hlb-parser

Playground to make changes to parser without worrying about checker/codegen.

Proposal

Goals:

• Address inconsistency across builtin effects and user defined as ( ... ) binding.
• Address inconsistency between all decls except function declaration (starting with keyword).
• Address inconsistency between CallStmt and CallExpr.
• Support if else, for loops, composite types, unary / binary operators (with operator precendence and associativity).
• Treat type association :: as first class rather than simply legal characters in Ident symbol.