Start a list of tasks and design issues related to QAST migration.

Author: jnthn

docs/QASTMAP

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+# QAST Roadmap
+
+This is an overall list of things that need doing and problems that need
+solving on the way to having a QAST-based Rakudo and NQP.
+
+## QAST Issues
+
+### Fix NQP regressions
+The toqast branch, even though QAST is only being used for regexes still,
+has some regressions over master. Fix them.
+
+### Finish lexical lookup handling
+Always-by-name lookups (for things like $_ that are lazy in Rakudo). Also
+handle looking at symbol table to find that things are lexical.
+
+### Register Type Coercions
+Get the various coercions in place, with the appropriate ones as HLL-level
+configurable operations.
+
+### Exceptions
+Design whatever mechanism is going to replace the PAST::Control and related
+machinery. Implement it.
+
+### Serialization Context
+Add some QAST handling for serialization contexts, so as to replace laodinit.
+
+### :op('for')
+Implement it
+
+### loop handling of various phasers
+Need to figure out the REDO bits, etc. Try and make it so we've a way to avoid
+the PIR code in MapIter and so getting while loop phasers in place in Rakudo is
+easy also.
+
+## Rakudo
+
+Overall plan: create a branch, start changing stuff to QAST, see what happens.
+List any design level issues here.
+
+## NQP
+
+NQP is currently somewhat half-Parroty, half-6modely. This causes various issues
+that will need to be addresses for portability reasons, and moving NQP to QAST is
+a good chance to do so.
+
+### Integer/Float/String and the ops
+Need to work out an approach to handling these.
+
+### Native types
+NQP should get natively typed lexicals and arguments.