Add const to a const method. NFC

llvm-svn: 300520

llvm/include/llvm/Support/Regex.h

@@ -57,7 +57,7 @@ namespace llvm {
 
     /// isValid - returns the error encountered during regex compilation, or
     /// matching, if any.
-    bool isValid(std::string &Error);
+    bool isValid(std::string &Error) const;
 
     /// getNumMatches - In a valid regex, return the number of parenthesized
     /// matches it contains.  The number filled in by match will include this

llvm/lib/Support/Regex.cpp

@@ -48,7 +48,7 @@ Regex::~Regex() {
   }
 }
 
-bool Regex::isValid(std::string &Error) {
+bool Regex::isValid(std::string &Error) const {
   if (!error)
     return true;