fix(sidekick/swift): handle metatype keywords (#5070)

TIL: for a few keywords the backtick escape does not work. We need to
resort to mangling.

Author: coryan

internal/sidekick/swift/names.go

@@ -140,7 +140,13 @@ var keywords = map[string]bool{
 
 // escapeKeyword escapes a string if it is a keyword.
 func escapeKeyword(s string) string {
-	if _, ok := keywords[s]; ok {
+	// In Swift we can use backtick escaping for most keywords except `Type`, `Protocol`, and `self`:
+	//   https://docs.swift.org/swift-book/documentation/the-swift-programming-language/types/#Metatype-Type
+	// In an expression like `Foo.Type` that is *always* the metatype of `Foo` and not the nested type `Type` even if `Foo` has such a nested type.
+	if s == "Protocol" || s == "Type" || s == "self" {
+		return fmt.Sprintf("%s_", s)
+	}
+	if keywords[s] {
 		return fmt.Sprintf("`%s`", s)
 	}
 	return s

internal/sidekick/swift/names_test.go

@@ -31,6 +31,10 @@ func TestEscapeKeyword(t *testing.T) {
 		{input: "func", want: "`func`"},
 		{input: "if", want: "`if`"},
 		{input: "while", want: "`while`"},
+		// Metatype-related keywords, need custom escaping
+		{input: "Type", want: "Type_"},
+		{input: "Protocol", want: "Protocol_"},
+		{input: "self", want: "self_"},
 
 		// Non-keywords requested NOT to be escaped
 		{input: "secret", want: "secret"},
@@ -53,10 +57,12 @@ func TestCamelCase(t *testing.T) {
 		{input: "secret_version", want: "secretVersion"},
 		{input: "display_name", want: "displayName"},
 		{input: "iam_policy", want: "iamPolicy"},
+		{input: "Type", want: "type"},
 
 		// Keywords that should be escaped after camelCase
 		{input: "protocol", want: "`protocol`"},
 		{input: "will_set", want: "`willSet`"},
+		{input: "Self", want: "self_"},
 	} {
 		t.Run(test.input, func(t *testing.T) {
 			got := camelCase(test.input)