Make assert! ensure the macro is parsed completely

src/libsyntax_ext/assert.rs

@@ -74,7 +74,7 @@ fn parse_assert<'a>(
         return Err(err);
     }
 
-    Ok(Assert {
+    let assert = Assert {
         cond_expr: parser.parse_expr()?,
         custom_message: if parser.eat(&token::Comma) {
             let ts = parser.parse_tokens();
@@ -86,5 +86,12 @@ fn parse_assert<'a>(
         } else {
             None
         },
-    })
+    };
+
+    if parser.token != token::Eof {
+        parser.expect_one_of(&[], &[])?;
+        unreachable!();
+    }
+
+    Ok(assert)
 }

src/test/ui/macros/assert-trailing-junk.rs

@@ -0,0 +1,14 @@
+// Ensure assert macro does not ignore trailing garbage.
+//
+// See https://github.com/rust-lang/rust/issues/60024 for details.
+
+fn main() {
+    assert!(true some extra junk, "whatever");
+    //~^ ERROR expected one of
+
+    assert!(true some extra junk);
+    //~^ ERROR expected one of
+
+    assert!(true, "whatever" blah);
+    //~^ ERROR no rules expected
+}

src/test/ui/macros/assert-trailing-junk.stderr

@@ -0,0 +1,22 @@
+error: expected one of `,`, `.`, `?`, or an operator, found `some`
+  --> $DIR/assert-trailing-junk.rs:6:18
+   |
+LL |     assert!(true some extra junk, "whatever");
+   |                  ^^^^ expected one of `,`, `.`, `?`, or an operator here
+
+error: expected one of `,`, `.`, `?`, or an operator, found `some`
+  --> $DIR/assert-trailing-junk.rs:9:18
+   |
+LL |     assert!(true some extra junk);
+   |                  ^^^^ expected one of `,`, `.`, `?`, or an operator here
+
+error: no rules expected the token `blah`
+  --> $DIR/assert-trailing-junk.rs:12:30
+   |
+LL |     assert!(true, "whatever" blah);
+   |                             -^^^^ no rules expected this token in macro call
+   |                             |
+   |                             help: missing comma here
+
+error: aborting due to 3 previous errors
+