Add Expression::extractLast

src/expression.c

@@ -1994,6 +1994,9 @@ int Expression::rvalue(bool allowVoid)
     return 1;
 }
 
+/**********************************
+ * Combine e1 and e2 by CommaExp if both are not NULL.
+ */
 Expression *Expression::combine(Expression *e1, Expression *e2)
 {
     if (e1)
@@ -2009,6 +2012,35 @@ Expression *Expression::combine(Expression *e1, Expression *e2)
     return e1;
 }
 
+/**********************************
+ * If 'e' is a tree of commas, returns the leftmost expression
+ * by stripping off it from the tree. The remained part of the tree
+ * is returned via *pe0.
+ * Otherwise 'e' is directly returned and *pe0 is set to NULL.
+ */
+Expression *Expression::extractLast(Expression *e, Expression **pe0)
+{
+    if (e->op == TOKcomma)
+    {
+        CommaExp *ce = (CommaExp *)e;
+        *pe0 = ce;
+
+        Expression **pe = &e;
+        while (((CommaExp *)(*pe))->e2->op == TOKcomma)
+        {
+            ce = (CommaExp *)(*pe);
+            pe = &ce->e2;
+        }
+
+        *pe = ce->e2;
+        if (pe == &e)
+            *pe0 = ce->e1;
+    }
+    else
+        *pe0 = NULL;
+    return e;
+}
+
 dinteger_t Expression::toInteger()
 {
     //printf("Expression %s\n", Token::toChars(op));

src/expression.h

@@ -165,6 +165,7 @@ class Expression : public RootObject
     // this new expression does not necessarily need to have valid D source code representation,
     // for example, it may include declaration expressions
     static Expression *combine(Expression *e1, Expression *e2);
+    static Expression *extractLast(Expression *e, Expression **pe0);
     static Expressions *arraySyntaxCopy(Expressions *exps);
 
     virtual dinteger_t toInteger();