Parse Struct Declarations

Signed-off-by: Will Hawkins <hawkinsw@obs.cr>

tree-sitter-p4/grammar.js

@@ -63,7 +63,11 @@ export default grammar({
         instantiation: $ => seq($.typeRef, '(', optional($.parameterList), ')', $.identifier),
 
         // Declarations
-        declaration: $ => seq(choice($.parserDeclaration, $.parserTypeDeclaration)),
+        declaration: $ => seq(choice($.parserDeclaration, $.parserTypeDeclaration, $.type_declaration)),
+
+        type_declaration: $=> choice($.struct_declaration),
+        struct_declaration: $ => seq($.struct, $.identifier, '{', optional($.struct_declaration_fields), '}'),
+        struct_declaration_fields: $=> repeat1(seq($.variableDeclaration)),
 
         // Make separate productions for the parser type and the parser type declaration because the latter can have type parameters.
         parserTypeDeclaration: $ => seq(optional($.annotations), $.parser, field('parser_name', $.identifier), optional($.typeParameters), '(', optional($.parameterList), ')'),

tree-sitter-p4/test/corpus/declarations.txt

@@ -232,3 +232,31 @@ parser simple() {
  )
 )
 
+=========================
+Simple Struct Type Declaration
+=========================
+struct Testing {
+  string fieldA;
+};
+---
+(p4program
+ (declaration
+  (type_declaration
+   (struct_declaration
+    (struct)
+    (identifier)
+    (struct_declaration_fields
+     (variableDeclaration
+      (typeRef
+       (baseType
+        (string)
+       )
+      )
+      (identifier)
+     )
+    )
+   )
+  )
+ )
+)
+