libSyntax: function declaration syntax should accept operators as name.

Author: nkcsgexi

test/Syntax/Outputs/round_trip_parse_gen.swift.withkinds

@@ -109,5 +109,7 @@ struct C <MemberDeclBlock>{<FunctionDecl><Attribute>
 @objc</Attribute><Attribute>
 @available(*, unavailable)</Attribute><DeclModifier>
 private </DeclModifier><DeclModifier>static </DeclModifier><DeclModifier>override </DeclModifier>func foo<GenericParameterClause><<GenericParameter>a, </GenericParameter><GenericParameter>b, </GenericParameter><GenericParameter>c</GenericParameter>></GenericParameterClause><FunctionSignature>(<FunctionParameter>a b: <SimpleTypeIdentifier>Int</SimpleTypeIdentifier>, </FunctionParameter><FunctionParameter>c: <SimpleTypeIdentifier>Int</SimpleTypeIdentifier></FunctionParameter>) throws -> <ArrayType>[<SimpleTypeIdentifier>Int</SimpleTypeIdentifier>] </ArrayType></FunctionSignature><GenericWhereClause>where <SameTypeRequirement><SimpleTypeIdentifier>a</SimpleTypeIdentifier>==<SimpleTypeIdentifier>p1</SimpleTypeIdentifier>, </SameTypeRequirement><ConformanceRequirement><SimpleTypeIdentifier>b</SimpleTypeIdentifier>:<SimpleTypeIdentifier>p2 </SimpleTypeIdentifier></ConformanceRequirement></GenericWhereClause><CodeBlock>{ <IdentifierExpr>ddd </IdentifierExpr>}</CodeBlock></FunctionDecl><FunctionDecl>
-func rootView<FunctionSignature>() -> <SimpleTypeIdentifier>Label </SimpleTypeIdentifier></FunctionSignature><CodeBlock>{}</CodeBlock></FunctionDecl>
+func rootView<FunctionSignature>() -> <SimpleTypeIdentifier>Label </SimpleTypeIdentifier></FunctionSignature><CodeBlock>{}</CodeBlock></FunctionDecl><FunctionDecl><DeclModifier>
+static </DeclModifier>func ==<FunctionSignature>() -> <SimpleTypeIdentifier>bool </SimpleTypeIdentifier></FunctionSignature><CodeBlock>{}</CodeBlock></FunctionDecl><FunctionDecl><DeclModifier>
+static </DeclModifier>func !=<GenericParameterClause><<GenericParameter>a, </GenericParameter><GenericParameter>b, </GenericParameter><GenericParameter>c</GenericParameter>></GenericParameterClause><FunctionSignature>() -> <SimpleTypeIdentifier>bool </SimpleTypeIdentifier></FunctionSignature><CodeBlock>{}</CodeBlock></FunctionDecl>
 }</MemberDeclBlock></StructDecl>

test/Syntax/round_trip_parse_gen.swift

@@ -110,4 +110,6 @@ struct C {
 @available(*, unavailable)
 private static override func foo<a, b, c>(a b: Int, c: Int) throws -> [Int] where a==p1, b:p2 { ddd }
 func rootView() -> Label {}
+static func ==() -> bool {}
+static func !=<a, b, c>() -> bool {}
 }

utils/gyb_syntax_support/DeclNodes.py

@@ -207,7 +207,15 @@
              Child('Modifiers', kind='ModifierList',
                    is_optional=True),
              Child('FuncKeyword', kind='FuncToken'),
-             Child('Identifier', kind='IdentifierToken'),
+             Child('Identifier', kind='Token',
+                   token_choices=[
+                       'IdentifierToken',
+                       'OperatorToken',
+                       'UnspacedBinaryOperatorToken',
+                       'SpacedBinaryOperatorToken',
+                       'PrefixOperatorToken',
+                       'PostfixOperatorToken',
+                   ]),
              Child('GenericParameterClause', kind='GenericParameterClause',
                    is_optional=True),
              Child('Signature', kind='FunctionSignature'),