Improve UI test coverage

With this commit I believe I've covered all `compile_error!`-based
errors.

test_suite/tests/ui/default-attribute/enum_path.rs

@@ -0,0 +1,8 @@
+#[macro_use]
+extern crate serde_derive;
+
+#[derive(Deserialize)]
+#[serde(default = "default_e")]
+enum E {
+    S { f: u8 },
+}

test_suite/tests/ui/default-attribute/enum_path.stderr

@@ -0,0 +1,8 @@
+error: #[serde(default = "...")] can only be used on structs with named fields
+ --> $DIR/enum_path.rs:6:1
+  |
+6 | enum E {
+  | ^^^^
+
+error: aborting due to previous error
+

test_suite/tests/ui/default-attribute/nameless_struct_fields_path.rs

@@ -0,0 +1,8 @@
+#[macro_use]
+extern crate serde_derive;
+
+#[derive(Deserialize)]
+#[serde(default = "default_t")]
+struct T(u8, u8);
+
+fn main() {}

test_suite/tests/ui/default-attribute/nameless_struct_fields_path.stderr

@@ -0,0 +1,8 @@
+error: #[serde(default = "...")] can only be used on structs with named fields
+ --> $DIR/nameless_struct_fields_path.rs:6:9
+  |
+6 | struct T(u8, u8);
+  |         ^^^^^^^^
+
+error: aborting due to previous error
+

test_suite/tests/ui/enum-representation/content-no-tag.rs

@@ -0,0 +1,11 @@
+#[macro_use]
+extern crate serde_derive;
+
+#[derive(Serialize)]
+#[serde(content = "c")]
+enum E {
+    A(u8),
+    B(String),
+}
+
+fn main() {}

test_suite/tests/ui/enum-representation/content-no-tag.stderr

@@ -0,0 +1,8 @@
+error: #[serde(tag = "...", content = "...")] must be used together
+ --> $DIR/content-no-tag.rs:5:9
+  |
+5 | #[serde(content = "c")]
+  |         ^^^^^^^
+
+error: aborting due to previous error
+

test_suite/tests/ui/enum-representation/untagged-and-adjacent.rs

@@ -0,0 +1,12 @@
+#[macro_use]
+extern crate serde_derive;
+
+#[derive(Serialize)]
+#[serde(untagged)]
+#[serde(tag = "t", content = "c")]
+enum E {
+    A(u8),
+    B(String),
+}
+
+fn main() {}

test_suite/tests/ui/enum-representation/untagged-and-adjacent.stderr

@@ -0,0 +1,20 @@
+error: untagged enum cannot have #[serde(tag = "...", content = "...")]
+ --> $DIR/untagged-and-adjacent.rs:5:9
+  |
+5 | #[serde(untagged)]
+  |         ^^^^^^^^
+
+error: untagged enum cannot have #[serde(tag = "...", content = "...")]
+ --> $DIR/untagged-and-adjacent.rs:6:9
+  |
+6 | #[serde(tag = "t", content = "c")]
+  |         ^^^
+
+error: untagged enum cannot have #[serde(tag = "...", content = "...")]
+ --> $DIR/untagged-and-adjacent.rs:6:20
+  |
+6 | #[serde(tag = "t", content = "c")]
+  |                    ^^^^^^^
+
+error: aborting due to 3 previous errors
+

test_suite/tests/ui/enum-representation/untagged-and-content.rs

@@ -0,0 +1,12 @@
+#[macro_use]
+extern crate serde_derive;
+
+#[derive(Serialize)]
+#[serde(untagged)]
+#[serde(content = "c")]
+enum E {
+    A(u8),
+    B(String),
+}
+
+fn main() {}

test_suite/tests/ui/enum-representation/untagged-and-content.stderr

@@ -0,0 +1,14 @@
+error: untagged enum cannot have #[serde(content = "...")]
+ --> $DIR/untagged-and-content.rs:5:9
+  |
+5 | #[serde(untagged)]
+  |         ^^^^^^^^
+
+error: untagged enum cannot have #[serde(content = "...")]
+ --> $DIR/untagged-and-content.rs:6:9
+  |
+6 | #[serde(content = "c")]
+  |         ^^^^^^^
+
+error: aborting due to 2 previous errors
+

test_suite/tests/ui/expected-string/boolean.rs

@@ -0,0 +1,10 @@
+#[macro_use]
+extern crate serde_derive;
+
+#[derive(Serialize)]
+struct S {
+    #[serde(rename = true)]
+    boolean: (),
+}
+
+fn main() {}

test_suite/tests/ui/expected-string/boolean.stderr

@@ -0,0 +1,8 @@
+error: expected serde rename attribute to be a string: `rename = "..."`
+ --> $DIR/boolean.rs:6:22
+  |
+6 |     #[serde(rename = true)]
+  |                      ^^^^
+
+error: aborting due to previous error
+

test_suite/tests/ui/expected-string/byte_character.rs

@@ -0,0 +1,10 @@
+#[macro_use]
+extern crate serde_derive;
+
+#[derive(Serialize)]
+struct S {
+    #[serde(rename = b'a')]
+    byte_character: (),
+}
+
+fn main() {}

test_suite/tests/ui/expected-string/byte_character.stderr

@@ -0,0 +1,8 @@
+error: expected serde rename attribute to be a string: `rename = "..."`
+ --> $DIR/byte_character.rs:6:22
+  |
+6 |     #[serde(rename = b'a')]
+  |                      ^^^^
+
+error: aborting due to previous error
+

test_suite/tests/ui/expected-string/byte_string.rs

@@ -0,0 +1,10 @@
+#[macro_use]
+extern crate serde_derive;
+
+#[derive(Serialize)]
+struct S {
+    #[serde(rename = b"byte string")]
+    byte_string: (),
+}
+
+fn main() {}

test_suite/tests/ui/expected-string/byte_string.stderr

@@ -0,0 +1,8 @@
+error: expected serde rename attribute to be a string: `rename = "..."`
+ --> $DIR/byte_string.rs:6:22
+  |
+6 |     #[serde(rename = b"byte string")]
+  |                      ^^^^^^^^^^^^^^
+
+error: aborting due to previous error
+

test_suite/tests/ui/expected-string/character.rs

@@ -0,0 +1,10 @@
+#[macro_use]
+extern crate serde_derive;
+
+#[derive(Serialize)]
+struct S {
+    #[serde(rename = 'a')]
+    character: (),
+}
+
+fn main() {}

test_suite/tests/ui/expected-string/character.stderr

@@ -0,0 +1,8 @@
+error: expected serde rename attribute to be a string: `rename = "..."`
+ --> $DIR/character.rs:6:22
+  |
+6 |     #[serde(rename = 'a')]
+  |                      ^^^
+
+error: aborting due to previous error
+

test_suite/tests/ui/expected-string/float.rs

@@ -0,0 +1,10 @@
+#[macro_use]
+extern crate serde_derive;
+
+#[derive(Serialize)]
+struct S {
+    #[serde(rename = 3.14)]
+    float: (),
+}
+
+fn main() {}

test_suite/tests/ui/expected-string/float.stderr

@@ -0,0 +1,8 @@
+error: expected serde rename attribute to be a string: `rename = "..."`
+ --> $DIR/float.rs:6:22
+  |
+6 |     #[serde(rename = 3.14)]
+  |                      ^^^^
+
+error: aborting due to previous error
+

test_suite/tests/ui/expected-string/integer.rs

@@ -0,0 +1,10 @@
+#[macro_use]
+extern crate serde_derive;
+
+#[derive(Serialize)]
+struct S {
+    #[serde(rename = 100)]
+    integer: (),
+}
+
+fn main() {}

test_suite/tests/ui/expected-string/integer.stderr

@@ -0,0 +1,8 @@
+error: expected serde rename attribute to be a string: `rename = "..."`
+ --> $DIR/integer.rs:6:22
+  |
+6 |     #[serde(rename = 100)]
+  |                      ^^^
+
+error: aborting due to previous error
+

test_suite/tests/ui/identifier/other_untagged.rs

@@ -0,0 +1,11 @@
+#[macro_use]
+extern crate serde_derive;
+
+#[derive(Deserialize)]
+#[serde(untagged)]
+enum F {
+    #[serde(other)]
+    Other,
+}
+
+fn main() {}

test_suite/tests/ui/identifier/other_untagged.stderr

@@ -0,0 +1,9 @@
+error: #[serde(other)] cannot appear on untagged enum
+ --> $DIR/other_untagged.rs:7:5
+  |
+7 | /     #[serde(other)]
+8 | |     Other,
+  | |_________^
+
+error: aborting due to previous error
+

test_suite/tests/ui/identifier/other_variant.rs

@@ -0,0 +1,11 @@
+#[macro_use]
+extern crate serde_derive;
+
+#[derive(Deserialize)]
+#[serde(variant_identifier)]
+enum F {
+    #[serde(other)]
+    Other,
+}
+
+fn main() {}

test_suite/tests/ui/identifier/other_variant.stderr

@@ -0,0 +1,9 @@
+error: #[serde(other)] may not be used on a variant identifier
+ --> $DIR/other_variant.rs:7:5
+  |
+7 | /     #[serde(other)]
+8 | |     Other,
+  | |_________^
+
+error: aborting due to previous error
+

test_suite/tests/ui/malformed/bound.rs

@@ -0,0 +1,10 @@
+#[macro_use]
+extern crate serde_derive;
+
+#[derive(Serialize)]
+struct S {
+    #[serde(bound(unknown))]
+    x: (),
+}
+
+fn main() {}

test_suite/tests/ui/malformed/bound.stderr

@@ -0,0 +1,8 @@
+error: malformed bound attribute, expected `bound(serialize = ..., deserialize = ...)`
+ --> $DIR/bound.rs:6:19
+  |
+6 |     #[serde(bound(unknown))]
+  |                   ^^^^^^^
+
+error: aborting due to previous error
+

test_suite/tests/ui/malformed/rename.rs

@@ -0,0 +1,10 @@
+#[macro_use]
+extern crate serde_derive;
+
+#[derive(Serialize)]
+struct S {
+    #[serde(rename(unknown))]
+    x: (),
+}
+
+fn main() {}

test_suite/tests/ui/malformed/rename.stderr

@@ -0,0 +1,8 @@
+error: malformed rename attribute, expected `rename(serialize = ..., deserialize = ...)`
+ --> $DIR/rename.rs:6:20
+  |
+6 |     #[serde(rename(unknown))]
+  |                    ^^^^^^^
+
+error: aborting due to previous error
+

test_suite/tests/ui/precondition/serialize_field_identifier.stderr

@@ -1,5 +1,5 @@
 error: field identifiers cannot be serialized
- --> $DIR/serialize.rs:5:1
+ --> $DIR/serialize_field_identifier.rs:5:1
   |
 5 | / #[serde(field_identifier)]
 6 | | enum F {

test_suite/tests/ui/precondition/serialize_variant_identifier.rs

@@ -0,0 +1,11 @@
+#[macro_use]
+extern crate serde_derive;
+
+#[derive(Serialize)]
+#[serde(variant_identifier)]
+enum F {
+    A,
+    B,
+}
+
+fn main() {}

test_suite/tests/ui/precondition/serialize_variant_identifier.stderr

@@ -0,0 +1,12 @@
+error: variant identifiers cannot be serialized
+ --> $DIR/serialize_variant_identifier.rs:5:1
+  |
+5 | / #[serde(variant_identifier)]
+6 | | enum F {
+7 | |     A,
+8 | |     B,
+9 | | }
+  | |_^
+
+error: aborting due to previous error
+

test_suite/tests/ui/rename/container_unknown_rename_rule.rs

@@ -0,0 +1,12 @@
+#[macro_use]
+extern crate serde_derive;
+
+#[derive(Serialize)]
+#[serde(rename_all = "abc")]
+struct S {
+    name: u8,
+    long_name: u8,
+    very_long_name: u8,
+}
+
+fn main() {}

test_suite/tests/ui/rename/container_unknown_rename_rule.stderr

@@ -0,0 +1,8 @@
+error: unknown rename rule for #[serde(rename_all = "abc")]
+ --> $DIR/container_unknown_rename_rule.rs:5:22
+  |
+5 | #[serde(rename_all = "abc")]
+  |                      ^^^^^
+
+error: aborting due to previous error
+

test_suite/tests/ui/rename/variant_unknown_rename_rule.rs

@@ -0,0 +1,14 @@
+#[macro_use]
+extern crate serde_derive;
+
+#[derive(Serialize)]
+enum S {
+    #[serde(rename_all = "abc")]
+    V {
+        name: u8,
+        long_name: u8,
+        very_long_name: u8,
+    },
+}
+
+fn main() {}

test_suite/tests/ui/rename/variant_unknown_rename_rule.stderr

@@ -0,0 +1,8 @@
+error: unknown rename rule for #[serde(rename_all = "abc")]
+ --> $DIR/variant_unknown_rename_rule.rs:6:26
+  |
+6 |     #[serde(rename_all = "abc")]
+  |                          ^^^^^
+
+error: aborting due to previous error
+

test_suite/tests/ui/transparent/enum.rs

@@ -0,0 +1,8 @@
+#[macro_use]
+extern crate serde_derive;
+
+#[derive(Serialize)]
+#[serde(transparent)]
+enum E {}
+
+fn main() {}

test_suite/tests/ui/transparent/enum.stderr

@@ -0,0 +1,9 @@
+error: #[serde(transparent)] is not allowed on an enum
+ --> $DIR/enum.rs:5:1
+  |
+5 | / #[serde(transparent)]
+6 | | enum E {}
+  | |_________^
+
+error: aborting due to previous error
+

test_suite/tests/ui/transparent/unit_struct.rs

@@ -0,0 +1,8 @@
+#[macro_use]
+extern crate serde_derive;
+
+#[derive(Serialize)]
+#[serde(transparent)]
+struct S;
+
+fn main() {}

test_suite/tests/ui/transparent/unit_struct.stderr

@@ -0,0 +1,9 @@
+error: #[serde(transparent)] is not allowed on a unit struct
+ --> $DIR/unit_struct.rs:5:1
+  |
+5 | / #[serde(transparent)]
+6 | | struct S;
+  | |_________^
+
+error: aborting due to previous error
+

test_suite/tests/ui/transparent/with_from.rs

@@ -0,0 +1,10 @@
+#[macro_use]
+extern crate serde_derive;
+
+#[derive(Serialize)]
+#[serde(transparent, from = "u64")]
+struct S {
+    a: u8,
+}
+
+fn main() {}

test_suite/tests/ui/transparent/with_from.stderr

@@ -0,0 +1,11 @@
+error: #[serde(transparent)] is not allowed with #[serde(from = "...")]
+ --> $DIR/with_from.rs:5:1
+  |
+5 | / #[serde(transparent, from = "u64")]
+6 | | struct S {
+7 | |     a: u8,
+8 | | }
+  | |_^
+
+error: aborting due to previous error
+

test_suite/tests/ui/transparent/with_into.rs

@@ -0,0 +1,10 @@
+#[macro_use]
+extern crate serde_derive;
+
+#[derive(Serialize)]
+#[serde(transparent, into = "u64")]
+struct S {
+    a: u8,
+}
+
+fn main() {}

test_suite/tests/ui/transparent/with_into.stderr

@@ -0,0 +1,11 @@
+error: #[serde(transparent)] is not allowed with #[serde(into = "...")]
+ --> $DIR/with_into.rs:5:1
+  |
+5 | / #[serde(transparent, into = "u64")]
+6 | | struct S {
+7 | |     a: u8,
+8 | | }
+  | |_^
+
+error: aborting due to previous error
+

test_suite/tests/ui/unexpected-literal/container.rs

@@ -0,0 +1,8 @@
+#[macro_use]
+extern crate serde_derive;
+
+#[derive(Serialize)]
+#[serde("literal")]
+struct S;
+
+fn main() {}

test_suite/tests/ui/unexpected-literal/container.stderr

@@ -0,0 +1,8 @@
+error: unexpected literal in serde container attribute
+ --> $DIR/container.rs:5:9
+  |
+5 | #[serde("literal")]
+  |         ^^^^^^^^^
+
+error: aborting due to previous error
+

test_suite/tests/ui/unexpected-literal/field.rs

@@ -0,0 +1,10 @@
+#[macro_use]
+extern crate serde_derive;
+
+#[derive(Serialize)]
+struct S {
+    #[serde("literal")]
+    x: (),
+}
+
+fn main() {}

test_suite/tests/ui/unexpected-literal/field.stderr

@@ -0,0 +1,8 @@
+error: unexpected literal in serde field attribute
+ --> $DIR/field.rs:6:13
+  |
+6 |     #[serde("literal")]
+  |             ^^^^^^^^^
+
+error: aborting due to previous error
+

test_suite/tests/ui/unexpected-literal/variant.rs

@@ -0,0 +1,10 @@
+#[macro_use]
+extern crate serde_derive;
+
+#[derive(Serialize)]
+enum E {
+    #[serde("literal")]
+    V,
+}
+
+fn main() {}

test_suite/tests/ui/unexpected-literal/variant.stderr

@@ -0,0 +1,8 @@
+error: unexpected literal in serde variant attribute
+ --> $DIR/variant.rs:6:13
+  |
+6 |     #[serde("literal")]
+  |             ^^^^^^^^^
+
+error: aborting due to previous error
+

test_suite/tests/ui/unsupported/union_de.rs

@@ -0,0 +1,10 @@
+#[macro_use]
+extern crate serde_derive;
+
+#[derive(Deserialize)]
+union Union {
+    x: u8,
+    y: (),
+}
+
+fn main() {}

test_suite/tests/ui/unsupported/union_de.stderr

@@ -0,0 +1,11 @@
+error: Serde does not support derive for unions
+ --> $DIR/union_de.rs:5:1
+  |
+5 | / union Union {
+6 | |     x: u8,
+7 | |     y: (),
+8 | | }
+  | |_^
+
+error: aborting due to previous error
+

test_suite/tests/ui/unsupported/union_ser.rs

@@ -0,0 +1,10 @@
+#[macro_use]
+extern crate serde_derive;
+
+#[derive(Deserialize)]
+union Union {
+    x: u8,
+    y: (),
+}
+
+fn main() {}

test_suite/tests/ui/unsupported/union_ser.stderr

@@ -0,0 +1,11 @@
+error: Serde does not support derive for unions
+ --> $DIR/union_ser.rs:5:1
+  |
+5 | / union Union {
+6 | |     x: u8,
+7 | |     y: (),
+8 | | }
+  | |_^
+
+error: aborting due to previous error
+