Use named constant instead of 0 (no functional change).

Author: marsupial

src/liboslcomp/typecheck.cpp

@@ -1017,26 +1017,26 @@ class CandidateFunctions {
                 ++fargs;
             case '\0':
                 if (fargs < m_nargs)
-                    return 0;
+                    return kNoMatch;
                 break;
 
             default:
                 // TODO: Scoring default function arguments would go here
                 // Curently an unused formal argument, so no match at all.
-                return 0;
+                return kNoMatch;
         }
         ASSERT (*formals == 0);
 
         int highscore = m_candidates.empty() ? 0 : m_candidates.front().ascore;
         if (argscore < highscore)
-            return 0;
+            return kNoMatch;
 
 
         if (argscore == highscore) {
             // Check for duplicate declarations
             for (auto& candidate : m_candidates) {
                 if (candidate.sym->argcodes() == func->argcodes())
-                    return 0;
+                    return kNoMatch;
             }
         } else  // clear any prior ambiguous matches
             m_candidates.clear();