Fix #520: Out of bounds error

Author: 0-v-0

src/dparse/ast.d

@@ -4084,6 +4084,25 @@ unittest //#365 : used to segfault
     Module m1 = parseModule(getTokensForParser(src, cf, &ca), "", &ra , &shut);
 }
 
+unittest // issue #520
+{
+    import dparse.lexer, dparse.parser, dparse.rollback_allocator;
+
+    string src = q{void foo(int s =};
+    final class Test : ASTVisitor
+    {
+    }
+
+    static void shut(string, size_t, size_t, string ,bool){}
+
+    RollbackAllocator ra;
+    auto cf = LexerConfig("", StringBehavior.source);
+    auto ca = StringCache(16);
+    Module m = parseModule(getTokensForParser(src, cf, &ca), "", &ra, &shut);
+    auto t = new Test;
+    t.visit(m);
+}
+
 unittest // issue #398: Support extern(C++, <string expressions...>)
 {
     import dparse.lexer : LexerConfig;

src/dparse/parser.d

@@ -7413,19 +7413,22 @@ class Parser
         auto startIndex = index;
         auto node = allocator.make!TemplateValueParameterDefault;
         mixin(tokenCheck!"=");
-        switch (current.type)
+        if (index < tokens.length)
         {
-        case tok!"__FILE__":
-        case tok!"__FILE_FULL_PATH__":
-        case tok!"__MODULE__":
-        case tok!"__LINE__":
-        case tok!"__FUNCTION__":
-        case tok!"__PRETTY_FUNCTION__":
-            node.token = advance();
-            break;
-        default:
-            mixin(parseNodeQ!(`node.assignExpression`, `AssignExpression`));
-            break;
+            switch (current.type)
+            {
+            case tok!"__FILE__":
+            case tok!"__FILE_FULL_PATH__":
+            case tok!"__MODULE__":
+            case tok!"__LINE__":
+            case tok!"__FUNCTION__":
+            case tok!"__PRETTY_FUNCTION__":
+                node.token = advance();
+                break;
+            default:
+                mixin(parseNodeQ!(`node.assignExpression`, `AssignExpression`));
+                break;
+            }
         }
         node.tokens = tokens[startIndex .. index];
         return node;