use unordered set

src/libexpr/eval.cc

@@ -92,24 +92,17 @@ RootValue allocRootValue(Value * v)
 #endif
 }
 
-// Reserved symbols that should be quoted when printing expressions.
-static inline bool isReservedSymbol(const std::string_view str)
+// Returns `true' is a string is a reserved keyword which requires quotation
+// when printing attribute set field names.
+static inline bool isReservedKeyword(const std::string_view str)
 {
-    return (str == "if")      ||
-           (str == "then")    ||
-           (str == "else")    ||
-           (str == "assert")  ||
-           (str == "with")    ||
-           (str == "let")     ||
-           (str == "in")      ||
-           (str == "rec")     ||
-           (str == "inherit") ||
-           (str == "or")      ||
-           (str == "throw")   ||
-           (str == "import");
+    static const std::unordered_set<std::string_view> reservedKeywords = {
+        "if", "then", "else", "assert", "with", "let", "in", "rec", "inherit",
+        "or", "throw", "import"
+    };
+    return reservedKeywords.contains(str);
 }
 
-
 void Value::print(const SymbolTable & symbols, std::ostream & str,
     std::set<const void *> * seen) const
 {
@@ -145,7 +138,9 @@ void Value::print(const SymbolTable & symbols, std::ostream & str,
         else {
             str << "{ ";
             for (auto & i : attrs->lexicographicOrder(symbols)) {
-                if (isReservedSymbol(symbols[i->name])) {
+                // Quote reserved keywords so that the output can be
+                // re-evaluated later without upsetting the lexer.
+                if (isReservedKeyword(symbols[i->name])) {
                     str << "\"" << symbols[i->name] << "\" = ";
                 } else {
                     str << symbols[i->name] << " = ";