1 files changed, 76 insertions, 0 deletions
diff --git a/third_party/rust/wast/tests/comments.rs b/third_party/rust/wast/tests/comments.rs
new file mode 100644
index 0000000000..97252650be
--- /dev/null
+++ b/third_party/rust/wast/tests/comments.rs
@@ -0,0 +1,76 @@
+use wast::parser::{self, Parse, ParseBuffer, Parser, Result};
+
+pub struct Comments<'a> {
+    comments: Vec<&'a str>,
+}
+
+impl<'a> Parse<'a> for Comments<'a> {
+    fn parse(parser: Parser<'a>) -> Result<Comments<'a>> {
+        let comments = parser.step(|mut cursor| {
+            let mut comments = Vec::new();
+            loop {
+                let (comment, c) = match cursor.comment() {
+                    Some(pair) => pair,
+                    None => break,
+                };
+                cursor = c;
+                comments.push(if comment.starts_with(";;") {
+                    &comment[2..]
+                } else {
+                    &comment[2..comment.len() - 2]
+                });
+            }
+            Ok((comments, cursor))
+        })?;
+        Ok(Comments { comments })
+    }
+}
+
+pub struct Documented<'a, T> {
+    comments: Comments<'a>,
+    item: T,
+}
+
+impl<'a, T: Parse<'a>> Parse<'a> for Documented<'a, T> {
+    fn parse(parser: Parser<'a>) -> Result<Self> {
+        let comments = parser.parse()?;
+        let item = parser.parens(T::parse)?;
+        Ok(Documented { comments, item })
+    }
+}
+
+#[test]
+fn parse_comments() -> anyhow::Result<()> {
+    let buf = ParseBuffer::new(
+        r#"
+;; hello
+(; again ;)
+(module)
+    "#,
+    )?;
+
+    let d: Documented<wast::core::Module> = parser::parse(&buf)?;
+    assert_eq!(d.comments.comments, vec![" hello", " again "]);
+    drop(d.item);
+
+    let buf = ParseBuffer::new(
+        r#"
+;; this
+(; is
+on
+multiple;)
+
+
+;; lines
+(func)
+    "#,
+    )?;
+
+    let d: Documented<wast::core::Func> = parser::parse(&buf)?;
+    assert_eq!(
+        d.comments.comments,
+        vec![" this", " is\non\nmultiple", " lines"]
+    );
+    drop(d.item);
+    Ok(())
+}