SwiftSyntax: add a mechanism to define traits of syntax nodes to allow abstract access to popular child kinds. NFC

tools/SwiftSyntax/SyntaxNodes.swift.gyb

@@ -1,6 +1,7 @@
 %{
   # -*- mode: Swift -*-
   from gyb_syntax_support import *
+  from gyb_syntax_support.Traits import TRAITS
   NODE_MAP = create_node_map()
   # Ignore the following admonition it applies to the resulting .swift file only
 }%
@@ -53,6 +54,19 @@ public struct UnknownSyntax: _SyntaxBase {
   }
 }
 
+% for trait in TRAITS:
+public protocol ${trait.trait_name} {
+% for child in trait.children:
+%   ret_type = child.type_name
+%   if child.is_optional:
+%       ret_type += '?'
+%    end
+  var ${child.swift_name}: ${ret_type} { get }
+  func with${child.name}(_ newChild: ${child.type_name}?) -> Self
+% end
+}
+% end
+
 % for node in SYNTAX_NODES:
 %   base_type = node.base_type
 %   if node.is_base():
@@ -61,7 +75,12 @@ public protocol ${node.name}: Syntax {}
 %   elif node.collection_element:
 %     pass
 %   else:
-public struct ${node.name}: ${base_type}, _SyntaxBase, Hashable {
+%     traits_list = ""
+%     if node.traits:
+%       traits_list = ", ".join(node.traits)
+%       traits_list = traits_list + ", "
+%     end
+public struct ${node.name}: ${traits_list} ${base_type}, _SyntaxBase, Hashable {
 %     if node.children:
   enum Cursor: Int {
 %       for child in node.children:

utils/gyb_syntax_support/CommonNodes.py

@@ -32,9 +32,10 @@
 
     # code-block -> '{' stmt-list '}'
     Node('CodeBlock', kind='Syntax',
+         traits=['BracedSyntax'],
          children=[
-             Child('OpenBrace', kind='LeftBraceToken'),
+             Child('LeftBrace', kind='LeftBraceToken'),
              Child('Statements', kind='CodeBlockItemList'),
-             Child('CloseBrace', kind='RightBraceToken'),
+             Child('RightBrace', kind='RightBraceToken'),
          ]),
 ]

utils/gyb_syntax_support/DeclNodes.py

@@ -157,7 +157,7 @@
     #                      generic-where-clause?
     #                     '{' class-members '}'
     # class-name -> identifier
-    Node('ClassDecl', kind='Decl',
+    Node('ClassDecl', kind='Decl', traits=['DeclGroupSyntax'],
          children=[
              Child('Attributes', kind='AttributeList',
                    is_optional=True),
@@ -181,7 +181,7 @@
     #                         generic-where-clause?
     #                         '{' struct-members '}'
     # struct-name -> identifier
-    Node('StructDecl', kind='Decl',
+    Node('StructDecl', kind='Decl', traits=['DeclGroupSyntax'],
          children=[
              Child('Attributes', kind='AttributeList',
                    is_optional=True),
@@ -198,7 +198,7 @@
              Child('Members', kind='MemberDeclBlock'),
          ]),
 
-    Node('ProtocolDecl', kind='Decl',
+    Node('ProtocolDecl', kind='Decl', traits=['DeclGroupSyntax'],
          children=[
              Child('Attributes', kind='AttributeList',
                    is_optional=True),
@@ -219,7 +219,7 @@
     #                            generic-where-clause?
     #                            '{' extension-members '}'
     # extension-name -> identifier
-    Node('ExtensionDecl', kind='Decl',
+    Node('ExtensionDecl', kind='Decl', traits=['DeclGroupSyntax'],
          children=[
              Child('Attributes', kind='AttributeList',
                    is_optional=True),
@@ -234,7 +234,7 @@
              Child('Members', kind='MemberDeclBlock'),
          ]),
 
-    Node('MemberDeclBlock', kind='Syntax',
+    Node('MemberDeclBlock', kind='Syntax', traits=['BracedSyntax'],
          children=[
              Child('LeftBrace', kind='LeftBraceToken'),
              Child('Members', kind='DeclList'),
@@ -464,7 +464,7 @@
 
     Node('AccessorList', kind="SyntaxCollection", element='AccessorDecl'),
 
-    Node('AccessorBlock', kind="Syntax",
+    Node('AccessorBlock', kind="Syntax", traits=['BracedSyntax'],
          children=[
              Child('LeftBrace', kind='LeftBraceToken'),
              Child('AccessorListOrStmtList', kind='Syntax',

utils/gyb_syntax_support/ExprNodes.py

@@ -384,6 +384,7 @@
          ]),
 
     Node('ClosureExpr', kind='Expr',
+         traits=['BracedSyntax'],
          children=[
              Child('LeftBrace', kind='LeftBraceToken'),
              Child('Signature', kind='ClosureSignature', is_optional=True),

utils/gyb_syntax_support/Node.py

@@ -16,12 +16,13 @@ class Node(object):
     subclass.
     """
 
-    def __init__(self, name, kind=None, children=None,
+    def __init__(self, name, kind=None, traits=None, children=None,
                  element=None, element_name=None, element_choices=None):
         self.syntax_kind = name
         self.swift_syntax_kind = lowercase_first_word(name)
         self.name = kind_to_type(self.syntax_kind)
 
+        self.traits = traits or []
         self.children = children or []
         self.base_kind = kind
         self.base_type = kind_to_type(self.base_kind)

utils/gyb_syntax_support/StmtNodes.py

@@ -91,16 +91,17 @@
     # switch-stmt -> identifier? ':'? 'switch' expr '{'
     #   switch-case-list '}' ';'?
     Node('SwitchStmt', kind='Stmt',
+         traits=['BracedSyntax'],
          children=[
              Child('LabelName', kind='IdentifierToken',
                    is_optional=True),
              Child('LabelColon', kind='ColonToken',
                    is_optional=True),
              Child('SwitchKeyword', kind='SwitchToken'),
              Child('Expression', kind='Expr'),
-             Child('OpenBrace', kind='LeftBraceToken'),
+             Child('LeftBrace', kind='LeftBraceToken'),
              Child('Cases', kind='SwitchCaseList'),
-             Child('CloseBrace', kind='RightBraceToken'),
+             Child('RightBrace', kind='RightBraceToken'),
          ]),
 
     # catch-clause-list -> catch-clause catch-clause-list?

utils/gyb_syntax_support/Traits.py

@@ -0,0 +1,24 @@
+from Child import Child
+
+
+class Trait(object):
+    def __init__(self, trait_name, children):
+        self.trait_name = trait_name
+        self.children = children
+
+
+TRAITS = [
+    Trait('DeclGroupSyntax',
+          children=[
+              Child('Attributes', kind='AttributeList', is_optional=True),
+              Child('AccessLevelModifier', kind='DeclModifier',
+                    is_optional=True),
+              Child('Members', kind='MemberDeclBlock'),
+          ]),
+
+    Trait('BracedSyntax',
+          children=[
+              Child('LeftBrace', kind='LeftBraceToken'),
+              Child('RightBrace', kind='RightBraceToken'),
+          ]),
+]