful {
+    ///     some_field: usize,
+    ///     last: [SomeType; 0],
+    /// }
+    /// ```
+    ///
+    /// Use instead:
+    /// ```rust
+    /// #[repr(C)]
+    /// struct MakesSense {
+    ///     some_field: usize,
+    ///     last: [SomeType; 0],
+    /// }
+    /// ```
+    pub TRAILING_ZERO_SIZED_ARRAY_WITHOUT_REPR_C,
+    nursery,
+    "struct with a trailing zero-sized array but without `repr(C)`"
+}
+declare_lint_pass!(TrailingZeroSizedArrayWithoutReprC => [TRAILING_ZERO_SIZED_ARRAY_WITHOUT_REPR_C]);
+
+impl LateLintPass<'_> for TrailingZeroSizedArrayWithoutReprC {
+    fn check_struct_def(&mut self, _: &LateContext<'tcx>, _: &'tcx rustc_hir::VariantData<'tcx>) {}
+
+    fn check_struct_def_post(&mut self, _: &LateContext<'tcx>, _: &'tcx rustc_hir::VariantData<'tcx>) {}
+    // https://doc.rust-lang.org/nightly/nightly-rustc/rustc_middle/ty/sty/enum.TyKind.html#variant.Array in latepass
+    // or https://doc.rust-lang.org/nightly/nightly-rustc/rustc_ast/ast/enum.TyKind.html#variant.Array in early pass
+
+    fn check_field_def(&mut self, _: &LateContext<'tcx>, _: &'tcx rustc_hir::FieldDef<'tcx>) {}
+
+    fn check_attribute(&mut self, _: &LateContext<'tcx>, _: &'tcx rustc_ast::Attribute) {}
+
+    fn enter_lint_attrs(&mut self, _: &LateContext<'tcx>, _: &'tcx [rustc_ast::Attribute]) {}
+
+    fn exit_lint_attrs(&mut self, _: &LateContext<'tcx>, _: &'tcx [rustc_ast::Attribute]) {}
+}
+//
+// TODO: Register the lint pass in `clippy_lints/src/lib.rs`,
+//       e.g. store.register_late_pass(||
+// Box::new(trailing_zero_sized_array_without_repr_c::TrailingZeroSizedArrayWithoutReprC));
+
+
+fn temp_alert() {
+    span_lint_and_sugg(cx, lint, sp, msg, help, sugg, applicability)
+}

tests/ui/trailing_zero_sized_array_without_repr_c.rs

@@ -0,0 +1,23 @@
+#![warn(clippy::trailing_zero_sized_array_without_repr_c)]
+
+struct RarelyUseful {
+    field: i32,
+    last: [SomeType; 0],
+}
+
+#[repr(C)]
+struct GoodReason {
+    field: i32,
+    last: [SomeType; 0],
+}
+
+struct OnlyFieldIsZeroSizeArray {
+    first_and_last: [SomeType; 0],
+}
+
+struct GenericArrayType<T> {
+    field: i32,
+    last: [T; 0],
+}
+
+fn main() {}