From 20309c56b830c37089975fe8c956fb7c69d7b059 Mon Sep 17 00:00:00 2001
From: Andre Bogus <andre.bogus@aleph-alpha.de>
Date: Thu, 28 May 2020 21:37:43 +0200
Subject: [PATCH] check for misplaced headers in missing_safety/error_doc

---
 clippy_lints/src/doc.rs    | 23 +++++++++++++++++++++--
 tests/ui/doc_unsafe.rs     | 17 +++++++++++++++++
 tests/ui/doc_unsafe.stderr | 10 +++++++++-
 3 files changed, 47 insertions(+), 3 deletions(-)

diff --git a/clippy_lints/src/doc.rs b/clippy_lints/src/doc.rs
index 8d1e91f9adbd..c43f4af00464 100644
--- a/clippy_lints/src/doc.rs
+++ b/clippy_lints/src/doc.rs
@@ -417,8 +417,9 @@ fn check_doc<'a, Events: Iterator<Item = (pulldown_cmark::Event<'a>, Range<usize
                     // text "http://example.com" by pulldown-cmark
                     continue;
                 }
-                headers.safety |= in_heading && text.trim() == "Safety";
-                headers.errors |= in_heading && text.trim() == "Errors";
+                let trimmed = text.trim();
+                headers.safety |= has_header(trimmed, in_heading, "# Safety");
+                headers.errors |= has_header(trimmed, in_heading, "# Errors");
                 let index = match spans.binary_search_by(|c| c.0.cmp(&range.start)) {
                     Ok(o) => o,
                     Err(e) => e - 1,
@@ -440,6 +441,24 @@ fn check_doc<'a, Events: Iterator<Item = (pulldown_cmark::Event<'a>, Range<usize
     headers
 }
 
+// Normally, the first `if` should suffice, but this also accounts for misplaced headings
+fn has_header(trimmed_text: &str, in_heading: bool, header: &'static str) -> bool {
+    if in_heading && trimmed_text == &header[2..] {
+        return true;
+    }
+    if let Some(index) = trimmed_text.find(header) {
+        let bytes = trimmed_text.as_bytes();
+        for &b in bytes[0..index].iter().rev() {
+            if b != b' ' && b != b'\t' {
+                return b == b'\n';
+            }
+        }
+        true
+    } else {
+        false
+    }
+}
+
 static LEAVE_MAIN_PATTERNS: &[&str] = &["static", "fn main() {}", "extern crate", "async fn main() {"];
 
 fn check_code(cx: &LateContext<'_, '_>, text: &str, span: Span) {
diff --git a/tests/ui/doc_unsafe.rs b/tests/ui/doc_unsafe.rs
index 484aa72d59a2..cf330a09278f 100644
--- a/tests/ui/doc_unsafe.rs
+++ b/tests/ui/doc_unsafe.rs
@@ -88,6 +88,21 @@ very_unsafe!();
 // we don't lint code from external macros
 undocd_unsafe!();
 
+/** This safety section is now recognized.
+
+   # Safety
+
+   No risk, no fun.
+*/
+pub unsafe fn strange_doc_comments() {
+    unimplemented!();
+}
+
+/// This is not a # Safety section.
+pub unsafe fn ceci_n_est_pas_un_titre() {
+    unimplemented!();
+}
+
 fn main() {
     unsafe {
         you_dont_see_me();
@@ -96,5 +111,7 @@ fn main() {
         apocalypse(&mut universe);
         private_mod::only_crate_wide_accessible();
         drive();
+        strange_doc_comments();
+        ceci_n_est_pas_un_titre();
     }
 }
diff --git a/tests/ui/doc_unsafe.stderr b/tests/ui/doc_unsafe.stderr
index c784d41ba172..e507034609ca 100644
--- a/tests/ui/doc_unsafe.stderr
+++ b/tests/ui/doc_unsafe.stderr
@@ -43,5 +43,13 @@ LL |   very_unsafe!();
    |
    = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
 
-error: aborting due to 5 previous errors
+error: unsafe function's docs miss `# Safety` section
+  --> $DIR/doc_unsafe.rs:102:1
+   |
+LL | / pub unsafe fn ceci_n_est_pas_un_titre() {
+LL | |     unimplemented!();
+LL | | }
+   | |_^
+
+error: aborting due to 6 previous errors