add mcve as test

src/test/rustdoc/auxiliary/issue-86620-1.rs

@@ -0,0 +1,11 @@
+#![crate_name = "issue_86620_1"]
+
+pub trait VZip {
+    fn vzip() -> usize;
+}
+
+impl<T> VZip for T {
+    fn vzip() -> usize {
+        0
+    }
+}

src/test/rustdoc/issue-86620.rs

@@ -0,0 +1,8 @@
+// aux-build:issue-86620-1.rs
+
+extern crate issue_86620_1;
+
+use issue_86620_1::*;
+
+// @!has issue_86620/struct.S.html '//div[@id="method.vzip"]//a[@class="fnname"]/@href' #tymethod.vzip
+pub struct S;