The source universe of reflection artifacts that will be processed.
The source universe of reflection artifacts that will be processed.
The target universe is universe that created this importer with mkImporter.
In the current universe, creates a position that corresponds to the provided position in the source universe.
In the current universe, locates or creates a symbol that corresponds to the provided symbol in the source universe.
In the current universe, locates or creates a symbol that corresponds to the provided symbol in the source universe. If necessary imports the owner chain, companions, type signature, annotations and attachments.
In the current universe, creates a tree that corresponds to the provided tree in the source universe.
In the current universe, creates a tree that corresponds to the provided tree in the source universe. If necessary imports the underlying symbols, types and attachments.
In the current universe, locates or creates a type that corresponds to the provided type in the source universe.
In the current universe, locates or creates a type that corresponds to the provided type in the source universe. If necessary imports the underlying symbols, annotations, scopes and trees.
An importer that works in reverse direction, namely:
imports reflection artifacts from the current universe to the universe specified in from.
This trait provides support for importers, a facility to migrate reflection artifacts between universes. Note: this trait should typically be used only rarely.
Reflection artifacts, such as Symbols and Types, are contained in Universes. Typically all processing happens within a single
Universe(e.g. a compile-time macroUniverseor a runtime reflectionUniverse), but sometimes there is a need to migrate artifacts from oneUniverseto another. For example, runtime compilation works by importing runtime reflection trees into a runtime compiler universe, compiling the importees and exporting the result back.Reflection artifacts are firmly grounded in their
Universes, which is reflected by the fact that types of artifacts from different universes are not compatible. By usingImporters, however, they be imported from one universe into another. For example, to importfoo.bar.Bazfrom the sourceUniverseto the targetUniverse, an importer will first check whether the entire owner chain exists in the targetUniverse. If it does, then nothing else will be done. Otherwise, the importer will recreate the entire owner chain and will import the corresponding type signatures into the targetUniverse.Since importers match
Symboltables of the source and the targetUniverses using plain string names, it is programmer's responsibility to make sure that imports don't distort semantics, e.g., thatfoo.bar.Bazin the sourceUniversemeans the same thatfoo.bar.Bazdoes in the targetUniverse.Example
Here's how one might implement a macro that performs compile-time evaluation of its argument by using a runtime compiler to compile and evaluate a tree that belongs to a compile-time compiler: