Add derive macro for Syntax (used to be Language) (#51)

test_suite/tests/ui/repr/missing_repr.rs

@@ -0,0 +1,10 @@
+use cstree::Syntax;
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Syntax)]
+pub enum SyntaxKind {
+    A,
+    #[static_text("b")]
+    B,
+}
+
+fn main() {}

test_suite/tests/ui/repr/missing_repr.stderr

@@ -0,0 +1,9 @@
+error: syntax kind definitions must be `#[repr(u32)]` to derive `Syntax`
+ --> tests/ui/repr/missing_repr.rs:4:1
+  |
+4 | / pub enum SyntaxKind {
+5 | |     A,
+6 | |     #[static_text("b")]
+7 | |     B,
+8 | | }
+  | |_^

test_suite/tests/ui/repr/wrong_repr_c.rs

@@ -0,0 +1,11 @@
+use cstree::Syntax;
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Syntax)]
+#[repr(C)]
+pub enum SyntaxKind {
+    A,
+    #[static_text("b")]
+    B,
+}
+
+fn main() {}

test_suite/tests/ui/repr/wrong_repr_c.stderr

@@ -0,0 +1,10 @@
+error: syntax kind definitions must be `#[repr(u32)]` to derive `Syntax`
+ --> tests/ui/repr/wrong_repr_c.rs:4:1
+  |
+4 | / #[repr(C)]
+5 | | pub enum SyntaxKind {
+6 | |     A,
+7 | |     #[static_text("b")]
+8 | |     B,
+9 | | }
+  | |_^

test_suite/tests/ui/repr/wrong_repr_u16.rs

@@ -0,0 +1,11 @@
+use cstree::Syntax;
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Syntax)]
+#[repr(u16)]
+pub enum SyntaxKind {
+    A,
+    #[static_text("b")]
+    B,
+}
+
+fn main() {}

test_suite/tests/ui/repr/wrong_repr_u16.stderr

@@ -0,0 +1,10 @@
+error: syntax kind definitions must be `#[repr(u32)]` to derive `Syntax`
+ --> tests/ui/repr/wrong_repr_u16.rs:4:1
+  |
+4 | / #[repr(u16)]
+5 | | pub enum SyntaxKind {
+6 | |     A,
+7 | |     #[static_text("b")]
+8 | |     B,
+9 | | }
+  | |_^