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!
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