add non-regression test for issue #76597

src/test/ui/issue-76597.rs

@@ -0,0 +1,7 @@
+fn f(
+                                     x: u8
+                                     y: u8,
+) {}
+//~^^ ERROR: expected one of `!`, `(`, `)`, `+`, `,`, `::`, or `<`, found `y`
+
+fn main() {}

src/test/ui/issue-76597.stderr

@@ -0,0 +1,14 @@
+error: expected one of `!`, `(`, `)`, `+`, `,`, `::`, or `<`, found `y`
+  --> $DIR/issue-76597.rs:3:38
+   |
+LL |   ...                   x: u8
+   |                              - expected one of 7 possible tokens
+   |  ____________________________|
+   | |
+LL | | ...                   y: u8,
+|  | |                       ^ unexpected token
+|  | |
+   |   help: missing `,`
+
+error: aborting due to previous error
+