Merge pull request #38 from ArendJan/patch-1

Statix remove optional requirement, add constructor requirement

source/langdev/meta/lang/statix/signature-generator.rst

@@ -30,7 +30,7 @@ For the generator to work correctly, your SDF3 must be well formed. In particula
 * not declare sorts that are not used in any rules
 * not use any implicitly declared sorts
 * not use complex injections, such as :sdf3:`Pair = Expr Expr`
-* not use optional terms, such as :sdf3:`Decl.VarDecl = ID Type?`
+* constructors must start with an upper-case letter
 * not use ``sdf2table: c``
 
 The generator generates strategies and signatures for each explicit declaration
@@ -265,4 +265,4 @@ Clean fails with an error such as this:
     -         declSortLex("MySort")
 
 You are using the old ``sdf2table: c``. Change this in ``metaborg.yaml`` into
-``sdf2table: java``.
+``sdf2table: java``.