2 files changed, 35 insertions, 0 deletions

diff --git a/crates/ide_db/src/helpers.rs b/crates/ide_db/src/helpers.rs
index 83a665b37..720de0d1f 100644
--- a/crates/ide_db/src/helpers.rs
+++ b/crates/ide_db/src/helpers.rs
@@ -1,6 +1,7 @@
 //! A module with ide helpers for high-level ide features.
 pub mod insert_use;
 pub mod import_assets;
+pub mod rust_doc;
 
 use std::collections::VecDeque;
 
diff --git a/crates/ide_db/src/helpers/rust_doc.rs b/crates/ide_db/src/helpers/rust_doc.rs
new file mode 100644
index 000000000..e27e23867
--- /dev/null
+++ b/crates/ide_db/src/helpers/rust_doc.rs
@@ -0,0 +1,34 @@
+//! Rustdoc specific doc comment handling
+
+// stripped down version of https://github.com/rust-lang/rust/blob/392ba2ba1a7d6c542d2459fb8133bebf62a4a423/src/librustdoc/html/markdown.rs#L810-L933
+pub fn is_rust_fence(s: &str) -> bool {
+    let mut seen_rust_tags = false;
+    let mut seen_other_tags = false;
+
+    let tokens = s
+        .trim()
+        .split(|c| c == ',' || c == ' ' || c == '\t')
+        .map(str::trim)
+        .filter(|t| !t.is_empty());
+
+    for token in tokens {
+        match token {
+            "should_panic" | "no_run" | "ignore" | "allow_fail" => {
+                seen_rust_tags = !seen_other_tags
+            }
+            "rust" => seen_rust_tags = true,
+            "test_harness" | "compile_fail" => seen_rust_tags = !seen_other_tags || seen_rust_tags,
+            x if x.starts_with("edition") => {}
+            x if x.starts_with('E') && x.len() == 5 => {
+                if x[1..].parse::<u32>().is_ok() {
+                    seen_rust_tags = !seen_other_tags || seen_rust_tags;
+                } else {
+                    seen_other_tags = true;
+                }
+            }
+            _ => seen_other_tags = true,
+        }
+    }
+
+    !seen_other_tags || seen_rust_tags
+}