add highlight scope for type parameters (#8660)

* rust: add highlight scope for type parameters

* handle optional type parameters

book/src/themes.md

@@ -155,6 +155,7 @@ We use a similar set of scopes as
 
 - `type` - Types
   - `builtin` - Primitive types provided by the language (`int`, `usize`)
+  - `parameter` - Generic type parameters (`T`)
   - `enum`
     - `variant`
 - `constructor`

runtime/queries/rust/highlights.scm

@@ -9,6 +9,13 @@
 ; Types
 ; -------
 
+(type_parameters
+  (type_identifier) @type.parameter)
+(constrained_type_parameter
+  left: (type_identifier) @type.parameter)
+(optional_type_parameter
+  name: (type_identifier) @type.parameter)
+
 ; ---
 ; Primitives
 ; ---

runtime/queries/rust/locals.scm

@@ -2,6 +2,12 @@
 
 [
   (function_item)
+  (struct_item)
+  (enum_item)
+  (union_item)
+  (type_item)
+  (trait_item)
+  (impl_item)
   (closure_expression)
   (block)
 ] @local.scope
@@ -11,8 +17,15 @@
 (parameter
   (identifier) @local.definition)
 
+(type_parameters
+  (type_identifier) @local.definition)
+(constrained_type_parameter
+  left: (type_identifier) @local.definition)
+(optional_type_parameter
+  name: (type_identifier) @local.definition)
+
 (closure_parameters (identifier) @local.definition)
 
 ; References
 (identifier) @local.reference
-
+(type_identifier) @local.reference