fix let-prefix prose misclassification as Cordial

core/src/doc.rs

@@ -37,10 +37,16 @@ pub fn classify_line(index: usize, raw: &str) -> ClassifiedLine {
 
 fn is_cordial(line: &str) -> bool {
     if line.starts_with("let ") {
-        return true;
+        let rest = &line[4..];
+        if let Some(eq_pos) = rest.find('=') {
+            let name = rest[..eq_pos].trim();
+            if is_ident(name) {
+                return true;
+            }
+        }
+        return false;
     }
 
-    // variable assignment: identifier = expr (but not ==)
     if let Some(eq_pos) = line.find('=') {
         if eq_pos > 0 {
             let before = &line[..eq_pos];
@@ -158,6 +164,18 @@ mod tests {
         assert_eq!(c.kind, LineKind::Markdown);
     }
 
+    #[test]
+    fn let_prose_not_cordial() {
+        let c = classify_line(0, "let us consider something");
+        assert_eq!(c.kind, LineKind::Markdown);
+    }
+
+    #[test]
+    fn let_without_equals_not_cordial() {
+        let c = classify_line(0, "let me explain");
+        assert_eq!(c.kind, LineKind::Markdown);
+    }
+
     #[test]
     fn single_line_block_comment() {
         let lines = classify_document("/* hello */");