first steps to implement object construction expressions

todo.txt

@@ -8,7 +8,10 @@ version 0.9.2
   * test libffi on windows
   * test: times.format with the FFI
 - acyclic vs prunable; introduce GC hints
-- implement constructors + full 'not nil' checking
+- implement constructors
+  - more checks
+  - C codegen for them
+  - document them
 - CGEN: ``restrict`` pragma + backend support; computed goto support
 - fix:
   - 'result' is not properly cleaned for NRVO
@@ -24,6 +27,7 @@ version 0.9.4
 - provide tool/API to track leaks/object counts
 - hybrid GC
 - use big blocks in the allocator
+- implement full 'not nil' checking
 - make 'bind' default for templates and introduce 'mixin';
   special rule for ``[]=``
 - implicit deref for parameter matching; overloading based on 'var T'