[C#] Add support for C#9 function pointers (#4376)

Fixes #3131

This commit adds `funcptr_...` contexts, implementing C#9 function pointers.

see: https://learn.microsoft.com/en-us/dotnet/csharp/language-reference/proposals/csharp-9.0/function-pointers

Author: deathaxe

C#/C#.sublime-syntax

@@ -471,7 +471,18 @@ contexts:
       pop: true
 
   delegate_declaration:
-    - match: \b(delegate)\b\s+
+    # delegate function pointer declaration
+    - match: \b(delegate)\s*(\*)
+      captures:
+        1: storage.type.delegate.cs
+        2: keyword.operator.pointer.cs
+      push:
+        - variables_declaration
+        - funcptr_type_meta
+        - funcptr_parameter_list
+        - funcptr_type_modifier
+    # delegate function declaration
+    - match: \b(delegate)\s+
       captures:
         1: storage.type.delegate.cs
       push: delegate_type
@@ -611,9 +622,7 @@ contexts:
   data_type_parameter:
     - match: '<'
       scope: meta.generic.cs punctuation.definition.generic.begin.cs
-      push:
-        - meta_content_scope: meta.generic.cs
-        - include: type_parameter
+      push: type_parameter
     - match: (?=\S)
       pop: true
 
@@ -1271,7 +1280,8 @@ contexts:
       pop: true
 
   keywords:
-    - match: '\b(this|base)\s*(\[)'
+    - include: funcptr_types
+    - match: \b(this|base)\s*(\[)
       captures:
         1: variable.language.cs
         2: meta.brackets.cs punctuation.section.brackets.begin.cs
@@ -1698,6 +1708,71 @@ contexts:
       pop: true
     - include: line_of_code_in
 
+  funcptr_types:
+    # https://learn.microsoft.com/en-us/dotnet/csharp/language-reference/proposals/csharp-9.0/function-pointers
+    - match: (delegate)\s*(\*)
+      captures:
+        1: storage.type.delegate.cs
+        2: keyword.operator.pointer.cs
+      push:
+        - funcptr_type_meta
+        - funcptr_parameter_list
+        - funcptr_type_modifier
+
+  funcptr_type_meta:
+    - meta_include_prototype: false
+    - meta_scope: meta.type.funcptr.cs
+    - match: ''
+      pop: true
+
+  funcptr_type_modifier:
+    - match: \s*(managed)\b
+      scope: storage.modifier.delegate.cs
+      pop: 1
+    - match: \s*(unmanaged)\b
+      scope: storage.modifier.delegate.cs
+      set: funcptr_type_calling_convention
+    - match: (?=[^\n])
+      pop: true
+
+  funcptr_type_calling_convention:
+    - match: \s*(\[)
+      captures:
+        1: meta.brackets.cs punctuation.section.brackets.begin.cs
+      set: inside_funcptr_type_calling_convention
+    - match: (?=[^\n])
+      pop: true
+
+  inside_funcptr_type_calling_convention:
+    - meta_content_scope: meta.brackets.cs
+    - match: \]
+      scope: meta.brackets.cs punctuation.section.brackets.end.cs
+      pop: true
+    - match: ','
+      scope: punctuation.separator.type.cs
+    - match: (?:Cdecl|Stdcall|Thiscall|Fastcall)\b
+      scope: storage.modifier.funcptr.cs
+    - include: type
+
+  funcptr_parameter_list:
+    - match: \s*(<)
+      captures:
+        1: meta.generic.cs punctuation.definition.generic.begin.cs
+      set: inside_funcptr_parameter_list
+    - match: (?=[^\n])
+      pop: true
+
+  inside_funcptr_parameter_list:
+    - meta_content_scope: meta.generic.cs
+    - match: '>'
+      scope: meta.generic.cs punctuation.definition.generic.end.cs
+      pop: true
+    - match: ','
+      scope: punctuation.separator.type.cs
+    - match: (?:in|out|ref|readonly)\b
+      scope: storage.modifier.cs
+    - include: type
+
   type:
     - include: type_common
     - match: (?=\()
@@ -1720,7 +1795,8 @@ contexts:
 
   type_common:
     - include: namespace_variables
-    - match: '(class|struct|enum)'
+    - include: funcptr_types
+    - match: (?:class|struct|enum)\b
       scope: storage.type.other.cs
     - match: 'new\s*\(\s*\)'
       scope: keyword.operator.new.cs
@@ -1750,8 +1826,6 @@ contexts:
       pop: true
 
   type_arg_param_common:
-    - match: ','
-      scope: punctuation.separator.type.cs
     - match: '(>){{type_suffix_capture}}'
       captures:
         1: meta.generic.cs punctuation.definition.generic.end.cs
@@ -1762,18 +1836,19 @@ contexts:
         6: punctuation.section.brackets.end.cs
         7: keyword.operator.pointer.cs
       pop: true
+    - match: ','
+      scope: punctuation.separator.type.cs
     - include: type
 
   type_argument:
     - meta_content_scope: meta.generic.cs
     - include: type_arg_param_common
 
   type_parameter:
-    - match: '(in|out)\b'
+    - meta_content_scope: meta.generic.cs
+    - match: (?:in|out)\b
       scope: storage.modifier.cs
     - include: type_arg_param_common
-    - match: '{{name}}'
-      scope: support.type.cs
 
   type_no_space:
     - include: type