This change redoes the way module exports are represented. The old
mechanism -- although laudible for its attempt at consistency -- was
wrong. For example, consider this case:
let v = 42;
export { v };
The old code would silently add *two* members, both with the name "v",
one of which would be dropped since the entries in the map collided.
It would be easy enough just to detect collisions, and update the
above to mark "v" as public, when the export was encountered. That
doesn't work either, as the following two examples demonstrate:
let v = 42;
export { v as w };
let x = w; // error!
This demonstrates:
* Exporting "v" with a different name, "w" to consumers of the
module. In particular, it should not be possible for module
consumers to access the member through the name "v".
* An inability to access the exported name "w" from within the
module itself. This is solely for external consumption.
Because of this, we will use an export table approach. The exports
live alongside the members, and we are smart about when to consult
the export table, versus the member table, during name binding.
This change refactors the interpreter hooks into a first class interface
with many relevant event handlers (including enter/leave functions for
packages, modules, and functions -- something necessary to generate object
monikers). It also includes a rudimentary start for tracking actual object
allocations and their dependencies, a step towards creating a MuGL graph.
This change looks up the main module from a package, and that module's
entrypoint, when performing evaluation. In any case, the arguments are
validated and bound to the resulting function's parameters.
This change further merges the new AST and MuPack/MuIL formats and
abstractions into the core of the compiler. A good amount of the old
code is gone now; I decided against ripping it all out in one fell
swoop so that I can methodically check that we are preserving all
relevant decisions and/or functionality we had in the old model.
The changes are too numerous to outline in this commit message,
however, here are the noteworthy ones:
* Split up the notion of symbols and tokens, resulting in:
- pkg/symbols for true compiler symbols (bound nodes)
- pkg/tokens for name-based tokens, identifiers, constants
* Several packages move underneath pkg/compiler:
- pkg/ast becomes pkg/compiler/ast
- pkg/errors becomes pkg/compiler/errors
- pkg/symbols becomes pkg/compiler/symbols
* pkg/ast/... becomes pkg/compiler/legacy/ast/...
* pkg/pack/ast becomes pkg/compiler/ast.
* pkg/options goes away, merged back into pkg/compiler.
* All binding functionality moves underneath a dedicated
package, pkg/compiler/binder. The legacy.go file contains
cruft that will eventually go away, while the other files
represent a halfway point between new and old, but are
expected to stay roughly in the current shape.
* All parsing functionality is moved underneath a new
pkg/compiler/metadata namespace, and we adopt new terminology
"metadata reading" since real parsing happens in the MetaMu
compilers. Hence, Parser has become metadata.Reader.
* In general phases of the compiler no longer share access to
the actual compiler.Compiler object. Instead, shared state is
moved to the core.Context object underneath pkg/compiler/core.
* Dependency resolution during binding has been rewritten to
the new model, including stashing bound package symbols in the
context object, and detecting import cycles.
* Compiler construction does not take a workspace object. Instead,
creation of a workspace is entirely hidden inside of the compiler's
constructor logic.
* There are three Compile* functions on the Compiler interface, to
support different styles of invoking compilation: Compile() auto-
detects a Mu package, based on the workspace; CompilePath(string)
loads the target as a Mu package and compiles it, regardless of
the workspace settings; and, CompilePackage(*pack.Package) will
compile a pre-loaded package AST, again regardless of workspace.
* Delete the _fe, _sema, and parsetree phases. They are no longer
relevant and the functionality is largely subsumed by the above.
...and so very much more. I'm surprised I ever got this to compile again!
