Set the error reporting limit to 100 for parity with C++ (google#534)

Make the standard environment initialization lazy (google#520)

Copy validated declarations between checker.Env instances on extension (

google#347)

* Refactor the type substitution checks for simplicity and performance. This simple change roughly doubles check-time performance
* Add an option to early-validate declarations and to propagate validated declarations from one checker.Env to derivations created using Extend
* Benchmarks and tests for validated declaration copying
* Updates based on review feedback
* kind guard before proto equality check

Fix runtime cost ref.Val stack (google#517)

Fix runtime cost ref.Val stack

Vendored dependencies (google#508)

Add nil check and fix costTracker in contextEval (google#507)

* Return proper err for nil context
* Fix costTracker in contextEval

Add rudimentary parsing benchmark (google#503)

Remove ineffective else clauses (google#464)

Unify overflow checking in operators, field setting (google#448)

* Unify overflow checking in operators, field setting
* Additional overflow case for timestamp subtraction
* NaN checks and tests based on review feedback

Fix infinite loop in AST prune (google#419)