error: message field `buf.test.Foo.x1` set multiple times
  --> testdata/options/values/singular.proto:10:5
   |
 9 |     x1: 1,
   |     -- first set here...
10 |     x1: 2, // Setting more than once is an error.
   |     ^^ ... also set here
...
20 |     optional int32 x1 = 1;
   |                    -- not a repeated field
   |
   = note: a non-`repeated` option may be set at most once

error: mismatched types
  --> testdata/options/values/singular.proto:12:9
   |
12 |     x2: [-1, 1], // Setting from an array is an error.
   |         ^^^^^^^ expected `int32`, found array expression
...
20 |     optional int32 x1 = 1;
21 |     optional int32 x2 = 2;
   |     -------------- expected due to this
   |
   = note: expected: scalar type `int32`
              found: array expression

error: message field `buf.test.Foo.x3` set multiple times
  --> testdata/options/values/singular.proto:15:5
   |
14 |     x3: -1,
   |     -- first set here...
15 |     x3: [0, "foo"], // Setting more than once with an array is an error,
   |     ^^ ... also set here
...
21 |     optional int32 x2 = 2;
22 |     optional int32 x3 = 3;
   |                    -- not a repeated field
   |
   = note: a non-`repeated` option may be set at most once

error: mismatched types
  --> testdata/options/values/singular.proto:15:9
   |
15 |     x3: [0, "foo"], // Setting more than once with an array is an error,
   |         ^^^^^^^^^^ expected `int32`, found array expression
...
21 |     optional int32 x2 = 2;
22 |     optional int32 x3 = 3;
   |     -------------- expected due to this
   |
   = note: expected: scalar type `int32`
              found: array expression

error: mismatched types
  --> testdata/options/values/singular.proto:15:13
   |
15 |     x3: [0, "foo"], // Setting more than once with an array is an error,
   |             ^^^^^ expected `int32`, found `string`
...
21 |     optional int32 x2 = 2;
22 |     optional int32 x3 = 3;
   |     -------------- expected due to this
   |
   = note: expected: scalar type `int32`
              found: scalar type `string`

encountered 5 errors
