new classes: assert that constructors are not callable and rewrite 'return;'

src/ast.h

Index: src/ast.h
diff --git a/src/ast.h b/src/ast.h
index fca3aabf3a1dfa27ed5e6410a2437525e4ec00eb..331dff7f74d8931c2d9ee907362ea5b83c3797a9 100644
--- a/src/ast.h
+++ b/src/ast.h
@@ -2630,7 +2630,7 @@ class FunctionLiteral FINAL : public Expression {
   class HasDuplicateParameters : public BitField<ParameterFlag, 3, 1> {};
   class IsFunction : public BitField<IsFunctionFlag, 4, 1> {};
   class IsParenthesized : public BitField<IsParenthesizedFlag, 5, 1> {};
-  class FunctionKindBits : public BitField<FunctionKind, 6, 5> {};
+  class FunctionKindBits : public BitField<FunctionKind, 6, 6> {};
 };