New lint [four_forward_slashes]

CHANGELOG.md

@@ -4867,6 +4867,7 @@ Released 2018-09-13
 [`forget_ref`]: https://rust-lang.github.io/rust-clippy/master/index.html#forget_ref
 [`format_in_format_args`]: https://rust-lang.github.io/rust-clippy/master/index.html#format_in_format_args
 [`format_push_string`]: https://rust-lang.github.io/rust-clippy/master/index.html#format_push_string
+[`four_forward_slashes`]: https://rust-lang.github.io/rust-clippy/master/index.html#four_forward_slashes
 [`from_iter_instead_of_collect`]: https://rust-lang.github.io/rust-clippy/master/index.html#from_iter_instead_of_collect
 [`from_over_into`]: https://rust-lang.github.io/rust-clippy/master/index.html#from_over_into
 [`from_raw_with_void_ptr`]: https://rust-lang.github.io/rust-clippy/master/index.html#from_raw_with_void_ptr

clippy_lints/src/declared_lints.rs

@@ -184,6 +184,7 @@ pub(crate) static LINTS: &[&crate::LintInfo] = &[
  crate::formatting::SUSPICIOUS_ASSIGNMENT_FORMATTING_INFO,
  crate::formatting::SUSPICIOUS_ELSE_FORMATTING_INFO,
  crate::formatting::SUSPICIOUS_UNARY_OP_FORMATTING_INFO,
+ crate::four_forward_slashes::FOUR_FORWARD_SLASHES_INFO,
  crate::from_over_into::FROM_OVER_INTO_INFO,
  crate::from_raw_with_void_ptr::FROM_RAW_WITH_VOID_PTR_INFO,
  crate::from_str_radix_10::FROM_STR_RADIX_10_INFO,

clippy_lints/src/four_forward_slashes.rs

@@ -0,0 +1,99 @@
+use clippy_utils::diagnostics::span_lint_and_then;
+use rustc_errors::Applicability;
+use rustc_hir::Item;
+use rustc_lint::{LateContext, LateLintPass, LintContext};
+use rustc_session::{declare_lint_pass, declare_tool_lint};
+use rustc_span::Span;
+
+declare_clippy_lint! {
+ /// ### What it does
+ /// Checks for outer doc comments written with 4 forward slashes (`////`).
+ ///
+ /// ### Why is this bad?
+ /// This is (probably) a typo, and results in it not being a doc comment; just a regular
+ /// comment.
+ ///
+ /// ### Example
+ /// ```rust
+ /// //// My amazing data structure
+ /// pub struct Foo {
+ /// // ...
+ /// }
+ /// ```
+ ///
+ /// Use instead:
+ /// ```rust
+ /// /// My amazing data structure
+ /// pub struct Foo {
+ /// // ...
+ /// }
+ /// ```
+ #[clippy::version = "1.72.0"]
+ pub FOUR_FORWARD_SLASHES,
+ suspicious,
+ "comments with 4 forward slashes (`////`) likely intended to be doc comments (`///`)"
+}
+declare_lint_pass!(FourForwardSlashes => [FOUR_FORWARD_SLASHES]);
+
+impl<'tcx> LateLintPass<'tcx> for FourForwardSlashes {
+ fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx Item<'tcx>) {
+ if item.span.from_expansion() {
+ return;
+ }
+ let sm = cx.sess().source_map();
+ let mut span = cx
+ .tcx
+ .hir()
+ .attrs(item.hir_id())
+ .iter()
+ .fold(item.span.shrink_to_lo(), |span, attr| span.to(attr.span));
+ let (Some(file), _, _, end_line, _) = sm.span_to_location_info(span) else {
+ return;
+ };
+ let mut bad_comments = vec![];
+ for line in (0..end_line.saturating_sub(1)).rev() {
+ let Some(contents) = file.get_line(line).map(|c| c.trim().to_owned()) else {
+ return;
+ };
+ // Keep searching until we find the next item
+ if !contents.is_empty() && !contents.starts_with("//") && !contents.starts_with("#[") {
+ break;
+ }
+
+ if contents.starts_with("////") && !matches!(contents.chars().nth(4), Some('/' | '!')) {
+ let bounds = file.line_bounds(line);
+ let line_span = Span::with_root_ctxt(bounds.start, bounds.end);
+ span = line_span.to(span);
+ bad_comments.push((line_span, contents));
+ }
+ }
+
+ if !bad_comments.is_empty() {
+ span_lint_and_then(
+ cx,
+ FOUR_FORWARD_SLASHES,
+ span,
+ "this item has comments with 4 forward slashes (`////`). These look like doc comments, but they aren't",
+ |diag| {
+ let msg = if bad_comments.len() == 1 {
+ "make this a doc comment by removing one `/`"
+ } else {
+ "turn these into doc comments by removing one `/`"
+ };
+
+ diag.multipart_suggestion(
+ msg,
+ bad_comments
+ .into_iter()
+ // It's a little unfortunate but the span includes the `\n` yet the contents
+ // do not, so we must add it back. If some codebase uses `\r\n` instead they
+ // will need normalization but it should be fine
+ .map(|(span, c)| (span, c.replacen("////", "///", 1) + "\n"))
+ .collect(),
+ Applicability::MachineApplicable,
+ );
+ },
+ );
+ }
+ }
+}

clippy_lints/src/lib.rs

@@ -137,6 +137,7 @@ mod format_args;
 mod format_impl;
 mod format_push_string;
 mod formatting;
+mod four_forward_slashes;
 mod from_over_into;
 mod from_raw_with_void_ptr;
 mod from_str_radix_10;
@@ -1081,6 +1082,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
  store.register_early_pass(|| Box::new(visibility::Visibility));
  store.register_late_pass(move |_| Box::new(tuple_array_conversions::TupleArrayConversions { msrv: msrv() }));
  store.register_late_pass(|_| Box::new(manual_float_methods::ManualFloatMethods));
+ store.register_late_pass(|_| Box::new(four_forward_slashes::FourForwardSlashes));
  // add lints here, do not remove this comment, it's used in `new_lint`
 }
 

tests/ui/four_forward_slashes.fixed

@@ -0,0 +1,48 @@
+//@run-rustfix
+//@aux-build:proc_macros.rs:proc-macro
+#![feature(custom_inner_attributes)]
+#![allow(unused)]
+#![warn(clippy::four_forward_slashes)]
+#![no_main]
+#![rustfmt::skip]
+
+#[macro_use]
+extern crate proc_macros;
+
+/// whoops
+fn a() {}
+
+/// whoops
+#[allow(dead_code)]
+fn b() {}
+
+/// whoops
+/// two borked comments!
+#[track_caller]
+fn c() {}
+
+fn d() {}
+
+#[test]
+/// between attributes
+#[allow(dead_code)]
+fn g() {}
+
+/// not very start of contents
+fn h() {}
+
+fn i() {
+ //// don't lint me bozo
+ todo!()
+}
+
+external! {
+ //// don't lint me bozo
+ fn e() {}
+}
+
+with_span! {
+ span
+ //// don't lint me bozo
+ fn f() {}
+}

tests/ui/four_forward_slashes.rs

@@ -0,0 +1,48 @@
+//@run-rustfix
+//@aux-build:proc_macros.rs:proc-macro
+#![feature(custom_inner_attributes)]
+#![allow(unused)]
+#![warn(clippy::four_forward_slashes)]
+#![no_main]
+#![rustfmt::skip]
+
+#[macro_use]
+extern crate proc_macros;
+
+//// whoops
+fn a() {}
+
+//// whoops
+#[allow(dead_code)]
+fn b() {}
+
+//// whoops
+//// two borked comments!
+#[track_caller]
+fn c() {}
+
+fn d() {}
+
+#[test]
+//// between attributes
+#[allow(dead_code)]
+fn g() {}
+
+ //// not very start of contents
+fn h() {}
+
+fn i() {
+ //// don't lint me bozo
+ todo!()
+}
+
+external! {
+ //// don't lint me bozo
+ fn e() {}
+}
+
+with_span! {
+ span
+ //// don't lint me bozo
+ fn f() {}
+}

tests/ui/four_forward_slashes.stderr

@@ -0,0 +1,68 @@
+error: this item has comments with 4 forward slashes (`////`). These look like doc comments, but they aren't
+ --> $DIR/four_forward_slashes.rs:12:1
+ |
+LL | / //// whoops
+LL | | fn a() {}
+ | |_
+ |
+ = note: `-D clippy::four-forward-slashes` implied by `-D warnings`
+help: make this a doc comment by removing one `/`
+ |
+LL + /// whoops
+ |
+
+error: this item has comments with 4 forward slashes (`////`). These look like doc comments, but they aren't
+ --> $DIR/four_forward_slashes.rs:15:1
+ |
+LL | / //// whoops
+LL | | #[allow(dead_code)]
+LL | | fn b() {}
+ | |_
+ |
+help: make this a doc comment by removing one `/`
+ |
+LL + /// whoops
+ |
+
+error: this item has comments with 4 forward slashes (`////`). These look like doc comments, but they aren't
+ --> $DIR/four_forward_slashes.rs:19:1
+ |
+LL | / //// whoops
+LL | | //// two borked comments!
+LL | | #[track_caller]
+LL | | fn c() {}
+ | |_
+ |
+help: turn these into doc comments by removing one `/`
+ |
+LL + /// whoops
+LL ~ /// two borked comments!
+ |
+
+error: this item has comments with 4 forward slashes (`////`). These look like doc comments, but they aren't
+ --> $DIR/four_forward_slashes.rs:27:1
+ |
+LL | / //// between attributes
+LL | | #[allow(dead_code)]
+LL | | fn g() {}
+ | |_
+ |
+help: make this a doc comment by removing one `/`
+ |
+LL + /// between attributes
+ |
+
+error: this item has comments with 4 forward slashes (`////`). These look like doc comments, but they aren't
+ --> $DIR/four_forward_slashes.rs:31:1
+ |
+LL | / //// not very start of contents
+LL | | fn h() {}
+ | |_
+ |
+help: make this a doc comment by removing one `/`
+ |
+LL + /// not very start of contents
+ |
+
+error: aborting due to 5 previous errors
+

tests/ui/four_forward_slashes_first_line.fixed

@@ -0,0 +1,7 @@
+/// borked doc comment on the first line. doesn't combust!
+fn a() {}
+
+//@run-rustfix
+// This test's entire purpose is to make sure we don't panic if the comment with four slashes
+// extends to the first line of the file. This is likely pretty rare in production, but an ICE is an
+// ICE.

tests/ui/four_forward_slashes_first_line.rs

@@ -0,0 +1,7 @@
+//// borked doc comment on the first line. doesn't combust!
+fn a() {}
+
+//@run-rustfix
+// This test's entire purpose is to make sure we don't panic if the comment with four slashes
+// extends to the first line of the file. This is likely pretty rare in production, but an ICE is an
+// ICE.

tests/ui/four_forward_slashes_first_line.stderr

@@ -0,0 +1,15 @@
+error: this item has comments with 4 forward slashes (`////`). These look like doc comments, but they aren't
+ --> $DIR/four_forward_slashes_first_line.rs:1:1
+ |
+LL | / //// borked doc comment on the first line. doesn't combust!
+LL | | fn a() {}
+ | |_
+ |
+ = note: `-D clippy::four-forward-slashes` implied by `-D warnings`
+help: make this a doc comment by removing one `/`
+ |
+LL + /// borked doc comment on the first line. doesn't combust!
+ |
+
+error: aborting due to previous error
+