ASTPrinter: add a utility to get the length of keywords or punctuators by token kinds.

Author: nkcsgexi

include/swift/AST/ASTPrinter.h

@@ -307,6 +307,9 @@ bool printRequirementStub(ValueDecl *Requirement, DeclContext *Adopter,
 /// Print a keyword or punctuator directly by its kind.
 llvm::raw_ostream &operator<<(llvm::raw_ostream &OS, tok keyword);
 
+/// Get the length of a keyword or punctuator by its kind.
+uint8_t getKeywordLen(tok keyword);
+
 } // namespace swift
 
 #endif // LLVM_SWIFT_AST_ASTPRINTER_H

lib/AST/ASTPrinter.cpp

@@ -594,6 +594,17 @@ operator<<(llvm::raw_ostream &OS, tok keyword) {
   return OS;
 }
 
+uint8_t swift::getKeywordLen(tok keyword) {
+  switch (keyword) {
+#define KEYWORD(KW) case tok::kw_##KW: return StringRef(#KW).size();
+#define POUND_KEYWORD(KW) case tok::pound_##KW: return StringRef("#"#KW).size();
+#define PUNCTUATOR(PUN, TEXT) case tok::PUN: return StringRef(TEXT).size();
+#include "swift/Syntax/TokenKinds.def"
+  default:
+    llvm_unreachable("unexpected keyword or punctuator kind");
+  }
+}
+
 ASTPrinter &operator<<(ASTPrinter &printer, tok keyword) {
   SmallString<16> Buffer;
   llvm::raw_svector_ostream OS(Buffer);