refactor GetFunctionName

Author: charles-zablit

lldb/source/Plugins/Language/Swift/SwiftLanguage.cpp

@@ -1768,14 +1768,12 @@ std::string SwiftLanguage::GetFunctionName(const SymbolContext &sc,
       SwiftLanguageRuntime::eSimplified, &sc, exe_ctx);
   if (name.empty())
     return {};
-  const char *cstr = name.data();
-  const char *open_paren = strchr(cstr, '(');
-  const char *generic = strchr(cstr, '<');
-  if (open_paren && generic && generic < open_paren)
-    return std::string(cstr, generic);
-  if (open_paren)
-    return std::string(cstr, open_paren);
-  return name;
+  size_t open_paren = name.find('(');
+  size_t generic = name.find('<');
+  size_t name_end = std::min(open_paren, generic);
+  if (name_end == std::string::npos)
+    return name;
+  return name.substr(0, name_end);
 }
 
 std::string SwiftLanguage::GetFunctionDisplayArgs(