set() can now reference other named token sets

compiler/syntax.go

@@ -379,6 +379,20 @@ func (c *syntaxLoader) convertSet(expr ast.SetExpression, nonterm *syntax.Nonter
 			default:
 				c.Errorf(op, "operator must be one of: first, last, precede or follow")
 			}
+		} else {
+			// Check if the reference targets another named set.
+			name := expr.Symbol().Name()
+			if index, ok := c.namedSets[name.Text()]; ok {
+				if index >= len(c.out.Sets) {
+					c.Errorf(expr.TmNode(), "forward references are not allowed")
+					return ret
+				}
+				if _, ok := c.resolveRefIndex(expr.Symbol()); ok {
+					c.Errorf(expr.TmNode(), "ambigious reference")
+					return ret
+				}
+				return c.out.Sets[index]
+			}
 		}
 		ret.Symbol, ret.Args = c.resolveRef(expr.Symbol(), nonterm)
 		return ret
@@ -510,7 +524,7 @@ func (c *syntaxLoader) instantiateOpt(name string, origin ast.Symref) (int, bool
 	return index, true
 }
 
-func (c *syntaxLoader) resolveRef(ref ast.Symref, nonterm *syntax.Nonterm) (int, []syntax.Arg) {
+func (c *syntaxLoader) resolveRefIndex(ref ast.Symref) (int, bool) {
 	name := ref.Name()
 	text := name.Text()
 	index, ok := c.resolver.syms[text]
@@ -523,6 +537,13 @@ func (c *syntaxLoader) resolveRef(ref ast.Symref, nonterm *syntax.Nonterm) (int,
 	if !ok && len(text) > 3 && strings.HasSuffix(text, "opt") {
 		index, ok = c.instantiateOpt(text, ref)
 	}
+	return index, ok
+}
+
+func (c *syntaxLoader) resolveRef(ref ast.Symref, nonterm *syntax.Nonterm) (int, []syntax.Arg) {
+	name := ref.Name()
+	text := name.Text()
+	index, ok := c.resolveRefIndex(ref)
 	if !ok {
 		c.Errorf(name, "unresolved reference '%v'", text)
 		return 0, nil // == eoi

parsers/test/parser_tables.go

@@ -224,5 +224,15 @@ var tmRuleType = [...]uint32{
 	0,                   // QualifiedNameopt :
 }
 
+// set(MINUS | PLUS) = MINUS, PLUS
+var plusMinus = []token.Type{
+	25, 27,
+}
+
+// set((MINUS | PLUS) | MINUSGT) = MINUS, MINUSGT, PLUS
+var plusMinusArrow = []token.Type{
+	25, 26, 27,
+}
+
 // set(follow ERROR) =
 var afterErr = []token.Type{}

parsers/test/test.tm

@@ -120,6 +120,9 @@ MultiLineComment -> MultiLineComment:  /\/\*/ (space)
 
 :: parser
 
+%generate plusMinus = set('-' | '+');
+%generate plusMinusArrow = set(plusMinus | '->');
+
 %input Test, Decl1;
 
 Test -> Test:
@@ -166,7 +169,7 @@ foo_la:
 ;
 
 foo_nonterm<A> :
-      IntegerConstant '.' expr 
+      IntegerConstant '.' expr
     | [A] IntegerConstant 'foo_' expr
 ;