error: expected string literal
 --> tests/ui/invalid_extend.rs:4:19
  |
4 | #[schemars(extend(x))]
  |                   ^

error: expected `=`
 --> tests/ui/invalid_extend.rs:5:22
  |
5 | #[schemars(extend("x"))]
  |                      ^

error: Expected extension value
 --> tests/ui/invalid_extend.rs:6:25
  |
6 | #[schemars(extend("x" = ))]
  |                         ^

error: Duplicate extension key 'y'
 --> tests/ui/invalid_extend.rs:7:32
  |
7 | #[schemars(extend("y" = "ok!", "y" = "duplicated!"), extend("y" = "duplicated!"))]
  |                                ^^^

error: Duplicate extension key 'y'
 --> tests/ui/invalid_extend.rs:7:61
  |
7 | #[schemars(extend("y" = "ok!", "y" = "duplicated!"), extend("y" = "duplicated!"))]
  |                                                             ^^^

error: Duplicate extension key 'y'
 --> tests/ui/invalid_extend.rs:8:19
  |
8 | #[schemars(extend("y" = "duplicated!"))]
  |                   ^^^