зеркало из https://github.com/mozilla/gecko-dev.git
93 строки
3.4 KiB
Plaintext
93 строки
3.4 KiB
Plaintext
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GOALS
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The purpose of this prototype is to provide a reusable (as in copiable)
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code base for exploring different aspects of the ES4 runtime compiler.
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The audience for this software consists of language developers. It is
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not likely to be useful as a language engine but it should be useful as
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a base for making a useful language engine - at least that's the goal
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Specific goals include:
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1/Implementing a parser for the full ES4 grammar
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2/Using E4X to explore the abstract syntax of ES4 programs
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3/Implementing the "definition" phase of the compiler
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4/Modelling all block structures (e.g. block statements,
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classes, functions) as prologue-block pairs in the abstract
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syntax, and emit those pairs uniformly as methods with traits
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5/Implementing packages and namespaces, import and use namespace
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6/Implementing multinames and unqualified name resolution
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NON-GOALS
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Specific non-goals:
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1/Efficent intermediate representation of programs. A later
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experiment will attempt a compiler that avoids the use of
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an intermediate a.s.t altogether
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2/Modelling types. There are serious practical issues with
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implementing classes and instances as vanilla activation
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objects, like I have done here. We will want to use the
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existing AVM support for types in any production version
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3/Implementing a useful subset of the language, including
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control flow statements and operator expressions
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4/Zero bugs
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AREAS FOR FURTHER INVESTIGATION
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1/Efficiency - e.g. merging compiler phases to avoid
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creation of a.s.t.s
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2/Compatibility with ES3/JS1
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3/Prototyping ES4 proposals
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* Static v. standard modes
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* Switch type
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* Enumerability
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* [done] Block scope (let)
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* Local packages
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* Iterators & generators
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* Date literals
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* Destructuring assignment
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* [done] Reserved words
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* Nullability
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* Namespace shadowing
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* Reformed ''with''
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* Type parameters
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* Self hosting object model
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* Structural types
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* is, as, to operators
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* Numbers (see Decmial)
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* Tail calls
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* Type definitions
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* Catchalls
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* Hashcodes
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* Intrinsic namespace
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* Operator overloading
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* Decimal
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* typeof
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* Regexp update
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* Unicode update
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* ES3 bug fixes
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ABOUT THE CODE
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* I've used type annotations as sparingly as possible to keep
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the coding process as fluid as possible. This lack of types
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sometimes leads to hairy debugging sessions, but on the whole
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has made the code more malleable than it would be otherwise
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* Variable names are all lower case with words separated by '_'
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* Method names are Java style except in some cases where
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they are part of a major interface and its leading lowercase
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verb is dropped. For example, in the Emitter class what would
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have been called 'emitGetProperty' is named 'GetProperty'
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* I've used dynamic object features such as E4X and Array and
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Object extensively and classes sparingly. Again this is to
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keep design decisions from getting prematurely encrusted in the
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code
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* I've used namespaces to switch modes at compile time (mostly).
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There are two pairs of opposing namespaces: 'debug' and 'release'
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are used to control the printing of trace information; 'avm' and
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'ast' are used as alternative interpreters - ast, the tree walking
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interpreter is currently too incomplete to be interesting - avm
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is the primary interpreter
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