* TODO =Symbol= primitive
* Statements [7/7]
** DONE [2020-12-21 Mon] BlockStatement
** DONE [2020-12-21 Mon] IfStatement
** DONE [2020-12-22 Tue] ForStatement
** DONE [2021-01-23 Sat] WhileStatement
** DONE [2021-01-23 Sat] DoWhileStatement
** DONE [2021-01-24 Sun] BreakStatement, ContinueStatement
*** DONE [2021-01-23 Sat] BreakStatement
*** DONE [2021-01-23 Sat] ContinueStatement
*** DONE [2021-01-23 Sat] LabeledStatement
*** DONE [2021-01-23 Sat] labeled break
*** DONE [2021-01-24 Sun] labeled continue
** DONE [2021-02-06 Sat] SwitchStatement
** DONE [2021-01-28 Thu] TryStatement
* Expressions [10/10]
** DONE [2020-12-21 Mon] ConditinalExpression
** DONE [2021-02-05 Fri] ForInExpression
** DONE [2021-01-23 Sat] UpdateExpression
** DONE [2021-01-19 Tue] LogicalExpression...
*** DONE [2021-01-19 Tue] &&
*** DONE [2021-01-19 Tue] ||
** DONE [2021-01-04 Mon] UnaryExpression
*** DONE [2021-01-03 Sun] everything, except...
*** DONE [2021-01-04 Mon] =delete=
** DONE [2021-02-06 Sat] SequenceExpression
** DONE [2021-02-07 Sun] BinaryExpression [17/17]
*** DONE [2020-12-30 Wed] ~==~ Abstract Equality Comparison
*** DONE [2020-12-22 Tue] ~<~ Abstract Relationl Comparison
*** DONE [2021-01-13 Wed] ~+~ between all types
*** DONE [2021-01-19 Tue] ~===~
*** DONE [2021-01-26 Tue] =<=
*** DONE [2021-01-26 Tue] ~<=~
*** DONE [2021-01-26 Tue] ~>~
*** DONE [2021-01-30 Sat] =instanceof=
*** DONE [2021-02-07 Sun] =in=
*** DONE [2021-02-07 Sun] =/=
*** DONE [2021-02-07 Sun] =%=
*** DONE [2021-02-07 Sun] =**=
*** DONE [2021-02-07 Sun] =|=
*** DONE [2021-02-07 Sun] =^=
*** DONE [2021-02-07 Sun] =<<=
*** DONE [2021-02-07 Sun] =>>=
*** DONE [2021-02-07 Sun] =>>>=
** DONE [2021-02-07 Sun] AssignmentExpression [7/7]
*** DONE [2020-12-21 Mon] ~=~
*** DONE [2021-01-02 Sat] ~+=~
*** DONE [2021-01-15 Fri] ~-=~
*** DONE [2021-01-14 Thu] ~*=~
*** DONE [2021-02-07 Sun] ~/=~
*** DONE [2021-02-07 Sun] ~&=~
*** DONE [2021-02-07 Sun] ~|=~
** DONE [2021-01-11 Mon] ArrayExpression
* Variables [6/8]
** DONE [2020-12-26 Sat] mutable values and assignment
** DONE [2021-01-11 Mon] array members get/assign
** DONE [2021-02-13 Sat] variable hoisting
** DONE [2021-02-13 Sat] assignment to an outer variable
** DONE [2021-02-13 Sat] free-variables analysis for closures
** DONE [2022-06-15 Sat] a new local scope in =catch {}=
** TODO =let= variables, block scope [1/2]
*** DONE [2022-06-19 Sun] initial hack: create an object scope for every block
*** TODO proper declarative lexical scope for blocks
** TODO =const= values
* Function calls [3/3]
** DONE [2021-01-01 Fri] CallExpression
** DONE [2021-01-16 Sun] immediate calls: ~(function(){})()~
** DONE [2021-01-23 Sat] array member calls: ~a[0]()~
* Builtin objects
** builtin functions [3/5]
*** DONE [2021-04-28 Wed] =parseFloat=
*** DONE [2021-01-09 Sat] =parseInt=
*** TODO proper =parseInt=
*** DONE [2022-07-05 Tue] =eval=
*** TODO =isNaN=
** builtin =Object= [10/26]
*** DONE [2021-01-05 Tue] create it!
*** DONE [2021-01-05 Tue] Object.getOwnPropertyDescriptor
*** DONE [2021-01-08 Fri] .constructor
*** DONE [2021-01-08 Fri] Object.is()
*** DONE [2021-01-18 Mon] Object() constructor
*** DONE [2021-01-18 Mon] .valueOf()
*** DONE [2021-02-10 Wed] Object.create()
*** DONE [2021-02-10 Wed] Object.defineProperties()
*** DONE [2021-02-13 Sat] Object.setPrototypeOf()
*** DONE [2021-02-13 Sat] .hasOwnProperty()
*** TODO Object.getPrototypeOf()
*** TODO Object.assign()
*** TODO Object.keys()
*** TODO Object.values()
*** TODO Object.entries()
*** TODO Object.fromEntries()
*** TODO Object.getOwnPropertyDescriptors()
*** TODO Object.getOwnPropertyNames()
*** TODO Object.freeze()
*** TODO Object.isFrozen()
*** TODO Object.preventExtensions()
*** TODO Object.isExtensible()
*** TODO Object.seal()
*** TODO Object.isSealed()
*** TODO .isPrototypeOf()
*** TODO .propertyIsEnumerable()
** builtin =Function= [4/6]
*** DONE [2021-01-06 Wed] =src/builtin/function.rs=
*** DONE [2021-01-17 Sun] .constructor
*** DONE [2021-01-20 Wed] .call()
*** DONE [2021-01-20 Wed] .apply()
*** TODO .bind()
*** TODO ...everything else
** builtin =Array= [6/10]
*** DONE [2021-01-10 Sun] =src/builtin/array.rs=
*** DONE [2021-01-15 Fri] (de)serialization
*** DONE [2021-01-16 Sat] .toString()
*** DONE [2021-05-16 Sun] .length
*** DONE [2021-05-16 Sun] .push()
*** DONE [2021-05-22 Sat] .pop()
*** TODO Array.from
*** TODO Array.of
*** TODO Array.isArray()
*** TODO ...everything else
** builtin =JSON= [/]
** builtin =Boolean= [3/3]
*** DONE [2021-01-20 Wed] scaffolding in =src/builtin/boolean.rs=
*** DONE [2021-01-20 Wed] Boolean constructor, =Object(true)=
*** DONE [2021-01-20 Wed] Boolean.prototype
**** DONE [2021-01-20 Wed] .valueOf
**** DONE [2021-01-20 Wed] .toString
** builtin =String= [10/20]
*** DONE [2021-03-10 Wed] .length
*** DONE [2021-04-24 Sat] string indexing
*** DONE [2021-04-24 Sat] =src/builtin/string.rs=
*** DONE [2021-04-24 Sat] String() constructor; Object("string")
*** DONE [2021-04-28 Wed] .charCodeAt()
*** DONE [2021-05-01 Sat] .charAt()
*** DONE [2021-05-01 Sat] .slice()
*** DONE [2021-05-22 Sat] .substr()
*** DONE [2021-05-30 Sun] .indexOf()
*** DONE [2022-07-09 Sat] .replace()
*** TODO =.replace(/regexp/)=
*** TODO check escape notation
*** TODO String.fromCharCode()
*** TODO String.fromCodePoint()
*** TODO String.raw()
*** TODO .concat()
*** TODO .includes()
*** TODO .endsWith()
*** TODO .lastIndexOf()
*** TODO .replace()
*** TODO ...
** builtin =Number= [/]
** MAYBE builtin =assert= object
** NOPE =console= in sljs
   This is I/O and should not live in the interpreter core.
* User functions [3/4]
** DONE FunctionExpression
*** DONE [2021-01-06 Wed] function scope
*** DONE [2021-01-17 Sun] closures
*** DONE [2021-01-23 Sat] =arguments=
** DONE [2021-01-06 Wed] ReturnExpression
** DONE [2021-01-23 Sat] FunctionDeclaration
** TODO recursive functions [1/3]
*** DONE [2021-01-17 Sun] make them work
*** TODO limit call stack, throw StackOverflow
*** MAYBE tail call optimization
* User objects [4/5]
** DONE [2021-01-09 Sat] prototype chain
** DONE [2021-01-17 Sun] ThisExpression
** DONE [2021-01-18 Mon] NewExpression
** DONE [2021-01-31 Sun] properties lookup on the chain
** TODO properties, =get=, =set=

* User exceptions [3/4]
** DONE [2021-01-27 Wed] =throw=
** DONE [2021-01-28 Thu] =try=, =catch=, =finally=
** DONE [2021-01-31 Sun] =Error= objects
** TODO stacktraces with source locations
* DONE [2021-01-14 Thu] rewrite the =Heap= to be =Vec<JSObject>=
* DONE [2020-12-31 Thu] make it a library
* DONE [2021-01-01 Fri] a repl executable
* testing [1/3]
** DONE [2022-06-19 Sun] move tests to =tests/=
** WIP split tests into internal =assert_eval= and external =assert_parse=
   Internal tests (=src/test/interp.rs=) should take an AST constructed via a DSL
   for AST construction.
   External tests (=tests/parse.rs=) verify parsing from a string to an AST.
** TODO write a test262 harness in Rust
* MAYBE optimizations [1/6]
** DONE Set up microbenchmarks
   *Why*: because optimization is not possible without metrics.
   *How*: cargo bench?
** TODO Use a streaming json parser
   *Why*: copying JSON into a huge String to be immediately discarded is wasteful.
   Making a complete intermediate JSON structure from it is also wasteful
   *How*: something like https://docs.rs/qjsonrs reads from a Read, producing JSON
   tokens, some of which trigger callbacks SAX-style. A bottom-up "parser" assembles
   pieces into a Program. Some intermediate JSON-like structures may be kept around.
** TODO Bytecode compilation
   *Why*: AST-based interpretation is dumb.
** MAYBE Intern all property names
   *Why*: all properties are currently stored by a =String= key.
   This means that each property key is 24 bytes and contains a pointer to its
   UTF8 buffer. A comparison of two keys means chasing two pointers and reading
   unknown extents of memory.
   *Interning*: all keys will become integer handles for interned strings. Each
   key lookup will be an int comparison.
   *Bonus*: =Symbol= will correspond to interned keys naturally.
** MAYBE Track hidden classes, especially after calling constructors
   *Why*: HashMap is not always the best storage; vector can be better.
   Abstracting property names into a hidden class can leave each object with a
   single vector of values and a pointer to the hidden class with the value
   description vector.
   Work: need to convert HashMap-based objects into class-based objects and back.
** MAYBE Frozen/sealed objects to store their properties in a vector.
   *Why*: frozen/sealed objects are by definition non-extensible.
   Attaching a hidden class looks like a good idea.
* TODO garbage collection [1/3]
** DONE [2021-05-31 Mon] SimpleCopyingGC draft
   It kinda works, but has a fatal flaw: ~JSRef~s are free-floating in
   the unmanaged code.
** MAYBE Introduce an explicit stack for references in use?
** MAYBE A garbage collector in another thread?
* TODO the **endgoal**: be able to run Esprima internally [4/6]
** DONE [2021-02-08 Sun] all of Esprima syntax is understood
** DONE [2021-03-02 Tue] all of Esprima code can be loaded
** DONE [2021-05-22 Sat] there is a binary doing parsing via internal Esprima
** DONE [2022-06-05 Sun] make parsing engines abstract
** TODO interpreter doing parsing with Esprima can parse Esprima.
   Blocked by: needs GC, 16 GB RAM is not enough.
** MAYBE try treesitter?
* DONE =eval=
  It's buggy, but it's metainterpreted now.


#+TODO: BUG TODO MAYBE WIP | DONE NOPE